<%BANNER%>

Influence of Cover Crops on Phosphorus Fractions and Soil Fertility in a Peruvian Cacao Agroforestry System

Permanent Link: http://ufdc.ufl.edu/UFE0022205/00001

Material Information

Title: Influence of Cover Crops on Phosphorus Fractions and Soil Fertility in a Peruvian Cacao Agroforestry System
Physical Description: 1 online resource (114 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: In many tropical soils, excessive weathering of primary minerals has resulted in the depletion of most plant soluble forms of P greatly hindering agricultural productivity. Long-term growth of cover crops in tropical agroforestry systems have been shown to influence soil P fractions, nutrient cycling, and soil organic matter pools. Several key soil characteristics associated with fertility, emphasizing soil P bioavailability were evaluated, after two years of cover crop establishment. Cover crop cultivation resulted in an increase in soil pH and organic matter pools and the hydrochloric acid extractable P fractions were accessed by cover crop species. The experimental design of this study included seven treatments in the understory of an experimental cacao agroforestry system in the San Martin district of Peru. The treatments were four perennial leguminous cover crops (Arachis pintoi, Calopogonium mucunoides, Canavalia ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), an inorganic fertilizer treatment, and a control treatment. Results of this study indicated that after two years of cover crop cultivation minor changes occurred in the soil pH, organic matter content, and extractable phosphorus pools. However, continued monitoring is required to develop a complete understanding of the ability of cover crop cultivation to accentuate soil fertility.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Li, Yuncong.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022205:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022205/00001

Material Information

Title: Influence of Cover Crops on Phosphorus Fractions and Soil Fertility in a Peruvian Cacao Agroforestry System
Physical Description: 1 online resource (114 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: Soil and Water Science -- Dissertations, Academic -- UF
Genre: Soil and Water Science thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: In many tropical soils, excessive weathering of primary minerals has resulted in the depletion of most plant soluble forms of P greatly hindering agricultural productivity. Long-term growth of cover crops in tropical agroforestry systems have been shown to influence soil P fractions, nutrient cycling, and soil organic matter pools. Several key soil characteristics associated with fertility, emphasizing soil P bioavailability were evaluated, after two years of cover crop establishment. Cover crop cultivation resulted in an increase in soil pH and organic matter pools and the hydrochloric acid extractable P fractions were accessed by cover crop species. The experimental design of this study included seven treatments in the understory of an experimental cacao agroforestry system in the San Martin district of Peru. The treatments were four perennial leguminous cover crops (Arachis pintoi, Calopogonium mucunoides, Canavalia ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), an inorganic fertilizer treatment, and a control treatment. Results of this study indicated that after two years of cover crop cultivation minor changes occurred in the soil pH, organic matter content, and extractable phosphorus pools. However, continued monitoring is required to develop a complete understanding of the ability of cover crop cultivation to accentuate soil fertility.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.S.)--University of Florida, 2008.
Local: Adviser: Li, Yuncong.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022205:00001


This item has the following downloads:


Full Text





INFLUENCE OF COVER CROP CULTIVATION ON PHOSPHORUS FRACTIONS AND
SOIL FERTILITY IN A PERUVIAN CACAO AGROFORESTRY SYSTEM




















By

HOLLIE HALL


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2008

































2008 Hollie Hall

































To my grandmother for encouraging me to play outside.









ACKNOWLEDGEMENTS

The author would like to thank the many sources of education and guidance, laboratory

and field assistance, and funding that made this work possible. In terms of educational growth

and guidance, the author is greatly appreciative to her committee members. Her academic

advisor, Dr. Yuncong Li offered her an opportunity in which she was able to develop research,

project management, and linguistic skills in the Peruvian Amazon where the resulting

information will be included in local efforts to improve soil productivity. Additionally, Dr. Li

encouraged the author to broaden her laboratory research experimentation to areas outside of her

foci resulting in a broader understanding of soil phosphorus fractions. The author thanks Dr. Li

for trusting and supporting her in the undertaking of this research project. The Co-Chair of her

academic committee, Dr. Nick Comerford provided the valuable opportunity for participation in

critical discussions of published research regarding soil phosphorus, its quantification and

interpretation. For this as well as for aiding in her development of understanding for the

mechanisms by which plants absorb soil nutrients, the author thanks Dr. Comerford. Committee

member and Professor Emeritus, Dr. Hugh Popenoe fueled the authors' inspiration and

knowledge regarding tropical agriculture through thought provoking lectures and conversations.

She is thankful to Dr. Popenoe for lending his lens of experience and personal support to her

research endeavors. Committee member and USDA Soil Scientist, Dr. Virupax Baligar made

this project possible by establishing the cover crop experiment in Tarapoto. In addition to his

role in the experiment establishment, the author thanks Dr. Baligar for providing her with

constructive criticism, thoughtful comments, and volumes of relevant published information to

aid in informing her research activities. Each member of the authors' academic committee filled

a unique niche and collectively provided her with important lessons in conducting quality

scientific research.









In terms of laboratory and field assistance, the author would like to acknowledge the many

people at the Forest Soils Laboratory, Tropical Research & Education Centers Soil and Water

Sciences Laboratory, and at the Instituto de Cultivos for their generosity with their time.

Specifically, at the Forest Soils Laboratory the author thanks Aja Stoppe for her continued

availability for answering numerous questions and for managing a well organized and stocked

laboratory space. At the Tropical Research & Education Centers Soil and Water Sciences

Laboratory, the author would like thank Guingin Yu, Yun Qian, and Laura Rosado for their

kindness and for providing her with training in laboratory techniques. At the Instituto de

Cultivos Tropicales, she would like to thank the Directors Mr. Enrique Arevelo-Gardini and Mr.

Luis B. Zufiiga Cernades and all of their employees, not only for assisting in conducting field

research but also for taking her in as part of their families, allowing her a full emersion

experience in Tarapoto, Peru.

In terms of funding, the author would like to thank the Soil and Water Science Department,

the Latin American Studies Research Grant fund, and the Tinker Grant fund at the University of

Florida for providing economic support for her research activities.









TABLE OF CONTENTS

page

A CK N O W LED G EM EN TS ............................................................................. .................. 4

L IS T O F T A B L E S ................................................................................. 8

LIST OF FIGURES ................................... .. .... .... ................. 10

A B S T R A C T ........................................... ................................................................. 1 1

CHAPTER

1 INTRODUCTION ............... .......................................................... 12

O bje ctiv e s ................... ...................1...................3..........
H y p o th e sis ..........................................................................13

2 L ITE R A TU R E R E V IE W ......................................................................... ........................ 14

Cacao Agroforestry: A Mode for Economic Gain....................................... ............... 14
Soil F ertility in the H um id T ropics............................................ ....................................... 18
O rg a n ic M atte r .................................................................................................................. 1 8
P hosphorus... ......... ..........................................19
N itro g en ................... ...................2...................0..........
S oil A cidity ................... ...................2...................0..........
Nutrient Cycling in Cacao Agroforestry Systems ...................................... ........... ....21
Benefits of U sing Legum inous Cover Crops ................................................................. 22
Cover Crops as Sources of Soil Organic Matter............................... ..... ............... 22
Cover Crops Enhance Soil Solution Inorganic Phosphorus ..................................... 23
Cover Crops as Sources of Biologically Fixed Nitrogen............... .............................24
Sequential Fractionation Procedures ..................................................... ............... .... 24







Introduction ............................ ...................... ..................35
M materials and M methods .......................................................... ...... 36
S tu d y S ite .......................................................3 6
E x p erim en tal D esig n ................................................................................................. 3 7
Soil Sam pling ............................... ...... .. .......... ............... 37
Soil Nitrogen, Carbon, Calcium, Potassium, Iron, Aluminum, Magnesium, pH, and
L o ss on Ignition ....................................................... 3 8
Mehlich I Extractable Phosphorus................. ...... ......... ................ 38
Sequential Fractionation of Phosphorus.......................... .......................... 39


6









Measurement of Extracted Inorganic Phosphorus........ ... ....................................... 39
Analysis of Phosphorus in Cover Crop Tissue............................................. ..........39
A analysis of Soil O rganic M atter........................................................... ............... 39
Statistical A n aly sis ................................................................4 0
Results ............. ......... ............... .................................. ...............40
Soil Total Nitrogen, Total Carbon, and Carbon to Nitrogen Ratio ..............................40
Soil Loss o Ignition and Organic Matter .................................. ...................41
S o il p H .......... ................................................................... 4 1
Soil Calcium, Potassium, Magnesium, Iron, and Aluminum ............................... 41
Mehlich I Extractable Phosphorus...................... ...... ............................ 42
Sequential Fractionation of Phosphorus........................................... ...............42
Six M olar HC1 Digest of Air-Dried Soil ........... .. ............................... .............. 43
Cover Crop Tissue Phosphorus Content................... ..... ..................44
Correlations Between Soil Extractable Phosphorus Fractions and Cover Crop
Tissue Phosphorus Percentage............................ ......... ..................... ............... 44
D iscu ssion .................... ...... ..... ..... ...... ....................................... 44
Soil Loss on Ignition and Organic M atter Content ............................... ............... .44
Soil Carbon Content ......................... ....... ................... ......... 46
Soil N itrogen C ontent............ .............................................................. ......... ....... 47
C arbon to N itrogen R atio ........................................................................ .................. 47
Soil Potassium, Calcium, and Magnesium......................................................48
Soil pH and Potential Aluminum Toxicity ......................... .......... ............... 48
C over Crop Tissue Phosphorus ........................................ ....... ........................... 49
Correlations Between Cover Crop Tissue and Soil Extractable Phosphorus................49
Half Molar HC1 Extractable Phosphorus............ .. ......... ........... .............. 49
Six M olar HC1 Extractable Phosphorus ........................................ ....... ............... 50
C o n c lu sio n .......................... ............. ... .........................................................5 0

APPENDIX A

U N TR A N SFO R M ED D A TA ..................................................................... .... .........................69

L IST O F R E F E R E N C E S ..................................................................................... ..................107

B IO G R A PH IC A L SK E T C H ......................................................................... ........................ 113
















7









LIST OF TABLES


Table page

2-1 Sequential fractionation of soil P procedures and interpretation................... ..............30

3-1 Sum m ary of significant findings.............................................. .............................. 53

3-2 Total nitrogen, total carbon, carbon to nitrogen ratio, pH, and loss on ignition
averaged data for all treatments at all depths............................................ .................. 55

3-4 Calcium, potassium, iron, aluminum, and magnesium averaged data.............................57

3-5 Mehlich I extraction of inorganic, organic, and total phosphorus averaged data .............58

3-6 Sequential extraction of phosphate and the digest of air-dried soil averaged data...........59

3-7 Phosphorus content of cover crop foliar tissue. ....................................... ............... 60

3-8 Soil organic matter, potassium, cation exchange capacity, cations, and base
saturation av eraged data ...................................................................... ....... .. ......6 1

3-9 Extractable phosphorus expressed in kilograms per hectare. .........................................62

A-i Soil sample collection co-ordinates. ............................................................................69

A-2 Soil total nitrogen, total carbon, pH, and carbon to nitrogen ratio unaltered data.............75

A -3 Loss on ignition unaltered data. ............................................... ............................... 77

A-4 Soil concentration of calcium, potassium, iron, aluminum, and magnesium unaltered
data........................................................... 80

A-5 Mehlich I extraction of inorganic phosphorus unaltered data. ............................. .....81

A-6 Mehlich I extraction of total phosphorus unaltered data. ...............................................83

A-7 Water extraction of inorganic phosphorus unaltered data. ................................. 85

A-8 One molar NH4C1 extraction of inorganic phosphorus unaltered data. ..........................88

A-9 One-tenth molar NaOH extraction of inorganic phosphorus unaltered data. ....................91

A-10 Digest of 0.1 M NaOH supernatant for the quantification of total 0.1 M NaOH
extractable phosphorus unaltered data. ........................................ ......................... 94

A-11 Half molar HC1 extraction of inorganic phosphorus unaltered data..............................98









A-12 Six molar HC1 digest and extraction of inorganic phosphorus from residual soil
unaltered data. .............................................................................10 1

A-13 Six molar HC1 digest and extraction of inorganic phosphorus from air-dried soil
unaltered data. .............................................................................104









LIST OF FIGURES


Figure page
3 1 M a p o f P e ru ................................................................................................................. 6 4

3-2 Experimental design ............................... ... ...... .. .......... ........ 65

3-3 Sequence for the fractionation of soil phosphorus pools............. ..................................66

3-4 Significant correlations between cover crop tissue and soil extracted phosphorus
p o o ls .........................................................................6 7

3-5 Physical symptoms of aluminum toxicity expressed in the mature leaves of cacao
plants at Instituto de Cultivos Tropicales...................................... ......................... 68









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

INFLUENCE OF COVER CROP CULTIVATION ON PHOSPHORUS FRACTIONS AND
SOIL FERTILITY IN A PERUVIAN CACAO AGROFORESTRY SYSTEM

By

Hollie Hall

May 2008

Chair: Yuncong Li
Major: Soil and Water Science

In many tropical soils, excessive weathering of primary minerals has resulted in the

depletion of most plant soluble forms of P greatly hindering agricultural productivity. Long-term

growth of cover crops in tropical agroforestry systems have been shown to influence soil P

fractions, nutrient cycling, and soil organic matter pools. Several key soil characteristics

associated with fertility, emphasizing soil P bioavailability were evaluated, after two years of

cover crop establishment. Cover crop cultivation resulted in an increase in soil pH and organic

matter pools and the hydrochloric acid extractable P fractions were accessed by cover crop

species. The experimental design of this study included seven treatments in the understory of an

experimental cacao agroforestry system in the San Martin district of Peru. The treatments were

four perennial leguminous cover crops (Arachispintoi, Calopogonium mucunoides, Canavalia

ensiformis, and Centrosema macrocarpum), a non-legume cover crop (Callisia repens), an

inorganic fertilizer treatment, and a control treatment. Results of this study indicated that after

two years of cover crop cultivation minor changes occurred in the soil pH, organic matter

content, and extractable phosphorus pools. However, continued monitoring is required to

develop a complete understanding of the ability of cover crop cultivation to accentuate soil

fertility.









CHAPTER 1
INTRODUCTION

Our study is aimed to elucidate the issues related to conversion of humid tropical forests to

agricultural land, and the potential for improved agricultural systems to aid in the sustainability

of these conversions. Our study focused on the potential for inclusion of leguminous cover crops

in cacao agroforestry systems to mediate tropical soil infertility that often results after prolonged

cultivation. We examined humid tropical regions hospitable to cacao cultivation, generally

defined as the area having an average annual precipitation greater than 1500 mm, mean annual

temperature >220C, and drought periods not exceeding 4 months (Vitousek and R.L. Sanford

1986). Soils most suitable for cacao production contain approximately 3% organic matter, and

have a pH ranging between 6 and 7.5 (Evans et al. 1998). In eastern Peru these conditions are

most favorable in river valley soils, where ultimately, minimum air temperatures of less than 100

C shape the distribution of cacao (Evans et al. 1998). Further more, the discussions contained

within this document focus on the problems associated with highly weathered tropical soils.

Nutrients in tropical soils have been depleted over time, naturally or by continuous

cultivation and harvest of plant products (Baligar et al. 2004). It is possible that with

conscientious management, fertility of these soils can be maintained or improved, making them a

renewable resource (Brady and Weil 1999). Leguminous cover crops are widely accepted for

their contribution to soil quality through additions of nitrogen (N) (Fageria et al. 2005). As

phosphorus (P) is often the most limited plant essential nutrient in tropical soils, inclusion of

leguminous cover crops on tropical soils may seem counter-intuitive. However, leguminous

cover crops can alter soil P forms through the addition of soil organic matter (SOM), deep soil

mining, and microbial priming (Brady and Weil 1999; Chapin-III et al. 2002).









The primary research contained in this document focuses on the effects of leguminous

cover crop inclusion in a cacao agroforestry system on soil phosphorus fractions and soil

fertility. This experiment complements ongoing research related to cacao agroforestry conducted

on an acidic tropical soil at Insituto de Cultivos Tropicales (ICT) in Tarapoto, Peru. The

research site exists at latitude 6028.734' S and longitude 76019.694' W, at an altitude of 467

meters above sea level, and receives an average of 1200 mm of rain per year (NOAA 2007). The

goal of the ICT experiment was to assess the potential benefit of leguminous cover crops in

improving soil quality factors and the subsequent benefits on cacao yield. The experimental area

was 1.05 hectares of acidic soils (pH 4.83- 6.04, with very low to moderate levels of organic

matter (OM) and P.

Objectives

1. To quantify the effects of two years of leguminous cover crop cultivation on soil
phosphorus fractions as extracted by various extractants; and

2. To quantify the effects of two years of leguminous cover crop cultivation on soil fertility
factors; organic matter content, loss on ignition, total nitrogen content, and pH at the 0-5
cm, 5-15 cm and 15-30 cm soil horizons.


Hypothesis

1. Cultivation of leguminous cover crops alters soil phosphorus pools.
2. Cultivation of leguminous cover crops alters soil fertility factors.









CHAPTER 2
LITERATURE REVIEW

Cacao Agroforestry: A Mode for Economic Gain

Under continued pressure of population growth, the sustainability of humid tropical forest

resources will depend upon improved agricultural management techniques that allow for

sustained land-use. Pressures on tropical forests are complex and relate to the methodology of

traditional agricultural practices, land ownership, and the disequilibria in nutrient cycles

precipitated by forest clearing (F.A.O 2005). Together, these pressures play an important role in

mediating the rate of deforestation, currently approximately 13 million hectares per year, and the

magnitude of food and economic insecurities in rural communities of the humid tropics (F.A.O

2005). Research testing and promotion of agroforestry systems that maintain or improve soil

fertility is critical to increasing the agricultural productivity of tropical regions while stabilizing

rates of deforestation. Compared to monocultural food cropping systems, cacao (Theobroma

cacao) agroforestry systems help to maintain soil fertility, improve economic and food income,

and protect native plant diversity by maintaining soil organic matter supplies, and producing a

diversity of agricultural products (Bridges 2006).

In semi-rural tropical regions, it is common for people to live a subsistence life style, in

which they are dependent on the productivity of the land they farm for food and economic gains

(Sanchez 2000). Often, traditional shifting agricultural methods achieve long-term tropical soil

productivity through nutrient replenishing fallow periods. Without fallow periods, the

sustainability of agricultural production on tropical soil is hindered by continued depletion of soil

nutrient pools (Ryan and Delhaize 2001). For people living in regions suitable for cacao

production, installations of agricultural technologies like agroforestry systems can improve soil

fertility and provide major food and economic gains (Hartemink 2005).









In 2005, 5 to 6 million cacao farmers created enough employment opportunities to support

40 to 50 million people (W.C.F. 2007). In this same year the global cacao market was valued at

$5.1 billion, and the demand for cacao has grown on an average of 3% per year for the last 100

years (W.C.F. 2007). When compared to the total agricultural productivity in West Africa, cacao

has earned a majority of the economic gains there (Duguma et al. 2001). The Ivory Coast alone

produces enough cacao to fulfill 40% of the world market (Hartemink 2005). Cacao exports

from Ghana account for approximately 60% of the country's foreign income (Hartemink 2005).

The majority of the marketed cacao is produced by small scale farmers (Hartemink 2005).

Peruvian farmers produced an average of 831 tons of cacao per year in 1992 and 1993 (USDA

and ARS 2007). In these years of low national cacao productivity, Peru imported from 100 (in

1993) to 3,591 (1994) tonnes of cocoa. However, by 1996 the annual production of cacao in

Peru had jumped to 22,867 tonnes and imports ceased (Evans et al. 1998). The Peruvian

economy supports infrastructure for the export of cacao products, ranging from 5,991 tonnes

exported in 1993 to 3,826 tonnes exported in 1996 (Evans et al. 1998). At the global scale, Peru

is not currently a major exporter of cacao, however the high value crop and government

subsidies are providing incentive for farmers to switch from coca (Erythroxylum coca) to cacao

farming in the San Martin region of Peru, a trend which may increase local dependency on, and

certainly productivity of this cropping system (Bridges 2006).

In San Martin, Peru, a guarantee of economic return on investments in cacao production

stems from a nearby manufacturer of high quality chocolate who purchases all locally grown

cacao beans. For cacao agroforesters in this region, nearly 100% of their harvested food crops

are sold suggesting a non-saturated market incentive for increased production. The generated









income from these sales allow for an improvement in the families overall nutrition through

diversified food intake, as well as increased educational opportunities (Hall unpublished data).

Tropical forests in the primary cacao producing countries are leading the world in rates of

deforestation at nearly 13 million hectares per year (F.A.O 2005). The main motivation for

deforestation in these regions is the expansion of agriculture land (F.A.O 2005). On a global

scale, shifting cultivation is responsible for approximately 60% of deforestation (Duguma et al.

2001). Traditional agricultural methods in the tropics involve shifting from one cleared forest

soil to the next, with fallow periods in between to allow regeneration of forest and soil fertility.

Now that land tenure is an issue, many people of the tropics, are attempting continuous

cultivation of single plots of land for indefinite time spans (Carter et al. 1993). If management of

soil fertility is successful, the continuous cultivation of land will play an important role in

stabilizing rates of deforestation. In Bahia, Brazil, one-half of the remaining forest canopy is

under management in the traditional 'cabruca' style cacao agroforestry systems, showing

potential for this type of agricultural system to succeed in protecting forest species (Bright 2001).

In deforested tropical soils, agricultural productivity ultimately depends on the anthropogenic

management for availability of plant essential mineral nutrients.

Cacao is generally cultivated between 20 north and south of the equator where

temperature and moisture regimes are suitable (W.C.F. 2007). The major limitations to cacao

cultivation are typically climatic and susceptibility to disease. Cacao plants prefer abundant

supplies of water, and typically grow best on well drained lowland area adjacent to rivers or

clayey upper slopes (Wessel 1971). A confounding factor of cacao's preference for moist

conditions is that the myriad of fungal diseases that commonly attack cacao plants also thrive

under moist conditions where precipitation exceeds 1800 mm yr1. However, the cacao plants









are tolerant of much less precipitation even withstanding drought periods of up to 4 consecutive

months (Wessel 1971). The benefit of drought tolerance is that dry periods of some duration aid

to reduce the devastation caused by fungal diseases. Cacao is absolutely intolerant of freezing

temperatures and grows best when the average annual temperature ranges between 24 and 28C

(Jonasson 1951).

In the less developed tropical regions around the world, momentum to implement

improvements to traditional agricultural methods has grown and many organizations are now in

place to aid farmers to overcome the obstacles of land tenure, soil infertility, inaccessibility of

inorganic fertilizers, and poverty. The United States Department of Agriculture (USDA) funds

agricultural research and produces educational materials. Most international projects funded by

USDA are operated, in part, by local people, providing them with the skills and knowledge

necessary to change the methods of land management (USDA 2007). One such USDA funded

research center, which is the location of the focus of our research, is the Instituto de Cultivos

Tropicales (ICT) in San Martin, Peru. ICT hosts field research related to the improvement of

productivity from cacao agroforestry systems, and laboratory research developing cacao fungal

disease resistance (I.C.T. 2007). ICT also conducts community outreach by hosting workshops,

growing cacao seedling, and providing on site assessments for local farmers. The works of this

organization and others with similar intentions are driving the momentum to install agroforestry

systems that improve soil fertility and the status of poor people in rural parts of the world. There

is hope on the horizon for reducing the food and economic insecurities of people living in the

tropics, and the hope stems from advancement in the way that food is grown in those regions.

With prioritized funding in place for the development and implementation of improved

agricultural systems, it is critical to test technologies prior to their widespread implementation.









Soil Fertility in the Humid Tropics

In undisturbed tropical forests, nutrients involved in plant growth are recycled via the litter

and detritus. The nutrients contained by the parent materials of these soils are depleted by

climatic and biotic weathering that occurred across the last million years (Uehara and Gillman

1981). However, the process for conversion of tropical forest to agricultural land involves the

removal of primary forest and burning of the organic materials on the land and in the upper layer

of soil. This process accelerates the rate of SOM cycling, nutrient mineralization and nutrient

leaching, effectively debilitating nutrient cycling that is mediated by organic pools (Davidson et

al. 2007). Once converted from forest to agriculture, these soils tend to have structure suitable

for plant growth but lack quantities of plant essential nutrient pools required for long-term

agricultural productivity. Depletion of soil nutrient pools continues through the harvest and

removal of animal or plant agricultural products. Without replenishment of nutrients via

management, the soil matrix is typically depleted of SOM and N, acidic, and abundant with Fe

and Al sesquioxides that are bound to P in a form that plants cannot absorb (Ryan and Delhaize

2001). Application of inorganic P containing fertilizers might remedy the infertility of these

soils, but without money to buy, or means to transport, the use of inorganic fertilizers is not an

option for many subsistence farmers. Improved methods for sustaining tropical soil fertility,

therefore, have great potential to slow the rate of tropical deforestation and halt agricultural land

abandonment (Baligar et al. 2004).

Organic Matter

Potentially, the maintenance of SOM is the single most critical factor influencing soil

fertility of humid tropical soils managed for agricultural productivity. SOM aids to reduce the P

fixing capacity ofFe- and Al- oxide rich soils, and stores and cycles essential plant nutrients

(Berkelaar 2001). Here, many agricultural soils lack easily soluble inorganic nutrients and rely









on the recycling of OM to maintain nutrient supply to plants. An example of the implications of

slash-and-bum farming on the SOM reserves and associated nutrients of a sandy ferralsol of the

Amazon rainforest in San Carlos de Rio Negro, Venezuela is drawn from the research conducted

by Tiessen et al. (1994). In this particular soil, the potential for the sustainable production from

an agricultural system was strongly correlated with the abundance of SOM in the upper 15 cm of

soil. The C content of the upper 15 cm of soil was measured to degrade by 29%, and the leaf

litter layer by 81% after 3 years of slash-and-burn management (Tiessen et al. 1994).

Additionally, the authors created an OM budget for the upper 60 cm of soil in the undisturbed

forest in an effort to quantify the rate of carbon cycling and associated nutrient release. With this

OM budget, they estimated 60% of the C, 65% of the N, and 50% of the P to reside in the

particulate OM, and to have a turnover time of less than 4 years. In contrast, these researchers

found that only 27% of the C, 29% of the N, and 33% of the organic phosphorus (Po) were

associated with mineral matter and in this form had a turnover time of near 50 years. This study

clearly demonstrated the importance of organic matter mediated nutrient cycling. Slash-and-

burn agriculture accelerates nutrient cycling causing a rapid depletion of the forest soil nutrient

pools stored in OM (Tiessen et al. 1994). For sustainable agricultural production from tropical

soils, rapid establishment and maintenance of SOM supplies are likely to shorten the phase

characterized by N limitation and lessen the severity of P limitations.

Phosphorus

The primary source of P in tropical soils is in the soils organic fractions, which can account

for up to 50-80% of the soils total P (TP) (Ewel 1986). In the absence of the SOM rich forest

floor, plant available P must come from adsorption and desorption processes occurring in the

soils mineral constituents. However, the mineral constituents of weathered, acidic tropical soils

do not favor P desorption (Vitousek and R.L. Sanford 1986). Rather, the acidic nature of tropical









soils favors reactions between phosphate (H2P04-) and active iron (Fe-) and aluminum (Al-)

hydroxides to form less soluble phosphates and maintain low concentrations of inorganic P [Pi]

in solution (Hinsinger 2001). Al- and Fe- oxides and hydrous oxides can occur as discrete

compounds in soils or as coatings on soil particles. They can also exist as amorphous Al-

hydroxide compounds between the layers of expandable Al- silicates (Sample et al. 1976). The

reactions of P with Fe- and Al-hydroxides decrease P solubility and limit the nutrients

availability for plant uptake and is referred to as "phosphorus fixation" (Graetz and Nair 1999;

Miller and Gardiner 2001c). In these soils, most of the organic P sorbs to the Fe- and Al- oxides

as well. Without proper management, P fixation, limits P availability to plants, causing severe

limitations to agricultural productivity.

Nitrogen

Like P, SOM contains most of the N stored in tropical forest and agricultural soils.

Burning associated with the management of agricultural lands volatizes 50% to 90% N stored in

soil surface vegetation and organic biomass (McGrath et al. 2001). It has been proposed that

limitations in P and N of tropical agricultural systems are directly related to the depletion of

SOM supplies and will fluctuate from P limitation early, to N limitation in the middle, and back

to P limitations in the later phases of development (Davidson et al. 2007; Ewel 1986). In

agricultural systems lacking the means to build and store SOM, limited access to [N] by plants

can hinder the systems productivity during the systems developmental phase between the initial

nutrient pulse after burning and prior to substantial root system development.

Soil Acidity

The acidity of tropical soils favors chemical transformations of aluminum compounds that

are toxic to plants. Tropical plants are adapted for optimal growth in slightly acidic soils ranging

in pH from about 5.5 to 6.0. The soil pH at the research site under investigation ranges from 5.0









- 5.6, and is considered acidic (Berkelaar 2001; Hall 2006). Within this range of pH, depending

on the chemistry of soil constituents, Al3+ may solubilize in soil solution, reducing the ability of

plant roots to take up soil solution (Uehara and Gillman 1981). Additionally, Al3+ in soil

solution inhibits the roots ability to effectively take up H2P04-, Ca2+ and Mg2+ (essential plant

nutrients) from soil solution (Silva et al. 2000).

Nutrient Cycling in Cacao Agroforestry Systems

In cacao-agroforestry systems, the majority of nutrient cycling occur in the upper 30 cm of

soil, this is the zone most influenced by root and litter turn-over (Alvim and Nair 1986). For

optimal growth, cacao requires deep nutrient rich, well-drained soils of moderate pH and low

concentrations of soluble Al+3 (Appiah et al. 1997).

Comparison of tropical forested soils with cacao agrosystems ranging in age from 3 to 40

years has shown slight decreases in soil pH (from 6.8 to 6.1). However, more pronounced

declines were observed in C (from 2.5 to 1.4%), N (from 0.24 to 0.13%), K (from 0.42 to 0.27

mg kg-1), Ca (from 15 to 8.6 mg kg-1), Mg (from 2.3 to 1.5 mg kg-1), and Bray and Kurtz

extractable P (from 26 to 10 mg kg-1) (Wessel 1971). These losses are likely due to continued

harvest and removal of the cacao pods without management of soil fertility in the systems.

These losses represent a 1.36 kg P, equivalent to 1.5 mg kg-1 in the 0-15 cm soil layer per 227 kg

of dry cacao beans harvested from one acre (Wessel 1971). Ten years of cacao cultivation in the

Western Region of Ghana removed an estimated 76,000 tonnes of N, 4,700 tonnes of P, and

18,000 tonnes of K from the soil via harvest and removal of beans (Appiah et al. 1997). In this

region, continued cultivation of the land without any type of fertilizer application has resulted in

the degradation of soil fertility and a decrease in cacao productivity. The failure of cacao

production has resulted in land abandonment and the clearing of additional forest (Appiah et al.

1997). If cacao cultivation is to become economically feasible obstacles to the loss of soil









fertility must be overcome. A successful shift from slash-and-burn agriculture to long-term

cacao agroforestry must include the development of management for sustainable soil fertility.

Benefits of Using Leguminous Cover Crops

The benefits derived from cultivation of leguminous cover crops range from physically

protecting the soil from erosion and temperature fluctuations, to the addition of biologically fixed

nitrogen, to the enhancement of habitat for soil biota. In this document, the focus is on the

services most beneficial to remediation of the soil fertility in the cacao agroforestry system under

investigation. These services are enhancement of fertility through additions of SOM,

enhancement of solution [Pi], the amelioration of soil acidity, and the biological fixation of

nitrogen (Dinesh et al. 2004; Li et al. 2007; Ryan and Delhaize 2001; Wortmann et al. 2000).

Combined, these processes have the potential to increase agricultural soil productivity and

sustainable use, alleviate the need to clear additional lands, and increase economic security of

small-scale agriculturalists (Baligar et al. 2008). In this experiment, we test the effects of five

perennial cover crop species: Arachispintoi (perennial peanut), Calopogonium mucunoides

(calopogonium), Canavalia ensiformis (jack bean), Callisia repens (turtle vine), and Centrosema

macrocarpum macrocarpumm) on phosphorus solubility in an experimental cacao agroforestry

system in Peru.

Cover Crops as Sources of Soil Organic Matter

As previously discussed, SOM is closely correlated to soil fertility. Cover crops aid in the

recuperation of SOM lost during the conversion of forested land to agrosystem. Cover crop

plants have a greater root volume than perennial trees, allowing for a much greater absorption of

mineral nutrients. The deposition of the nutrient rich OM associated with cover crop root and

foliar residues enhances the biological cycling of nutrients in agrosystems (Chapin et al. 2002;

Vitousek et al. 2002). In addition to enhancing nutrient cycling within agrosystems, deposition









of cover-crop detritus: enhances water holding capacity, reduces leaching of nutrients, and

alleviates Al toxicity (Berkelaar 2001; Fageria et al. 2005; Mafongoya et al. 2004). The

maintenance of SOM pools and associated cycling of nutrients allows tropical soils to support

the sustainable production of agricultural crops a process now recognized as being largely

dependant on land management practices (Barber 1995).

Cover Crops Enhance Soil Solution Inorganic Phosphorus

Cultivation of cover crops enhances the total root volume in agricultural system, thus

increasing the surface area by which nutrients are absorbed and the total volume of exudates

potentially released by plant roots (Ryan and Delhaize 2001). Root exudates alter rhizosphere

pH and participate in ligand exchange reactions with chelating metals (Hinsinger 2001). The

equilibrium of soil P between the liquid and solid phases controls the solution [Pi] which is the

immediate source of plant available P. The soil P equilibrium is shifted by changes in soil pH,

anion concentration, and metal concentration and form (Weintraub et al. 2007). Organic anions

exuded by plant roots compete with phosphate anions to participate in ligand exchange reactions

with Al3+ and Fe3+ metal oxides (Hinsinger 2001). Ligand exchange reactions occur between P

sorbed to the surfaces of metal oxides when the solution concentration of phosphate anions is

less than the solution concentration of other anions such as citrate or oxalate. When organic

anions successfully out compete phosphate groups for binding sites in the soil, forming strong

complexes with A13+ and Fe3+, the solution [Pi] is increased (Weintraub et al. 2007). Organic

anions enhance rhizosphere biological communities through microbial priming which enhance

phosphatase production (Hedley et al. 1982b; Hinsinger 2001). In acidic soils, phosphate ions

precipitate with Al and Fe cations. The formed metal phosphate compounds have a low

solubility and are likely not readily available for uptake by plants at low pH. However, Al- and

Fe-phosphates are increasingly soluble as pH increases. Changes in soil pH are associated with









increases in the labile P pools. Plants are constantly taking up and releasing anions and cations

to and from the rhizosphere, to maintain appropriate intercellular acidity while absorbing

nutrients from the soil solution. Depending on the form of available nutrients rhizosphere pH

may be decreased or increased as a result of the exudation of organic anions, OM additions, or

release of H+ or OH- / HCO3- and alter the soil solution [Pi] (Fageria et al. 2005; Hedley et al.

1982b).

Cover Crops as Sources of Biologically Fixed Nitrogen

Symbiotic root nodules found in many leguminous cover crops biologically fix

atmospheric N and increase total soil-[N] a process that could improve crop biomass

production under conditions ofN and P co-limitation. Combined, N-fixing leguminous cover

crops could ameliorate the need for N fertilizer additions. Additionally, legume litter generally

has a low C:N ratio favoring rapid decomposition and nutrient return (McGrath et al. 2001). In

the initial stage of many agroforestry systems, the open canopy of young shade trees exposes

nutrient rich surface soil to erosion and N-volatilization (Hartemink 2005). Utilization of cover

crops on in young open canopy agroforestry systems reduces nitrogen losses through

volatilization and contributes to soil nitrogen pools through the biological fixation of nitrogen

(Graetz and Nair 1999; Hedley et al. 1982a; Hieltjes and Lijklema 1980; Kuo 1996a; Levy and

Schlesinger 1999; Nair et al. 1995).

Sequential Fractionation Procedures

Soil P ions participate in the processes of adsorption, desorption, precipitation, dissolution,

mineralization, and immobilization with metals, and organic materials. These processes are

mediated by the activities of microbial organism populations, root uptake of nutrients, and root

release of exudates. The goal of sequential extraction of soil P procedures is to separate the soil

P pools into the most and least labile pools using neutral, alkaline, acidic, heated, and oxidizing









extractants. Incongmencies between interpretations of sequential fractionation of soil P

procedures exist. These incongruencies may be due to the varying results obtained by

researchers analyzing unique soil materials. Generally, extracted P-pools are assumed to

originate from pre-defined soil constituents (labile Pi, Ca-P, Al-P, Fe-P, Po, or Residual P) or

more simply by the extractant employed. Table 2-1 summarizes the authors and dates of several

procedures for the sequential extraction of P, as well as the chemicals utilized to extract, and the

interpretation for the extracted P pools. As you can see from this table, the interpretations for the

various extracted pools generally have a mineralogical or chemical bases rather than one based

on plant availability. Also from the table you can see that interpretations vary between

researchers. Discussion related to the various interpretations of sequential fractionation methods,

their interpretations, and relevance to determining plant available pools are presented in the

following paragraphs.

Interpretations of sequential fractionation of soil P pools that aim to identify the extractable

P pools in terms of plant availability and time spans for P cycling provide the greatest service to

the scientific community. Such interpretations of fractionation results allow for the successful

understanding of the fate of applied P fertilizer, and the implications of management on soil [P]

(Chang and Jackson 1957; Wessel 1971). In 1971, Wessel implemented a fractionation

procedure to compare the P pools of similar non-fertilized and fertilized soils cultivated by

cacao. He found the NaOH extractable [Pi] pool to be greater in the fertilized soil. He

interpreted this finding to indicate that the soils iron compounds were fixing the added P,

meaning that NaOH extracts from the Fe-P pool (Wessel 1971). Hedley (1982a) utilized his

fractionation procedure to evaluate changes in P pools in soils cultivated in wheat for 65 years.

His evaluations were accomplished through comparisons of an A horizon soil of adjacent









unfertilized cultivated and pasture plots. Hedley's fractionation procedure is intended "to allow

soil P to be separated and characterized as P released to an anion exchange resin, and P soluble

in alkali and acid of varying strengths." With this procedure Hedley found that the extractable

Po, extractable Pi, and Residual P pools in the cultivated soils were depleted compared to the

prairie soil (NaOH [P] by 22%, resin + NaOH + HC1 [P] by 26%, H2SO4 + H202 digest [P] by

52%) indicating access to these pools by plants. The loss of these less soluble P pools which

make up 21% of the TP in the pasture soil indicates that without fertilizer additions wheat

production from the same soil is not sustainable.

There are weakness associated with the use of sequential fractionation procedures for

general soil comparisons. First, is the fact that soils originating from various parent materials

will yield varying proportions of P per extractant when all other factors are equal. Second,

sequential fractionation research results not related to P plant availability or a soil P storage time

scale provide little use to land managers. Third, there is a general lack of cross research

comparisons of sequential fraction results due to the frequent modifications made to the

procedures to account in differences between soil chemical characteristics. With each scientist

establishing their own methodology, the body of data for comparison is slim. Finally, while it is

clearly demonstrated that procedures for sequential extractions of P do not extract from discreet

soil constituent bound pools, the insistence for utilizing this approach to define the extracted P

pools has weakened the usefulness of some published interpretations (Chang and Jackson 1957;

Wessel 1971).

Chang and Jackson (1957) provide a good example of the confusing nature associated with

interpretations of fractionation results. The authors assert that soil Pi can be classified into four

distinct groups Ca-P, Al-P, Fe-P and the reductant-soluble-P. However, analysis of their









published data set and discussion weakens these ascertains. For example Chang and Jackson

indicate that "10 per cent of the iron phosphate as obtained by subsequent NaOH extraction may

be subtracted from aluminum phosphate and added to the iron phosphate (Chang and Jackson

1957)." The authors fail to explain how the 10% extractable Fe-P by NaOH was calculated. It is

not clear that that the authors were successful in determining exactly what percent the quantity of

Al-P vs. Fe-P is extracted with NaOH. Furthermore, even though Chang and Jackson found Al-

and/or Fe-P to be soluble in each of the extractants clearly indicating that the procedure does not

succeed to clearly devise soil P into defined discreet pools, they continue to pretend that all of

the soil Al-/Fe-P is removed with the NH4F and NaOH extractions. To further baffle, these

authors refer to the NH4C1 extractable P pool as the water (H20) extractable P, why this is done

without a comparison with an actual H20 extractable P pool in unknown. Considering the fact

that the authors admit that their extractants all remove Al- and Fe-P, I am concerned that their

assertions that this method fractionates soil P into discrete chemical forms is not accurate.

The experiences of Hieltjes and Lijklema (1980) in attempting to define the extracted P

pools further elucidate the vague nature of the definitions. Using synthetic P compounds Hieltjes

and Lijklema (1980) found 1M NH4C1 to extract between 3 and 7% of the orthophosphate from

Cas(PO4)30H, Ca3(P04)2, Fe-P, and hydrated A1PO4. However, they still suggest utilizing 1M

NH4C1 to remove calcium carbonate prior to extracting the Al- and Fe-P. Considering this

information it is not possible to confidently identify the origin of 1M NH4C1 extracted P. They

found 0.1M NaOH to extract less than 1% of the TP from each of Ca5(Po4)30H and

Ca3(P04)2, while extracting more than 90% from the Fe-P and hydrated A1PO4 pools, making it

feasible to determine from which pool this extraction extracts. NaOH/citrate-diothinonine-

bicarbonate (CDB) extracted -30% of the Ca-P pools, more than 99% of the Fe-P pool and









-13% of the Al-P pool, making it almost ineffectual for delineating P-pool origin. 0.5M HCI

extracted more than 95% of the P from all materials; it also cannot be used to identify the source

of P pools. A comparison of the TPi extracted with the Kurmies, Hieltjes, and Hieltjes

procedures without the NH4C1 step showed each of the three procedures to extract nearly the

same amount of TPi for a given soil indicating that the TPi extracted by each of these methods

can be compared across similar soils. Hieltjes and Lijklema (1980) found that the sequential

methods varied for P per fraction extracted depending on soils mineral constituents. For

example, they found that use of CDB to separate the Ca-P from the Fe- and Al-P, as was done by

Williams (1971), to be inappropriate. Williams (1971) method was developed using naturally

occurring apatite. Hieltjes and Lijklema (1980) used sediments not containing apatite, and found

citrate to extract significant quantities of Ca-P. These significant differences in the pools

extracted were attributed to the difference in the chemistry of the soil materials (Hieltjes and

Lijklema 1980).

Sequential Fractionation of Plant Available Soil Phosphorus

The plant available P pools are most convincingly defined as those extracted pools that

correlate with plant foliar P, plant response to fertilization, or cultivation of plants (Wessel

1971). Wessel (1971) found the cacao foliar P and response to fertilizer to correlate well with all

extractable Pi fractions indicating that all extracted soil P pools contribute to the plant available

P. Hedley (1982a) rationally interprets depletions in soil P pools to indicate accessibility of

those pools to plants. Hedley acknowledges that the majority of P depleted in the cultivated soil

passed through the plant-available Pi pool prior to uptake by wheat. It is reasonable to assess

that the sequential fractionation procedures provide a snapshot in time of the general strength of

P adsorption to soil materials, as well as pools of depletion or fixation. The fact that

considerable portions of soil P are cycled via microbial and rhizosphere process mediated









mineralization cannot be ignored. Other researchers have not been as explicit with their

definition of the plant available P fraction. Chang and Jackson (1957) defined the plant available

pool to depend simply on the 'extensity of the phosphate surface of various chemical species.'

Hedley et al (1982a) further warns that decreases in the 'less extractable Po' and 'residual P'

indicate a limit to mineralizable soil P, and a need for P fertilizer in the system to sustain plant

productivity. This rational is supported by the notion that these less soluble fractions result from

long term processes that can not replenish at a rate suitable to support the sustainable

productivity of agriculture (Dinesh et al. 2004). Regardless of the incongruencies between

methods and interpretations, sequential fractionation procedures can be utilized to provide

information regarding the effects of land cultivation of soil P pools, and the fate of applied P

inorganic or organic fertilizer.









Table 2-1. Sequential fractionation of soil P procedures and interpretation
Extraction Sequence P Fraction Comments / Materials analyzed a
Chang and Jackson (1956)


1M NH4Cl

Neutral 0.5M NH4F
O.1M NaOH
0.5M H2SO4

Na2S204-citrate
Neutral 0.5M NH4F
O.1M NaOH


NH4Cl
NH4F

NaOH


H2SO4

Perchloric acid digestion
Ignition


O.1M NaOH / 1M NaC1,
followed by 0.3M
Na3C6H507 / Na2S204 /
1M NaHCO3 digest
0.5M HC1


Water-soluble and loosely-bound
P; Exchangeable Ca
Al-P completely; Fe-P slightly
Al-P; Fe-P; Po
Ca-P completely; Al- and Fe-P
considerably
Fe-P completely; Al-P negligibly
Occluded Al-P
Occluded Al- and Fe-P
Wessel (1971)
Water-soluble P; Loosely bound P
Al-P

Fe-P


Ca-P

TP
Organic P
Williams et al. (1971)
Fe- and Al-P


Ca-P


Kurmies (1972)
Loosely bound


1M NH4C1

0.1M NaOH
0.5M HC1


1M NH4C1

0.1M NaOH
0.5M HC1


Various soils and synthetic minerals.











South-western Nigerian cacao soils.
Modification of Chang and Jackson
(1956).
Considers the first four fractions
extractablee or non-occluded
inorganic P'.
Occluded P = TP sum of
extractions


Calcareous lake sediments.
Citrate/dithionite/ bicarbonate =
CDB

As interpreted by Hieltjes and
Lijklema (1980) and Graetz and Nair
(1999).


As interpreted by Hieltjes and
Lijklema (1980).


Fe- and Al-P
Ca-P


Hieltjes and Lijklema (1980)
Loosely bound P


Fe- + Al-P
Ca-P


Calcareous sediments and synthetic
minerals.
Modification of Kurmies (1972).









Table 2-1. Continued

Extraction Sequence


Anion exchange resin

0.5M NaHCO3


0.1M NaOH


Sonification in 0.1M
NaOH
1M HCI

H2SO4 + H202 digest


1M MgC12


0.1M NaOH / 1M NaC1,
followed by 0.3M
Na3C6H507 / Na2S204 /
IM NaHCO3 digest at pH
7.6
Acetate buffer at pH 4
1M HCI
Ingnition / 1M HCI


Anion exchange resin

0.5M NaHCO3

0.1M NaOH


1M NaOH
1M HCI

Ignition / HC1 digest


P Fraction
Hedley (1982a)
Most of the biologically available
Pi; Negligible [Po]
Labile Pi + Po sorbed on soil
surfaces; Small amount of
microbial P
Pi + Po compounds held by
chemisorption to Fe- + Al- of soil
surfaces.
Pi + Po held at the internal
surfaces of soil aggregates.
Apatite-type minerals; Occluded
P; Negligible [Po]
More chemically stable Po forms;
Relatively insoluble Pi forms;
Residual P
Ruttenberg (1992)
Exchangeable; Loosley sorbed P

Easily reducible or reactive Fe-P





Dauthigenic apatite P
Detrital apatite P
Organic P

Hedley (1982b)
Form of soil P from which plants
normally draw their supply.
Plant available Pi; More labile
forms of soil Po.
Partial dissolution of labile soil Po
and Fe- + Al-P; Desorbs Pi from
the surfaces of sesquioxides.
More Po
Acid-soluble Ca-P; Some
sesquioxide occluded Pi.
Most stable Po; Occluded Pi


Comments / Materials analyzed a


Agricultural soils.

Modified in part from Williams et al.
(1971, 1980).


As interpreted by Graetz and Nair
(1999)
CDB





Marine sediments


Rhizosphere of Rape seedling soils.











Table 2-1. Continued
Extraction Sequence


P Fraction


Comments / Materials analyzed a


Nair and Graetz (1995)
1M NH4C1 Easily removable/soluble; Labile South Florida dairy soils.
P; Loosely adsorbed;
0.1M NaOH Fe- + Al-P; Some hydrolized Po. Modification ofHieltjes and
Lijklema (1980);
NaOH extract digest 0.1M NaOH extractable Po
0.5M HC1 Ca- + Mg-P
Ingnition / 6m HC1 digest Residual P; Recalcitrant P;
Primarily Po.
Total P = sum of all extracts.
Crews (1996)
Anion exchange resin Most labile P; Plant available P Mexican alfalfa soils.
NaHCO3 Labile Pi from sesquioxide and Modification of Hedley (1982a);
carbonate surfaces; Easily
mineralizable pools of Po from
nucleic acids and microbial P.
NaOH Pi that is more strongly bound to
Fe- + Al- hydroxides and clay
surfaces; Retained Pi; Could still
be biologically active in the future;
Relatively stable Po with slow
turnover rates; Relatively labile Po
associated with cellulose, humic
compounds, or inositol-P sorbed to
Al- + Fe- hydroxides.
HC1 Primary apatite minerals; Ca-P
secondary minerals.
H202/ H2SO4 digestion Residual P; Sesquioxides occluded
Pi; Constituent Pi in resistant
primary minerals; non-extractable,
very stable Po associated with
humic and fulvic acids and
sesquioxide-stablilized inositols.














Table 2.1 Continued
Extraction Sequence


Anion exchange resin
Digest of resin extract

0.5M NaHCO3


0.1M NaOH

HC104 digest of residual
soil
HC104 digest of air-dried
soil


P Fraction


Phiri et al. (2001)
Freely exchangeable Pi;
Resin extractable Po

Labile Pi; Po sorbed to soil
surface; Small amount of
microbial P.
Pi more strongly bound to Fe- +
Al- and humic compounds.
Residual P; Insoluble Pi; More
stable Po
TP


Comments / Materials analyzed a


Colombian volcanic-ash soil
Modification of Tiessen and Moir
(1993)


Zhang et al. (2002)


Deionized water

0.5M NaHCO3

Acidified (NH4)2S208
digest of 0.5M NaHCO3
extract
0.1M NaOH
Acidified (NH4)2S208
digest of 0.1M NaOH
extract
1M HCI
HC104 digest


Water-soluble P; Loosely-bound
P; Exchangeable Ca
Bioavailable Pi; Readily
mineralizable Po
TP of 0.5M NaHCO3 extract.


Potentially bioavailable Po
TP of 0.1M NaOH extract


Acid-soluble P; Ca-P
Soil TP
Residual P = TP sum extracted P


Florida sandy agricultural soils;

Modification ofHedley et al (1982).


Szulczewski and Li (unpublished)
Deionized water Water-soluble P Southern Florida calcareous soils;
1M NH4C1 Exchangeable-P Modification ofNair and Graetz
(1995)
0.1M NaOH Fe- + Al-P
Digest of NaOH extract NaOH extractable Po
0.5M HC1 Ca- + Mg-P
HN03 / H202 digest of Residual P; Po compounds
residual soil











Table 2.1 Continued
Extraction Sequence P Fr
HN03 / H202 digest of Soil TP
air-dried soil
a Table format adapted from Graetz and Nair (1999).


action


Comments / Materials analyzed a









CHAPTER 3
COVER CROP CULTIVATION EFFECTS ON SOIL FERTILITY AND PHOSPHORUS
FRACTIONS IN A PERUVIAN CACAO AGROFORESTRY SYSTEM

Introduction

Nutrients in tropical soils have been depleted over time naturally or by continuous

cultivation and harvest of plant products (Baligar et al. 2004). It is possible that with

conscientious management, fertility of these soils can be maintained or improved upon, making

them a renewable resource (Brady and Weil 1999). Leguminous cover crops are widely

accepted for their contribution to soil quality- namely through addition ofN (Fageria et al. 2005).

As P is often the most limited plant essential nutrient in tropical soils, inclusion of leguminous

cover crops on tropical soils may seem counter-intuitive. However, leguminous cover crops

influence the soil P forms through the addition of SOM, deep soil mining, and microbial priming

(Brady and Weil 1999; Chapin-III et al. 2002; Dinesh et al. 2004; Li et al. 2007).

Phosphorus is an essential element for plant growth and exists in the soil in a variety of

chemical forms (Elrashidi 2006; Phiri et al. 2001). The orthophosphate anion exists in soil

solution and is the form of P most easily utilized by plants and microbes. When P adsorbs to

clay particles or binds to Fe or Al oxides, compounds are formed that are not as easily utilized by

plants and microbes (Chapin-III et al. 2002). Phosphorus enters the soil solution by desorption

or dissolution of inorganic P (Pi) associated with the mineral soil or by the mineralization of

organic P (Po) (Tiessen and Moir 1993). Organic P compounds must be converted to inorganic

forms before they are available for plant or mycorrhizae uptake (Hopkins and Huner 2004; Paul

and Clark 1989). Leguminous plants produce organic anions and hydrogen protons from their

root systems, together these compounds disrupt the equilibrium between the solid and solution P

pools allowing an increase in the P pools that are most available for plant uptake (Hinsinger

2001; Hopkins and Huner 2004; Paul and Clark 1989).









Phosphorus fractionation methods sequentially remove P forms with increasingly stronger

extractants. These procedures are thought to extract increasing less soluble forms of soil-P into

pools of organic or inorganic P that may be more or less available for plant uptake. Fractionation

of soil P may provide insight into the fate and transformation of legume litter bound P added to

the soil (Graetz and Nair 1999; Li et al. 2007).

The focus of this research is on comparing soil P fractions and changes to soil fertility

factors after two years of growth in a cacao agroforestry system. The four leguminous species

included in the experiment are Arachispintoi (perennial peanut), Calopogonium mucunoides

(calopogonium), Canavalia ensiformis (jack bean), and Centrosema macrocarpum

macrocarpumm). In addition to these treatments are one inorganic nitrogen fertilizer treatment

and one control. Soil P was extracted using the Mehlich I procedure commonly utilized to

measure the plant available P pool and an un-published method for the sequential fractionation of

soil P. Other measured soil characters are loss upon ignition (LOI), pH, TC, TN, % Ca, % Mg,

% Fe, and % Al.

Materials and Methods

Study Site

The Tarapoto, Peru study site at Insituto de Cultivos Tropicales (ICT) lies at latitude

6028.734' S and longitude: 76019.694' W, with an elevation of 356 meters above sea level, map

shown in Figure 3-1 (NOAA 2007). The site receives an average of 1200 mm of precipitation

per year (NOAA 2007). The mean annual maximum temperature is 32 C, the minimum 19 C.

The landscape of the San Martin Region of Peru is best described as hillsides feathered by rivers

and streams. The soils here are acidic loamy sand Inceptisols (pH 4.8 6.0). Other than

inclusion of cover crops, the agroforestry system management style is that of the traditional

methods of local cacao farmers in the San Martin Region of Peru.









Experimental Design

To test the influence of leguminous cover cropping on soil fertility in an experimental

cacao agroforestry system, a randomized block design was established on 1.05 hectares, utilizing

leguminous cover crop treatments in the understory of a cacao agroforestry system. Site

preparation commenced in June 2004 with clearing, burning, and subsequent planting of cover

crops, cacao, and bananas on the site. At the time cacao seedlings were transplanted into the

fertilized treatment 200 g of Super Guano was applied to each plant. Two or three months after

cacao seedling were transplanted into the fertilized plot Urea (46% N) was applied to each cacao

plant.

The four leguminous crops included in the experiment were Arachispintoi (perennial

peanut), Calopogonium mucunoides (calo), Canavalia ensiformis (jack bean), and Centrosema

macrocarpum macrocarpumm). Additionally, one non-legume cover crop Callisia repens (inch

plant), one fertilized treatment having agroforestry species without a cover crop, and one control

treatment having agroforestry species without a cover crop or fertilization was included in the

experiment. Each treatment was replicated 3 times, once in each of 3 randomized blocks, each

block is 10 x 45 meters with a 2-meter buffer between each treatment. This experimental design

is shown in Figure 3-2.

Soil Sampling

Soil samples were collected in mid July of 2006. Ten soil samples were collected from the

0-5 cm, 5-15 cm, 0-15 cm and 15-30 cm soil depths of each replicate using a 5 cm diameter

stainless steel sampling tube. The statistical software program JMP 5.1 generated random

sampling locations from a minimum distance of one meter from the treatment border, Table A-i

contains those randomly generated co-ordinates (S.A.S. 2007). The ten soil samples

corresponding by treatment, depth, and block were combined at the time of sampling to form one









composite sample. This sampling scheme resulted in 84 composite samples collected from the

entire cover crop management experiment. All collected soil samples were transported to the

laboratory, labeled, and air-dried. One time per week for 4 weeks, the soil samples were crushed

and mixed by hand. Once air-dried, cleaned of visible roots, crushed, and passed through a 2-

mm sieve, the <2 mm soil fraction was utilized for soil chemical analysis (Basamba et al. 2006;

Graetz and Nair 1999; Phiri et al. 2001).

Soil Nitrogen, Carbon, Calcium, Potassium, Iron, Aluminum, Magnesium, pH, and Loss on
Ignition

Total N (TN) and C (TC) contents of soil for all treatments and depths were determined

using a CNS analyzer (Elementar, Vario MAX Elemental Analyzer, Elementar Analysensysteme

GmbH, Germany). Total calcium (Ca), potassium (K), iron (Fe), aluminum (Al), and

magnesium (Mg) in soils from the Control treatment at all depths were measured utilizing an

Atomic Absorption Spectrophotometer (AA-6300, Shimadzu Scientific Instruments, Columbia,

MD). Soil pH and Loss on ignition (LOI) were determined for all treatments and soil depths

using methods published by the Soil Science Society of America (SSSA) and the American

Society of Agronomy (ASA) (Nelson and Sommers 1996a; Thomas 1996). Although LOI tends

to slightly over estimate the organic matter proportion of a soil due to the ignition of inorganic

materials at high temperatures, it is often utilized to estimate soil organic matter content (Heiri et

al. 2001; Nelson and Sommers 1996a).

Mehlich I Extractable Phosphorus

Mehlich I extractions of P was conducted on air-dried soil from the 0-15 cm depth

following established methods (Thomas 1996). To measure organic P (Po) in the Mehlich I

extraction, the supernatant was digested at 340C in concentrated sulfuric acid (H2SO4) and









hydrogen peroxide (H202), and Po was determined by subtraction of the concentration in the

undigested from the digested sample.

Sequential Fractionation of Phosphorus

The utilized sequential fractionation of phosphorus procedure was based upon an

unpublished method by Szulczewski and Li (2007) and is modified from those published by Nair

et. al. (1995). The single modification is that the utilized method preceded the Nair et. al.

method with a deionized H20 extraction (Nair et al. 1995; Szulczewski and Li unpublished). A

schematic of the utilized extraction procedure is shown in Figure 3-3.

Measurement of Extracted Inorganic Phosphorus

Concentrations of extracted inorganic P contained within extract solutions was measured

using methods published by SSSA and ASA, commonly known as The Murphy and Riley

method (Kuo 1996b). Strongly alkaline or acid extract solutions were neutralized prior to

analysis.

Analysis of Phosphorus in Cover Crop Tissue

Analysis of cover crop tissue phosphorus content was conducted by the Universidad

Nacional Agraria La Molina in Lima, Peru and resulting data were provided to me courtesy of

Institute de Cultivos Tropicales, Tarapoto Peru. The analysis were conducted on September 05,

2006.

Analysis of Soil Organic Matter

Analysis of soil organic matter (SOM) content was conducted using the Walkley-Black

Method (Nelson and Sommers 1996b). The averaged data from this analysis was provided

courtesy of ICT. No statistical analysis was conducted on the SOM data.









Statistical Analysis

Determinations of significant treatment and depth effects were made using JMP IN 5.1

statistical software. When necessary, data transformations to meet assumptions of normality

were conducted using Box and Cox Transformations. Initial significance of variance between

the pooled data of all treatments and depths was determined, followed by an analysis of variance

between treatments at each depth. Secondary analysis of variance was assessed between

treatments within each depth. When the F values were significant, post hoc comparisons of

means were made using Dunnett's Method and Tukey-Kramers HSD. Dunnett's Method

determines significant differences in variance between the data of any treatment and that of the

control at an alpha level of 0.05. Tukey-Kramers HSD determines significant differences in

variance between the data of any treatment and that of any other treatment.

Results

A summary of all significant findings is presented in Table 3-1.

Soil Total Nitrogen, Total Carbon, and Carbon to Nitrogen Ratio

The total nitrogen content of this soil ranged from 790 kg/ha in the 0-5 cm horizon to

1,961 kg/ha in the 15-30 cm depth with no significant differences between treatments or the

Control. An analysis of variance of the pooled data revealed no significant differences between

any treatment or depth for C:N. In the 5-15 cm soil depth the analysis of variance revealed

Cannavalia ensiformis to contribute significantly more TC to the soil than C. macrocarpum ,A.

pintoi, C. mucunoides, or the Control treatment (1.53%, 0.98%, 1.04%, 1.05%. and 1.14%

respectively). The averaged data, with significant differences indicated for TN, TC, and C:N are

presented in Table 3-2 and the raw data is contained in Table A-2.









Soil Loss o Ignition and Organic Matter

An analysis of variance for the 0-30 cm soil depth revealed C. ensiformis to lose

significantly more weight than A. pintoi on ignition (4.93% vs. 2.79%). At the 5-15 cm soil

depth C. repens, C. mucunoides, and C. ensiformis all lost significantly more on ignition than did

A. pintoi (5.18%, 5.17%, 4.84%, 1.44% respectively). No significant differences occurred

between any treatments at the 0-5 cm and 15-30 cm depths. The averaged data for LOI is in

Table 3-2 and the raw data for LOI in contained in Table A-3.

Soil pH

An analysis of variance between pooled data revealed the 0-5 cm soil depth to have a

significantly higher pH than the underlying soil horizons (5.41, 5.13, and 5.03 from the surface

depth downward) these data are presented in Table 3-3. Exclusion of the non-legume treatments

(Fertilizer, C. repens) from the analysis revealed the A. pintoi treatment to have a significantly

higher pH in the 0-5 cm depth than the C. ensiformis and Control treatments (5.55, 5.44, and

5.18 respectively); data presented in Table 3-2.

Soil Calcium, Potassium, Magnesium, Iron, and Aluminum

Calcium, potassium, iron, aluminum, and magnesium concentrations were quantified for

three soil depths in the Control treatment. In the 0-5 cm depth: [Ca] = 1.57 mg kg-1, [K] = 3.54

mg kg-1, [Fe] = 40.59 mg kg-1, [Al] = 57.19 mg kg-1, and [Mg] = 1.20 mg kg-1. In the 5-15 cm

depth: [Ca] = 0.93 mg kg-1, [K] = 3.69 mg kg-1, [Fe] = 48.11 mg kg-1, [Al] = 75.28 mg kg-1, and

[Mg] = 1.27 mg kg-1. In the 15-30 cm depth: [Ca] = 1.19 mg kg-1, [K] = 3.95 mg kg-1, [Fe] =

59.60 mg kg-1, [Al] = 98.59 mg kg-1, and [Mg] = 1.28 mg kg-1. All concentrations except Ca

increased with depth. This averaged data is presented in Table 3-4 and the un-average data is

presented in Table A-4.









Mehlich I Extractable Phosphorus

Mehlich I extractable phosphorus pools were not significantly influenced by the inclusion

of cover crops. When the Mehlich I extracted Pi and OP were converted to a proportion of the

Mehlich I TP the ratio was nearly a constant 1 to 3 ratio. The data utilized to calculate Mehlich I

extractable inorganic phosphorus are presented in Table A-5, the data utilized to calculate

Mehlich I extractable total phosphorus are presented in Table A-6, and the averaged data for the

Mehlich I extractable inorganic, organic, and total phosphorus is presented in Table 3-5.

Sequential Fractionation of Phosphorus

The first extractant in the sequential fractionation series is H20. Analysis of variance for

the pooled data revealed the 0-5 cm soil depth to contain significantly greater concentrations of

H20 extractable P than the underlying depths (0.12 mg kg-1, 0.05 mg kg-1, 0.05 mg kg-1

respectively). There were no significant differences between H20 extractable [Pi] between

treatments. Data averaged by depth per treatment for all extractants are presented in Table 3-4.

The averaged sequential fractionation of phosphorus data by depth for all extractants and

treatments are presented in Table 3-6. The data from which H20 extractable [Pi] was calculated

are presented in Table A-7.

The second extractant in the sequential fractionation series is 1.0 M ammonium chloride

(NH4C1). The analysis of variance did not reveal any significant differences between NH4C1

extractable [Pi] between any treatment. However, for the pooled data the 0-5 cm soil depth

contains significantly greater concentrations of 1.0 MNH4Cl extractable P than do the underlying

depths (0.21 mg kg-1, 0.07 mg kg-1, 0.08 mg kg-1 respectively). The data from which 1 M NH4C1

extractable [Pi] was calculated are presented in Table A-8.

The third extractant in the sequential fractionation series is 0.1 M sodium hydroxide

(NaOH). The analysis of variance did not reveal any significant differences between NaOH









extractable [Pi] between any treatment. However, for the pooled data the 0-5 cm soil depth

contains significantly greater concentration of 0.1M NaOH extractable TP than do the underlying

depths (43.44 mg kg-1, 35.61 mg kg-1, 26.02 mg kg-1 respectively). The data from which 0.1 M

NaOH extractable [Pi] was calculated are presented in Table A-9. The data from which 0.1 M

NaOH extractable [TP] was calculated are presented in Table A-10.

The fourth extractant in the sequential fractionation series is 0.5 M hydrochloric acid (0.5

M HC1). The analysis of variance revealed significant differences between 0.5 M HCI

extractable [Pi] in the 0-5 cm depth between the Control and all other treatments as follows:

Control 32.90 mg kg-1, A. pintoi 21.38 mg kg-1, C. ensiformis 10.33 mg kg-1, C. macrocarpum

24.42 mg kg-1, C. mucunoides 11.51 mg kg-1; C. repens 11.54 mg kg-1, and Fertilized 22.27 mg

kg- No other significant differences between treatments or depth existed for the 0.5 M HCI

extractable [Pi]. The data from which 0.5 M HC1 extractable phosphorus was calculated are

presented in Table A-11.

The fifth extraction in the sequential fractionation series is a 6.0 M hydrochloric acid (6.0

M HC1) digestion of the residual soil. The analysis of variance between the data pooled across

depths for each treatment revealed a significant difference between the 6.0 M HC1 extractable [P]

between the C. ensiformis and the Control treatments (328.83 mg kg-1 vs. 234.92 mg kg-'). No

other significant differences between 6.0 M HCL extractable [P] between any depths or

treatments were present. The data from which 6 M HC1 extractable phosphorus was calculated

are presented in Table A-12.

Six Molar HCI Digest of Air-Dried Soil

The analysis of variance of [P] data resulting from an 6.0 M HC1 digest of air-dried soil

revealed the C. ensiformis treatment to contain significantly more [P] in the 5-15 cm depth than

A. pintoi or C. macrocarpum (255.66 mg kg-1, 188.13 mg kg-1, and 190.64 mg kg-1 respectively).









The data from which the [P] extracted from a 6.0 M HC1 digest of air dried soil was calculated is

presented in Table A-13 and the averaged data from this extractions is presented in Table 3-6.

Cover Crop Tissue Phosphorus Content

The analysis of variance between the phosphorus content of cover crop tissue revealed C.

ensiformis to contain significantly more foliar P than C. repens or C. mucunoides (0.2%, 0.09%,

and 0.11% respectively). The cover crop foliar phosphorus percentages by treatment and block

are presented in Table 3-7.

Correlations Between Soil Extractable Phosphorus Fractions and Cover Crop Tissue
Phosphorus Percentage

Correlations between cover crop tissue [P] and extractable soil pools of P revealed

significant relationships between cover crop P content and Mehlich I soil extractable [Pi] in the

0-15 cm depth (R2 = 0.41, P = 0.026), as well as between cover crop tissue P content and H20

soil extractable [Pi] in the 0-5 cm depth (R2 = 0.44, P = 0.018). The linear regressions for these

plots are shown in Figure 3-4.

Discussion

In the following paragraphs, I will discuss the suitability of this soil for cacao cultivation

and the influence of cover crop cultivation on phosphorus fractions and soil fertility using

nutrient guidelines established for the upper 15 cm of soil (Wood 1975; Wood and Lass 2001).

Soils that do not meet the nutrient criteria established by G.A.R. Wood are likely to have

inadequate nutrient supplies for optimal growth and production of cacao.

Soil Loss on Ignition and Organic Matter Content

The ideal soil for cacao growth and productivity should contain at least 3.0% of organic

matter in the upper 15 cm of soil (Wood 1975). Soils from all of the seven treatments in this

study contain approximately 2% of organic matter in the upper 20 cm of soil as determined by









the Walkley Black Method (Table 3-8). However, loss on ignition data, while including a

portion of inorganic materials, provides a good representation of the organic soil pool (Heiri et

al. 2001). Statistical analysis of the loss on ignition data showed that in the 5-15 and the 0-30

cm soil depths cover crop cultivation significantly influenced the proportions of ignitable soil

materials (Table 3-1 and Table 3-2). In the 5-15 cm soil depth, A. pintoi lost significantly less

weight on ignition that did C. ensiformis, C. mucunoides, or C. repens. Compared to the Control

data at this depth, A. pintoi and C. macrocarpum cultivation appear to have reduced the LOI

pools. Also at this depth, when compared to the Control, C. mucunoides, C. ensiformis, and C.

repens appear to have increased the LOI pools.

A good example of the differences in combustible pools between treatments is illustrated

through a comparison with the Control. In the 5-15 soil depth the A. pintoi contained 31,050

kg/ha less combustible materials than the Control, C. macrocarpum contained 27000 kg/ha less

than the Control, C. ensiformis 19,950 kg/ha more than the Control, C. mucunoides 24,900 kg/ha

more than the Control, and C. repens 25,050 kg/ha more than the Control soil at this depth. In

the 0-30 cm soil depth, the A. pintoi leguminous cover crop lost significantly less on ignition

than did the C. ensiformis leguminous cover crop. When compared to the Control A. pintoi lost

38,700 kg/ha less, and C. ensiformis lost 57,600 kg/ha more on ignition, seemingly substantial

differences in combustible soil materials. These differences in the amount of ignitable materials

indicate that the rooting systems of A. pintoi and C. macrocarpum have a slow turn over rate, and

during the growth process have taken up mineralized organic soil components, and are now

storing organic materials. On the contrary, the rooting systems of C. mucunoides, C. ensiformis,

and C. repens have stimulated the LOI pool, likely through a more rapid decomposition rate of









their fine roots. The differences in the loss on ignition pools between treatments and the Control

indicate that cover crop cultivation has influenced soil organic matter pools.

Increasing the soil organic matter content at this site is important for improving cacao

production in the area, as the benefits of abundant supplies of organic matter include increased

nutrient availability, and a reduction in the soils phosphorus fixation capacity (Young 1997). It

is likely that the crop productivity and soil fertility of the system under investigation would

greatly benefit from increased soil organic matter supplies. Therefore, this experiment provides

an excellent opportunity for assessing the ability of cover crop cultivation to remediate acidic

soils and alter soil fertility parameters such as soil organic matter pools.

Soil Carbon Content

Total soil carbon data, while including a heterogeneous mixture of various carbon sources,

from plant residue to charcoal, provide a good insight to the organic matter pools of a soil

(Russell 2002a). In the 5-15 cm depth, cover crop cultivation appears to have an affect on the

proportions of carbon containing constituents, see Table 3-1 and Table 3-2. In this depth, C.

ensiformis contained significantly more total carbon than did A. pintoi, C. macrocarpum, C.

mucunoides, or the Control treatments. The significant contribution of carbon to this soil depth

by Cannavalia ensiformis likely represents a carbon contribution from the degradation of the

root system of the cover crop. The total carbon data mirrored the findings of the loss on ignition

data very well. For example for both analysis C. repens and C. ensiformis contained relatively

more carbon and lost more on ignition than the other treatments, and A. pintoi and C.

macrocarpum contained relatively less carbon and lost less on ignition than did the other

treatments. Abundant soil carbon supplies are necessary to maintain abundant microorganism

populations as this element is a necessary component of their cellular constituents and is required

in greater amounts than any other nutrient (Alexander 1998). It is likely that both total carbon









and loss on ignition provide a comparatively simple means for monitoring the organic matter

pools of these soils.

Soil Nitrogen Content

The role of leguminous cover crops in enhancing soil nitrogen pools are widely

documented (Baligar et al. 2008; Brady and Weil 1999; Dinesh et al. 2004; Fageria et al. 2005;

Schroth et al. 2000; Vitousek et al. 2002; Wang et al. 2007). Yet no cover crop treatment

significantly altered the total soil nitrogen content at this research site. The potential causes for a

lack of differences in soil nitrogen between the Control, legume, and non-legume treatments are:

absence of inoculation with rhizobium at time of legume planting, low concentrations of soil

phosphorus, aluminum toxicity, or adequate supplies of soil nitrogen (Mafongoya et al. 2004;

Peoples and Baldock 2001; Vitousek et al. 2002). At the three depths analyzed the nitrogen

requirement of 200 kg/ha was easily surpassed clearly indicating an abundance of nitrogen in this

soil, see Table 3-2.

Carbon to Nitrogen Ratio

For optimal cacao growth and productivity the upper 15 cm of soil will contain a carbon to

nitrogen ratio (C:N) of approximately 10:1 (Wood 1975). This low C:N ratio is similar to that of

soil bacteria, actinomycetes, fungi, and soil humus and is unlikely to occur in weathered, sandy,

acidic soils (Miller and Gardiner 2001b). The quantified C:N ration for this soil ranges from

about 13:1 to 19:1, a consistently wider ratio than is recommended, C:N ratio data is in Table 3-

2. The C:N ratio in this soil is higher than recommended for optimal cacao production, however,

it is on par with that of other legume materials and ultimately should not bar optimal cacao

productivity. For example, the C:N ratio of young alfalfa is 13:1 and that of mature clover is

20:1, both plants are legumes (Miller and Gardiner 2001b). Considering the low organic matter

content of the soil, it is reasonable that the C:N ratio would be wider than ideal.









Soil Potassium, Calcium, and Magnesium

The recommended content of the upper 15 cm for K is 300 kg/ha, Ca is 140 kg/ha, and Mg

is 71 kg/ha (Wood and Lass 2001). On average, the soil at the research site under the Control

treatment contains more of all of these nutrients at all three depths than is recommended 1,024

kg/ha K, 320 kg/ha Ca, and 358 kg/ha Mg, data presented in Table 3-4.

Soil pH and Potential Aluminum Toxicity

In the upper 15 cm the soil pH should range between 6.0 to 7.5. In the subsurface horizons

the pH should not fall below 4.0 (Wood 1975). The pH in the upper 15 cm of soil under

investigation ranges from about 5.0-5.5, data in Table 3-3. The A. pintoi treatment significantly

increased soil pH in the 0-5 cm depth compared to the Control suggesting a potential for this

cultivar to aid in the amelioration of soil acidity. Amelioration of soil acidity on this site will

favor rhizobium growth and attachment to legume root hairs favoring conditions for biological

nitrogen fixation (Zuberer 1998). Amelioration of soil acidity will also aid in the agroforestry

plants ability to uptake calcium and phosphorus (Miller and Gardiner 2001a). At soil pH 4 to 5.5

A13+ solubilizes in soil solution and is toxic to plants (Evans et al. 1998; Miller and Gardiner

2001a). However, crops differ in their ability to withstand aluminum toxicity so it is difficult to

establish a precise pH at which soluble A13 begins to cause damage to the rooting system,

limiting plant uptake of Ca, and P (Miller and Gardiner 2001a; Russell 2002b; Wood and Lass

2001). Though, the quantity of Al in this soil supersedes that of the known tolerance for some

legumes and may inhibit biological nitrogen fixation by the legumes (Al averages 9,677 mg kg-1

in the upper 15 cm of soil) (Brady and Weil 1999). For example, aluminum toxicity has

impaired the growth of the rooting system of the legume Medicago sativa (alfalfa) at 8 mg kg-1,

the nodulation of Vigna unguiculata (cow pea) is inhibited at 25 mg kg-1 Al, and the most

resistant rhizobia can tolerate 100 mg kg-1 Al (Zuberer 1998). The visual indicators of aluminum









toxicity, yellowing of the interveinal leaf tip area of mature leaves that slowly progresses into a

full scorching of the leaf tip are present in several cacao plants at the research site (Wood and

Lass 2001). Images of these symptoms in cacao plants at the research site are shown in Figure 3-

5. Considering this information, it is likely that the optimal cacao productivity at this site may be

limited by aluminum toxicity.

Cover Crop Tissue Phosphorus

Phosphorus is absorbed by plant roots and transported to plant tissues (Schactman et al.

1998). The tissue analysis showed the C. ensiformis cover crop to absorb significantly more

phosphorus than they other cover crops did, indicating an advantage in phosphorus absorption

mechanisms or tolerance to soil acidity or aluminum toxicity.

Correlations Between Cover Crop Tissue and Soil Extractable Phosphorus

The significant correlations between cover crop tissue content and the Mehlich I and water

extractable phosphorus pools indicate that a strong relationship exists between the two. Water is

the conduit for plant uptake of nutrients via mass flow and diffusion (Barber 1995). The

Mehlich I extracting solution is commonly utilized to extract a soil phosphorus pool

representative of the plant available pool (Kuo 1996b). It is likely that plants are able to absorb

both the water and Mehlich I extractable phosphorus pools.

Half Molar HCI Extractable Phosphorus

Cover crop cultivation appears to have altered the 0.5 M HC1 extractable phosphorus pool

in the 0-5 cm depth. At this depth, every treatment contained less phosphorus extracted by 0.5 M

HC1 than did the Control. This represents a loss of approximately 9 kg/ha P for A. pintoi, 17

kg/ha P for C. ensiformis, 6 kg/ha P for C. macrocarpum, and 16 kg/ha P for C. mucunoides and

C. repens when compared to the Control. To absorb nutrients, fungal hyphae must be close

proximity to organic materials (Sylvia et al. 1998). As this rooting depth is largely absent of









cover crop roots, yet in close proximity to cover crop leaf litter, it is likely that the depletion of

0.5 M HC1 extractable P in the 0-5 cm is due to hyphal colonization of this horizon.

Six Molar HCI Extractable Phosphorus

In the 5-15 cm soil depth, cover crop cultivation altered the 6.0 M HC1 extractable

phosphorus pool. While for this extraction, there were no significant differences between the

Control and any treatment, some extractions treated soil contained more and some less

extractable phosphorus than the Control. As compared to the Control treatment the 5-15 cm

depth of air dried soil associated with A. pintoi contained approximately 21 kg/ha less, C.

ensiformis contained approximately 80 kg/ha more, C. macrocarpum contained approximately

18 kg/ha more, C. mucunoides 3 kg/ha more, and C. repens 68 kg/ha more 6 M HC1 extractable

phosphorus. Prior research has found the HC1 extractable phosphorus pool to be accessible by

plants (Hedley et al. 1982a). Cover crops vary in their ability to tolerate soil acidity and

aluminum toxicity which can affect a plants ability to uptake phosphorus (Baligar et al. 2008).

As this soil depth is dominated by cover crop root systems, it is likely that the variation in

tolerance of soil acidity and aluminum toxicity between the individual cover crops used in the

experiment are reflected in their ability to deplete the 6.0 M HC1 extractable P pools.

Conclusion

In the previously described experiment, we tested the ability of cover crops to remediate

the fertility of an acidic, low organic matter containing sandy loam soil utilized for cacao

cultivation. We found that the effects of cover crop cultivation is species dependant. However,

some cover crops included in our experiment increased surface soil pH and soil organic matter

supplies. Our research showed the surface soil at our site to have a significantly higher pH, and

water, NH4C1, and NaOH extractable phosphorus pools, indicating the importance of this soil

depth in storing and supplying the nutrients needed for soil fertility and crop production.









While the soil under investigation currently contains inadequate organic matter supplies, it

is likely that as the cover crops mature the surface horizon under their growth will accumulate

organic residues. However, the cover crops included in this experiment vary in their rates of

organic matter deposition. The Arachispintoi and Centrosema macrocarpum treatments appear

to be storing organic matter and the Cannavalia ensiformis, Calopogonium mucunoides, and

Callisia repens appear to be contributing organic matter to the soil. Building and maintaining

high contents of organic matter in surface soils are important for crop production and minimizing

soil erosion. The influence of cover crop cultivation on soil organic matter content should

continue to be monitored to establish a clear trend of their effect on soil organic matter

accumulation in the long term, as it is likely that soil organic matter additions will aid to mediate

the sustainability of soil fertility.

The soil under investigation has an acidity level that puts the plants at risk of suffering

from aluminum toxicity, thus hindering the plants ability to uptake calcium and phosphorus.

However, the cover crop species vary in their tolerance of soil acidity, and one in particular; A.

pintoi significantly increased surface soil pH. An improvement in the soil fertility of this site

must include an over all increase in soil pH, which affects nutrient availability and crop

productivity of acid soils.

The recommended soil phosphorus concentration for optimal cacao growth and

productivity is 25 kg/ha of 'available phosphorus' (Wood 1975; Wood and Lass 2001). Cover

crop tissue phosphorus content regresses nicely with water and Mehlich I extractable phosphorus

pools, and the 0.5 M HC1 and 6 M HC1 extractable pools have been affected by cover crop

cultivation indicating that all of these pools represent plant available phosphorus to some extent.

Extracted phosphorus concentrations expressed as kilograms per hectare are presented in Table









3-9. The Mehlich I extractable phosphorus amounts to about 5 kg ha-1 P; water extractable

phosphorus 2 kg ha-1, 0.5 M HC1 50 kg ha-1, and 6 M HC1 450 kg ha-1. Unless the plants are

indeed accessing the HC1 extractable phosphorus pools, their growth and productivity will be

severely limited by a lack of phosphorus in these soils. However, quantification of the plant

available soil phosphorus pool requires continued monitoring of the phosphorus content of all

species included in the agroforestry system as well as the fluctuations in extractable soil

phosphorus pools over time.

The cacao agroforestry site managed by the Instituto de Cultivos Tropicales provides an

ideal setting for examining the effects of cover crop cultivation on soil fertility. In this area, the

soil fertility is hindered by soil acidity, high levels of aluminum, and low organic matter content.

Additionally, cultivation of the land provides much needed food and economic income to the

people of this region. The identification of inexpensive and low technology techniques for

improving the fertility of the soils here will have a direct and positive impact on the livelihoods

of the people in this region. Continued research and development of cover crop applications in

cacao agroforestry are needed to identify the best cover crops for ameliorating soil fertility issues

in this region.










Table 3-1. Summary of significant findings.

6.0 M
0.1M 0.5 M 6 MHC1 HC1 air
NH4C1 NaOH HC1 residual dried Foliar
Treatment Depth TC LOI pH H20 [Pi] [Pi] [TP] [Pi] soil [P] soil [Pi] [P]


c;m /L o
A.pintoi 0-5 2.44 5.04 5.55aab
C. ensiformis 0-5 2.23 6.91 5.44
C. macrocarpum 0-5 2.04 6.39 5.43
C. mucunoides 0-5 1.50 4.22 5.26
C. repens 0-5 2.07 2.49 5.56
Fertilized 0-5 2.02 5.05 5.43
Control 0-5 1.56 4.06 5.18b
A. pintoi 5-15 1.04a 1.44a 5.15
C. ensiformis 5-15 1.53b 4.84b 5.09
C. macrocarpum 5-15 0.98a 1.71 5.05
C. mucunoides 5-15 1.05a 5.17b 5.09
C. repens 5-15 1.48 5.18b 5.18
Fertilized 5-15 1.44 4.49 5.23
Control 5-15 1.14a 3.51 5.12
A. pintoi 0-30 1.41 2.79b 5.26
C. ensiformis 0-30 1.52 4.93a 5.20
C. macrocarpum 0-30 1.27 3.78 5.16
C. mucunoides 0-30 1.17 4.26 5.12
C. repens 0-30 1.49 3.66 5.24
Fertilized 0-30 1.44 4.19 5.24


mg g mg g mg g mg g mg g mg %


0.84
1.53
0.94
1.24
1.25
2.93
0.82
0.54
0.59
0.64
0.40
0.52
0.98
0.42
0.70
0.88
0.70
0.69
0.76
1.52


0.09
0.31
0.15
0.01
0.17
0.59
0.14
0.01
0.04
0.15
0.02
0.05
0.12
0.09
0.04
0.12
0.11
0.01
0.22
0.25


29.24
55.33
41.99
29.26
42.79
66.21
39.28
32.18
34.66
27.98
28.40
44.39
51.63
30.07
29.76
37.54
32.36
28.24
36.40
47.13


21.38a
10.33a
24.42a
11.51a
11.54a
22.27a
32.90b
33.32
16.50
16.50
24.85
28.89
21.76
24.55
28.32
18.02
20.87
15.42
19.23
22.70


ndc
394.76
213.4
nd
nd
357.40
184.43
nd
339.93
231.28
nd
nd
312.77
227.35
nd
328.83a
232.15
nd
nd
325.05


213.85
278.07
239.20
193.58
288.85
272.35
177.49
188.13a
255.66b
190.64a
204.41
247.74
265.07
202.49
197.57
245.59
207.94
208.09
270.23
254.97


nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.11
0.2a
0.11
0.1lb
0.09b
nd


0-30 1.23 3.65 5.11 0.59 0.08


33.76 23.76 234.92b 196.48 nd


Control









Table 3-1 Continued

6.0 M
0.1M 0.5 M 6 MHC1 HC1 air
NH4C1 NaOH HC1 residual dried Foliar
Treatment Depth TC LOI pH H20 [Pi] [Pi] [TP] [Pi] soil [P] soil [Pi] [P]
cm % % mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 %
Combined 0-5 1.98 4.88 5.41a 0.12a 0.21a 43.44a 19.19 287.50 237.63 nd
Combined 5-15 1.24 3.76 5.13b 0.05b 0.07b 35.61b 23.77 277.83 222.02 nd
Combined 15-30 0.87 3.04 5.03b 0.05b 0.08b 26.02b 20.61 275.38 217.87 nd
a Mean values followed by different letters within the same depth section indicate significant differences at the P < 0.05 level.
b Mean values in bold are significant.
c nd indicates no data for that depth.
d Combined in the Treatment column indicates that data across treatments was averaged per depth.










Table 3-2. Total nitrogen, total carbon, carbon to nitrogen ratio, pH, and loss on ignition


Treatment Depth Total N Total C C/N pH LOI
cm % % %


A. pintoi
C. repens
C. mucunoides
C. ensiformis
C. macrocarpum
Control
Fertilized
A. pintoi
C. repens
C. mucunoides
C. ensiformis
C. macrocarpum
Control
Fertilized
A. pintoi
C. repens
C. mucunoides
C. ensiformis
C. macrocarpum
Control
Fertilized


0-5
0-5
0-5
0-5
0-5
0-5
0-5
5-15
5-15
5-15
5-15
5-15
5-15
5-15
15-30
15-30
15-30
15-30
15-30
15-30
15-30


0.13
0.13
0.11
0.15
0.13
0.10
0.13
0.07
0.10
0.07
0.10
0.07
0.08
0.12
0.06
0.07
0.07
0.06
0.06
0.07
0.09


2.44
2.07
1.50
2.23
2.04
1.56
2.02
1.04
1.48
1.05
1.53a'
0.98b
1.14b
1.44
0.76
0.91
0.94
0.79
0.80
1.00
0.87


18.71
15.84
14.26
15.14
15.25
15.57
15.84
14.65
14.48
14.90
14.94
13.19
15.20
11.83
13.33
13.33
13.28
12.90
13.37
13.60
9.95


5.55a
5.56
5.26
5.44a
5.43
5.18b
5.43
5.15
5.18
5.09
5.09
5.05
5.12
5.23
5.10
5.00
5.02
5.06
5.00
5.02
5.04


5.04
2.49
4.22
6.91
6.39
4.06
5.05
1.44a
5.18b
5.17b
4.84b
1.71
3.51
4.49
1.90a
3.30
3.39
3.04b
3.25
3.37
3.05


N
kg/ha
977.12
979.35
790.61
1106.57
1004.28
752.24
956.82
1065.78
1532.27
1057.37
1536.23
1114.46
1125.06
1828.68
1282.48
1538.12
1597.55
1378.82
1338.28
1659.96
1961.91


a Bulk density is assumed to be 1500 kg/m3.
b Nutrient quantity is for the entire associated depth.
c Mean values followed by different letters indicate significant differences at the P < 0.05 level


v


averaged data for all treatments at all depths.
C LOI
kg/ha kg/ha
18278.78 37800.00
15517.58 18662.32
11277.30 31619.27
16752.53 51825.00
15314.63 47940.96
11708.85 30464.16
15155.93 37840.34
15612.90 10800.00
22186.50 38850.00
15755.25 38775.00
22950.00 36300.00
14700.00 12815.62
17100.00 26340.08
21630.75 33695.15
17097.98 14250.00
20510.10 24770.54
21212.55 25396.30
17783.78 22800.00
17891.33 24357.67
22571.55 25294.26
19520.33 22842.83









Table 3-3. Water, pH, and NH4C1, NaOH, and HC1 extractable inorganic phosphorus averaged
data.
6M 6M
0.5 HC1 HC1 air
NH4C1 NaOH NaOH HCL residual dried
Depth pH Water [P] [P] [P] [TP] [P] soil [P] soil [P]
cm mg kg1 mg kg1 mg kg1 mg kg1 mg kg1 mg kg1 mg kg1
0-5 5.41a 0.12a 0.21a 34.86 43.44a 19.19 287.50a 237.63
5-15 5.13b 0.05b 0.07b 29.21 35.61b 23.61 277.83b 222.02
15-30 5.03b 0.05b 0.08b 23.60 26.02b 20.61 275.38b 217.87
a Mean values followed by different letters indicate significant differences at the P < 0.05 level.










Table 3-4. Calcium, potassium, iron, aluminum, and magnesium averaged data.


Treatment Depth Ca K Fe Al Mg Ca K Fe Al Mg
cm % % % % % kg/ha kg/ha kg/ha kg/ha kg/ha


Control
Control
Control
Control
Control
Control
Control
Control
Control


0-5
0-5
0-5
5-15
5-15
5-15
15-30
15-30
15-30


0.02
0.01
0.02
0.01
0.01
0.01
0.02
0.02
0.01


0.06
0.05
0.03
0.05
0.06
0.03
0.04
0.06


0.56
0.50
0.46
0.49
0.65
0.66
0.46
0.81


0.64
0.86
0.65
0.71
1.06
1.06
0.75
1.29


0.02
0.02
0.01
0.02
0.02
0.01
0.02
0.02


171.09a
104.72
164.78
207.49
181.73
131.49
422.83
457.12


413.61
390.45
192.20
680.06
903.88
491.98
973.32
1345.61


4201.20
3760.79
3453.51
7373.74
9823.14
9863.31
10250.33
18260.83


4773.84
6467.06
4842.75
10610.81
15828.38
15907.13
16772.63
28999.41


145.58
132.92
85.58
258.11
278.85
174.98
375.61
402.98


0.05 0.97 1.66 0.01 124.26 1015.62 21773.36 37416.38 303.22


a Bulk density is assumed to be 1500 kg/m3.
b Nutrient quantity is for the entire associated depth.









Table 3-5. Mehlich I extraction of inorganic, organic, and total phosphorus averaged data.
Inorganic Organic Inorganic Organic
Treatment Depth [P] [P] Total [P] P P
cm mg kg1 mg kg1 mg kg-1 % %


A. pintoi 0-15 2.03 6.31 8.34 24.35 75.65
C. repens 0-15 3.14 10.89 14.03 22.38 77.62
C. mucunoides 0-15 2.79 8.63 11.42 24.41 75.59
C. ensiformis 0-15 3.92 12.16 16.08 24.40 75.60
C. macrocarpum 0-15 2.54 7.86 10.39 24.40 75.60
Control 0-15 2.47 7.66 10.13 24.40 75.60
Fertilized 0-15 3.87 11.98 15.85 24.40 75.60










6 M HC1 6.0 M HCI
NH4C1 NaOH NaOH 0.5 HCL residual air dried
Treatment Depth H20 [P] [P] [P] [TP] [P] soil [P] soil [Pi]
cm mg kg- mg kg- mg kg- mg kg- mg kg1 mg kg1 mg kg1
A. pintoi 0-5 0.84 0.09 18.66 29.24 21.38a mdpa 213.85
C. ensiformis 0-5 1.53 0.31 31.24 55.33 10.33a 394.76ab 288.85
C. macrocarpum 0-5 0.94 0.15 31.27 41.99 24.42a 213.40 193.58
C. mucunoides 0-5 1.24 0.01 41.53 29.26 11.51a mdp 278.07
C. repens 0-5 1.25 0.17 36.08 42.79 11.54a mdp 239.20
Control 0-5 0.82 0.14 34.05 39.28 32.90b 184.43b 177.49
Fertilized 0-5 2.93 0.59 45.79 66.21 22.27a 357.40 272.35
A. pintoi 5-15 0.54 0.01 20.02 32.18 33.32 mdp 188.13aa
C. ensiformis 5-15 0.59 0.04 25.93 34.66 16.50 339.93a 247.74
C. macrocarpum 5-15 0.64 0.15 28.99 27.98 16.50 231.28 204.41
C. mucunoides 5-15 0.40 0.02 17.84 28.40 24.85 mdp 255.66b
C. repens 5-15 0.52 0.05 39.17 44.39 28.89 mdp 190.64a
Control 5-15 0.42 0.09 25.01 30.07 24.55 227.35b 202.49
Fertilized 5-15 0.98 0.12 44.46 51.63 21.76 312.77 265.07
A. pintoi 15-30 0.73 0.01 17.87 27.84 30.28 mdp 190.74
C. ensiformis 15-30 0.53 0.02 19.82 22.64 27.22 251.79a 274.10
C. macrocarpum 15-30 0.52 0.01 23.43 27.12 21.70 251.78 226.27
C. mucunoides 15-30 0.44 0.01 20.76 27.07 9.91 mdp 203.04
C. repens 15-30 0.49 0.45 29.53 22.01 17.26 mdp 193.97
Control 15-30 0.52 0.02 27.50 31.92 13.82 292.99b 209.45
Fertilized 15-30 0.66 0.03 22.87 23.54 24.06 304.98 227.49
a Mean values followed by different letters indicate significant differences at the P < 0.05 level.
b mdp indicates a missing data point


Table 3-6. Sequential extraction of phosphate and


the digest of air-dried soil averaged data.









Table 3-7. Phosphorus content of cover crop foliar tissue.
Treatment Block P Mean P Mean P
% % kg ha-
Arachispintoi 1 0.12 0.11 0.0013
Arachis pintoi 2 0.11
Arachis pintoi 3 0.11
Calopogonium mucunoides 1 0.16 0. 10aa 0.0006
Calopogonium mucunoides 2 0.07
Calopogonium mucunoides 3 0.07
Callisia repens 1 0.11 0.09a 0.0003
Callisia repens 2 0.08
Callisia repens 3 0.08
Cannavalia ensiformis 1 0.18 0.20b 0.0014
Cannavalia ensiformis 2 0.17
Cannavalia ensiformis 3 0.25
Centrocema macrocarpum 1 0.09 0.10 0.0015
Centrocema macrocarpum 2 0.12
Centrocema macrocarpum 3 0.11
a Mean values followed by different letters indicate significant differences at the P < 0.05 level.










Table 3-8. Soil organic matter, potassium, cation exchange capacity, cations, and base saturation
averaged data.


Treatment


Control
Fertilizer
C. repens
C. mucunoides
C. macrocarpum
C. ensiformis


Depth SOM
cm %
0-20 1.90
0-20 2.20
0-20 2.20
0-20 2.00
0-20 2.00


CEC
cmol/kg
5.97
7.13
4.86
4.25
6.27


0-20 2.10 3.92


Ca2+
cmol/kg
2.03
3.01
3.12
2.69
2.25


Mg2+
cmol/kg
3.04
3.25
0.87
0.69
3.07


K+
cmol/kg
0.15
0.19
0.23
0.26
0.24


2.33 0.69 0.29


A. pintoi 0-20 1.90 6.04 2.06 3.14 0.25
a data provided courtesy of Instituto de Cultivos Tropicales (Baligar et al. 2008).


A13+ + H+
cmol/kg
0.75
0.68
0.65
0.61
0.71
0.61
0.58


Base Sat
%
87.44
90.46
86.83
85.65
88.68
84.44
90.40










Table 3-9. Extractable phosphorus expressed in kilograms per hectare.
0.5 M 6 M HC1 Air
Water NH4Cl NaOH NaOH HCL Dried Soil Mehlich Mehlich Mehlich
Treatment Depth [Pi] [Pi] [Pi] [TP] [Pi] [Pi] [Pi] [Po] [TP]
cm kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha


A. pintoi
C. ensiformis
C. macrocarpum
C. mucunoides
C. repens
Control
Fertilized
A. pintoi
C. ensiformis
C. macrocarpum
C. mucunoides
C. repens
Control
Fertilized
A. pintoi
C. ensiformis
C. macrocarpum
C. mucunoides
C. repens
Control
Fertilized


0-5
0-5
0-5
0-5
0-5
0-5
0-5
5-15
5-15
5-15
5-15
5-15
5-15
5-15
15-30
15-30
15-30
15-30
15-30
15-30
15-30


0.63
1.14
0.71
0.93
0.94
0.61
2.19
0.81
0.88
0.96
0.60
0.79
0.64
1.47
1.63
1.20
1.16
0.98
1.10
1.18
1.49


0.07
0.24
0.12
0.01
0.13
0.11
0.44
0.01
0.06
0.23
0.03
0.08
0.14
0.18
0.02
0.04
0.03
0.02
1.00
0.04
0.07


13.99
23.43
23.45
31.15
27.06
25.54
34.34
30.03
38.90
43.48
26.76
58.75
37.51
66.69
40.21
44.60
52.72
46.71
66.44
61.88
51.46


21.93
41.50
31.49
21.94
32.09
29.46
49.66
48.27
51.98
41.97
42.60
66.59
45.10
77.44
62.65
50.94
61.01
60.92
49.52
71.82
52.96


16.04
7.75
18.32
8.63
8.66
24.68
16.70
49.98
24.74
24.75
37.28
43.34
36.82
32.64
68.12
61.25
48.81
22.30
38.83
31.09
54.14


160.39
208.55
179.40
145.19
216.64
204.26
133.12
282.20
383.49
285.96
306.62
371.61
397.61
303.74
444.53
552.58
467.87
468.20
608.02
573.68
442.08


nda
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd


nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd


nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd










Table 3-9 Continued


Treatment


A. pintoi
C. ensiformis
C. macrocarpum
C. mucunoides
C. repens
Control


Depth
cm
0-15
0-15
0-15
0-15
0-15
0-15


0.5 M 6 M HC1 Air
Water NH4Cl NaOH NaOH HCL Dried Soil
[Pi] [Pi] [Pi] [TP] [Pi] [Pi]
kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha
1.44 0.08 44.03 70.20 66.01 442.58
2.02 0.30 62.32 93.48 32.49 592.04
1.67 0.35 66.93 73.46 43.07 465.36
1.52 0.04 57.91 64.54 45.91 451.80
1.72 0.20 85.81 98.68 51.99 588.25
1.25 0.24 63.04 74.56 61.50 436.85


Mehlich Mehlich Mehlich


[Pi]
kg/ha
4.57
7.07
6.27
8.83
5.71
5.56


[Po]
kg/ha
14.19
24.50
19.42
27.35
17.68
17.23


[TP]
kg/ha
18.76
31.57
25.70
36.18
23.38
22.79


Fertilized 0-15 3.67
and indicates no data for that depth.


0.62


101 03 127.10 4934 601.87


8 70 26 95 35 65

































BRAZIL


SOUTH
PACiFiC
OCEAN


I" --


PERU

-.-..- Depe"fnn Baamdory
Dpimfln BrOfifn

g Dopmmalnan ak





.-- n ,n m O nm
Rivrs
C; LID I tf OfW 0 1ft CO-W UWr
dalaHu LrA m hnFmeumrltm

i e I
4o 1 w 2. 0 mf 4
IGO 2MW firmw


Figure 3-1. Map of Peru, with an arrow indicating the location of Tarapoto, the outskirts of
which is the location of this research.
















1 2 3 4 5 6 7 45 m












7 4 6 1 3 2 5


Block 2


1:::~I 2m






3 5 7 2 6 4 1


Block 3



10m
Figure 3-2. Experimental design consisted of three randomized blocks, each containing one
replicate each of seven ground cover types in the understory of a cacao agroforestry
system. Each number indicates the placement of ground cover type as follows: 1 = A.
pintoi, 2 = Control, 3= C. mucunoides, 4 = C.ensiformis, 5 = C. repens, 6 = C.
macrocarpum and 7= Fertilized.











Soil H20 1M NH4I 0.1M 0.5M HCI
Air dried Deionized 20 mL NaOH 20 mL Residual 6M HCI
2mm 20 mL Shake 2 20 mL Shake 24 Soil Digest
fraction Shake 2 hours Shake 17 hours


H20 NH4Cl NaOH HCIQuan
Supernatant Supernatant Supernatant Supernatant


Quantify Quantify Quantify Quantify
[P] [P] [P] [P]


NaOH
Supernatant
4
Kjeldahl
Digest



Quantify
[P]




Figure 3-3. Sequence for the fractionation of soil phosphorus pools. Adapted from (Nair et al.
1995).







-0.10 -0.10
-0.12 -0.12
S -0.14 -0.14
-0.16 -0.16 -
S-0.18 -0.18
= .-0.20 -0.20
S-0.22 -0.22
U -024- -0.24
: 5 -0.26 -0.26
-0.28 -0.28 *
-0.30 -----A. -0.30 B.
95 100 105 110 115 120 125 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50

Box-Cox transformed Mehlich 1 extractable [Pi] Box-Cox transformed water extractable [Pi]

Figure 3-4. Significant correlations between cover crop tissue and soil extracted phosphorus
pools. A. A significant linear regression between cover crop foliar phosphorus and
Mehlich 1 soil extractable phosphorus (R2 = 0.41, P = 0.026). B. A significant linear
regression between cover crop foliar phosphorus and water extractable soil
phosphorus (R2 = 0.44, P = 0.018) in the 0-5 cm depth.
























































Figure 3-5. Physical symptoms of aluminum toxicity expressed in the mature leaves of cacao
plants at Instituto de Cultivos Tropicales. A. Yellowing of the interveinal regions of
the distal end of a mature leaf. B. Progression of leaf tip scorch. C. Leaf tip scorch
in conjunction with interveinal yellowing.










APPENDIX A
UNTRANSFORMED DATA

Table A-1. Soil sample collection co-ordinates.
Block Replicate Width ordinate Length ordinate
m m
1 1 7.0 19.5
1 1 4.9 12.5
1 1 5.1 0.4
1 1 6.5 34.9
1 1 7.5 14.7
1 1 3.8 1.5
1 1 2.9 22.0
1 1 3.6 37.8
1 1 5.2 37.4
1 1 1.2 12.3
1 2 4.4 12.9
1 2 2.9 9.5
1 2 5.3 3.7
1 2 4.0 29.8
1 2 2.0 18.3
1 2 5.1 19.1
1 2 4.1 6.8
1 2 4.5 8.3
1 2 6.8 26.9
1 2 3.6 27.6
1 3 6.3 12.4
1 3 2.9 15.0
1 3 8.0 8.2
1 3 7.1 17.0
1 3 5.6 27.5
1 3 0.1 29.2
1 3 7.2 30.4
1 3 6.8 7.3
1 3 5.0 10.6
1 3 2.1 16.7
1 4 1.0 5.3
1 4 5.4 24.1
1 4 4.2 26.9
1 4 2.9 34.0
1 4 3.0 2.2
1 4 6.2 14.3










Table A-1 Continued
Block Replicate


Width ordinate
m


Length ordinate
m
24.7
25.2
17.3
13.7
4.5
34.4
13.9
15.5
24.8
39.0
17.6
39.1
29.8
2.7
19.6
22.3
20.8
32.4
25.5
41.1
41.4
42.5
17.8
30.2
40.1
33.7
21.2
27.8
1.5
38.8
18.5
8.3
1.0
35.1
19.5
12.5
0.4
34.9










Table A-1 Continued
Block Replicate


Width ordinate
m


Length ordinate
m
14.7
1.5
22.0
37.8
37.4
12.3
12.9
9.5
3.7
29.8
18.3
19.1
6.8
8.3
26.9
27.6
12.4
15.0
8.2
17.0
27.5
29.2
30.4
7.3
10.6
16.7
5.3
24.1
26.9
34.0
2.2
14.3
24.7
25.2
17.3
13.7
4.5
34.4










Table A-1 Continued
Block Replicate


Width ordinate
m


Length ordinate
m
13.9
15.5
24.8
39.0
17.6
39.1
29.8
2.7
19.6
22.3
20.8
32.4
25.5
41.1
41.4
42.5
17.8
30.2
40.1
33.7
21.2
27.8
1.5
38.8
18.5
8.3
1.0
35.1
19.5
12.5
0.4
34.9
14.7
1.5
22.0
37.8
37.4
12.3










Table A-1 Continued
Block Replicate


Width ordinate
m


Length ordinate
m
12.9
9.5
3.7
29.8
18.3
19.1
6.8
8.3
26.9
27.6
12.4
15.0
8.2
17.0
27.5
29.2
30.4
7.3
10.6
16.7
5.3
24.1
26.9
34.0
2.2
14.3
24.7
25.2
17.3
13.7
4.5
34.4
13.9
15.5
24.8
39.0
17.6
39.1










Table A-1 Continued
Block Replicate


Width ordinate
m


Length ordinate
m
29.8
2.7
19.6
22.3
20.8
32.4
25.5
41.1
41.4
42.5
17.8
30.2
40.1
33.7
21.2
27.8
1.5
38.8
18.5
8.3
1.0
35.1










Table A-2. Soil total nitrogen, total carbon, pH, and carbon to nitrogen ratio unaltered data.
Treatment Block Depth N C C/N pH
# cm % %
Arachis pintoi 1 0-5 0.16 2.67 16.32 5.62
Arachispintoi 2 0-5 0.11 2.05 17.89 5.47
Arachis pintoi 3 0-5 0.11 2.59 23.01 5.56
Arachispintoi 1 5-15 0.10 1.23 12.32 5.24
Arachispintoi 2 5-15 0.07 1.04 15.40 5.16
Arachispintoi 3 5-15 0.05 0.86 18.58 5.04
Arachispintoi 1 15-30 0.05 0.67 14.15 5.09
Arachispintoi 2 15-30 0.06 0.75 13.13 5.16
Arachispintoi 3 15-30 0.07 0.85 12.92 5.04
Callisia repens 1 0-5 0.19 2.97 15.25 6.04
Callisia repens 2 0-5 0.12 1.81 14.76 5.37
Callisia repens 3 0-5 0.07 1.42 19.19 5.26
Callisia repens 1 5-15 0.14 1.96 13.66 5.28
Callisia repens 2 5-15 0.08 1.11 13.54 5.14
Callisia repens 3 5-15 0.08 1.37 16.88 5.11
Callisia repens 1 15-30 0.09 1.08 11.75 4.97
Callisia repens 2 15-30 0.06 0.76 11.73 5.10
Callisia repens 3 15-30 0.05 0.90 18.46 4.92
Calopogonium mucunoides 1 0-5 0.16 2.15 13.25 5.37
Calopogonium mucunoides 2 0-5 0.09 1.26 13.82 5.06
Calopogonium mucunoides 3 0-5 0.06 1.10 17.52 5.36
Calopogonium mucunoides 1 5-15 0.08 1.12 13.48 5.15
Calopogonium mucunoides 2 5-15 0.07 1.19 16.37 5.06
Calopogonium mucunoides 3 5-15 0.06 0.84 15.11 5.05
Calopogonium mucunoides 1 15-30 0.09 1.15 12.97 4.84
Calopogonium mucunoides 2 15-30 0.07 0.94 13.56 5.14
Calopogonium mucunoides 3 15-30 0.05 0.73 13.42 5.08
Cannavalia ensiformis 1 0-5 0.16 2.01 12.78 5.41
Cannavalia ensiformis 2 0-5 0.17 2.69 15.62 5.50
Cannavalia ensiformis 3 0-5 0.11 1.99 17.71 5.42
Cannavalia ensiformis 1 5-15 0.14 1.67 12.20 5.15
Cannavalia ensiformis 2 5-15 0.10 1.51 15.23 5.13
Cannavalia ensiformis 3 5-15 0.07 1.41 19.66 5.00
Cannavalia ensiformis 1 15-30 0.06 0.77 12.39 5.00
Cannavalia ensiformis 2 15-30 0.07 0.83 11.08 5.22
Cannavalia ensiformis 3 15-30 0.05 0.78 16.43 4.97
Centrosema macrocarpum 1 0-5 0.14 1.97 14.29 5.43
Centrosema macrocarpum 2 0-5 0.13 1.87 14.88 5.47










Table A-2 Continued
Treatment Block Depth N C C/N pH
# cm % %
Centrosema macrocarpum 3 0-5 0.14 2.29 16.53 5.38
Centrosema macrocarpum 1 5-15 0.08 1.07 13.07 5.13
Centrosema macrocarpum 2 5-15 0.07 0.97 13.98 5.11
Centrosema macrocarpum 3 5-15 0.07 0.89 12.40 4.92
Centrosema macrocarpum 1 15-30 0.06 0.83 14.00 4.97
Centrosema macrocarpum 2 15-30 0.07 0.77 10.32 5.21
Centrosema macrocarpum 3 15-30 0.04 0.79 17.60 4.83
Control 1 0-5 0.12 1.58 12.75 5.26
Control 2 0-5 0.08 1.35 17.21 5.24
Control 3 0-5 0.10 1.76 17.81 5.04
Control 1 5-15 0.09 1.31 15.13 5.09
Control 2 5-15 0.07 1.10 15.77 5.13
Control 3 5-15 0.07 1.01 14.66 5.15
Control 1 15-30 0.09 1.29 14.34 5.09
Control 2 15-30 0.05 0.78 14.77 5.02
Control 3 15-30 0.08 0.95 11.98 4.94
Fertilized 1 0-5 0.15 2.17 14.18 5.65
Fertilized 2 0-5 0.08 1.73 20.61 5.35
Fertilized 3 0-5 0.15 2.16 14.82 5.30
Fertilized 1 5-15 0.09 1.58 17.62 5.40
Fertilized 2 5-15 0.15 1.22 7.95 5.20
Fertilized 3 5-15 0.12 1.53 12.44 5.09
Fertilized 1 15-30 0.05 0.95 17.76 5.09
Fertilized 2 15-30 0.05 0.82 17.01 5.13
Fertilized 3 15-30 0.16 0.84 5.23 4.91










Table A-3. Loss on ignition unaltered data.

Post ignite Post
Volumetric volumetric + ignite Loss on
Treatment Block Depth Sample Volumetric Soil + soil ash ash ignition
# cm # g g g g g %


A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides


1
1
1
2
2
2
3
3
3
1
1
1
2
2
2
3
3

1
1
1
2
2
2
3


0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25


29.42
31.67
31.59
30.82
28.37
28.62
28.66
28.66
28.77
28.81
29.20
28.55
28.60
30.94
29.18
28.98
29.68
28.76
29.91
30.90
28.75
28.67
28.80
32.00
28.71


0.21
0.21
0.22
0.24
0.23
0.21
0.22
0.23
0.21
0.20
0.21
0.20
0.22
0.23
0.21
0.22
0.20
0.22
0.22
0.21
0.21
0.23
0.22
0.22
0.22


29.63
31.88
31.81
31.05
28.60
28.83
28.88
28.88
28.98
29.01
29.41
28.75
28.82
31.17
29.39
29.20
29.88
28.98
30.12
31.11
28.96
28.89
29.02
32.22
28.92


29.60
31.87
31.82
31.06
28.61
28.84
28.88
28.89
28.99
29.01
29.40
28.74
28.81
31.15
29.38
29.19
29.87
28.97
30.11
31.10
28.95
28.88
29.01
32.21
28.92


0.18
0.20
0.22
0.23
0.23
0.20
0.22
0.23
0.21
0.20
0.20
0.19
0.22
0.21
0.21
0.21
0.20
0.21
0.20
0.20
0.20
0.21
0.21
0.21
0.21


3.91
3.85
0.46
0.43
0.43
4.76
0.77
0.04
0.49
1.82
5.61
5.39
3.15
6.55
2.19
2.50
3.37
2.33
5.12
6.54
5.27
5.96
4.91
3.49
1.57










Table A-3 Continued


C.e

C.n

C.n

C.n


C.e

C.e

C.e

C.e

C.e
Con
Co.
Coe
Coe
Coe
C. e
C.e
C. e
C.e
C. e


Con
Con
Con
Con
Con


Treatment Block
#ucuno s
mucunoides 3
mucunoides 3
macrocarpum 1
macrocarpum 1
macrocarpum 1
macrocarpum 2
macrocarpum 2
macrocarpum 2
macrocarpum 3
macrocarpum 3
nacrocarpum 3
nsiformis 1
nsiformis 1
nsiformis 2
nsiformis 2
nsiformis 2
nsiformis 3
nsiformis 3
nsiformis 3
nsiformis 3
Itrol 1
Itrol 1
Itrol 1

Itrol 2
Itrol 2


Post ignite
Volumetric volumetric +
Volumetric Soil + soil ash


Depth Sample
cm #
5-15 26
15-30 27
0-5 28
5-15 29
15-30 30
0-5 31
5-15 32
15-30 33
0-5 34
5-15 35
15-30 36
0-5 37
5-15 38
15-30 39
0-5 40
5-15 41
15-30 42
0-5 43
5-15 44
15-30 45
0-5 46
5-15 47
15-30 48
0-5 49
5-15 50


g
28.72
31.73
28.60
30.83
30.89
32.13
31.08
30.57
29.22
30.95
28.65
30.53
30.78
28.71
29.92
31.21
31.74
29.90
31.03
28.52
31.35
28.86
28.72
32.18
28.73


g
0.21
0.22
0.21
0.20
0.21
0.21
0.24
0.24
0.21
0.24
0.21
0.23
0.21
0.23
0.23
0.20
0.21
0.22
0.21
0.23
0.23
0.21
0.24
0.20
0.20


g
28.93
31.94
28.81
31.03
31.11
32.34
31.32
30.81
29.43
31.19
28.86
30.76
30.99
28.94
30.16
31.41
31.96
30.11
31.24
28.75
31.58
29.08
28.95
32.39
28.93


g
28.92
31.94
28.80
31.03
31.10
32.32
31.31
30.80
29.42
31.19
28.85
30.74
30.98
28.93
30.14
31.40
31.95
30.10
31.23
28.74
31.57
29.07
28.94
32.38
28.92


Post
ignite
ash
g
0.20
0.21
0.20
0.20
0.21
0.20
0.23
0.23
0.20
0.24
0.20
0.22
0.20
0.22
0.22
0.19
0.21
0.20
0.20
0.22
0.22
0.21
0.22
0.20
0.19


Loss on
ignition
%
4.05
1.40
7.02
0.88
2.47
7.76
2.34
4.55
4.40
1.91
2.72
7.61
4.29
3.86
6.92
5.42
2.48
6.19
4.81
2.78
4.47
3.36
5.85
3.27
4.90










Table A-3 Continued


Treatment Block
#Contro
Control 2
Control 3
Control 3
Control 3
Fertilized 1
Fertilized 1
Fertilized 1
Fertilized 2
Fertilized 2
Fertilized 2
Fertilized 3
Fertilized 3
Fertilized 3


Depth
cm
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30


Sample
#
51
52
53
54
55


Volumetric
g
31.01
30.96
31.15
28.68
29.79


56 31.91
57 28.49
58 31.26
59 28.68
60 28.92
61 30.15
62 28.81
63 28.67


Soil
g0
0.21
0.21
0.22
0.20


Post ignite
Volumetric volumetric +
+ soil ash


g
31.22
31.17
31.37
28.88


0.20 29.99
0.22 32.13


0.21
0.23
0.21
0.20
0.21
0.23
0.21


28.70
31.49
28.89
29.12
30.35
29.04
28.87


g
31.21
31.16
31.36
28.88
29.98
32.12
28.69
31.48
28.88
29.11
30.34
29.03
28.87


Post
ignite
ash
g
0.20
0.20
0.22
0.20
0.19
0.21
0.20
0.22
0.20
0.19
0.19
0.22
0.20


Loss on
ignition
%
2.88
4.44
2.27
1.38
5.88
6.24
3.12
2.63
3.00
4.51
6.63
4.24
1.51










Table A-4. Soil concentration of calcium, potassium, iron, aluminum, and magnesium unaltered
data.
Depth Ca K Fe Al Mg
cm mg kg1 mg kg1 mg kg1 mg kg1 mg kg1
0-5 1.83 4.41 44.81 50.92 1.55
0-5 1.12 4.16 40.12 68.98 1.42
0-5 1.76 2.05 36.84 51.66 0.91
5-15 1.11 3.63 39.33 56.59 1.38
5-15 0.97 4.82 52.39 84.42 1.49
5-15 0.70 2.62 52.60 84.84 0.93
15-30 1.50 3.46 36.45 59.64 1.34
15-30 1.63 4.78 64.93 103.11 1.43
15-30 0.44 3.61 77.42 133.04 1.08










Table A-5. Mehlich I extraction of inorganic


Treatment


A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
Control
Control
Control
Control
Control
Control
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
Fertilized


Block
#
1
1
2
2
3
3
1
1
2
2
3
3
1
1
2
2
3
3
1
1
2
2
3
3
1


Sample
#
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24


Soil Mehlich
g ml
5.09 20.5
5.29 20.5
5.33 20.5
5.14 20.5
5.16 20.5
5.42 20.5
5.11 20.5
5.03 20.5
5.14 20.5
5.23 20.5
5.25 20.5
5.16 20.5
5.08 20.5
5.0 20.5
5.2 20.5
5.09 20.5
5.02 20.5
5.2 20.5
5.04 20.5
5.12 20.5
5.05 20.5
5.22 20.5
5.09 20.5
5.17 20.5
5.02 20.5


Total Murphy
& Riley
ml
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0


Sample in
Murphy &
Riley


Spectro-
photometer [P]
mg kg-'
0.15
0.15
0.13
0.12
0.11
0.10
0.25
0.26
0.17
0.17
0.21
0.21
0.05
0.06
0.20
0.19
0.19
0.20
0.15
0.15
0.43
0.31
0.18
0.19
0.24


Calculated
[Pi]
mg kg-1
2.47
2.35
2.04
2.03
1.75
1.57
4.11
4.47
2.89
2.78
3.34
3.50
0.89
1.06
3.23
3.16
3.28
3.21
2.53
2.50
7.29
5.06
3.05
3.11
4.08


phosphorus unaltered data.










Table A-5 Continued


Treatment


Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides


Block
#
1
2
2
3
3
1
1
2
2
3
3
1
1
2
2
3
3


Sample
#
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41


a mdp indicates a missing data point.


Soil Mehlich
g ml
5.13 20.5
5.05 20.5
5.27 20.5
5.2 20.5
5.14 20.5
5.13 20.5
5.04 20.5
5.02 20.5
5.08 20.5
5.15 20.5
5.23 20.5
5.17 20.5
5.07 20.5
5.04 20.5
5.05 20.5
5.04 20.5
5.05 20.5


Total Murphy
& Riley
ml
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0


Sample in
Murphy &
Riley


Spectro-
photometer [P]
mg kg-'
0.23
0.31
0.31
0.19
mdpa
0.12
0.11
0.14
0.14
0.12
0.13
0.28
0.27
0.16
0.17
0.12
0.12


Calculated
[Pi]
mg kg-1
3.82
5.17
5.02
3.11
mdp
2.01
1.95
2.32
2.33
2.00
2.05
4.57
4.49
2.64
2.86
1.96
1.99










Table A-6. Mehlich I extraction of total phosphorus unaltered data.
Digest in
Mehlich Digest Mehlich Murphy & Murphy & Spec. Calculated
Treatment Block Sample Soil Pi total total in digest Riley total Riley Conc. [TP]
mg
# # g ml ml ml ml ml kg-1 mg kg'1


A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
Control
Control
Control
Control
Control
Control
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis


5.09
5.29
5.33
5.14
5.16
5.42
5.11
5.03
5.14
5.23
5.25
5.16
5.08
5.00
5.20
5.09
5.02
5.20
5.04
5.12
5.05
5.22
5.09
5.17


20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0


35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0


25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0


10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0


0.15
0.15
0.13
0.12
0.11
0.10
0.25
0.26
0.17
0.17
0.21
0.21
0.05
0.06
0.20
0.19
0.19
0.20
0.15
0.15
0.43
0.31
0.18
0.19


10.14
9.65
8.34
8.31
7.18
6.43
16.84
18.31
11.83
11.40
13.70
14.34
3.65
4.36
13.24
12.93
13.45
13.14
10.36
10.25
29.88
20.75
12.51
12.73










Table A-6 Continued


Mehlich Digest Mehlich Murphy &


Treatment Block Sample


Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized


macrocarpum
C.
macrocarpum
C.
macrocarpum
C.
macrocarpum
C.
macrocarpum
C.
macrocarpum
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides


Soil

g
5.02
5.13
5.05
5.27
5.20
5.14


Pi total


ml
20.0
20.0
20.0
20.0
20.0
20.0


1 30 5.13 20.0

1 31 5.04 20.0

2 32 5.02 20.0

2 33 5.08 20.0

3 34 5.15 20.0


a mdp indicates a missing data point.


5.23
5.17
5.07
5.04
5.05
5.04
5.05


20.0
20.0
20.0
20.0
20.0
20.0
20.0


total in digest Riley total


ml
35.0
35.0
35.0
35.0
35.0
35.0
35.0

35.0

35.0

35.0

35.0

35.0

35.0
35.0
35.0
35.0
35.0
35.0


ml
25.0
25.0
25.0
25.0
25.0
25.0

25.0

25.0

25.0

25.0

25.0

25.0
25.0
25.0
25.0
25.0
25.0
25.0


Digest in
Murphy &


Spec. Calculated


Riley Conc.
mg
ml kg-
10.0 0.24
10.0 0.23
10.0 0.31
10.0 0.31
10.0 0.19
10.0 mdpa


10.0

10.0

10.0

10.0

10.0

10.0
10.0
10.0
10.0
10.0
10.0
10.0


[TP]


mg kg-'
16.70
15.66
21.17
20.59
12.74
mdp


0.12 8.22

0.11 7.98

0.14 9.52

0.14 9.54

0.12 8.18


0.13
0.28
0.27
0.16
0.17
0.12
0.12


8.42
18.72
18.40
10.81
11.73
8.02
8.15










Table A-7. Water extraction of inorganic phosphorus unaltered data.


Treatment Depth
cm
A. pintoi 0-5
A. pintoi 5-15
A. pintoi 15-30
A. pintoi 0-5
A. pintoi 5-15
A. pintoi 15-30
A. pintoi 0-5
A. pintoi 5-15
A. pintoi 15-30
C. repens 0-5
C. repens 5-15
C. repens 15-30
C. repens 0-5
C. repens 5-15
C. repens 15-30
C. repens 0-5
C. repens 5-15
C. repens 15-30
C. mucunoides 0-5
C. mucunoides 5-15
C. mucunoides 15-30
C. mucunoides 0-5
C. mucunoides 5-15
C. mucunoides 15-30


Spec.
Conc.
mg kg-1
0.07
0.04
0.05
0.12
0.05
0.07
0.05
0.06
0.08
0.26
0.07
0.06
0.03
0.02
0.02
0.05
0.05
0.04
0.30
0.05
0.03
0.02
0.02
0.05


Blank
ABS mean
mg kg1
0.05 0.00
0.03 0.00
0.03 0.00
0.08 0.00
0.03 0.00
0.05 0.00
0.04 0.00
0.04 0.00
0.05 0.00
0.17 0.00
0.05 0.00
0.04 0.00
0.02 0.00
0.02 0.00
0.02 0.00
0.03 0.00
0.03 0.00
0.03 0.00
0.20 0.00
0.03 0.00
0.02 0.00
0.01 0.00
0.02 0.00
0.03 0.00


Tube
g
10.38
10.32
10.34
10.29
10.23
10.37
10.36
10.36
10.38
10.31
10.28
10.32
10.23
10.36
10.31
10.36
10.35
10.26
10.25
10.27
10.33
10.28
10.34
10.22


Soil
g
2.55
2.18
2.01
2.04
2.03
2.00
2.28
2.19
2.22
2.03
2.07
2.08
2.38
2.05
2.07
2.27
2.16
1.99
2.22
2.29
2.07
2.06
2.04
2.11


Tube
+ Soil
g
12.93
12.50
12.35
12.33
12.26
12.37
12.64
12.55
12.60
12.34
12.35
12.40
12.61
12.41
12.38
12.63
12.51
12.25
12.47
12.56
12.40
12.34
12.38
12.33


Tube
+ Soil
+
H20
g
32.85
32.46
32.40
32.35
32.17
32.55
32.66
32.51
32.57
32.35
32.48
32.35
32.65
32.43
32.50
32.84
32.63
32.35
32.65
32.58
32.44
32.49
32.45
32.48


H20
g
19.92
19.96
20.05
20.02
19.91
20.18
20.02
19.96
19.97
20.01
20.13
19.95
20.04
20.02
20.12
20.21
20.12
20.10
20.18
20.02
20.04
20.15
20.07
20.15


H20 [P]
mg kg1
0.62
0.42
0.55
1.35
0.53
0.84
0.54
0.68
0.79
2.94
0.79
0.70
0.32
0.27
0.26
0.50
0.51
0.51
3.15
0.50
0.33
0.22
0.26
0.49


Remaining
H20 in
tube
g
4.50
3.73
2.58
3.47
2.90
3.55
3.63
3.01
2.37
4.30
3.20
3.12
3.28
2.56
2.54
3.23
2.18
4.73
2.69
3.10
2.25
4.91
2.51
2.66


[P] in
remaining
H20
mg kg-
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00
0.00
0.00










Table A-7 Continued


Treatment Depth
cm
C. mucunoides 0-5
C. mucunoides 5-15
C. mucunoides 15-30


macrocarpum

macrocarpum
C.
macrocarpum
macrocarum
macrocarpum
C.
macrocarpum
C.


macrocarpum
C.
macrocarpum
C.
macrocarpum


C.nsiformis
macrocarpum
C.


macrocarpum
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis


Spec.
Conc.
mg kg-1
0.03
0.04
0.05


0-5 0.11

5-15 0.04

15-30 0.04


Blank
ABS mean
mg kg1
0.02 0.00
0.03 0.00
0.03 0.00

0.07 0.00

0.03 0.00

0.03 0.00


0-5 0.09 0.06 0.00


5-15 0.04


0.03 0.00


15-30 0.06 0.04 0.00

0-5 0.05 0.04 0.00

5-15 0.09 0.06 0.00


15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5


0.04
0.06
0.06
0.04
0.23
0.05
0.05
0.11


0.03
0.04
0.04
0.02
0.15
0.03
0.03
0.07


0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


Tube
g
10.13
10.28
10.32


Soil
g
2.11
2.34
2.20


Tube
+ Soil
g
12.24
12.62
12.52


Tube
+ Soil
+
H20
g
32.44
32.67
32.59


H20
g
20.20
20.05
20.07


H20 [P]
mg kg1
0.33
0.44
0.48


10.35 2.03 12.38 32.43 20.05 1.25

10.27 2.07 12.34 32.39 20.05 0.46

10.34 2.01 12.35 32.37 20.02 0.51

10.11 2.02 12.13 32.27 20.14 0.98

10.37 2.04 12.41 32.51 20.10 0.45

10.31 2.28 12.59 32.58 19.99 0.60

10.33 2.03 12.36 32.44 20.08 0.60

10.34 2.01 12.35 32.53 20.18 1.02


10.34
10.22
10.38
10.28
10.26
10.34
10.35
10.31


2.01
2.02
2.02
2.03
2.05
2.02
2.12
2.04


12.35
12.24
12.40
12.31
12.31
12.36
12.47
12.35


32.46
32.44
32.43
32.53
32.46
32.50
32.67
32.55


20.11
20.20
20.03
20.22
20.15
20.14
20.20
20.20


0.45
0.68
0.68
0.42
2.62
0.57
0.57
1.28


Remaining
H20 in
tube
g
1.74
4.15
3.67


3.55

3.01

3.95

3.79

2.41

3.05

4.28

3.19

2.78
2.28
2.65
2.11
2.32
1.85
2.76
2.83


[P] in
remaining
H20
mg kg-
0.00
0.00
0.00


0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00
0.00
0.00
0.00
0.01
0.00
0.00
0.00










Table A-7 Continued


Spec.
Treatment Depth Conc.
cm mg kg-1
C. ensiformis 5-15 0.05
C. ensiformis 15-30 0.05
Control 0-5 0.11
Control 5-15 0.04
Control 15-30 0.05
Control 0-5 0.04
Control 5-15 0.04
Control 15-30 0.06
Control 0-5 0.07
Control 5-15 0.03
Control 15-30 0.03
Fertilized 0-5 0.43
Fertilized 5-15 0.08
Fertilized 15-30 0.03
Fertilized 0-5 0.15
Fertilized 5-15 0.05
Fertilized 15-30 0.10
Fertilized 0-5 0.19
Fertilized 5-15 0.13
Fertilized 15-30 0.04
Blank ndpa 0.00
Blank ndp 0.00
Blank ndp 0.00


Blank
ABS mean
mg kg-1
0.03 0.00
0.04 0.00
0.07 0.00
0.03 0.00
0.04 0.00
0.03 0.00
0.03 0.00
0.04 0.00
0.05 0.00
0.02 0.00
0.02 0.00
0.29 0.00
0.05 0.00
0.02 0.00
0.10 0.00
0.03 0.00
0.07 0.00
0.13 0.00
0.09 0.00
0.03 0.00
0.00 0.00
0.00 0.00
0.00 0.00


a ndp indicates that there is no data point.


Tube Soil
g g
10.32 2.05
10.34 2.07
10.37 2.00
10.23 2.07
10.35 2.07
10.27 2.07
10.36 2.07
10.35 2.06
10.34 2.02
10.36 2.00
10.34 2.03
10.30 2.01
10.27 2.01
10.38 2.00
10.34 2.03
10.31 2.09
10.31 2.06
10.32 2.04
10.35 2.00
10.25 2.06
10.30 0.00
10.39 0.00
10.36 0.00


Tube
+ Soil
Tube +
+ Soil H20


g
12.37
12.41
12.37
12.30
12.42
12.34
12.43
12.41
12.36
12.36
12.37
12.31
12.28
12.38
12.37
12.40
12.37
12.36
12.35
12.31
10.30
10.39
10.36


g
32.44
32.71
32.48
32.36
32.54
32.50
32.71
32.57
32.50
32.46
32.52
32.38
32.47
32.68
32.59
32.64
32.50
32.51
32.49
32.63
ndp
ndp
ndp


H20 H20 [P]
g mg kg-1
20.07 0.51
20.30 0.61
20.11 1.23
20.06 0.49
20.12 0.59
20.16 0.43
20.28 0.43
20.16 0.67
20.14 0.78
20.10 0.36
20.15 0.32
20.07 4.93
20.19 0.89
20.30 0.39
20.22 1.66
20.24 0.54
20.13 1.17
20.15 2.19
20.14 1.52
20.32 0.43
22.29 ndp
22.15 ndp
22.18 ndp


Remaining [P] in
H20 in remaining
tube H20
g mg kg-1
1.77 0.00
3.01 0.00
3.11 0.00
2.97 0.00
3.23 0.00
2.61 0.00
2.82 0.00
2.33 0.00
5.12 0.00
2.81 0.00
3.17 0.00
2.47 0.01
2.78 0.00
1.86 0.00
2.43 0.00
2.78 0.00
3.52 0.00
3.78 0.01
2.86 0.00
2.60 0.00
0.15 ndp
0.06 ndp
0.06 ndp










Table A-8. One molar NH4C1 extraction of inorganic phosphorus unaltered data.
P Final
Spec. Blank Tube NH4Cl Remain remaining NH4Cl
Treatment Depth conc. ABS mean Tube Soil + soil NH4Cl [P] NH4Cl in NH4Cl [P]
cm mg kg-1 mg kg-1 g g g g mg kg-1 ml mg kg-1 mg kg-1


A. pintoi 0-5 0.01 0.01
A. pintoi 5-15 0.00 0.00
A. pintoi 15-30 0.00 0.00
A. pintoi 0-5 0.01 0.01
A. pintoi 5-15 0.00 0.00
A. pintoi 15-30 0.00 0.00
A. pintoi 0-5 0.00 0.00
A. pintoi 5-15 0.00 0.00
A. pintoi 15-30 0.00 0.00
C. repens 0-5 0.04 0.03
C. repens 5-15 0.01 0.01
C. repens 15-30 0.11 0.07
C. repens 0-5 0.00 0.00
C. repens 5-15 0.00 0.00
C. repens 15-30 0.00 0.00
C. repens 0-5 0.00 0.00
C. repens 5-15 0.00 0.00
C. repens 15-30 0.01 0.01
C. mucunoides 0-5 0.00 0.00
C. mucunoides 5-15 0.00 0.00
C. mucunoides 15-30 0.00 0.00
C. mucunoides 0-5 0.00 0.00
C. mucunoides 5-15 0.00 0.00
C. mucunoides 15-30 0.00 0.00
C. mucunoides 0-5 0.00 0.00


0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


10.38
10.32
10.34
10.29
10.23
10.37
10.36
10.36
10.38
10.31
10.28
10.32
10.23
10.36
10.31
10.36
10.35
10.26
10.25
10.27
10.33
10.28
10.34
10.22
10.13


2.55
2.18
2.01
2.04
2.03
2.00
2.28
2.19
2.22
2.03
2.07
2.08
2.38
2.05
2.07
2.27
2.16
1.99
2.22
2.29
2.07
2.06
2.04
2.11
2.11


12.93
12.50
12.35
12.33
12.26
12.37
12.64
12.55
12.60
12.34
12.35
12.40
12.61
12.41
12.38
12.63
12.51
12.25
12.47
12.56
12.40
12.34
12.38
12.33
12.24


20.26
20.26
20.43
20.33
20.35
20.27
20.39
20.34
20.41
20.37
20.34
20.33
20.33
20.26
20.39
20.34
20.51
20.42
20.29
20.44
20.33
20.26
20.32
20.33
20.32


0.12
0.01
0.01
0.15
0.01
0.01
0.01
0.01
0.01
0.49
0.09
1.23
0.01
0.01
0.04
0.01
0.05
0.08
0.01
0.03
0.01
0.02
0.01
0.01
0.01


2.12
2.09
1.67
2.34
1.43
1.9
2.44
1.32
1.2
1.85
1.3
1.46
1.51
1.59
1.49
2.06
1.57
1.01
1.39
2.09
1.46
1.78
2.01
1.87
1.3


0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


0.12
0.01
0.01
0.15
0.01
0.01
0.01
0.01
0.01
0.49
0.09
1.22
0.01
0.01
0.04
0.01
0.05
0.08
0.01
0.03
0.01
0.02
0.01
0.01
0.01










Table A-8 Continued


Treatment


C. mucunoides
C. mucunoides
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
Control
Control
Control
Control
Control


Depth
cm
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15


Spec.
conc.
mg kg-1
0.00
0.00
0.02
0.00
0.00
0.02
0.00
0.00
0.00
0.04
0.00
0.00
0.00
0.00
0.05
0.01
0.00
0.03
0.00
0.00
0.01
0.00
0.00
0.03
0.02


Blank
ABS mean
mg kg1
0.00 0.00
0.00 0.00
0.01 0.00
0.00 0.00
0.00 0.00
0.01 0.00
0.00 0.00
0.00 0.00
0.01 0.00
0.03 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.00 0.00
0.03 0.00
0.01 0.00
0.00 0.00
0.02 0.00
0.00 0.00
0.00 0.00
0.01 0.00
0.00 0.00
0.00 0.00
0.02 0.00
0.02 0.00


Tube
g
10.28
10.32
10.35
10.27
10.34
10.11
10.37
10.31
10.33
10.34
10.34
10.22
10.38
10.28
10.26
10.34
10.35
10.31
10.32
10.34
10.37
10.23
10.35
10.27
10.36


Soil
g
2.34
2.20
2.03
2.07
2.01
2.02
2.04
2.28
2.03
2.01
2.01
2.02
2.02
2.03
2.05
2.02
2.12
2.04
2.05
2.07
2.00
2.07
2.07
2.07
2.07


Tube
+ soil
g
12.62
12.52
12.38
12.34
12.35
12.13
12.41
12.59
12.36
12.35
12.35
12.24
12.40
12.31
12.31
12.36
12.47
12.35
12.37
12.41
12.37
12.30
12.42
12.34
12.43


NH4Cl
g
20.14
20.19
20.19
20.20
20.32
20.26
20.24
20.18
20.32
20.20
20.22
20.30
20.46
20.27
20.29
20.38
20.18
20.12
20.24
20.36
20.17
20.25
20.16
20.37
20.28


NH4Cl
[P]
mg kg-1
0.01
0.01
0.19
0.01
0.01
0.21
0.01
0.01
0.06
0.44
0.02
0.02
0.01
0.01
0.60
0.10
0.03
0.33
0.01
0.01
0.07
0.00
0.03
0.29
0.26


Remain
NH4Cl
ml
1.42
1.17
2.15
1.81
1.27
1.57
1.38
0.94
1.3
1.73
1.61
1.97
2.55
1.76
2.85
1.34
1.58
2.54
1.67
1.5
1.27
1.34
1.5
2.86
3.02


P Final
remaining NH4Cl
in NH4Cl [P]
mg kg-1 mg kg-1
0.00 0.01
0.00 0.01
0.00 0.19
0.00 0.01
0.00 0.01
0.00 0.21
0.00 0.01
0.00 0.01
0.00 0.06
0.00 0.44
0.00 0.02
0.00 0.02
0.00 0.01
0.00 0.01
0.00 0.60
0.00 0.10
0.00 0.03
0.00 0.33
0.00 0.01
0.00 0.01
0.00 0.07
0.00 0.00
0.00 0.03
0.00 0.29
0.00 0.26










Table A-8 Continued


Depth
cm
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15


Spec.
cone.
mg kg-1
0.00
0.01
0.00
0.00
0.06
0.00
0.00
0.03
0.00
0.00
0.06
0.02


Control
Control
Control
Control
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized


Blank
ABS mean
mg kg1
0.00 0.00
0.01 0.00
0.00 0.00
0.00 0.00
0.04 0.00
0.00 0.00
0.00 0.00
0.02 0.00
0.00 0.00
0.00 0.00
0.04 0.00
0.02 0.00
0.01 0.00


Tube
g
10.35
10.34
10.36
10.34
10.30
10.27
10.38
10.34
10.31
10.31
10.32
10.35


Soil
g
2.06
2.02
2.00
2.03
2.01
2.01
2.00
2.03
2.09
2.06
2.04
2.00


Tube
+ soil
g
12.41
12.36
12.36
12.37
12.31
12.28
12.38
12.37
12.40
12.37
12.36
12.35


NH4Cl
g
20.22
20.27
20.17
20.30
20.31
18.35
20.25
20.35
20.36
20.34
20.30
20.18


NH4Cl
[P]
mg kg-1
0.01
0.06
0.01
0.01
0.74
0.05
0.01
0.33
0.03
0.01
0.69
0.28


10.25 2.06 12.31 20.30 0.07


Remain
NH4Cl
ml
1.31
1.81
1.62
1.81
2.74
1.35
1.92
1.33
1.46
1.29
1.61
1.61


rema
in N
mg k
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


1.49 0.00


P Final
ining NH4Cl
H4C1 [P]
g-1 mg kg-1
0.01
0.06
0.01
0.01
0.74
0.05
0.01
0.33
0.03
0.01
0.69
0.28
0.07


Treatment


15-30 0.01










Table A-9. One-tenth molar NaOH extraction of inorganic phosphorus unaltered data.
Sample Sample
in in NaOH
Mean Y Spec. Digest digestion Murphy Murphy extractable
Treatment Block Depth ABS blank intercept conc. NaOH solution solution & Riley & Riley [Pi]
# cm mg kg-1 g g ml ml ml mg kg-1


A. pintoi 1 0-5 0.29 0 1.64
A. pintoi 1 5-15 0.19 0 1.64
A. pintoi 1 15-30 mdpa 0 1.64
A. pintoi 2 0-5 mdp 0 1.64
A. pintoi 2 5-15 mdp 0 1.64
A. pintoi 2 15-30 mdp 0 1.64
A. pintoi 3 0-5 0.18 0 1.64
A. pintoi 3 5-15 0.26 0 1.64
A. pintoi 3 15-30 0.20 0 1.64
C. repens 1 0-5 0.59 0 1.64
C. repens 1 5-15 0.64 0 1.64
C. repens 1 15-30 0.36 0 1.64
C. repens 2 0-5 0.38 0 1.64
C. repens 2 5-15 0.33 0 1.64
C. repens 2 15-30 0.30 0 1.64
C. repens 3 0-5 0.25 0 1.64
C. repens 3 5-15 0.28 0 1.64
C. repens 3 15-30 0.27 0 1.64
C. mucunoides 1 0-5 0.67 0 1.64
C. mucunoides 1 5-15 0.20 0 1.64
C. mucunoides 1 15-30 0.33 0 1.64
C. mucunoides 2 0-5 0.36 0 1.64
C. mucunoides 2 5-15 0.14 0 1.64
C. mucunoides 2 15-30 0.13 0 1.64


0.48
0.32
mdp
mdp
mdp
mdp
0.29
0.42
0.33
0.96
1.05
0.59
0.62
0.54
0.49
0.41
0.46
0.44
1.10
0.33
0.55
0.59
0.23
0.22


19.95
19.99
20.12
19.86
20.07
19.90
20.15
19.99
20.13
20.11
20.25
20.10
19.99
20.02
20.17
20.03
20.19
20.08
20.06
20.08
19.93
19.98
19.99
19.97


10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39


10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00


5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70


1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00


22.08
17.35
mdp
mdp
mdp
mdp
15.23
22.70
17.87
56.32
60.65
33.80
30.64
31.26
28.46
21.26
25.60
26.34
59.07
17.32
31.33
34.01
13.25
12.39










Table A-9 Continued


Treatment


C. mucunoides
C. mucunoides
C. mucunoides
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
C.ensiformis
Control
Control


Mean Y Spec.
Block Depth ABS blank intercept conc.
# cm mg kg-1
3 0-5 0.34 0 1.64 0.56
3 5-15 0.28 0 1.64 0.45
3 15-30 0.21 0 1.64 0.34
1 0-5 0.30 0 1.64 0.50
1 5-15 0.30 0 1.64 0.49
1 15-30 0.29 0 1.64 0.48
2 0-5 0.42 0 1.64 0.69
2 5-15 0.28 0 1.64 0.46
2 15-30 0.27 0 1.64 0.44
3 0-5 0.25 0 1.64 0.41
3 5-15 0.33 0 1.64 0.54
3 15-30 0.20 0 1.64 0.33
1 0-5 0.56 0 1.64 0.92
1 5-15 0.21 0 1.64 0.35
1 15-30 0.22 0 1.64 0.35
2 0-5 0.22 0 1.64 0.36
2 5-15 0.36 0 1.64 0.59
2 15-30 0.23 0 1.64 0.38
3 0-5 0.20 0 1.64 0.32
3 5-15 0.24 0 1.64 0.39
3 15-30 0.19 0 1.64 0.31
1 0-5 0.63 0 1.64 1.04
1 5-15 0.45 0 1.64 0.73


NaOH
g
20.12
19.99
20.07
20.16
20.13
19.91
20.09
20.01
19.86
20.07
20.08
19.93
20.00
20.18
19.94
20.05
20.15
19.97
20.14
19.99
20.04
19.97
20.12


Digest
solution
g
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39
10.39


Sample
in
digestio
n
solution
ml
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00
10.00


Murphy
& Riley
ml
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70
5.70


Sample
in
Murphy
& Riley
ml
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00


NaOH
extractable
[Pi]
mg kg-1
31.51
22.95
18.55
29.35
28.31
28.20
40.53
26.96
22.50
23.93
31.70
19.58
54.13
20.47
20.52
20.80
35.03
21.13
18.78
22.28
17.80
61.26
42.11










Table A-9 Continued
Sample Sample
Y in in NaOH
Mean intercep Spec. Digest digestion Murphy Murphy extractable
Treatment Block Depth ABS blank t conc. NaOH solution solution & Riley & Riley [Pi]
# cm mg kg-1 g g ml ml ml mg kg-1
Control 1 15-30 0.47 0 1.64 0.77 19.97 10.39 10.00 5.70 1.00 43.78
Control 2 0-5 0.13 0 1.64 0.21 20.10 10.39 10.00 5.70 1.00 12.27
Control 2 5-15 0.11 0 1.64 0.19 20.13 10.39 10.00 5.70 1.00 10.74
Control 2 15-30 0.28 0 1.64 0.47 20.12 10.39 10.00 5.70 1.00 26.97
Control 3 0-5 0.30 0 1.64 0.49 19.94 10.39 10.00 5.70 1.00 28.61
Control 3 5-15 0.23 0 1.64 0.38 19.88 10.39 10.00 5.70 1.00 22.17
Control 3 15-30 0.12 0 1.64 0.20 19.97 10.39 10.00 5.70 1.00 11.74
Fertilized 1 0-5 0.37 0 1.64 0.61 20.01 10.39 10.00 5.70 1.00 35.94
Fertilized 1 5-15 0.67 0 1.64 1.10 20.00 10.39 10.00 5.70 1.00 64.78
Fertilized 1 15-30 0.20 0 1.64 0.34 19.99 10.39 10.00 5.70 1.00 19.88
Fertilized 2 0-5 0.61 0 1.64 1.00 20.00 10.39 10.00 5.70 1.00 58.53
Fertilized 2 5-15 0.42 0 1.64 0.69 20.12 10.39 10.00 5.70 1.00 39.22
Fertilized 2 15-30 0.27 0 1.64 0.45 20.10 10.39 10.00 5.70 1.00 25.80
Fertilized 3 0-5 0.45 0 1.64 0.74 20.04 10.39 10.00 5.70 1.00 42.90
Fertilized 3 5-15 0.30 0 1.64 0.50 19.95 10.39 10.00 5.70 1.00 29.37
Fertilized 3 15-30 0.24 0 1.64 0.40 20.10 10.39 10.00 5.70 1.00 22.93
a mdp indicates a missing data point










Table A-10. Digest of 0.1 M NaOH supernatant for the quantification of total 0.1 M NaOH
extractable phosphorus unaltered data.
0.1M
0.1 M NaOH
Treatment Depth Soil ,
NaOH Volume Total Dilute Spec. extractable
Sample of H20 sample times conc. [TP]
cm g g ml ml ml mg kg1 mg kg-1
A. pintoi 0-5 20.15 2.02 0.12 10.07 10.19 85.43 0.03 24.95
A. pintoi 0-5 20.15 2.04 0.12 10.07 10.19 85.43 0.02 17.72
A. pintoi 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.04 33.12
A. pintoi 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.04 31.02
A. pintoi 15-30 20.15 2.15 0.12 10.07 10.19 85.43 0.03 24.31
A. pintoi 15-30 20.15 2.06 0.12 10.07 10.19 85.43 0.03 25.05
A. pintoi 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.05 45.06
A. pintoi 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 48.48
A. pintoi 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.04 32.39
A. pintoi 5-15 20.15 2.12 0.12 10.07 10.19 85.43 0.04 30.62
A. pintoi 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.04 34.18
A. pintoi 15-30 20.15 2.00 0.12 10.07 10.19 85.43 0.02 21.42
A. pintoi 0-5 20.15 2.10 0.12 10.07 10.19 85.43 0.05 39.26
A. pintoi 0-5 20.15 2.07 0.12 10.07 10.19 85.43 0.04 35.73
A. pintoi 5-15 20.15 2.14 0.12 10.07 10.19 85.43 0.02 18.56
A. pintoi 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 22.56
A. pintoi 15-30 20.15 2.06 0.12 10.07 10.19 85.43 0.04 29.93
A. pintoi 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.04 32.76
C. repens 0-5 20.15 2.03 0.12 10.07 10.19 85.43 0.04 31.46
C. repens 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 55.55
C. repens 5-15 20.15 2.00 0.12 10.07 10.19 85.43 0.08 66.03
C. repens 5-15 20.15 2.01 0.12 10.07 10.19 85.43 0.05 40.10
C. repens 15-30 20.15 2.08 0.12 10.07 10.19 85.43 0.03 25.38
C. repens 15-30 20.15 2.03 mdpa mdp mdp mdp mdp mdp
C. repens 0-5 20.15 2.11 0.12 10.07 10.19 85.43 0.05 41.35
C. repens 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 45.78
C. repens 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.03 27.05
C. repens 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 26.40
C. repens 15-30 20.15 2.12 0.12 10.07 10.19 85.43 0.02 18.48
C. repens 15-30 20.15 2.04 0.12 10.07 10.19 85.43 0.03 22.17
C. repens 0-5 20.15 2.08 0.12 10.07 10.19 85.43 0.05 38.93
C. repens 0-5 20.15 2.04 0.12 10.07 10.19 85.43 0.04 36.87
C. repens 5-15 20.15 2.04 0.12 10.07 10.19 85.43 0.03 28.33
C. repens 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 23.17
C. repens 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.03 22.42









Table A-10 Continued
0.1M
0.1 M NaOH
Treatment Depth NaO Soi Volume Total Dilute Spec. extractable
Sample of H20 sample times conc. [TP]
cm g g ml ml ml mg kg1 mg kg-1


C. repens 15-30 20.15 2.07 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.08 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.08 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.05 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.07 0.12 10.07 10.19 85.43
C. mucunoides 15-30 20.15 2.06 mdp mdp mdp mdp
C. mucunoides 15-30 20.15 2.02 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.01 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.14 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.02 0.12 10.07 10.19 85.43
C. mucunoides 15-30 20.15 2.02 0.12 10.07 10.19 85.43
C. mucunoides 15-30 20.15 2.05 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.15 0.12 10.07 10.19 85.43
C. mucunoides 0-5 20.15 2.09 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43
C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43
C. mucunoides 15-30 20.15 2.01 0.12 10.07 10.19 85.43
C. mucunoides 15-30 20.15 2.09 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.04 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.02 mdp mdp mdp mdp
C. macrocarpum 5-15 20.15 2.01 0.12 10.07 10.19 85.43
C. macrocarpum 5-15 20.15 2.02 0.12 10.07 10.19 85.43
C. macrocarpum 15-30 20.15 2.00 0.12 10.07 10.19 85.43
C. macrocarpum 15-30 20.15 2.08 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.01 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.14 0.12 10.07 10.19 85.43
C. macrocarpum 5-15 20.15 2.03 0.12 10.07 10.19 85.43
C. macrocarpum 5-15 20.15 2.14 0.12 10.07 10.19 85.43
C. macrocarpum 15-30 20.15 2.09 0.12 10.07 10.19 85.43
C. macrocarpum 15-30 20.15 2.13 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.01 0.12 10.07 10.19 85.43
C. macrocarpum 0-5 20.15 2.03 0.12 10.07 10.19 85.43
C. macrocarpum 5-15 20.15 2.02 0.12 10.07 10.19 85.43
C. macrocarpum 5-15 20.15 2.07 0.12 10.07 10.19 85.43
C. macrocarpum 15-30 20.15 2.10 0.12 10.07 10.19 85.43


0.02
0.02
0.04
0.04
0.04
mdp
0.01
0.05
0.05
0.02
0.03
0.05
0.04
0.05
0.07
0.05
0.04
0.03
0.04
0.05
mdp
0.04
0.04
0.03
0.04
0.04
0.06
0.03
0.03
0.02
0.03
0.05
0.05
0.03
0.04
0.02


13.49
12.49
30.45
31.16
33.97
mdp
5.19
44.84
44.03
20.07
29.43
42.34
33.69
39.51
54.97
38.59
32.48
28.85
29.16
43.78
mdp
30.45
31.90
29.93
30.93
33.70
48.49
21.59
24.20
20.49
23.48
41.52
43.95
26.99
29.05
19.94









Table A-10 Continued
0.1M
0.1 M NaOH
Treatment Depth NaOH Soil Volume Total Dilute Spec. extractable
Sample of H20 sample times conc. [TP]
cm g g ml ml ml mg kg1 mg kg-1


C. macrocarpum 15-30 20.15 2.03 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.11 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.03 0.12 10.07 10.19 85.43
C. ensiformis 5-15 20.15 2.01 mdp mdp mdp mdp
C. ensiformis 5-15 20.15 2.09 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.02 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.13 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.00 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.00 0.12 10.07 10.19 85.43
C. ensiformis 5-15 20.15 2.10 0.12 10.07 10.19 85.43
C. ensiformis 5-15 20.15 2.05 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.10 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.07 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.01 0.12 10.07 10.19 85.43
C. ensiformis 0-5 20.15 2.01 0.12 10.07 10.19 85.43
C. ensiformis 5-15 20.15 2.02 0.12 10.07 10.19 85.43
C. ensiformis 5-15 20.15 2.11 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.08 0.12 10.07 10.19 85.43
C. ensiformis 15-30 20.15 2.08 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.09 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.01 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.06 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43
Control 15-30 20.15 2.13 0.12 10.07 10.19 85.43
Control 15-30 20.15 2.03 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.14 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.00 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43
Control 15-30 20.15 2.14 0.12 10.07 10.19 85.43
Control 15-30 20.15 2.01 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.02 0.12 10.07 10.19 85.43
Control 0-5 20.15 2.07 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.13 0.12 10.07 10.19 85.43
Control 5-15 20.15 2.10 0.12 10.07 10.19 85.43
Control 15-30 20.15 2.11 0.12 10.07 10.19 85.43


0.03
0.07
0.07
mdp
0.05
0.03
0.02
0.06
0.06
0.04
0.04
0.03
0.03
0.04
0.05
0.03
0.04
0.03
0.03
0.05
0.05
0.04
0.03
0.05
0.04
0.04
0.04
0.04
0.02
0.03
0.02
0.03
0.03
0.03
0.03
0.04


26.75
56.65
61.46
mdp
43.33
25.52
18.19
47.88
47.75
29.92
30.71
24.21
27.42
32.46
44.01
25.02
33.26
20.90
27.19
42.49
43.34
31.16
29.05
37.44
37.11
32.02
32.94
29.99
19.91
21.21
16.97
22.98
21.82
28.17
25.55
30.94










Table A-10 Continued
0.1M
0.1 M NaOH
Treatment Depth NaOH Soil Volume Total Dilute Spec. extractable
Sample of H20 sample times conc. [TP]
cm g g ml ml ml mg kg- mg kg-


Control
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Blank
Blank
Blank


15-30
0-5
0-5
5-15
5-15
15-30
15-30
0-5
0-5
5-15
5-15
15-30
15-30
0-5
0-5
5-15
5-15
15-30
15-30


20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15
20.15


2.03
2.05
2.06
2.05
2.09
2.00
2.02
2.14
2.03
2.09
2.01
2.01
2.02
2.06
2.07
2.06
2.05
2.04
2.05
0.00
0.00
0.00


a mdp indicates a missing data point.


0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12
0.12


10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07
10.07


10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19
10.19


85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43
85.43


0.04
0.09
0.09
0.08
0.06
0.03
0.05
0.06
0.06
0.05
0.04
0.04
0.05
0.04
0.04
0.03
0.02
0.02
0.02
0.00
0.00
0.00


37.74
77.91
72.44
69.87
45.66
23.54
44.68
48.29
50.95
39.35
37.45
34.93
41.34
32.18
35.94
23.47
18.42
18.46
14.38
mdp
mdp
mdp










Table A- 1. Half molar HC1 extraction of inorganic phosphorus unaltered data.
Sample HCI
Spec. Y Mean Murphy in extractable
Treatment Depth conc. ABS intercept blank Soil HC1 & Riley M&R [P]
cm mg kg1 mg kg1 g g ml ml mg kg-


A. pintoi
A. pintoi
A. pintoi
C. ensiformis
C. ensiformis
C. ensiformis
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. mucunoides
C. mucunoides
C. mucunoides
C. repens
C. repens
C. repens
Control
Control
Control
Fertilized
Fertilized
Fertilized
A. pintoi
A. pintoi
A. pintoi
C. ensiformis


0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
15-30
15-30
15-30
15-30


1.81
2.06
2.27
1.13
0.96
0.58
0.99
2.52
2.77
1.59
1.43
0.11
1.48
0.76
0.94
2.38
3.33
2.78
1.36
2.62
1.75
3.17
3.22
1.46
1.72


1.14
1.30
1.43
0.71
0.60
0.36
0.63
1.58
1.74
1.00
0.90
0.07
0.93
0.48
0.59
1.50
2.09
1.75
0.85
1.65
1.10
1.99
2.03
0.92
1.09


1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59


0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


2.55
2.04
2.28
2.02
2.05
2.04
2.03
2.02
2.03
2.22
2.06
2.11
2.03
2.38
2.27
2.00
2.07
2.02
2.01
2.03
2.04
2.01
2.00
2.22
2.03


19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70


6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00


5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00


16.77
23.85
23.51
13.24
11.05
6.69
11.57
29.46
32.23
16.89
16.43
1.22
17.22
7.59
9.82
28.14
37.99
32.58
15.96
30.54
20.31
37.23
38.10
15.50
20.08










Table A-11 Continued


Sample HC1


Treatment


C. ensiformis
C. ensiformis
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. mucunoides
C. mucunoides
C. mucunoides
C. repens
C. repens
C. repens
Control
Control
Control
Fertilized
Fertilized
Fertilized
A. pintoi
A. pintoi
A. pintoi
C. ensiformis
C. ensiformis
C. ensiformis
C. macrocarpum
C. macrocarpum


Depth
cm
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
15-30
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15


Spec.
cone.
mg kg-i
1.76
3.67
0.59
1.68
3.46
1.67
0.67
0.29
1.97
1.40
1.13
1.60
0.21
1.78
2.66
1.73
1.82
2.78
3.03
3.20
1.84
0.70
1.71
0.48
2.39


Y Mean
ABS intercept blank
mg kg-
1.11 1.59 0.00
2.31 1.59 0.00
0.37 1.59 0.00
1.06 1.59 0.00
2.18 1.59 0.00
1.05 1.59 0.00
0.42 1.59 0.00
0.18 1.59 0.00
1.24 1.59 0.00
0.88 1.59 0.00
0.71 1.59 0.00
1.01 1.59 0.00
0.13 1.59 0.00
1.12 1.59 0.00
1.68 1.59 0.00
1.09 1.59 0.00
1.15 1.59 0.00
1.75 1.59 0.00
1.91 1.59 0.00
2.01 1.59 0.00
1.16 1.59 0.00
0.44 1.59 0.00
1.08 1.59 0.00
0.30 1.59 0.00
1.51 1.59 0.00


Soil
g
2.12
2.07
2.01
2.28
2.01
2.07
2.11
2.20
2.08
2.07
1.99
2.07
2.06
2.03
2.00
2.06
2.06
2.18
2.03
2.19
2.02
2.02
2.05
2.07
2.04


HCI
g
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70


Murphy
& Riley
ml
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00


in
M&R
ml
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00


extractable
[P]
mg kg-1
19.63
41.96
6.94
17.46
40.68
19.11
7.54
3.08
22.36
15.96
13.45
18.32
2.36
20.77
31.47
19.82
20.90
30.14
35.27
34.54
21.57
8.20
19.71
5.44
27.75










Table A-11 Continued


Treatment

C. macrocarpum
C. mucunoides
C. mucunoides
C. mucunoides
C. repens
C. repens
C. repens
Control
Control
Control
Fertilized
Fertilized
Fertilized
Blank
Blank
Blank


Depth
cm
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15
5-15


Spec.
cone.
mg kg-i
1.39
1.14
mdpa
3.55
2.35
1.34
4.05
1.61
3.11
1.67
2.14
1.66
1.80
0.00
0.00
mdp


Y
ABS intercept


0.87
0.72
mdp
2.24
1.48
0.84
2.55
1.02
1.96
1.05
1.35
1.04
1.14
0.00
0.00
mdp


a mdp indicates a missing data point.


1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59
1.59


Mean
blank
mg kg-
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00


Soil
g
2.01
2.29
2.04
2.34
2.07
2.05
2.16
2.07
2.07
2.00
2.01
2.09
2.00
mdp
mdp
mdp


HCI
g
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70
19.70


Murphy
& Riley
ml
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00
6.00


Sample HC1
in extractable
M&R [P]
ml mg kg-1
5.00 16.32
5.00 11.76
5.00 mdp
5.00 35.91
5.00 26.88
5.00 15.46
5.00 44.33
5.00 18.43
5.00 35.50
5.00 19.72
5.00 25.21
5.00 18.76
5.00 21.32
5.00 mdp
5.00 mdp
5.00 mdp









Table A-12. Six molar HC1 digest and extraction of inorganic phosphorus from residual soil unaltered data.


Treatment

A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides


Mean
Depth ABS. blank
cm mg kg-1
0-5 mdpa 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0
15-30 mdp 0
0-5 mdp 0
5-15 mdp 0


Y
intercept Spec.
ofR2 conc.


1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75


mg kg-1
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp


Sample
Post in
digest Color- color- 6 M HC1
solution metric metric extractable
Glass Soil volume solution solution [P]


g g ml
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50
mdp mdp 50


ml
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4


mg kg-
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp
mdp










Table A-12 Continued


Treatment

C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
Control


Mean
Depth ABS. blank
cm mg kg-1
15-30 mdp 0
0-5 mdp 0
5-15 0.23 0
15-30 0.42 0
0-5 0.21 0
5-15 0.18 0
15-30 0.19 0
0-5 0.33 0
5-15 0.31 0
15-30 0.31 0
0-5 0.18 0
5-15 0.23 0
15-30 0.31 0
0-5 0.49 0
5-15 0.63 0
15-30 0.29 0
0-5 0.43 0
5-15 0.18 0
15-30 0.23 0
0-5 0.33 0
5-15 0.31 0
15-30 0.34 0
0-5 0.16 0


intercept Spec.
ofR2 conc.
mg kg-1
1.75 mdp
1.75 mdp
1.75 0.40
1.75 0.73
1.75 0.36
1.75 0.32
1.75 0.32
1.75 0.57
1.75 0.53
1.75 0.55
1.75 0.32
1.75 0.41
1.75 0.54
1.75 0.85
1.75 1.10
1.75 0.50
1.75 0.75
1.75 0.31
1.75 0.40
1.75 0.57
1.75 0.55
1.75 0.60
1.75 0.28


Glass
g
mdp
mdp
28.80
31.63
30.06
28.74
29.18
28.73
28.67
31.40
29.02
31.27
31.03
31.85
28.56
30.58
28.62
31.15
28.47
28.62
31.55
30.75
28.76


Soil
g
mdp
mdp
0.22
0.21
0.23
0.21
0.22
0.22
0.21
0.21
0.22
0.21
0.21
0.20
0.22
0.24
0.21
0.22
0.21
0.22
0.21
0.23
0.22


Post
digest
solution
volume
ml
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50


Color-
metric
solution
ml
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4


Sample
in
color-
metric
solution
ml
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5


6M HC1
extractable
[P]
mg kg1
mdp
mdp
203.29
402.49
181.61
176.85
170.61
293.86
292.99
299.02
164.73
224.00
285.70
476.16
559.50
240.00
410.05
162.05
222.30
298.09
298.26
293.08
149.36










Table A-12 Continued


Treatment

Control
Control
Control
Control
Control
Control
Control
Control
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized


Mean
Depth ABS. blank
cm mg kg-1
5-15 0.17 0
15-30 0.25 0
0-5 0.34 0
5-15 0.34 0
15-30 0.33 0
0-5 0.14 0
5-15 0.29 0
15-30 0.39 0
0-5 0.61 0
5-15 0.40 0
15-30 0.36 0
0-5 0.24 0
5-15 0.22 0
15-30 0.39 0
0-5 0.32 0
5-15 0.37 0
15-30 0.29 0


a mdp indicates a missing data point.


intercept Spec.
ofR2 conc.
mg kg-1
1.75 0.29
1.75 0.44
1.75 0.59
1.75 0.59
1.75 0.58
1.75 0.24
1.75 0.50
1.75 0.67
1.75 1.07
1.75 0.70
1.75 0.62
1.75 0.43
1.75 0.39
1.75 0.68
1.75 0.56
1.75 0.65
1.75 0.50


Glass
g
28.63
28.50
30.69
28.69
28.70
28.69
30.95
28.92
32.21
28.28
28.55
30.53
29.79
28.73
28.76
29.08
28.61


Post
digest
solution
volume
ml
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50
50


Soil
g
0.23
0.22
0.24
0.23
0.22
0.23
0.24
0.22
0.22
0.22
0.22
0.22
0.20
0.24
0.22
0.21
0.21


Color-
metric
solution
ml
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4
11.4


Sample
in
color-
metric
solution
ml
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5


6M HC1
extractable
[P]
mg kg1
148.52
226.87
284.66
292.60
304.36
119.28
240.93
347.73
553.02
366.99
318.36
224.69
217.63
324.79
294.49
353.71
271.77










digest and extraction of inorganic phosphorus from air-dried soil unaltered data.


Treatment

A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
A. pintoi
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. repens
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides
C. mucunoides


Depth
cm
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5


Mean
ABS blank
mg kg-1
0.27 0.00
0.21 0.00
0.16 0.00
0.23 0.00
0.21 0.00
0.22 0.00
0.21 0.00
0.20 0.00
0.23 0.00
0.44 0.00
0.33 0.00
0.41 0.00
0.26 0.00
0.25 0.00
0.23 0.00
0.21 0.00
0.22 0.00
0.22 0.00
0.25 0.00
0.22 0.00
0.29 0.00
0.24 0.00
0.25 0.00
0.22 0.00
0.16 0.00


Y
Intercept

1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75


Spec.
cone.
mg kg1
0.47
0.37
0.28
0.41
0.37
0.38
0.37
0.35
0.39
0.78
0.58
0.72
0.46
0.43
0.40
0.38
0.39
0.38
0.43
0.39
0.50
0.41
0.43
0.39
0.27


Glass
g
29.42
31.67
31.59
30.82
28.37
28.62
28.66
28.66
28.77
28.81
29.20
28.55
28.60
30.94
29.18
28.98
29.68
28.76
29.91
30.90
28.75
28.67
28.80
32.00
28.71


Soil
g
0.21
0.21
0.22
0.24
0.23
0.21
0.22
0.23
0.21
0.20
0.21
0.20
0.22
0.23
0.21
0.22
0.20
0.22
0.22
0.21
0.21
0.23
0.22
0.22
0.22


Post
digest
solution
ml
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00


Murphy
& Riley
ml
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40


Sample
in
M&R
ml
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00


6.0 M HC1
extractable
[P]
mg kg-
251.11
203.16
149.33
196.84
183.79
205.30
193.61
177.44
217.60
434.34
308.52
401.80
234.55
213.47
218.95
197.66
221.24
201.54
229.87
205.28
267.19
208.01
221.26
204.17
142.84


Table A-13. Six molar HCI










Table A-13 Continued


Treatment

C. mucunoides
C. mucunoides
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. macrocarpum
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
C. ensiformis
Control
Control
Control
Control
Control


Depth
cm
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15


Mean
ABS blank
mg kg-1
0.20 0.00
0.22 0.00
0.27 0.00
0.19 0.00
0.20 0.00
0.23 0.00
0.22 0.00
0.23 0.00
0.25 0.00
0.25 0.00
0.21 0.00
0.42 0.00
0.33 0.00
0.20 0.00
0.33 0.00
0.22 0.00
0.24 0.00
0.21 0.00
0.26 0.00
0.24 0.00
0.28 0.00
0.23 0.00
0.24 0.00
0.13 0.00
0.21 0.00


Y
Intercept

1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75


Spec.
cone.
mg kg-1
0.35
0.39
0.48
0.33
0.35
0.41
0.38
0.41
0.44
0.43
0.37
0.73
0.57
0.35
0.58
0.38
0.42
0.37
0.46
0.42
0.49
0.40
0.42
0.22
0.36


Glass
g
28.72
31.73
28.60
30.83
30.89
32.13
31.08
30.57
29.22
30.95
28.65
30.53
30.78
28.71
29.92
31.21
31.74
29.90
31.03
28.52
31.35
28.86
28.72
32.18
28.73


Soil
g
0.21
0.22
0.21
0.20
0.21
0.21
0.24
0.24
0.21
0.24
0.21
0.23
0.21
0.23
0.23
0.20
0.21
0.22
0.21
0.23
0.23
0.21
0.24
0.20
0.20


Post
digest
solution
ml
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00


Murphy
& Riley
ml
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40


Sample
in
M&R
ml
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00


6.0 M HC1
extractable
[P]
mg kg-1
186.69
207.47
257.40
183.10
188.55
220.04
183.24
189.67
240.15
205.58
203.69
356.09
308.23
175.36
281.74
211.01
225.64
196.38
247.73
208.12
242.69
211.87
202.76
123.69
203.53










Table A-13 Continued


Mean
ABS blank
mg kg-1
0.22 0.00
0.17 0.00
0.21 0.00
0.22 0.00
0.38 0.00
0.35 0.00
0.22 0.00
0.28 0.00
0.25 0.00
0.21 0.00
0.22 0.00
0.28 0.00
0.26 0.00


Treatment

Control
Control
Control
Control
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized
Fertilized


Depth
cm
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30
0-5
5-15
15-30


Y
Intercept

1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75
1.75


Spec.
cone.
mg kg-1
0.38
0.30
0.37
0.39
0.66
0.61
0.39
0.48
0.44
0.37
0.38
0.49
0.46


Glass
g
31.01
30.96
31.15
28.68
29.79
31.91
28.49
31.26
28.68
28.92
30.15
28.81
28.67


Post
digest
solution
ml
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00


Soil
g
0.21
0.21
0.22
0.20
0.20
0.22
0.21
0.23
0.21
0.20
0.21
0.23
0.21


Murphy
& Riley
ml
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40
11.40


Sample
in
M&R
ml
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00
5.00


6.0 M HC1
extractable
[P]
mg kg-1
206.41
166.09
192.08
219.16
367.74
313.19
216.78
240.33
236.58
209.39
208.96
245.42
256.30









LIST OF REFERENCES


Alexander D B 1998 Bacteria and Archaea. In Principles and Applications of Soil Microbiology,
Eds D M Sylvia, J J Fuhrmann, P G Hartel and D A Zuberer. pp 44-71. Prentice Hall,
New Jersey, NJ.

Alvim R and Nair P K R 1986 Combination of cacao with other plantation crops: an agroforestry
system in Southeast Bahia, Brazil. Agroforestry Systems 4, 3-15.

Appiah M R, Sackey S T, Ofori-Frimpong K and Afrifa A A 1997 The consequences of cacao
production on soil fertility in Ghana: A review. Ghana Journal of Agricultural Science
30, 183-190.

Baligar V C, Elson M K and Meinhardt W L 2008 Cover crops useful for improving soil
productivity under cacao. In Theobroma cacao: Biology, Chemistry and Human Health.,
Eds A B Bennett, C Keen and H Shapiro. Wiley Publishers, Beltsville, MD. In press.

Baligar V C, Fageria N K, Eswaran H, Wilson M J and He Z 2004 Nature and Properties of Red
Soil of the World. In The Red Soils of China: Their Nature, Management and Utilization,
Eds M J Wilson, Z He and X Yang. pp 7-27. Kluwer Academic Publishers, Beltsville,
MD.

Barber S A 1995 Nutrient Absorption by Plant Roots. In Soil Nutrient Bioavailability: A
Mechanistic Approach, Ed S A Barber. pp 49-84. John Wiley & Sons, Inc., New York,
NY.

Basamba T A, Barrios E, Amezquita E, Rao I M and Singh B R 2006 Tillage effects on maize
yield in a Colombian Savanna oxisol: Soil organic matter and P fractions. Soil and
Tillage Research, In Press.

Berkelaar E 2001 The effect of aluminum in acidic soils on plant growth. ECHO Development
Notes 71, 1-3.

Brady N C and Weil R R 1999 The Nature and Properties of Soils. Prentice-Hall, Inc. 881 p.
Bridges T 2006 New road aims to turn farmers away from coca. In World. Knight Ridder
Newspapers, Kansas City, KS.

Bright C 2001 Chocolate Could Bring the Forest Back. World Watch, 17-28.

Carter M E, Gamez R and Gliessman S 1993 Sustainable Agriculture and the Environment in the
Humid Tropics. National Academy Press, Washington D.C.

Chang S C and Jackson M L 1957 Fractionation of soil phosphorus. Soil Science Society of
America Journal 84, 133-144.

Chapin F S, Matson P A and Mooney H A 2002 Principles of Terrestrial Ecosystem Ecology.
Springer, New York, NY.










Davidson E A, Carvalho C J R, Figueira A M, Ishida F Y, Ometto J P H B, Nardoto G B, Saba R
T, Hayashi S N, Leal E C, Vieira I C G and Martinelli L A 2007 Recuperation of nitrogen
cycling in Amazonian forests following agricultural abandonment. Nature 447.

Dinesh R, Suryanarayana M A, Chaudhuri S G and Sheeja T E 2004 Long-term influence of
leguminous cover crops on the biochemical properties of a sandy clay loam Fluventic
Sulfaquent in a humid tropical region of India. Soil and Tillage Research 77, 69-77.

Duguma B, Gockowski J and Bakala J 2001 Smallholder Cacao (Theobroma cacao Linn.)
cultivation in agroforestry systems of West and Central Africa challenges and
opportunities. Agroforestry Systems 51, 177-188.

Elrashidi M A 2006 Selection of an Appropriate Phosphorus Test for Soils, Ed U N R a C
Service. Soil Survey Laboratory.

Evans H C, Krauss U, Rutz R R, Acosta T Z and Arevalo-Gardini E 1998 Cacoa in Peru. Cocoa
Growers Bulletin No. 51, 7-51.

Ewel J J 1986 Designing Agricultural Ecosystems for the Humid Tropics. Annual Review of
Ecology and Systematics 17, 245-271.

F.A.O 2005 Global Forest Resources Assessment. Food and Agriculture Organization.

Fageria N K, Baligar V C and Bailey B A 2005 Role of Cover Crops in Improving Soil and Row
Crop Productivity. Communications in Soil Science and Plant Analysis 36, 2733-2757.

Graetz D A and Nair V D 1999 Inorganic Forms of Phosphorus in Soils and Sediments. In
Phosphorus Biogeochemistry in Subtropical Ecosystems, Eds K R Reddy, G A O'Connor
and C L Schelske. pp 171-186. Lewis Publishers, Gainesville, FL.

Hall H unpublished data Informal interviews with cacao agroforesters in San Martin, Peru,
Tarapoto.

Hall H 2006 pH determination of cacao agroforestry soils in San Martin, Peru. University of
Florida.

Hartemink A E 2005 Nutrient Stocks, Nutrient Cycling, and Soil Changes in Cocoa Ecosystems:
A Review. In Advances in Agronomy. pp 227-253. ISRIC-CABI Publishing,
Wallingford, CT.

Hedley M J, Stewart J W B and Chauman B S 1982a Changes in Inorganic and Organic Soil
Phosphorus Fractions Induced by Cultivation Practices and by Laboratory Incubations.
Soil Science Society of America Journal 46, 970-976.









Hedley M J, White R E and Nye P H 1982b Plant-induced changes in the rhizosphere of Rape
(Brassica napus var. Emerald) seedlings. III. Changes in L Value, Soil Phosphate
Fractions and Phosphatase Activity. The New Phytologist 91, 45-56.

Heiri O, Lotter A F and Lemcke G 2001 Loss on ignition as a method for estimating organic and
corbonate content in sediments: reproducibility and comparability of results. Journal of
Paleolimnology 25, 101-110.

Hieltjes A H M and Lijklema L 1980 Fractionation of Inorganic Phosphates in Calcareous
Sediments. Journal of Environmental Quality 9, 405-407.

Hinsinger P 2001 Bioavailability of soil inorganic P in the rhizosphere as affected by root-
induced chemical changes: a review. Plant and Soil 237, 173-195.

Hopkins W G and Huner N P A 2004 Introduction to Plant Physiology. John Wiley and Sons,
Inc., New York, NY.

I.C.T. 2007 Instituto de Cultivos Tropicales Home Page. I.C.T., Tarapoto, Peru.

Jonasson O 1951 Potential Areas of Cacao Cultivation in South America: A Review. Economic
Geography 27, 90-93.

Kuo S 1996a Extraction with Dilute Concentration of Strong Acids. In Methods in Soil Analysis.
Part 3. Chemical Analysis. pp 893-894. Soil Society of America and American Society of
Agronomy, Madison, WI.

Kuo S 1996b Phosphorus. In Methods of Soil Analysis. Part 3. Chemical Methods, Ed S S S o A
a A S o Agronomy. pp 869-919. Soil Science Society of America and American Society
of Agronomy, Madison, WI.


Levy E T and Schlesinger W H 1999 A comparison of fractionation methods for forms of
phosphorus in soils. Biogeochemistry 47, 25-38.

Li L, Li S-M, Sun J-H, Zhou L-L, Bao X-G, Zhang H-G and Zhang F-S 2007 Diversity enhances
agricultural productivity via rhizosphere phosphorus facilitation on phosphorus-deficient
soils. PNAS 104, 11192-11196.

Mafongoya P L, Giller D E, Odee D, Gathumbi S, Nduga S K and Sitompul S M 2004
Benefiting from N2-Fixation and Managing Rhizobia. In Below-ground Interactions in
Tropical Agroecosystems. pp 227-242. CAB International.

McGrath D A, Smith C K, Gholz H L and Oliveira F d A 2001 Effects of Land-Use Change on
Soil Nutrient Dynamics in Amazonia. Ecosystems 4, 625-645.









Miller R W and Gardiner D T 2001a Acidic Soils. In Soils in Our Envirnoment, Ed D Yarnell.
pp 242-258. Prentice Hall, New Jersey, NJ.

Miller R W and Gardiner D T 2001b Organisms and Their Residues. In Soils in Our
Environment, Ed D Yarnell. pp 164-203. Prentice Hall, New Jersey, NJ.

Miller R W and Gardiner D T 2001c Plant Nutrients: Nitrogen, Phosphorus, and Potassium. In
Soils in Our Environment. pp 302-309. Prentice Hall, New Jersey, NJ.

Nair V D, Graetz D A and Portier K M 1995 Forms of Phosphorus in Soil Profiles from Dairies
of South Florida. Soil Science Society of America Journal 59, 1244-1249.

Nelson D W and Sommers L E 1996a Loss-On-Ignition Method. In Methods of Soil Analysis.
Part 3. Chemical Methods. pp 1004-1005. Soil Science Society of America and American
Society of Agronomy, Madison, WI.

Nelson D W and Sommers L E 1996b Walkley-Black Method. In Methods of Soil Analysis. Part
3. Chemical Methods. SSSA Book Series no. 5., Ed J M Bartels. pp 995-996. Soil
Science Society of America and American Society of Agronomy, Madison, WI.

NOAA 2007 Climate and Daylight Chart for Tarapoto, Peru. ClimateCharts.com.

Paul E A and Clark F E 1989 Soil Microbiology and Biochemistry. Academic Press, Inc.

Peoples M B and Baldock J A 2001 Nitrogen dynamic of pastures: nitrogen fixation inputs, the
impact of legumes on soil nitrogen fertility, and the contributions of fixed nitrogen to
Australian farming systems. Australian Journal of Experimental Agriculture 41, 327-346.

Phiri S, Barrios E, Rao I M and Singh B R 2001 Changes in soil organic matter and phosphorus
fractions under planted fallow and a crop rotation system on a Colombian volcanic-ash
soil. Plant and Soil 231, 211-223.

Russell S E J 2002a The Composition of Soil Organic Matter. In Soil Conditions & Plant
Growth. pp 255-285. Biotech Books, New Dehli, India.

Russell S E J 2002b The Effect of Soil Acidity and Alkalinity on Plant Growth. In Soil
Conditions & Plant Growth, Ed E W Russell. pp 473-481. Biotech Books, New Delhi,
India.

Ryan P and Delhaize E 2001 Function and Mechanism of Organic Anion Exudation from Plant
Roots. Annual Review of Plant Physiology & Plant Molecular Biology 52, 527-560.

S.A.S. 2007 JMP Statistical Software. S.A.S Institute.

Sample E C, Soper R J and Racz G J 1976 Reaction of Phosphate Fertilizers in Soil. In The Role
of Phosphorus in Agriculture, Alabama, 1976.










Sanchez P A 2000 Linking climate change research with food security and poverty reduction in
the tropics. Agriculture, Ecosystems & Environment 82, 371-383.

Schactman D P, Reid R J and Ayling S M 1998 Phosphorus uptake by plants: From soil to cell.
Plany Physiology 116, 447-453.

Schroth G, Teixeira W G, Seixas R, Silva L F d, Schaller M, Macedo J L V and Zech W 2000
Effect of five tree crops and a cover crop in multi-strata agroforestry at two fertilization
levels on soil fertility and soil solution chemistry in central Amazon. Plant and Soil 221,
143-156.

Silva I R, Smyth T J, Moxley D F, Carter T E, Allen N S and Rufty T W 2000 Aluminum
Accumulation at Nuclei of Cells in the Root Tip. Fluorescence Detection Using
Lumogallion and Confocal Laser Scanning Microscopy. Plant Physiology 123, 543-552.

Sylvia D M, Fuhrmann J J, Hartel P G and Zuberer D A 1998 Fungi. In Principles and
Applications of Soil Microbiology, Ed D M Sylvia. pp 72-93. Prentice Hall, Inc., New
Jersey, NJ.

Szulczewski M D and Li Y unpublished Phosphorus Fractions in Calcareous Soils from the
Southern Everglades and Nearby Farmlands. University of Florida.

Thomas G W 1996 Determination-pH in water. In Methods of Soil Analysis. Part 3. Chemical
Methods. pp 487. Soil Science Society of America and American Society of Agronomy,
Madison, WI.

Tiessen H, Cuevas E and Chacon P 1994 The role of soil organic matter in sustaining soil
fertility. Nature 371, 783-785.

Tiessen H and Moir J 0 1993 Characterization of Available P by Sequential Extraction. In Soil
Sampling and Methods of Analysis, Ed M R Carter. pp 75-86. Canadian Society of Soil
Science.

Uehara G and Gillman G 1981 The Mineralogy, Chemistry, and Physics of Tropical Soils with
Variable Charge Clays. Westview Press.

USDA 2007 ARS Office of International Research Programs.

USDA and ARS 2007 Fighting a fungal siege on cacao farms. In New & Events, Ed USDA.
USDA ARS.

Vitousek P M, Cassman K, Cleveland C, Crews T, Field C B, Grimm N B, Howarth R W,
Marino R, Martinelli L, Rastetter E B and Sprent J I 2002 Towards an ecological
understanding of biological nitrogen fixation. Biogeochemistry 57/58, 1-45.









Vitousek P M and R.L. Sanford J 1986 Nutrient Cycling in Moist Tropical Forest. Annual
Review of Ecology and Systematics 17, 137-167.

W.C.F. 2007 Encouraging Sustainable, Responsible Cocoa Growing. World Cacoa Foundation.

Wang Q R, Li Y C and Klassen W 2007 Changes in Soil Microbial Biomass Carbon and
Nitrogen with Cover Crops and Irrigation in a Tomato Field. Journal of Plant Nutrition
30, 623-639.

Weintraub M N, Scott-Denton L E, Schmidt S K and Monson R K 2007 The effects of tree
rhizodeposition on soil exoenyme activity, dissolved organic carbon, and nutrient
availability in a subalpine forest ecosystem. Oecologia 154, 327-338.

Wessel M 1971 Fertilizer Requirements of Cacao (Theobroma cacao L.) in South-western
Nigeria. Department of Agricultural Research of the Royal Tropical Institute,
Amsterdam.

Wood GA R 1975 Cocoa. Longman Group Limited, Great Britian.

Wood G A R and Lass R A 2001 Cocoa. Blackwell Science.

Wortmann C S, McIntyre B D and Kaizzi C K 2000 Annual soil improving legumes: agronomic
effectiveness, nutrient uptake, nitrogen fixation and water use. Field Crops Research 68,
75-83.

Young A 1997 Soil Organic Matter and Physical Properties. In Agroforestry for Soil
Management. pp 98-110. CABI Publishing.

Zuberer D A 1998 Biological Dinitrogen Fixation: Symbiotic. In Principles and Applications of
Soil Microbiology, Eds D M Sylvia, J J Fuhrmann, P G Hartel and D A Zuberer. pp 322-
345. Prentice Hall, New Jersey, NJ.









BIOGRAPHICAL SKETCH

The author began her studies in soil science through lectures, laboratories, and field

excursions while fulfilling the requirement of a Bachelor of Science (BS) in the Rangeland

Resource Management program at Humboldt State University (HSU) in northern California.

Believing soils to provide the foundation of life on the planet and aiming to secure a career

allowing the inclusion of this spectrum of ecosystem components to solve resource use issues the

author has been diligent in her efforts to include plants, people, and water in her studies of soil

science.

To this end, the author supplemented her Rangeland Resources program at HSU with a

minor in botany, and an option in wildland soil science, and several internship and volunteer

activities. A one-year Co-Directorship of the Campus Center for Appropriate Technology at

HSU fostered the development of teamwork and project management skills while maintaining an

educational forum from which the authors' community could learn to reduce their consumption

of natural resources. A summer internship working on the big island of Hawaii with the Natural

Resource Conservation Service as a soil conservation technician allowed the author to gain

exposure to the resource conservation issues associated with agricultural production in the

tropics, and experience taxonomically describing soils. In a second summer internship, the

author worked as a Biological Technician for the National Forest Service in the Sierra Nevada

Mountain Range of California. This work allowed the author to use her skills in soil science to

assess the impact of cattle grazing on the physical characters of meadow soils. In a third summer

internship, working as a research assistant for plant ecologist Dr. Eric Jules, the author and a

dendro-chronologist collected soil and tree age data from spruce forests throughout the

Redwoods State and National Parks in an effort to map the historic grassland range as it existed

under Native North American management. After completing her BS degree at HSU the author









took a 1-year hiatus from academia to implement watershed restoration technologies throughout

the Mattole River watershed in Northern California before moving to Gainesville, Florida to

pursue a Master of Science degree from the Soil and Water Science Department. At the

University of Florida, the author worked under the guidance of her academic committee to

investigate the influence of cover crops on phosphorus fractions and soil fertility in a cacao

agroforestry system located in the Peruvian Amazon. Having completed her Masters of Science

degree requirements the author will continue in the Soil and Water Sciences department to

pursue a PhD program as part of a National Science Foundation funded Integrated Graduate

Education and Research Traineeship focused on using Adaptive Management theories for the

wise use of water.





PAGE 1

1 INFLUENCE OF COVER CROP CULTIVATION ON PHOSPHORUS FRACTIONS AND SOIL FERTILITY IN A PERUVIAN CACAO AGROFORESTRY SYSTEM By HOLLIE HALL A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2008

PAGE 2

2 2008 Hollie Hall

PAGE 3

3 To my grandmother for encour aging me to play outside.

PAGE 4

4 ACKNOWLEDGEMENTS The author would like to thank the m any sour ces of education and guidance, laboratory and field assistance, and funding th at made this work possible. In terms of educational growth and guidance, the author is gr eatly appreciative to her committee members. Her academic advisor, Dr. Yuncong Li offered her an opportunity in which she was able to develop research, project management, and linguistic skills in the Peruvian Amazon where the resulting information will be included in local efforts to improve soil productivity. Additionally, Dr. Li encouraged the author to broade n her laboratory research experime ntation to areas outside of her foci resulting in a broader understanding of soil phosphorus fractions. The author thanks Dr. Li for trusting and supporting her in th e undertaking of this research pr oject. The Co-Chair of her academic committee, Dr. Nick Comerford provided the valuable opportunity for participation in critical discussions of publis hed research regarding soil p hosphorus, its quantification and interpretation. For this as well as for ai ding in her development of understanding for the mechanisms by which plants absorb soil nutrients the author thanks Dr Comerford. Committee member and Professor Emeritus, Dr. Hugh Pope noe fueled the authors inspiration and knowledge regarding tropical agriculture through thought provoking lectures and conversations. She is thankful to Dr. Popenoe for lending his lens of experience and personal support to her research endeavors. Committee member and US DA Soil Scientist, Dr. Virupax Baligar made this project possible by establishing the cover crop experiment in Ta rapoto. In addition to his role in the experiment establishment, the au thor thanks Dr. Baligar for providing her with constructive criticism, thoughtful comments, and volumes of rele vant published information to aid in informing her research activities. Each member of the authors academic committee filled a unique niche and collectively provided her w ith important lessons in conducting quality scientific research.

PAGE 5

5 In terms of laboratory and field assistance, th e author would like to acknowledge the many people at the Forest Soils Labor atory, Tropical Research & Ed ucation Centers Soil and Water Sciences Laboratory, and at the In stituto de Cultivos for their generosity with their time. Specifically, at the Forest Soils Laboratory th e author thanks Aja St oppe for her continued availability for answering numerous questions and for managing a well organized and stocked laboratory space. At the Tropical Research & Education Centers Soil and Water Sciences Laboratory, the author would like thank Guingi n Yu, Yun Qian, and Laura Rosado for their kindness and for providing her with training in la boratory techniques. At the Instituto de Cultivos Tropicales, she would like to thank the Directors Mr. Enrique Arvelo-Gardini and Mr. Luis B. Ziga Cernades and all of their empl oyees, not only for assist ing in conducting field research but also for taking her in as part of their families, allowing her a full emersion experience in Tarapoto, Peru. In terms of funding, the author would like to thank the Soil and Water Science Department, the Latin American Studies Research Grant fund, and the Tinker Grant fund at the University of Florida for providing economic support for her research activities.

PAGE 6

6 TABLE OF CONTENTS page ACKNOWLEDGEMENTS.............................................................................................................4 LIST OF TABLES................................................................................................................. ..........8 LIST OF FIGURES.......................................................................................................................10 ABSTRACT...................................................................................................................................11 CHAP TER 1 INTRODUCTION..................................................................................................................12 Objectives...............................................................................................................................13 Hypothesis..............................................................................................................................13 2 LITERATURE REVIEW.......................................................................................................14 Cacao Agroforestry: A Mode for Economic Gain.................................................................. 14 Soil Fertility in the Humid Tropics......................................................................................... 18 Organic Matter........................................................................................................................18 Phosphorus..............................................................................................................................19 Nitrogen..................................................................................................................................20 Soil Acidity.............................................................................................................................20 Nutrient Cycling in Cacao Agroforestry Systems.................................................................. 21 Benefits of Using Leguminous Cover Crops.......................................................................... 22 Cover Crops as Sources of Soil Organic Matter..................................................................... 22 Cover Crops Enhance Soil Solution Inorganic Phosphorus................................................... 23 Cover Crops as Sources of Biologically Fixed Nitrogen........................................................ 24 Sequential Fractionation Procedures...................................................................................... 24 Sequential Fractionation of Plant Available Soil Phosphorus................................................ 28 3 COVER CROP CULTIVATION EFFECT S ON SOIL FE RTILITY AND PHOSPHORUS FRACTIONS IN A PERUVIAN CACAO AGROFORESTRY SYSTEM......................................................................................................................... ........35 Introduction................................................................................................................... ..........35 Materials and Methods...........................................................................................................36 Study Site..................................................................................................................... ....36 Experimental Design....................................................................................................... 37 Soil Sampling.................................................................................................................. 37 Soil Nitrogen, Carbon, Calcium, Potassium, Iron, Aluminum, Magnesium, pH, and Loss on Ignition ...........................................................................................................38 Mehlich I Extractable Phosphorus................................................................................... 38 Sequential Fractionation of Phosphorus.......................................................................... 39

PAGE 7

7 Measurement of Extracted Inorganic Phosphorus........................................................... 39 Analysis of Phosphorus in Cover Crop Tissue................................................................ 39 Analysis of Soil Organic Matter......................................................................................39 Statistical Analysis.......................................................................................................... 40 Results.....................................................................................................................................40 Soil Total Nitrogen, Total Car bon, and Carbon to Nitrogen Ratio ................................. 40 Soil Loss o Ignition and Organic Matter......................................................................... 41 Soil pH.............................................................................................................................41 Soil Calcium, Potassium, Magnesium, Iron, and Aluminum.......................................... 41 Mehlich I Extractable Phosphorus................................................................................... 42 Sequential Fractionation of Phosphorus.......................................................................... 42 Six Molar HCl Digest of Air-Dried Soil......................................................................... 43 Cover Crop Tissue Phosphorus Content..........................................................................44 Correlations Between Soil Extractable Phosphorus Fractions and Cover Crop Tissue Phosphorus Percentage .....................................................................................44 Discussion...............................................................................................................................44 Soil Loss on Ignition and Organic Matter Content......................................................... 44 Soil Carbon Content........................................................................................................ 46 Soil Nitrogen Content......................................................................................................47 Carbon to Nitrogen Ratio................................................................................................47 Soil Potassium, Calcium, and Magnesium...................................................................... 48 Soil pH and Potential Alum inum Toxicity...................................................................... 48 Cover Crop Tissue Phosphorus.......................................................................................49 Correlations Between Cover Crop Tissu e and Soil Extractable Phosphorus .................. 49 Half Molar HCl Extractable Phosphorus......................................................................... 49 Six Molar HCl Extractable Phosphorus.......................................................................... 50 Conclusion..............................................................................................................................50 APPENDIX A UNTRANSFORMED DATA........................................................................................................ 69 LIST OF REFERENCES.............................................................................................................107 BIOGRAPHICAL SKETCH.......................................................................................................113

PAGE 8

8 LIST OF TABLES Table page 2-1 Sequential fractionation of soil P procedures and interpretation ....................................... 30 3-1 Summary of si gnificant findings. ....................................................................................... 53 3-2 Total nitrogen, total carbon, carbon to nitrogen ratio, pH, an d loss on ignition averaged data for all treatments at all depths..................................................................... 55 3-4 Calcium, potassium, iron, aluminum, and magnesium averaged data............................... 57 3-5 Mehlich I extraction of inorganic, orga nic, and total phosphorus averaged data. ............. 58 3-6 Sequential extraction of phosphate and the digest of air-dried soil averaged data. ...........59 3-7 Phosphorus content of cover crop foliar tissue. ................................................................. 60 3-8 Soil organic matter, potassium, catio n exchange capacity, cations, and base saturation averaged data. .................................................................................................... 61 3-9 Extractable phosphorus expresse d in kilogram s per hectare............................................. 62 A-1 Soil sample collection co-ordinates................................................................................... 69 A-2 Soil total nitrogen, total carbon, pH, and carbon to nitrogen ra tio unaltered data. ............75 A-3 Loss on ignition unaltered data..........................................................................................77 A-4 Soil concentration of calcium, potassi um iron, aluminum, and magnesium unaltered data.....................................................................................................................................80 A-5 Mehlich I extraction of inorga nic phosphorus unaltered data. ..........................................81 A-6 Mehlich I extraction of tota l phosphorus unaltered data. .................................................. 83 A-7 Water extraction of inorgani c phosphorus unaltered data. ................................................85 A-8 One molar NH4Cl extraction of inorganic phosphorus unaltered data..............................88 A-9 One-tenth molar NaOH extraction of inorganic phosphorus unaltered data. .................... 91 A-10 Digest of 0.1 M NaOH supernatant fo r the quantification of total 0.1 M N aOH extractable phosphorus unaltered data............................................................................... 94 A-11 Half molar HCl extr action of inorganic phosphorus unaltered data. .................................98

PAGE 9

9 A-12 Six molar HCl digest and extraction of inorganic phosphorus from residual soil unaltered data...................................................................................................................101 A-13 Six molar HCl digest and extraction of inorganic phosphorus from air-dried soil unaltered data...................................................................................................................104

PAGE 10

10 LIST OF FIGURES Figure page 3-1 Map of Peru.......................................................................................................................64 3-2 Experimental design........................................................................................................ ...65 3-3 Sequence for the fractionation of soil phosphorus pools................................................... 66 3-4 Significant correlations between cover crop tissue and soil extracted phosphorus pools.. .................................................................................................................................67 3-5 Physical symptoms of aluminum toxicity expressed in th e mature leaves of cacao plants at Instituto de Cultivos Tropicales...........................................................................68

PAGE 11

11 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science INFLUENCE OF COVER CROP CULTIVATION ON PHOSPHORUS FRACTIONS AND SOIL FERTILITY IN A PERUVIAN CACAO AGROFORESTRY SYSTEM By Hollie Hall May 2008 Chair: Yuncong Li Major: Soil and Water Science In many tropical soils, excessive weathering of primary minerals has resulted in the depletion of most plant soluble forms of P gr eatly hindering agricultural productivity. Long-term growth of cover crops in tropi cal agroforestry systems have been shown to influence soil P fractions, nutrient cycling, and soil organic ma tter pools. Several key soil characteristics associated with fertility, emphasizing soil P bioava ilability were evaluated, after two years of cover crop establishment. Cover crop cultivation resulted in an increase in soil pH and organic matter pools and the hydrochloric acid extracta ble P fractions were accessed by cover crop species. The experimental design of this study in cluded seven treatments in the understory of an experimental cacao agroforestry system in the San Martin district of Peru. The treatments were four perennial leguminous cover crops ( Arachis pintoi, Calopogonium mucunoides, Canavalia ensiformis and Centrosema macrocarpum ), a non-legume cover crop (Callisia repens ), an inorganic fertilizer treatment, and a control treatme nt. Results of this study indicated that after two years of cover crop cultivat ion minor changes occurred in the soil pH, organic matter content, and extractable phosphor us pools. However, continued monitoring is required to develop a complete understanding of the ability of cover crop cultivation to accentuate soil fertility.

PAGE 12

12 CHAPTER 1 INTRODUCTION Our study is aim ed to elucidate the issues related to conversi on of humid tropical forests to agricultural land, and the potential for improved agricultural systems to ai d in the sustainability of these conversions. Our study focused on the pot ential for inclusion of leguminous cover crops in cacao agroforestry systems to mediate tropical soil infertility that ofte n results after prolonged cultivation. We examined humid tropical re gions hospitable to cacao cultivation, generally defined as the area having an average annual pr ecipitation greater than 1500 mm, mean annual temperature >22C, and drought periods not exce eding 4 months (Vitousek and R.L. Sanford 1986). Soils most suitable for cacao production c ontain approximately 3% organic matter, and have a pH ranging between 6 and 7.5 (Evans et al. 1998). In eastern Peru these conditions are most favorable in river valley so ils, where ultimately, minimum ai r temperatures of less than 10 C shape the distribution of cacao (Evans et al. 1998). Further more, the discussions contained within this document focus on the problems asso ciated with highly weathered tropical soils. Nutrients in tropical soils have been depl eted over time, naturally or by continuous cultivation and harvest of plant products (Baligar et al. 2004) It is possible that with conscientious management, fertility of these soils can be maintained or improved, making them a renewable resource (Brady and Weil 1999). Legu minous cover crops are widely accepted for their contribution to soil quality through additions of nitrogen (N ) (Fageria et al. 2005). As phosphorus (P) is often the most limited plant es sential nutrient in tropical soils, inclusion of leguminous cover crops on tropical soils may s eem counter-intuitive. However, leguminous cover crops can alter soil P forms through the ad dition of soil organic matter (SOM), deep soil mining, and microbial priming (Brady and Weil 1999; Chapin-III et al. 2002).

PAGE 13

13 The primary research contained in this doc ument focuses on the effects of leguminous cover crop inclusion in a cacao agroforestry system on soil phosphorus fractions and soil fertility. This experiment complements ongoing re search related to cacao agroforestry conducted on an acidic tropical soil at Insituto de Culti vos Tropicales (ICT) in Tarapoto, Peru. The research site exists at latit ude 6.734' S and longitude 76.694' W, at an altitude of 467 meters above sea level, and receives an aver age of 1200 mm of rain pe r year (NOAA 2007). The goal of the ICT experiment was to assess the potential benefit of leguminous cover crops in improving soil quality factors and the subsequent benefits on cacao yield. The experimental area was 1.05 hectares of acidic soils (pH 4.836.04, with very low to moderate levels of organic matter (OM) and P. Objectives 1. To quantify the effects of two years of leguminous cover crop cultivation on soil phosphorus fractions as extracte d by various extractants; and 2. To quantify the effects of two years of legum inous cover crop cultivation on soil fertility factors; organic matter conten t, loss on ignition, total nitrogen content, and pH at the 0-5 cm, 5-15 cm and 15-30 cm soil horizons. Hypothesis 1. Cultivation of leguminous cover crop s alters soil phosphorus pools. 2. Cultivation of leguminous cover crops alters soil fertility factors.

PAGE 14

14 CHAPTER 2 LITERATURE REVIEW Cacao Agroforestry: A Mode for Economic Gain Under continued pressure of population growth, the sustainability of hum id tropical forest resources will depend upon improved agricultura l management techniques that allow for sustained land-use. Pressures on tropical forest s are complex and relate to the methodology of traditional agricultural practices, land ownershi p, and the disequilibria in nutrient cycles precipitated by forest clearing (F.A .O 2005). Together, these pressure s play an important role in mediating the rate of deforestation, currently ap proximately 13 million hectares per year, and the magnitude of food and economic insecurities in ru ral communities of the humid tropics (F.A.O 2005). Research testing and promotion of agroforestry systems that maintain or improve soil fertility is critical to increasi ng the agricultural productivity of tropical regions while stabilizing rates of deforestation. Compared to monocultural food cropping systems, cacao ( Theobroma cacao) agroforestry systems help to maintain soil fertility, improve economic and food income, and protect native plant diversity by maintaini ng soil organic matter supplies, and producing a diversity of agri cultural products (Bridges 2006). In semi-rural tropical regions, it is common for people to live a subsistence life style, in which they are dependent on the productivity of the land they farm for food and economic gains (Sanchez 2000). Often, traditional shifting agricu ltural methods achieve long-term tropical soil productivity through nutrient replenishing fallo w periods. Without fallow periods, the sustainability of agricultural product ion on tropical soil is hindered by continued depletion of soil nutrient pools (Ryan and Delhaize 2001). For people living in regions suitable for cacao production, installations of agricult ural technologies like agroforestry systems can improve soil fertility and provide major food and economic gains (Hartemink 2005).

PAGE 15

15 In 2005, 5 to 6 million cacao farmers created enough employment opportunities to support 40 to 50 million people (W.C.F. 2007). In this same year the global cacao market was valued at $5.1 billion, and the demand for cacao has grown on an average of 3% per year for the last 100 years (W.C.F. 2007). When compared to the total agricultural productivity in West Africa, cacao has earned a majority of the economic gains ther e (Duguma et al. 2001). The Ivory Coast alone produces enough cacao to fulfill 40% of the worl d market (Hartemink 2005). Cacao exports from Ghana account for approximately 60% of th e countrys foreign income (Hartemink 2005). The majority of the marketed cacao is pr oduced by small scale farmers (Hartemink 2005). Peruvian farmers produced an average of 831 tons of cacao per year in 1992 and 1993 (USDA and ARS 2007). In these years of low nationa l cacao productivity, Peru imported from 100 (in 1993) to 3,591 (1994) tonnes of cocoa. However, by 1996 the annual production of cacao in Peru had jumped to 22,867 tonnes and imports ceased (Evans et al. 1998). The Peruvian economy supports infrastructure for the expor t of cacao products, ranging from 5,991 tonnes exported in 1993 to 3,826 tonnes exported in 1996 (Eva ns et al. 1998). At the global scale, Peru is not currently a major e xporter of cacao, however the high value crop and government subsidies are providing incentive for farmers to switch from coca ( Erythroxylum coca) to cacao farming in the San Martin region of Peru, a tr end which may increase local dependency on, and certainly productivity of this cropping system (Bridges 2006). In San Martin, Peru, a guarantee of economic return on investments in cacao production stems from a nearby manufacturer of high qualit y chocolate who purchas es all locally grown cacao beans. For cacao agroforesters in this region, nearly 100% of their harvested food crops are sold suggesting a non-satura ted market incentive for increas ed production. The generated

PAGE 16

16 income from these sales allow for an impr ovement in the families overall nutrition through diversified food intake, as well as increased educatio nal opportunities (Hall unpublished data). Tropical forests in the primary cacao producing c ountries are leading th e world in rates of deforestation at nearly 13 million hectares pe r year (F.A.O 2005). The main motivation for deforestation in these regions is the expansion of agricultur e land (F.A.O 2005). On a global scale, shifting cultivation is responsible for appr oximately 60% of deforestation (Duguma et al. 2001). Traditional agricultural methods in the tr opics involve shifting from one cleared forest soil to the next, with fallow periods in between to allow regeneration of fore st and soil fertility. Now that land tenure is an issue, many peopl e of the tropics, are attempting continuous cultivation of single plots of land for indefinite ti me spans (Carter et al. 1993). If management of soil fertility is successful, the c ontinuous cultivation of land w ill play an important role in stabilizing rates of deforestation. In Bahia, Brazil, one-half of the remaining forest canopy is under management in the tradit ional cabruca style cacao ag roforestry systems, showing potential for this type of agricultural system to succeed in protecting forest species (Bright 2001). In deforested tropical soils, ag ricultural productivity ultimately depends on the anthropogenic management for availability of plan t essential minera l nutrients. Cacao is generally cultivated between 20 north and south of the equator where temperature and moisture regimes are suitable (W.C.F. 2007). The major limitations to cacao cultivation are typically climatic and susceptibility to disease. Cacao plants prefer abundant supplies of water, and typically grow best on well drained lowla nd area adjacent to rivers or clayey upper slopes (Wessel 1971). A confoundi ng factor of cacaos preference for moist conditions is that the myriad of fungal diseases that commonly attack cacao plants also thrive under moist conditions where precipitation exceeds 1800 mm yr-1. However, the cacao plants

PAGE 17

17 are tolerant of much less precipitation even with standing drought periods of up to 4 consecutive months (Wessel 1971). The benefit of drought tolera nce is that dry period s of some duration aid to reduce the devastation caused by fungal diseases. Cacao is absolutely intolerant of freezing temperatures and grows best when the averag e annual temperature ranges between 24 and 28C (Jonasson 1951). In the less developed tropical regions around the world, momentum to implement improvements to traditional agricultural methods has grown and many organizations are now in place to aid farmers to overcome the obstacles of land tenure, soil infertility, inaccessibility of inorganic fertilizers, and poverty. The United St ates Department of Ag riculture (USDA) funds agricultural research and produces educational materials. Most international projects funded by USDA are operated, in part, by local people, pr oviding them with th e skills and knowledge necessary to change the methods of land management (USDA 2007). One such USDA funded research center, which is the location of the focus of our research, is the Instituto de Cultivos Tropicales (ICT) in San Martin, Peru. ICT hosts field research related to the improvement of productivity from cacao agroforestry systems, and laboratory research developing cacao fungal disease resistance (I.C.T. 2007). ICT also c onducts community outreach by hosting workshops, growing cacao seedling, and providing on site assessments for local farmers. The works of this organization and others with sim ilar intentions are driving the mo mentum to install agroforestry systems that improve soil fertility and the status of poor people in rural pa rts of the world. There is hope on the horizon for reducing the food and economic insecurities of people living in the tropics, and the hope stems from advancement in the way that food is grown in those regions. With prioritized funding in place for the development and implementation of improved agricultural systems, it is critical to test technologies prio r to their widespread implementation.

PAGE 18

18 Soil Fertility in the Humid Tropics In undisturbed tropical f orests, nutrients involved in plant grow th are recycled via the litter and detritus. The nutrients contained by the parent materials of these soils are depleted by climatic and biotic weathering that occurred across the last million years (Uehara and Gillman 1981). However, the process for conversion of tropi cal forest to agricult ural land involves the removal of primary forest and burning of the orga nic materials on the land and in the upper layer of soil. This process accelerates the rate of SOM cycling, nutrient mine ralization and nutrient leaching, effectively debilitating nutrient cycling that is mediated by organic pools (Davidson et al. 2007). Once converted from forest to agricultu re, these soils tend to have structure suitable for plant growth but lack quantities of plant essential nutrient pools re quired for long-term agricultural productivity. Depl etion of soil nutrient pools con tinues through the harvest and removal of animal or plant agricultural produc ts. Without replenishment of nutrients via management, the soil matrix is typically deplet ed of SOM and N, acidic, and abundant with Fe and Al sesquioxides that are bound to P in a form that plants cannot absorb (Ryan and Delhaize 2001). Application of inorganic P containing fertilizers might remedy the infertility of these soils, but without money to buy, or means to transpor t, the use of inorganic fertilizers is not an option for many subsistence farmers. Improved methods for sustaining tropical soil fertility, therefore, have great potential to slow the rate of tropical defo restation and halt agricultural land abandonment (Baligar et al. 2004). Organic Matter Potentially, the m aintenance of SOM is the si ngle most critical f actor influencing soil fertility of humid tropical soils managed for agri cultural productivity. SO M aids to reduce the P fixing capacity of Feand Aloxide rich soils, and stores and cy cles essential plant nutrients (Berkelaar 2001). Here, many agricultural soils lack eas ily soluble inorganic nutrients and rely

PAGE 19

19 on the recycling of OM to maintain nutrient supply to plants. An example of the implications of slash-and-burn farming on the SOM reserves and associated nutrients of a sandy ferralsol of the Amazon rainforest in San Carlos de Rio Negro, Venezuela is drawn from the research conducted by Tiessen et al. (1994). In this particular soil, the potential fo r the sustainable production from an agricultural system was strongly correlated with the abundance of SOM in the upper 15 cm of soil. The C content of the uppe r 15 cm of soil was measured to degrade by 29%, and the leaf litter layer by 81% after 3 y ears of slash-and-burn manage ment (Tiessen et al. 1994). Additionally, the authors created an OM budget fo r the upper 60 cm of soil in the undisturbed forest in an effort to quantify the rate of carbon cy cling and associated nutrie nt release. With this OM budget, they estimated 60% of the C, 65% of the N, and 50% of the P to reside in the particulate OM, and to have a turnover time of le ss than 4 years. In contrast, these researchers found that only 27% of the C, 29% of the N, and 33% of the organic phosphorus (PO) were associated with mineral matter and in this form ha d a turnover time of near 50 years. This study clearly demonstrated the importance of organi c matter mediated nutrient cycling. Slash-andburn agriculture accelerates nutrien t cycling causing a rapid depleti on of the forest soil nutrient pools stored in OM (Tiessen et al. 1994). For sustainable agricultural production from tropical soils, rapid establishment and maintenance of SOM supplies are likely to shorten the phase characterized by N limitation and lessen the severity of P limitations. Phosphorus The prim ary source of P in tropical soils is in the soils organic frac tions, which can account for up to 50-80% of the soils total P (TP) (Ewel 1986). In the absence of the SOM rich forest floor, plant available P must come from adsorp tion and desorption processes occurring in the soils mineral constituents. However, the mineral constituents of weathere d, acidic tropical soils do not favor P desorption (Vitousek and R.L. Sanford 1986). Rather, the acidic nature of tropical

PAGE 20

20 soils favors reactions between phosphate (H2PO4 -) and active iron (Fe-) and aluminum (Al-) hydroxides to form less soluble phosphates and main tain low concentrations of inorganic P [Pi] in solution (Hinsinger 2001). Aland Feoxi des and hydrous oxides can occur as discrete compounds in soils or as coatin gs on soil particles. They can also exist as amorphous Alhydroxide compounds between the layers of expanda ble Alsilicates (Sampl e et al. 1976). The reactions of P with Feand Al-hydroxides de crease P solubility and limit the nutrients availability for plant uptake and is referred to as phosphorus fixation (Graetz and Nair 1999; Miller and Gardiner 2001c). In these soils, most of the organic P sorbs to the Feand Aloxides as well. Without proper management, P fixation, limits P availability to plants, causing severe limitations to agricu ltural productivity. Nitrogen Like P, SOM contains most of the N stored in tropical fore st and agricultural soils. Burning associated with the m anagement of agri cultural lands volatizes 50 % to 90% N stored in soil surface vegetation and organic biomass (McGrath et al. 2001). It has been proposed that limitations in P and N of tropical agricultural syst ems are directly relate d to the depletion of SOM supplies and will fluctuate from P limitation early, to N limitation in the middle, and back to P limitations in the later phases of devel opment (Davidson et al. 2007; Ewel 1986). In agricultural systems lacking the means to build and store SOM, limited access to [N] by plants can hinder the systems productivity during the sy stems developmental phase between the initial nutrient pulse after burning and prior to subs tantial root system development. Soil Acidity The acidity of tropical soils favors chem ical transformations of alum inum compounds that are toxic to plants. Tropical plants are adapted for optimal growth in slightly acidic soils ranging in pH from about 5.5 to 6.0. The soil pH at the research site under invest igation ranges from 5.0

PAGE 21

21 5.6, and is considered acidic (Berkelaar 2001; Hall 2006 ). Within this range of pH, depending on the chemistry of soil constituents, Al3+ may solubilize in soil soluti on, reducing the ability of plant roots to take up soil solution (U ehara and Gillman 1981). Additionally, Al3+ in soil solution inhibits the roots abil ity to effectively take up H2PO4 -, Ca2+ and Mg2+ (essential plant nutrients) from soil solu tion (Silva et al. 2000). Nutrient Cycling in Cacao Agroforestry Systems In cacao -agroforestry systems, the majority of nutrient cycling occur in the upper 30 cm of soil, this is the zone most influenced by root and litter turn-over (Alv im and Nair 1986). For optimal growth, cacao requires deep nutrient ric h, well-drained soils of moderate pH and low concentrations of soluble Al+3 (Appiah et al. 1997). Comparison of tropical forested soils with cacao agrosystems ranging in age from 3 to 40 years has shown slight decrea ses in soil pH (from 6.8 to 6.1). However, more pronounced declines were observed in C (from 2.5 to 1.4 %), N (from 0.24 to 0.13%), K ( from 0.42 to 0.27 mg kg-1), Ca (from 15 to 8.6 mg kg-1), Mg (from 2.3 to 1.5 mg kg-1), and Bray and Kurtz extractable P (from 26 to 10 mg kg-1) (Wessel 1971). These losses are likely due to continued harvest and removal of the cacao pods without ma nagement of soil fertility in the systems. These losses represent a 1.36 kg P, equivalent to 1.5 mg kg-1 in the 0-15 cm soil layer per 227 kg of dry cacao beans harvested from one acre (Wesse l 1971). Ten years of cacao cultivation in the Western Region of Ghana removed an estima ted 76,000 tonnes of N, 4,700 tonnes of P, and 18,000 tonnes of K from the soil via harvest and removal of beans (A ppiah et al. 1997). In this region, continued cultivation of th e land without any type of ferti lizer application has resulted in the degradation of soil fertilit y and a decrease in cacao produc tivity. The failure of cacao production has resulted in land abandonment and the clearing of additional fo rest (Appiah et al. 1997). If cacao cultivation is to become economically feasible obstacles to the loss of soil

PAGE 22

22 fertility must be overcome. A successful shif t from slash-and-burn agriculture to long-term cacao agroforestry must include the development of management for sustainable soil fertility. Benefits of Using Leguminous Cover Crops The benefits derived from cultivation of leguminous cover crops range from physically protecting the soil from erosion a nd temperature fluctuations, to th e addition of biologically fixed nitrogen, to the enhancement of habitat for soil bi ota. In this document, the focus is on the services most beneficial to remediation of the soil fertility in the cacao agroforestry system under investigation. These services are enhancem ent of fertility through additions of SOM, enhancement of solution [Pi], the amelioration of soil acidity, and the biological fixation of nitrogen (Dinesh et al. 2004; Li et al. 2007; Ryan and Delhai ze 2001; Wortmann et al. 2000). Combined, these processes have the potential to increase agricultural soil pr oductivity and sustainable use, alleviate the n eed to clear additional lands, and increase economic security of small-scale agriculturalists (Baligar et al. 2008). In this experime nt, we test the effects of five perennial cover crop species: Arachis pintoi (perennial peanut), Calopogonium mucunoides (calopogonium) Canavalia ensiformis (jack bean), Callisia repens (turtle vine), and Centrosema macrocarpum (macrocarpum) on phosphorus solubility in an experimental cacao agroforestry system in Peru. Cover Crops as Sources of Soil Organic Matter As previously discussed, SOM is closely correlate d to soil fertility. Cover crops aid in the recuperation of SOM lost duri ng the conversion of forested la nd to agrosystem. Cover crop plants have a greater root volum e than perennial trees, allowing for a much greater absorption of mineral nutrients. The deposition of the nutrient rich OM associated with cover crop root and foliar residues enhances the biol ogical cycling of nutrients in agrosystems (Chapin et al. 2002; Vitousek et al. 2002). In additi on to enhancing nutrient cycling within agrosystems, deposition

PAGE 23

23 of cover-crop detritus: enhances water holding capacity, reduces leaching of nutrients, and alleviates Al toxicity (Ber kelaar 2001; Fageria et al. 2005; Mafongoya et al. 2004). The maintenance of SOM pools and asso ciated cycling of nutrients a llows tropical soils to support the sustainable production of agricultural crops a process now recogni zed as being largely dependant on land management practices (Barber 1995). Cover Crops Enhance Soil Solution Inorganic Phosphorus Cultiva tion of cover crops enhances the tota l root volume in agricultural system, thus increasing the surface area by which nutrients are absorbed and the total volume of exudates potentially released by plant r oots (Ryan and Delhaize 2001). R oot exudates alter rhizosphere pH and participate in ligand exchan ge reactions with chelating metals (Hinsinger 2001). The equilibrium of soil P between the liquid and solid phases controls the solution [Pi] which is the immediate source of plant available P. The soil P equilibrium is shifted by changes in soil pH, anion concentration, and metal concentration and form (Weintraub et al. 2007). Organic anions exuded by plant roots compete with phosphate anions to participat e in ligand exchange reactions with Al3+ and Fe3+ metal oxides (Hinsinger 2001). Liga nd exchange reactions occur between P sorbed to the surfaces of meta l oxides when the solution concen tration of phosphate anions is less than the solution concentration of other anio ns such as citrate or oxalate. When organic anions successfully out compete phosphate groups for binding sites in th e soil, forming strong complexes with Al3 + and Fe3 +, the solution [Pi] is increased (Weintraub et al. 2007). Organic anions enhance rhizosphere biological commun ities through microbial priming which enhance phosphatase production (Hedley et al. 1982b; Hinsinger 2001). In acidic soils, phosphate ions precipitate with Al and Fe cations. The formed metal phosphate compounds have a low solubility and are likely not r eadily available for uptake by plants at low pH. However, Aland Fe-phosphates are increasingly solubl e as pH increases. Changes in soil pH are associated with

PAGE 24

24 increases in the labile P pools. Plants are constantly taking up and releasing anions and cations to and from the rhizosphere, to maintain appropriate intercellular acidity while absorbing nutrients from the soil solution. Depending on the form of available nutrients rhizosphere pH may be decreased or increased as a result of the exuda tion of organic anions, OM additions, or release of H+ or OH/ HCO3 and alter the soil solution [Pi] (Fageria et al. 2005; Hedley et al. 1982b). Cover Crops as Sources of Biologically Fixed Nitrogen Sym biotic root nodules found in many le guminous cover crops biologically fix atmospheric N and increase total soil-[N] a process that could improve crop biomass production under conditions of N and P co-limitation. Combined, N-fixing leguminous cover crops could ameliorate the need for N fertilizer additions. Additionally, legume litter generally has a low C:N ratio favoring rapid decomposition and nutrient return (McGra th et al. 2001). In the initial stage of ma ny agroforestry systems, the open canopy of young shade trees exposes nutrient rich surface soil to erosion and N-volat ilization (Hartemink 2005). Utilization of cover crops on in young open canopy agroforestry systems reduces nitrogen losses through volatilization and contributes to soil nitrogen pools th rough the biological fi xation of nitrogen (Graetz and Nair 1999; Hedley et al. 1982a; Hieltjes and Lijklema 1980; Kuo 1996a; Levy and Schlesinger 1999; Nair et al. 1995). Sequential Fractionation Procedures Soil P ions participate in th e processes of adsorption, desorption, precipitation, dissolution, m ineralization, and immobilization with metals, and organic materials. These processes are mediated by the activities of mi crobial organism populations, root uptake of nutrients, and root release of exudates. The goal of sequential extracti on of soil P procedures is to separate the soil P pools into the most and least labile pools using neutral, alkaline, acid ic, heated, and oxidizing

PAGE 25

25 extractants. Incongruencies between interpre tations of sequential fractionation of soil P procedures exist. These incongruencies ma y be due to the varying results obtained by researchers analyzing unique so il materials. Generally, extracted P-pools are assumed to originate from pre-defined soil c onstituents (labile Pi, Ca-P, Al-P Fe-P, Po, or Residual P) or more simply by the extractant employed. Table 2-1 summarizes the authors and dates of several procedures for the sequential extrac tion of P, as well as the chemi cals utilized to extract, and the interpretation for the extracted P pools. As you can see from this table, th e interpretations for the various extracted pools ge nerally have a mineralogical or chem ical bases rather than one based on plant availability. Also from the table you can see that interpretations vary between researchers. Discussion related to the various interpretations of sequential fractionation methods, their interpretations, and relevance to determin ing plant available pools are presented in the following paragraphs. Interpretations of sequential fr actionation of soil P pools that ai m to identify the extractable P pools in terms of plant availabi lity and time spans for P cycling provide the greatest service to the scientific community. Such interpretations of fractionation results allow for the successful understanding of the fate of app lied P fertilizer, and the implicat ions of management on soil [P] (Chang and Jackson 1957; Wessel 1971). In 1971, Wessel implemented a fractionation procedure to compare the P pools of similar non-fe rtilized and fertilized soils cultivated by cacao. He found the NaOH extractable [Pi] pool to be greater in the fertilized soil. He interpreted this finding to indicate that the soils iron compounds were fixing the added P, meaning that NaOH extracts from the Fe-P pool (Wessel 1971). Hedley (1982a) utilized his fractionation procedure to evaluate changes in P pool s in soils cultivated in wheat for 65 years. His evaluations were accomplished through comp arisons of an A horizon soil of adjacent

PAGE 26

26 unfertilized cultivated and pastur e plots. Hedleys fractionation procedure is intended to allow soil P to be separated and characterized as P rele ased to an anion exchange resin, and P soluble in alkali and acid of varying strengths. With this procedure Hedley f ound that the extractable Po, extractable Pi, and Residual P pools in the cultivated soils were depleted compared to the prairie soil (NaOH [P] by 22%, resin + NaOH + HC l [P] by 26%, H2SO4 + H2O2 digest [P] by 52%) indicating access to these pools by plants. The loss of these less soluble P pools which make up 21% of the TP in the pasture soil indicates that with out fertilizer additions wheat production from the same so il is not sustainable. There are weakness associated with the use of sequential fractionation procedures for general soil comparisons. First, is the fact that soils originatin g from various parent materials will yield varying proportions of P per extractant when all othe r factors are equal. Second, sequential fractionation research results not related to P plant availability or a soil P storage time scale provide little use to land managers. Third, there is a general lack of cross research comparisons of sequential fraction results due to the frequent modifications made to the procedures to account in differences between soil chemical characteristics. With each scientist establishing their own methodology, th e body of data for comparison is slim. Finally, while it is clearly demonstrated that procedures for sequent ial extractions of P do not extract from discreet soil constituent bound pools, the insistence for utilizing this a pproach to define the extracted P pools has weakened the usefulness of some pub lished interpretations (Chang and Jackson 1957; Wessel 1971). Chang and Jackson (1957) provide a good example of the confusing nature associated with interpretations of fractionation results. The authors a ssert that soil Pi can be classified into four distinct groups Ca-P, Al-P, Fe-P and the reductant-soluble-P. However, analysis of their

PAGE 27

27 published data set and discussion weakens these ascertains. For example Chang and Jackson indicate that per cent of the iron phosphate as obtained by subsequent NaOH extraction may be subtracted from aluminum phosphate and ad ded to the iron phosphate (Chang and Jackson 1957). The authors fail to expl ain how the 10% extractable Fe-P by NaOH was calculated. It is not clear that that the authors we re successful in determining exac tly what percent the quantity of Al-P vs. Fe-P is extracted with NaOH. Furthermore, even though Chang and Jackson found Aland/or Fe-P to be soluble in each of the extractants clearly indicating that the procedure does not succeed to clearly devise soil P into defined discr eet pools, they continue to pretend that all of the soil Al-/Fe-P is removed with the NH4F and NaOH extractions. To further baffle, these authors refer to the NH4Cl extractable P pool as the water (H2O) extractable P, why this is done without a comparison with an actual H2O extractable P pool in unknown. Considering the fact that the authors admit that their extractants all remove Aland Fe-P, I am concerned that their assertions that this method frac tionates soil P into discrete chem ical forms is not accurate. The experiences of Hieltjes and Lijklema ( 1980) in attempting to define the extracted P pools further elucidate the vague nature of the definitions. Using synthetic P compounds Hieltjes and Lijklema (1980) found 1M NH4Cl to extract between 3 and 7% of the orthophosphate from Ca5(PO4)3OH, Ca3(PO4)2, Fe-P, and hydrated AlPO4. However, they still suggest utilizing 1M NH4Cl to remove calcium carbonate prior to extr acting the Aland Fe-P. Considering this information it is not possible to conf idently identify the origin of 1M NH4Cl extracted P. They found 0.1M NaOH to extract less than 1% of the TP from each of Ca5(Po4)3OH and Ca3(PO4)2, while extracting more than 90% from the Fe-P and hydrated AlPO4 pools, making it feasible to determine from which pool this ex traction extracts. NaOH/ citrate-diothinoninebicarbonate (CDB) extracted ~30% of the Ca-P pools, more than 99% of the Fe-P pool and

PAGE 28

28 ~13% of the Al-P pool, making it almost ineffect ual for delineating P-po ol origin. 0.5M HCl extracted more than 95% of the P from all material s; it also cannot be used to identify the source of P pools. A comparison of the TPi extracted with the Kurmies, Hieltjes, and Hieltjes procedures without the NH4Cl step showed each of the three procedures to extract nearly the same amount of TPi for a given soil indicating that th e TPi extracted by each of these methods can be compared across similar soils. Hieltjes and Lijklema (1980) found that the sequential methods varied for P per fraction extracted depending on soils mineral constituents. For example, they found that use of CDB to separate the Ca-P from the Feand Al-P, as was done by Williams (1971), to be inappropriate. Williams (1971) method was developed using naturally occurring apatite. Hieltjes a nd Lijklema (1980) used sediments not containing apatite, and found citrate to extract significant qua ntities of Ca-P. These signif icant differences in the pools extracted were attributed to the difference in the chemistry of the soil materials (Hieltjes and Lijklema 1980). Sequential Fractionation of Pl ant Available S oil Phosphorus The plant available P pools are most convinc ingly defined as thos e extracted pools that correlate with plant foliar P, plant response to fertilization, or cultivat ion of plants (Wessel 1971). Wessel (1971) found the cacao foliar P and res ponse to fertilizer to correlate well with all extractable Pi fractions indicating that all extrac ted soil P pools contribute to the plant available P. Hedley (1982a) rationally interprets deple tions in soil P pools to indicate accessibility of those pools to plants. Hedley ac knowledges that the majority of P depleted in the cultivated soil passed through the plant-availabl e Pi pool prior to uptake by wheat It is reasonable to assess that the sequential fractionation pr ocedures provide a snapshot in time of the general strength of P adsorption to soil materials, as well as pool s of depletion or fixa tion. The fact that considerable portions of soil P are cycled via microbial and rhizosphere process mediated

PAGE 29

29 mineralization cannot be ignored. Other research ers have not been as explicit with their definition of the plant available P fraction. Chan g and Jackson (1957) defined the plant available pool to depend simply on the extensity of the ph osphate surface of various chemical species. Hedley et al (1982a) further warn s that decreases in the less ex tractable Po and residual P indicate a limit to mineralizable soil P, and a need for P fertilizer in the system to sustain plant productivity. This rational is supported by the no tion that these less soluble fractions result from long term processes that can not replenish at a rate suitable to support the sustainable productivity of agriculture (Din esh et al. 2004). Regardless of the incongruencies between methods and interpretations, sequential fractiona tion procedures can be utilized to provide information regarding the effects of land cultivation of soil P pools, and the fate of applied P inorganic or orga nic fertilizer.

PAGE 30

30 Table 2-1. Sequential fractionation of soil P procedures and interpretation Extraction Sequence P Fraction Comments / Materials analyzed a Chang and Jackson (1956) 1M NH4Cl Water-soluble and loosely-bound P; Exchangeable Ca Various soils and synthetic minerals. Neutral 0.5M NH4F Al-P completely; Fe-P slightly 0.1M NaOH Al-P; Fe-P; Po 0.5M H2SO4 Ca-P completely; Aland Fe-P considerably Na2S2O4-citrate Fe-P completely; Al-P negligibly Neutral 0.5M NH4F Occluded Al-P 0.1M NaOH Occluded Aland Fe-P Wessel (1971) NH4Cl Water-soluble P; Loosely bound P South-western Nigerian cacao soils. NH4F Al-P Modification of Chang and Jackson (1956). NaOH Fe-P Considers the first four fractions 'extractable or non-occluded inorganic P'. H2SO4 Ca-P Occluded P = TP sum of extractions Perchloric acid digestion TP Ignition Organic P Williams et al. (1971) 0.1M NaOH / 1M NaCl, followed by 0.3M Na3C6H5O7 / Na2S2O4 / 1M NaHCO3 digest Feand Al-P Calcareous lake sediments. Citrate/dithionite/ bicarbonate = CDB 0.5M HCl Ca-P As interpreted by Hieltjes and Lijklema (1980) and Graetz and Nair (1999). Kurmies (1972) 1M NH4Cl Loosely bound As interpreted by Hieltjes and Lijklema (1980). 0.1M NaOH Feand Al-P 0.5M HCl Ca-P Hieltjes and Lijklema (1980) 1M NH4Cl Loosely bound P Calcar eous sediments and synthetic minerals. 0.1M NaOH Fe+ Al-P Modification of Kurmies (1972). 0.5M HCl Ca-P

PAGE 31

31 Table 2-1. Continued Extraction Sequence P Fraction Comments / Materials analyzed a Hedley (1982a) Anion exchange resin Most of the biologically available Pi; Negligible [Po] Agricultural soils. 0.5M NaHCO3 Labile Pi + Po sorbed on soil surfaces; Small amount of microbial P Modified in part from Williams et al. (1971, 1980). 0.1M NaOH Pi + Po compounds held by chemisorption to Fe+ Alof soil surfaces. Sonification in 0.1M NaOH Pi + Po held at the internal surfaces of soil aggregates. 1M HCl Apatite-type minerals; Occluded P; Negligible [Po] H2SO4 + H2O2 digest More ch emically stable Po forms; Relatively insoluble Pi forms; Residual P Ruttenberg (1992) 1M MgCl2 Exchangeable; Loosley sorbed P As interpreted by Graetz and Nair (1999) 0.1M NaOH / 1M NaCl, followed by 0.3M Na3C6H5O7 / Na2S2O4 / 1M NaHCO3 digest at pH 7.6 Easily reducible or reactive Fe-P CDB Acetate buffer at pH 4 Dauthigenic apatite P Marine sediments 1M HCl Detrital apatite P Ingnition / 1M HCl Organic P Hedley (1982b) Anion exchange resin Form of soil P from which plants normally draw their supply. Rhizosphere of Rape seedling soils. 0.5M NaHCO3 Plant availalble Pi; More labile forms of soil Po. 0.1M NaOH Partial dissolu tion of labile soil Po and Fe+ Al-P; Desorbs Pi from the surfaces of sesquioxides. 1M NaOH More Po 1M HCl Acid-soluble Ca-P; Some sesquioxide occluded Pi. Ignition / HCl digest Most stable Po; Occluded Pi

PAGE 32

32 Table 2-1. Continued Extraction Sequence P Fraction Comments / Materials analyzed a Nair and Graetz (1995) 1M NH4Cl Easily removable/soluble ; Labile P; Loosely adsorbed; South Florida dairy soils. 0.1M NaOH Fe+ Al-P; Some hydrolized Po. Modification of Hieltjes and Lijklema (1980); NaOH extract digest 0.1M NaOH extractable Po 0.5M HCl Ca+ Mg-P Ingnition / 6m HCl digest Re sidual P; Recalcitrant P; Primarily Po. Total P = sum of all extracts. Crews (1996) Anion exchange resin Most labile P; Plan t available P Mexican alfalfa soils. NaHCO3 Labile Pi from sesquioxide and carbonate surfaces; Easily mineralizable pools of Po from nucleic acids and microbial P. Modification of Hedley (1982a); NaOH Pi that is more strongly bound to Fe+ Alhydroxides and clay surfaces; Retained Pi; Could still be biologically active in the future; Relatively stable Po with slow turnover rates; Relatively labile Po associated with cellulose, humic compounds, or inositol-P sorbed to Al+ Fehydroxides. HCl Primary apatite minerals; Ca-P secondary minerals. H2O2/ H2SO4 digestion Residua l P; Sesquioxides occluded Pi; Constituent Pi in resistant primary minerals; non-extractable, very stable Po associated with humic and fulvic acids and sesquioxide-stablilized inositols.

PAGE 33

33 Table 2.1 Continued Extraction Sequence P Fraction Comments / Materials analyzed a Phiri et al. (2001) Anion exchange resin Freely exchangeable Pi; Colombian volcanic-ash soil Digest of resin extract Resin extractabl e Po Modification of Tiessen and Moir (1993) 0.5M NaHCO3 Labile Pi; Po sorbed to soil surface; Small amount of microbial P. 0.1M NaOH Pi more strongly bound to Fe+ Aland humic compounds. HClO4 digest of residual soil Residual P; Insoluble Pi; More stable Po HClO4 digest of air-dried soil TP Zhang et al. (2002) Deionized water Water-soluble P; Loosely-bound P; Exchangeable Ca Florida sandy agricultural soils; 0.5M NaHCO3 Bioavailable Pi; Readily mineralizable Po Modification of Hedl ey et al (1982). Acidified (NH4)2S2O8 digest of 0.5M NaHCO3 extract TP of 0.5M NaHCO3 extract. 0.1M NaOH Potentially bioavailable Po Acidified (NH4)2S2O8 digest of 0.1M NaOH extract TP of 0.1M NaOH extract 1M HCl Acid-soluble P; Ca-P HClO4 digest Soil TP Residual P = TP sum extracted P Szulczewski and Li (unpublished) Deionized water Water-soluble P Sout hern Florida calcareous soils; 1M NH4Cl Exchangeable-P Modification of Nair and Graetz (1995) 0.1M NaOH Fe+ Al-P Digest of NaOH extract NaOH extractable Po 0.5M HCl Ca+ Mg-P HNO3 / H2O2 digest of residual soil Residual P; Po compounds

PAGE 34

34 Table 2.1 Continued Extraction Sequence P Fraction Comments / Materials analyzed a HNO3 / H2O2 digest of air-dried soil Soil TP a Table format adapted from Graetz and Nair (1999).

PAGE 35

35 CHAPTER 3 COVER CROP CULTIVATION EFFECTS ON SOIL FE RTILITY AND PHOSPHORUS FRACTIONS IN A PERUVIAN CA CAO AGROFORESTRY SYSTEM Introduction Nutrients in tropical soils have been de pleted over tim e natura lly or by continuous cultivation and harvest of plant products (Baligar et al. 2004) It is possible that with conscientious management, fertility of these soils can be maintained or improved upon, making them a renewable resource (Brady and Weil 1999). Leguminous cover crops are widely accepted for their contribution to soil qualityname ly through addition of N (Fageria et al. 2005). As P is often the most limited plant essential nu trient in tropical soils, inclusion of leguminous cover crops on tropical soils may seem counter-i ntuitive. However, leguminous cover crops influence the soil P forms through the addition of SOM, deep soil mining, and microbial priming (Brady and Weil 1999; Chapin-III et al. 2002; Di nesh et al. 2004; Li et al. 2007). Phosphorus is an essential element for plant grow th and exists in the soil in a variety of chemical forms (Elrashidi 2006; Phiri et al. 2001). The orthophosphate anion exists in soil solution and is the form of P most easily utili zed by plants and microbes. When P adsorbs to clay particles or binds to Fe or Al oxides, compounds are formed that are not as easily utilized by plants and microbes (Chapin-III et al. 2002). Phosphorus enters the soil solution by desorption or dissolution of inorganic P (P i) associated with the mineral soil or by the mineralization of organic P (Po) (Tiessen and Moir 1993). Organic P compounds must be converted to inorganic forms before they are available for plant or mycorrhizae uptake (Hopkins and Huner 2004; Paul and Clark 1989). Leguminous plants produce organic anions and hydrogen protons from their root systems, together these compounds disrupt the equilibrium between the solid and solution P pools allowing an increase in the P pools that are most available for plant uptake (Hinsinger 2001; Hopkins and Huner 2004; Paul and Clark 1989).

PAGE 36

36 Phosphorus fractionation methods sequentially remove P forms with increasingly stronger extractants. These procedures ar e thought to extract in creasing less soluble forms of soil-P into pools of organic or inorga nic P that may be more or less ava ilable for plant uptake. Fractionation of soil P may provide insight in to the fate and transformation of legume litter bound P added to the soil (Graetz and Nair 1999; Li et al. 2007). The focus of this research is on comparing soil P fractions and changes to soil fertility factors after two years of growth in a cacao agroforestry sy stem. The four leguminous species included in the experiment are Arachis pintoi (perennial peanut) Calopogonium mucunoides (calopogonium) Canavalia ensiformis (jack bean), and Centrosema macrocarpum (macrocarpum). In addition to these treatments are one inorganic nitrogen fertilizer treatment and one control. Soil P was extracted using the Mehlich I procedure commonly utilized to measure the plant available P pool and an un-published method for the sequential fractionation of soil P. Other measured soil characters are lo ss upon ignition (LOI), pH, TC, TN, % Ca, % Mg, % Fe, and % Al. Materials and Methods Study Site The Tarapoto, Peru study site at Insituto de Cultivos Tropica les (ICT) lies at latitude 6.734' S and longitude: 76.694' W, with an el evation of 356 meters above sea level, map shown in Figure 3-1 (NOAA 2007). The site recei ves an average of 120 0 mm of precipitation per year (NOAA 2007). The mean annual maximum temperature is 32 C, the minimum 19 C. The landscape of the San Martin Region of Peru is best described as hill sides feathered by rivers and streams. The soils here are acidic lo amy sand Inceptisols (pH 4.8 6.0). Other than inclusion of cover crops, the agroforestry system management style is that of the traditional methods of local cacao farmers in the San Martin Region of Peru.

PAGE 37

37 Experimental Design To test the influence of legum inous cover cr opping on soil fertility in an experimental cacao agroforestry system, a randomized block de sign was established on 1.05 hectares, utilizing leguminous cover crop treatments in the understo ry of a cacao agroforestry system. Site preparation commenced in June 2004 with clea ring, burning, and subseque nt planting of cover crops, cacao, and bananas on the site. At the ti me cacao seedlings were transplanted into the fertilized treatment 200 g of Super Guano was applie d to each plant. Two or three months after cacao seedling were transplanted into the fertilize d plot Urea (46% N) was applied to each cacao plant. The four leguminous crops included in the experiment were Arachis pintoi (perennial peanut), Calopogonium mucunoides (calo) Canavalia ensiformis (jack bean) and Centrosema macrocarpum (macrocarpum) Additionally, one non-legume cover crop Callisia repens (inch plant), one fertilized treatment having agroforest ry species without a co ver crop, and one control treatment having agroforestry sp ecies without a cover crop or fe rtilization was included in the experiment. Each treatment was replicated 3 times, once in each of 3 randomized blocks, each block is 10 x 45 meters with a 2-meter buffer be tween each treatment. This experimental design is shown in Figure 3-2. Soil Sampling Soil sam ples were collected in mid July of 2006. Ten soil samples were collected from the 0-5 cm, 5-15 cm, 0-15 cm and 15-30 cm soil depths of each replicate using a 5 cm diameter stainless steel sampling tube. Th e statistical software program JMP 5.1 generated random sampling locations from a minimum distance of one meter from the treatment border, Table A-1 contains those randomly generated co-ordinates (S.A.S. 2007). The ten soil samples corresponding by treatment, depth, and block were combined at the time of sampling to form one

PAGE 38

38 composite sample. This sampling scheme resulte d in 84 composite samples collected from the entire cover crop management experiment. All collected soil samples were transported to the laboratory, labeled, and air-dried. One time per w eek for 4 weeks, the soil samples were crushed and mixed by hand. Once air-dried, cleaned of visible roots, crushed, and passed through a 2mm sieve, the <2 mm soil fraction was utilized for soil ch emical analysis (Basamba et al. 2006; Graetz and Nair 1999; Phir i et al. 2001). Soil Nitrogen, Carbon, Calcium, Potassium, Ir on, Aluminum, Magnesium, pH, and Loss on Ignition Total N (TN) and C (TC) contents of soil for all treatm ents and depths were determined using a CNS analyzer (Elementar, Vario MAX El emental Analyzer, Elementar Analysensysteme GmbH, Germany). Total calcium (Ca), potassi um (K), iron (Fe), aluminum (Al), and magnesium (Mg) in soils from th e Control treatment at all depths were measured utilizing an Atomic Absorption Spectrophotometer (AA-6300, Sh imadzu Scientific Instruments, Columbia, MD). Soil pH and Loss on ignition (LOI) were de termined for all treatments and soil depths using methods published by the Soil Science So ciety of America (SSSA) and the American Society of Agronomy (ASA) (Nelson and So mmers 1996a; Thomas 1996). Although LOI tends to slightly over estimate the organic matter prop ortion of a soil due to the ignition of inorganic materials at high temperatures, it is often utilized to estimate soil organic matter content (Heiri et al. 2001; Nelson and Sommers 1996a). Mehlich I Extractable Phosphorus Mehlich I extractions of P was conducted on air-dried soil from the 0-15 cm depth following established m ethods (Thomas 1996). To measure organic P (P o) in the Mehlich I extraction, the supernatant was digested at 340 C in concentrated sulfuric acid (H2SO4) and

PAGE 39

39 hydrogen peroxide (H2O2), and Po was determined by subtra ction of the concentration in the undigested from the digested sample. Sequential Fractionation of Phosphorus The utilized sequential fractionation of phosphorus procedure was based upon an unpublished method by Szulczewski and Li (2007) a nd is modified from those published by Nair et. al. (1995). The single modification is that the utilized method preceded the Nair et. al. method with a deionized H2O extraction (Nair et al. 1995; Szulczewski and Li unpublished). A schematic of the utilized extraction procedure is shown in Figure 3-3. Measurement of Extracted Inorganic Phosphorus Concentrations of extracted inorganic P cont a ined within extract solutions was measured using methods published by SSSA and ASA, commonly known as The Murphy and Riley method (Kuo 1996b). Strongly alkaline or acid extract solutions were neutralized prior to analysis. Analysis of Phosphorus in Cover Crop Tissue Analysis of cover crop tissue phosphorus content was conducted by the U niversidad Nacional Agraria La Molina in Lima, Peru and re sulting data were provided to me courtesy of Instituto de Cultivos Tropicales Tarapoto Peru. The analysis were conducted on September 05, 2006. Analysis of Soil Organic Matter Analysis of soil organic m atter (SOM) cont ent was conducted using the Walkley-Black Method (Nelson and Sommers 1996b). The averaged data from this analysis was provided courtesy of ICT. No statistical analys is was conducted on the SOM data.

PAGE 40

40 Statistical Analysis Determ inations of significant treatment and depth effects were made using JMP IN 5.1 statistical software. When necessary, data transformations to meet assumptions of normality were conducted using Box and Cox Transformati ons. Initial significance of variance between the pooled data of all treatments and depths wa s determined, followed by an analysis of variance between treatments at each depth. Secondary analysis of variance was assessed between treatments within each depth. When the F values were significant, post hoc comparisons of means were made using Dunnetts Method a nd Tukey-Kramers HSD. Dunnetts Method determines significant differences in variance betw een the data of any treatment and that of the control at an alpha level of 0.05. Tukey-Kramers HSD determines significant differences in variance between the data of any treatment and that of any other treatment. Results A summ ary of all significant findi ngs is presented in Table 3-1. Soil Total Nitrogen, Total Carbon, and Carbon to Nitrogen Ratio The total nitrogen content of this soil ra nged from 790 kg/ha in the 0-5 cm horizon to 1,961 kg/ha in the 15-30 cm depth with no signif icant differences between treatments or the Control. An analysis of varian ce of the pooled data revealed no significant differences between any treatment or depth for C:N. In the 5-15 cm soil depth the analysis of variance revealed Cannavalia ensiformis to contribute significantly mo re TC to the soil than C. macrocarpum ,A. pintoi, C. mucunoides, or the Control treatment (1.53%, 0.98%, 1.04%, 1.05%. and 1.14% respectively). The averaged data, with significan t differences indicated for TN, TC, and C:N are presented in Table 3-2 and the raw data is contained in Table A-2.

PAGE 41

41 Soil Loss o Ignition and Organic Matter An analysis of variance f or th e 0-30 cm soil depth revealed C. ensiformis to lose significantly more weight than A. pintoi on ignition (4.93% vs. 2.79%). At the 5-15 cm soil depth C. repens, C. mucunoides, and C. ensiformis all lost significantly more on ignition than did A. pintoi (5.18%, 5.17%, 4.84%, 1.44% respectively). No significant differences occurred between any treatments at the 0-5 cm and 15-30 cm depths. The averaged data for LOI is in Table 3-2 and the raw data for LOI in contained in Table A-3. Soil pH An analysis of variance between pooled data revealed the 0-5 cm soil depth to have a significantly higher pH than the underlying soil horizons (5.41, 5.13, and 5.03 from the surface depth downward) these data are presented in Ta ble 3-3. Exclusion of the non-legume treatments (Fertilizer, C. repens ) from the analysis revealed the A. pintoi treatment to have a significantly higher pH in the 0-5 cm depth than the C. ensiformis and Control treatments (5.55, 5.44, and 5.18 respectively); data presente d in Table 3-2. Soil Calcium, Potassium, Magnesium, Iron, and Aluminum Calcium potassium, iron, aluminum, and magne sium concentrations were quantified for three soil depths in the Control treatment. In the 0-5 cm depth: [Ca] = 1.57 mg kg-1, [K] = 3.54 mg kg-1, [Fe] = 40.59 mg kg-1, [Al] = 57.19 mg kg-1, and [Mg] = 1.20 mg kg-1. In the 5-15 cm depth: [Ca] = 0.93 mg kg-1, [K] = 3.69 mg kg-1, [Fe] = 48.11 mg kg-1, [Al] = 75.28 mg kg-1, and [Mg] = 1.27 mg kg-1. In the 15-30 cm depth: [Ca] = 1.19 mg kg-1, [K] = 3.95 mg kg-1, [Fe] = 59.60 mg kg-1, [Al] = 98.59 mg kg-1, and [Mg] = 1.28 mg kg-1. All concentra tions except Ca increased with depth. This averaged data is pr esented in Table 3-4 and the un-average data is presented in Table A-4.

PAGE 42

42 Mehlich I Extractable Phosphorus Mehlich I extractable phosphorus pools were not significantly influenced by the inclusion of cover crops. W hen the Mehlich I extracted Pi and OP were converted to a proportion of the Mehlich I TP the ratio was nearly a constant 1 to 3 ratio. The data utilized to calculate Mehlich I extractable inorganic phosphorus are presented in Table A-5, the data utilized to calculate Mehlich I extractable total phosphor us are presented in Table A-6, and the averaged data for the Mehlich I extractable inorganic, organic, and total phosphorus is presented in Table 3-5. Sequential Fractionation of Phosphorus The f irst extractant in the sequential fractionation series is H2O. Analysis of variance for the pooled data revealed the 0-5 cm soil depth to contain significantly grea ter concentrations of H2O extractable P than the underlying depths (0.12 mg kg-1, 0.05 mg kg-1, 0.05 mg kg-1 respectively). There were no si gnificant differences between H2O extractable [Pi] between treatments. Data averaged by de pth per treatment for all extractan ts are presented in Table 3-4. The averaged sequential fractionation of phosphor us data by depth for all extractants and treatments are presented in Table 3-6. The data from which H2O extractable [Pi] was calculated are presented in Table A-7. The second extractant in the sequential fract ionation series is 1.0 M ammonium chloride (NH4Cl). The analysis of variance did not reveal any significant differences between NH4Cl extractable [Pi] between any treatment. However, for the pooled data the 0-5 cm soil depth contains significantly greater concentrations of 1.0 MNH4Cl extractable P than do the underlying depths (0.21 mg kg-1, 0.07 mg kg-1, 0.08 mg kg-1 respectively). The data from which 1 M NH4Cl extractable [Pi] was calculated are presented in Table A-8. The third extractant in the sequential frac tionation series is 0.1 M sodium hydroxide (NaOH). The analysis of va riance did not reveal any signi ficant differences between NaOH

PAGE 43

43 extractable [Pi] between any treatment. However, for the pooled data the 0-5 cm soil depth contains significantly greater concentration of 0.1M NaOH extrac table TP than do the underlying depths (43.44 mg kg-1, 35.61 mg kg-1, 26.02 mg kg-1 respectively). The data from which 0.1 M NaOH extractable [Pi] was calculated are presen ted in Table A-9. The data from which 0.1 M NaOH extractable [TP] was calcula ted are presented in Table A-10. The fourth extractant in the sequential fract ionation series is 0.5 M hydrochloric acid (0.5 M HCl). The analysis of variance revealed significant differences between 0.5 M HCl extractable [Pi] in the 0-5 cm depth between th e Control and all other treatments as follows: Control 32.90 mg kg-1, A. pintoi 21.38 mg kg-1, C. ensiformis 10.33 mg kg-1, C. macrocarpum 24.42 mg kg-1, C. mucunoides 11.51 mg kg-1; C. repens 11.54 mg kg-1, and Fertilized 22.27 mg kg-1. No other significant differe nces between treatments or depth existed for the 0.5 M HCl extractable [Pi]. The data from which 0.5 M HCl extractable phosphor us was calculated are presented in Table A-11. The fifth extraction in the sequential fractiona tion series is a 6.0 M hydrochloric acid (6.0 M HCl) digestion of the residual soil. The analysis of variance between the data pooled across depths for each treatment revealed a significant difference between the 6.0 M HCl extractable [P] between the C. ensiformis and the Control treatments (328.83 mg kg-1 vs. 234.92 mg kg-1). No other significant differences between 6.0 M HC L extractable [P] betw een any depths or treatments were present. The data from wh ich 6 M HCl extractable phosphorus was calculated are presented in Table A-12. Six Molar HCl Digest of Air-Dried Soil The analysis of variance of [P ] data resulting from an 6.0 M HCl digest of air-dried soil revealed the C. ensiformis treatm ent to contain significantly more [P] in the 5-15 cm depth than A. pintoi or C. macrocarpum (255.66 mg kg-1, 188.13 mg kg-1, and 190.64 mg kg-1 respectively).

PAGE 44

44 The data from which the [P] extracted from a 6.0 M HCl digest of air drie d soil was calculated is presented in Table A-13 and the averag ed data from this extractions is pr esented in Table 3-6. Cover Crop Tissue Phosphorus Content The analysis of variance be tween the phosphorus content of cover crop tis sue revealed C. ensiformis to contain significantly more foliar P than C. repens or C. mucunoides (0.2%, 0.09%, and 0.11% respectively). The cover crop foliar phosphorus percentages by treatm ent and block are presented in Table 3-7. Correlations Between Soil Extractable Phos phorus Fractions and Cover Crop Tissue Phosphorus Percentage Correlations between cover cr op tissue [P] and e xtractabl e soil pools of P revealed significant relationships between co ver crop P content and Mehlich I soil extractable [Pi] in the 0-15 cm depth (R2 = 0.41, P = 0.026), as well as between cover crop tissue P content and H2O soil extractable [Pi] in the 0-5 cm depth (R2 = 0.44, P = 0.018). The linear regressions for these plots are shown in Figure 3-4. Discussion In the follo wing paragraphs, I will discuss th e suitability of this soil for cacao cultivation and the influence of cover crop cultivation on phosphor us fractions and soil fertility using nutrient guidelines established for the upper 15 cm of soil (Wood 1975; Wood and Lass 2001). Soils that do not meet the nutrient criteria established by G.A.R. W ood are likely to have inadequate nutrient supplies for optimal growth and production of cacao. Soil Loss on Ignition and Organic Matter Content The ideal soil for cacao growth and productivity should contain at least 3.0% of organic m atter in the upper 15 cm of soil (Wood 1975). Soils from all of the seven treatments in this study contain approximately 2% of organic matter in the upper 20 cm of soil as determined by

PAGE 45

45 the Walkley Black Method (Table 3-8). Howeve r, loss on ignition data while including a portion of inorganic materials, provides a good representation of the organi c soil pool (Heiri et al. 2001). Statistical analysis of the loss on i gnition data showed that in the 5-15 and the 0-30 cm soil depths cover crop cultivation significantl y influenced the proportions of ignitable soil materials (Table 3-1 and Table 32). In the 5-15 cm soil depth, A. pintoi lost significantly less weight on ignition that did C. ensiformis, C. mucunoides, or C. repens. Compared to the Control data at this depth, A. pintoi and C. macrocarpum cultivation appear to have reduced the LOI pools. Also at this depth, wh en compared to the Control, C. mucunoides, C. ensiformis, and C. repens appear to have increas ed the LOI pools. A good example of the differences in combustib le pools between treatments is illustrated through a comparison with the Contro l. In the 5-15 soil depth the A. pintoi contained 31,050 kg/ha less combustible materials than the Control, C. macrocarpum contained 27000 kg/ha less than the Control, C. ensiformis 19,950 kg/ha more than the Control, C. mucunoides 24,900 kg/ha more than the Control, and C. repens 25,050 kg/ha more than the Control soil at this depth. In the 0-30 cm soil depth, the A. pintoi leguminous cover crop lost significantly less on ignition than did the C ensiformis leguminous cover crop. When compared to the Control A. pintoi lost 38,700 kg/ha less, and C ensiformis lost 57,600 kg/ha more on igni tion, seemingly substantial differences in combustible soil materials. Thes e differences in the amoun t of ignitable materials indicate that the rooting systems of A. pintoi and C. macrocarpum have a slow turn over rate, and during the growth process have taken up mine ralized organic soil components, and are now storing organic materials. On th e contrary, the rooting systems of C. mucunoides C. ensiformis and C. repens have stimulated the LOI pool, likely th rough a more rapid decomposition rate of

PAGE 46

46 their fine roots. The differences in the loss on ignition pools between tr eatments and the Control indicate that cover crop cultivation has influenced soil organic matter pools. Increasing the soil organic matter content at this site is important for improving cacao production in the area, as the benefits of abunda nt supplies of organic matter include increased nutrient availability, and a reduction in the soils phosphorus fixation capacity (Young 1997). It is likely that the crop productiv ity and soil fertility of the sy stem under investigation would greatly benefit from increased soil organic matter supplies. Therefore, this experiment provides an excellent opportunity for assessi ng the ability of cover crop cu ltivation to remediate acidic soils and alter soil fertility parameters such as soil organic matter pools. Soil Carbon Content Total soil carbon data, w hile in cluding a heterogeneous mixtur e of various carbon sources, from plant residue to charcoal, provide a good insight to the organic matter pools of a soil (Russell 2002a). In the 5-15 cm depth, cover crop cultivation appears to have an affect on the proportions of carbon containing constituents, see Table 3-1 and Table 3-2. In this depth, C. ensiformis contained significantly mo re total carbon than did A. pintoi, C. macrocarpum, C. mucunoides, or the Control treatments. The significan t contribution of carbon to this soil depth by Cannavalia ensiformis likely represents a carbon contribut ion from the degradation of the root system of the cover crop. The total carbon data mirrored the findings of the loss on ignition data very well. For ex ample for both analysis C. repens and C. ensiformis contained relatively more carbon and lost more on ignition than the other treatments, and A. pintoi and C. macrocarpum contained relatively less carbon and lost less on ignition than did the other treatments. Abundant soil carbon supplies are necessary to main tain abundant microorganism populations as this element is a necessary component of their cellu lar constituents and is required in greater amounts than any other nutrient (Alexander 1998). It is likely that both total carbon

PAGE 47

47 and loss on ignition provide a comparatively simp le means for monitoring the organic matter pools of these soils. Soil Nitrogen Content The role of legum inous cover crops in enhancing soil nitrogen pools are widely documented (Baligar et al. 2008; Brady and Weil 1999; Dinesh et al. 2004; Fageria et al. 2005; Schroth et al. 2000; Vitousek et al. 2002; Wang et al. 2007). Yet no cover crop treatment significantly altered the total soil nitrogen content at this research site. The potential causes for a lack of differences in soil nitrogen between the Control, legume, and non-legume treatments are: absence of inoculation with rh izobium at time of legume planti ng, low concentrations of soil phosphorus, aluminum toxicity, or adequate s upplies of soil nitrogen (Mafongoya et al. 2004; Peoples and Baldock 2001; Vitous ek et al. 2002). At the thre e depths analyzed the nitrogen requirement of 200 kg/ha was easily surpassed clearl y indicating an abundance of nitrogen in this soil, see Table 3-2. Carbon to Nitrogen Ratio For optim al cacao growth and productivity the upper 15 cm of soil w ill contain a carbon to nitrogen ratio (C:N) of approximately 10:1 (Wood 1975). This lo w C:N ratio is similar to that of soil bacteria, actinomycetes, fungi, and soil humus and is unlikely to occur in weathered, sandy, acidic soils (Miller and Gardiner 2001b). The qua ntified C:N ration for this soil ranges from about 13:1 to 19:1, a consistently wider ratio than is recommended, C:N ratio data is in Table 32. The C:N ratio in this soil is higher than recommended for optimal cacao production, however, it is on par with that of other legume materi als and ultimately should not bar optimal cacao productivity. For example, the C:N ratio of young alfalfa is 13:1 and that of mature clover is 20:1, both plants are legumes (Miller and Gardin er 2001b). Considering the low organic matter content of the soil, it is reasonable that th e C:N ratio would be wider than ideal.

PAGE 48

48 Soil Potassium, Calcium, and Magnesium The recommended content of the upper 15 cm for K is 300 kg/ha, Ca is 140 kg/ha, and Mg is 71 kg/ha (Wood and Lass 2001). On average, the soil at the re search site under the Control treatment contains more of all of these nutrien ts at all three depths than is recommended 1,024 kg/ha K, 320 kg/ha Ca, and 358 kg/ha Mg, data presented in Ta ble 3-4. Soil pH and Potential Aluminum Toxicity In the upper 15 cm the soil pH should range be tween 6.0 to 7.5. In the subsurface horizons the pH should not fall below 4.0 (Wood 1975). The pH in the upper 15 cm of soil under investigation ranges from about 5.0-5.5, data in Table 3-3. The A. pintoi treatment significantly increased soil pH in the 0-5 cm depth compared to the Control suggesting a potential for this cultivar to aid in the amelioration of soil acidit y. Amelioration of soil acidity on this site will favor rhizobium growth and attachment to legum e root hairs favoring conditions for biological nitrogen fixation (Zuberer 1998). Amelioration of soil acidity will also aid in the agroforestry plants ability to uptake calcium and phosphorus (Miller and Gardiner 2001a). At soil pH 4 to 5.5 Al3+ solubilizes in soil solution and is toxic to plants (Evans et al. 1998; Miller and Gardiner 2001a). However, crops differ in their ability to w ithstand aluminum toxicity so it is difficult to establish a precise pH at which soluble Al3+ begins to cause damage to the rooting system, limiting plant uptake of Ca, and P (Miller a nd Gardiner 2001a; Russell 2002b; Wood and Lass 2001). Though, the quantity of Al in this soil supersedes that of the known tolerance for some legumes and may inhibit biological nitrogen fixation by the legumes (A l averages 9,677 mg kg-1 in the upper 15 cm of soil) (B rady and Weil 1999). For example, aluminum toxicity has impaired the growth of the rooting system of the legume Medicago sativa ( alfalfa ) at 8 mg kg-1, the nodulation of Vigna unguiculata (cow pea) is i nhibited at 25 mg kg-1 Al, and the most resistant rhizobia can tolerate 100 mg kg-1 Al (Zuberer 1998). The visu al indicators of aluminum

PAGE 49

49 toxicity, yellowing of the intervei nal leaf tip area of mature leaves that slowly progresses into a full scorching of the leaf tip are present in se veral cacao plants at the research site (Wood and Lass 2001). Images of these symptoms in cacao plan ts at the research site are shown in Figure 35. Considering this information, it is likely that the optimal cacao productivity at this site may be limited by aluminum toxicity. Cover Crop Tissue Phosphorus Phosphorus is absorbed by plant roots and transported to plant tissues (Schactm an et al. 1998). The tissue analysis showed the C. ensiformis cover crop to absorb significantly more phosphorus than they other cover crops did, indi cating an advantage in phosphorus absorption mechanisms or tolerance to soil acidity or aluminum toxicity. Correlations Between Cover Crop Ti ssue and Soil Extractable Phosphorus The significant correlations between cover cr op tissue con tent and th e Mehlich I and water extractable phosphorus pools indicate that a strong relationship exis ts between the two. Water is the conduit for plant uptake of nutrients via mass flow and diffusion (Barber 1995). The Mehlich I extracting solution is commonly utilized to extract a soil phosphorus pool representative of the plant availa ble pool (Kuo 1996b). It is likely th at plants are able to absorb both the water and Mehlich I extractable phosphorus pools. Half Molar HCl Extractable Phosphorus Cover crop cultivation appear s to have altered the 0.5 M HCl extractable phosphorus pool in the 0-5 cm depth. At this depth, every tr eatm ent contained less phosphorus extracted by 0.5 M HCl than did the Control. This represen ts a loss of approxima tely 9 kg/ha P for A. pintoi 17 kg/ha P for C. ensiformis 6 kg/ha P for C. macrocarpum and 16 kg/ha P for C. mucunoides and C. repens when compared to the Control. To absorb nutrients, fungal hyphae must be close proximity to organic materials (Sylvia et al. 1998). As this rooting dept h is largely absent of

PAGE 50

50 cover crop roots, yet in close proximity to cover cr op leaf litter, it is likely that the depletion of 0.5 M HCl extractable P in the 0-5 cm is due to hyphal colonization of this horizon. Six Molar HCl Extractable Phosphorus In the 5-15 cm soil depth, cover crop cult ivation a ltered the 6.0 M HCl extractable phosphorus pool. While for this extraction, there were no significant differences between the Control and any treatment, some extractions treated soil contained more and some less extractable phosphorus than the Control. As co mpared to the Control treatment the 5-15 cm depth of air dried soil associated with A. pintoi contained approximately 21 kg/ha less, C. ensiformis contained approximately 80 kg/ha more, C. macrocarpum contained approximately 18 kg/ha more, C. mucunoides 3 kg/ha more, and C. repens 68 kg/ha more 6 M HCl extractable phosphorus. Prior research has found the HCl ex tractable phosphorus pool to be accessible by plants (Hedley et al. 1982a). Cover crops vary in their ability to to lerate soil acidity and aluminum toxicity which can affect a plants ab ility to uptake phosphorus (Baligar et al. 2008). As this soil depth is dominated by cover crop r oot systems, it is likely that the variation in tolerance of soil acidity and alum inum toxicity between the individual cover crops used in the experiment are reflected in their ability to depl ete the 6.0 M HCl extractabl e P pools. Conclusion In the previously described experim ent, we te sted the ability of cover crops to remediate the fertility of an acidic, low organic matte r containing sandy loam soil utilized for cacao cultivation. We found that the e ffects of cover crop cultivation is species dependant. However, some cover crops included in our experiment in creased surface soil pH and soil organic matter supplies. Our research showed the surface soil at our site to have a significantly higher pH, and water, NH4Cl, and NaOH extractable phosphorus pools, indicating the importance of this soil depth in storing and supplying the nutrients needed for soil fe rtility and crop production.

PAGE 51

51 While the soil under investigati on currently contains inadequa te organic matter supplies, it is likely that as the cover crops mature the su rface horizon under their growth will accumulate organic residues. However, the cover crops included in this expe riment vary in their rates of organic matter deposition. The Arachis pintoi and Centrosema macrocarpum treatments appear to be storing organic matter and the Cannavalia ensiformis Calopogonium mucunoides, and Callisia repens appear to be contributing organic matte r to the soil. Building and maintaining high contents of organic matter in surface soils are important for crop production and minimizing soil erosion. The influence of cover crop cu ltivation on soil organic matter content should continue to be monitored to establish a clea r trend of their effect on soil organic matter accumulation in the long term, as it is likely that soil organic matter additions will aid to mediate the sustainability of soil fertility. The soil under investigation has an acidity leve l that puts the plants at risk of suffering from aluminum toxicity, thus hindering the plan ts ability to uptake calcium and phosphorus. However, the cover crop species vary in their to lerance of soil acidity, and one in particular; A. pintoi significantly increased surface soil pH. An im provement in the soil fertility of this site must include an over all increase in soil pH which affects nutrient availability and crop productivity of acid soils. The recommended soil phosphorus concentration for optimal cacao growth and productivity is 25 kg/ha of available phos phorus (Wood 1975; Wood and Lass 2001). Cover crop tissue phosphorus content regresses nicely with water and Mehlich I extractable phosphorus pools, and the 0.5 M HCl and 6 M HCl extracta ble pools have been affected by cover crop cultivation indicating that all of these pools represent plant av ailable phosphorus to some extent. Extracted phosphorus concentratio ns expressed as kilograms per hectare are presented in Table

PAGE 52

52 3-9. The Mehlich I extractable phosphorus amounts to about 5 kg ha-1 P; water extractable phosphorus 2 kg ha-1, 0.5 M HCl 50 kg ha-1, and 6 M HCl 450 kg ha-1. Unless the plants are indeed accessing the HCl extractable phosphorus pools, their growth and productivity will be severely limited by a lack of phosphorus in these soils. Howeve r, quantificati on of the plant available soil phosphorus pool requires continue d monitoring of the phosphorus content of all species included in the agroforestry system as well as the fluctuations in extractable soil phosphorus pools over time. The cacao agroforestry site managed by the In stituto de Cultivos Tropicales provides an ideal setting for examining the eff ects of cover crop cultiv ation on soil fertility. In this area, the soil fertility is hindered by soil acidity, high levels of aluminum, and low organic matter content. Additionally, cultivation of the land provides much needed food and economic income to the people of this region. The identification of inexpensive and low technology techniques for improving the fertility of the soils here will have a direct and positive impact on the livelihoods of the people in this region. C ontinued research and development of cover crop applications in cacao agroforestry are needed to identify the best cover crops for ameliorating soil fertility issues in this region.

PAGE 53

53Table 3-1. Summary of significant findings. Treatment Depth TC LOI pH H20 [Pi] NH4Cl [Pi] 0.1 M NaOH [TP] 0.5 M HCl [Pi] 6 M HCl residual soil [P] 6.0 M HCl air dried soil [Pi] Foliar [P] cm % % mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 % A. pintoi 0-5 2.44 5.04 5.55aab 0.84 0.09 29.24 21.38a ndc 213.85 nd C. ensiformis 0-5 2.23 6.91 5.44 1.53 0.31 55.33 10.33a 394.76 278.07 nd C. macrocarpum 0-5 2.04 6.39 5.43 0.94 0.15 41.99 24.42a 213.4 239.20 nd C. mucunoides 0-5 1.50 4.22 5.26 1.24 0.01 29.26 11.51a nd 193.58 nd C. repens 0-5 2.07 2.49 5.56 1.25 0.17 42.79 11.54a nd 288.85 nd Fertilized 0-5 2.02 5.05 5.43 2.93 0.59 66.21 22.27a 357.40 272.35 nd Control 0-5 1.56 4.06 5.18b 0.82 0.14 39.28 32.90b 184.43 177.49 nd A. pintoi 5-15 1.04a 1.44a 5.15 0.54 0.01 32.18 33.32 nd 188.13a nd C. ensiformis 5-15 1.53b 4.84b 5.09 0.59 0.04 34.66 16.50 339.93 255.66b nd C. macrocarpum 5-15 0.98a 1.71 5.05 0.64 0.15 27.98 16.50 231.28 190.64a nd C. mucunoides 5-15 1.05a 5.17b 5.09 0.40 0.02 28.40 24.85 nd 204.41 nd C. repens 5-15 1.48 5.18b 5.18 0.52 0.05 44.39 28.89 nd 247.74 nd Fertilized 5-15 1.44 4.49 5.23 0.98 0.12 51.63 21.76 312.77 265.07 nd Control 5-15 1.14a 3.51 5.12 0.42 0.09 30.07 24.55 227.35 202.49 nd A. pintoi 0-30 1.41 2.79b 5.26 0.70 0.04 29.76 28.32 nd 197.57 0.11 C. ensiformis 0-30 1.52 4.93a 5.20 0.88 0.12 37.54 18.02 328.83a 245.59 0.2a C. macrocarpum 0-30 1.27 3.78 5.16 0.70 0.11 32.36 20.87 232.15 207.94 0.11 C. mucunoides 0-30 1.17 4.26 5.12 0.69 0.01 28.24 15.42 nd 208.09 0.11b C. repens 0-30 1.49 3.66 5.24 0.76 0.22 36.40 19.23 nd 270.23 0.09b Fertilized 0-30 1.44 4.19 5.24 1.52 0.25 47.13 22.70 325.05 254.97 nd Control 0-30 1.23 3.65 5.11 0.59 0.08 33.76 23.76 234.92b 196.48 nd

PAGE 54

54Table 3-1 Continued Treatment Depth TC LOI pH H20 [Pi] NH4Cl [Pi] 0.1 M NaOH [TP] 0.5 M HCl [Pi] 6 M HCl residual soil [P] 6.0 M HCl air dried soil [Pi] Foliar [P] cm % % mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 % Combinedd 0-5 1.98 4.88 5.41a 0.12a 0.21a 43.44a 19.19 287.50 237.63 nd Combined 5-15 1.24 3.76 5.13b 0.05b 0.07b 35.61b 23.77 277.83 222.02 nd Combined 15-30 0.87 3.04 5.03b 0.05b 0.08b 26.02b 20.61 275.38 217.87 nd a Mean values followed by different letters within the same de pth section indicate significant differences at the P < 0.05 level. b Mean values in bold are significant. c nd indicates no data for that depth. d Combined in the Treatment column indicates that data across treatments was averaged per depth.

PAGE 55

55Table 3-2. Total nitrogen, tota l carbon, carbon to nitrogen rati o, pH, and loss on ignition averaged data for all treatments at all depths. Treatment Depth Total N Total C C/N pH LOI N C LOI cm % % % kg/ha kg/ha kg/ha A. pintoi 0-5 0.13 2.44 18.71 5.55a 5.04 977.12ab 18278.7837800.00 C. repens 0-5 0.13 2.07 15.84 5.56 2.49 979.35 15517.5818662.32C. mucunoides 0-5 0.11 1.50 14.26 5.26 4.22 790.61 11277.3031619.27C. ensiformis 0-5 0.15 2.23 15.14 5.44a 6.91 1106.57 16752.5351825.00C. macrocarpum 0-5 0.13 2.04 15.25 5.43 6.39 1004.28 15314.6347940.96Control 0-5 0.10 1.56 15.57 5.18b 4.06 752.24 11708.8530464.16Fertilized 0-5 0.13 2.02 15.84 5.43 5.05 956.82 15155.9337840.34A. pintoi 5-15 0.07 1.04 14.65 5.15 1.44a 1065.78 15612.9010800.00C. repens 5-15 0.10 1.48 14.48 5.18 5.18b 1532.27 22186.5038850.00C. mucunoides 5-15 0.07 1.05 14.90 5.09 5.17b 1057.37 15755.2538775.00C. ensiformis 5-15 0.10 1.53ac 14.94 5.09 4.84b 1536.23 22950.0036300.00C. macrocarpum 5-15 0.07 0.98b 13.19 5.05 1.71 1114.46 14700.0012815.62Control 5-15 0.08 1.14b 15.20 5.12 3.51 1125.06 17100.0026340.08Fertilized 5-15 0.12 1.44 11.83 5.23 4.49 1828.68 21630.7533695.15A. pintoi 15-30 0.06 0.76 13.33 5.10 1.90a 1282.48 17097.9814250.00C. repens 15-30 0.07 0.91 13.33 5.00 3.30 1538.12 20510.1024770.54C. mucunoides 15-30 0.07 0.94 13.28 5.02 3.39 1597.55 21212.5525396.30C. ensiformis 15-30 0.06 0.79 12.90 5.06 3.04b 1378.82 17783.7822800.00C. macrocarpum 15-30 0.06 0.80 13.37 5.00 3.25 1338.28 17891.3324357.67Control 15-30 0.07 1.00 13.60 5.02 3.37 1659.96 22571.5525294.26Fertilized 15-30 0.09 0.87 9.95 5.04 3.05 1961.91 19520.3322842.83 a Bulk density is assume d to be 1500 kg/m3. b Nutrient quantity is for the entire associated depth. c Mean values followed by different letters indicat e significant differences at the P < 0.05 level

PAGE 56

56 Table 3-3. Water, pH, and NH4Cl, NaOH, and HCl extractable inorganic phosphorus averaged data. Depth pH Water [P] NH4Cl [P] NaOH [P] NaOH [TP] 0.5 HCL [P] 6 M HCl residual soil [P] 6 M HCl air dried soil [P] cm mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 0-5 5.41a 0.12a 0.21a 34.86 43.44a 19.19287.50a 237.63 5-15 5.13b 0.05b 0.07b 29.21 35.61b 23.61277.83b 222.0215-30 5.03b 0.05b 0.08b 23.60 26.02b 20.61275.38b 217.87 a Mean values followed by different letters indicate significant differences at the P < 0.05 level.

PAGE 57

57Table 3-4. Calcium, potassium, iron, alum inum, and magnesium averaged data. Treatment Depth Ca K Fe Al Mg Ca K Fe Al Mg cm % % % % % kg/ha kg/ha kg/ha kg/ha kg/ha Control 0-5 0.02 0.060.560.640.02171.09ab 413.61 4201.20 4773.84 145.58 Control 0-5 0.01 0.050.500.860.02104.72 390.45 3760.79 6467.06 132.92 Control 0-5 0.02 0.030.460.650.01164.78 192.20 3453.51 4842.75 85.58 Control 5-15 0.01 0.050.490.710.02207.49 680.06 7373.74 10610.81 258.11 Control 5-15 0.01 0.060.651.060.02181.73 903.88 9823.14 15828.38 278.85 Control 5-15 0.01 0.030.661.060.01131.49 491.98 9863.31 15907.13 174.98 Control 15-30 0.02 0.040.460.750.02422.83 973.32 10250.3316772.63 375.61 Control 15-30 0.02 0.060.811.290.02457.12 1345.61 18260.8328999.41 402.98 Control 15-30 0.01 0.050.971.660.01124.26 1015.62 21773.3637416.38 303.22 a Bulk density is assume d to be 1500 kg/m3. b Nutrient quantity is for the entire associated depth.

PAGE 58

58 Table 3-5. Mehlich I extraction of inorganic, organic, and to tal phosphorus averaged data. Treatment Depth Inorganic [P] Organic [P] Total [P] Inorganic P Organic P cm mg kg-1 mg kg-1 mg kg-1 % % A. pintoi 0-15 2.036.318.3424.35 75.65 C. repens 0-15 3.1410.8914.0322.38 77.62 C. mucunoides 0-15 2.798.6311.4224.41 75.59 C. ensiformis 0-15 3.9212.1616.0824.40 75.60 C. macrocarpum 0-15 2.547.8610.3924.40 75.60 Control 0-15 2.477.6610.1324.40 75.60 Fertilized 0-15 3.8711.9815.8524.40 75.60

PAGE 59

59 Table 3-6. Sequential extraction of phosphate and the digest of air-dried soil averaged data. Treatment Depth H2O [P] NH4Cl [P] NaOH [P] NaOH [TP] 0.5 HCL [P] 6 M HCl residual soil [P] 6.0 M HCl air dried soil [Pi] cm mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 A. pintoi 0-5 0.84 0.09 18.66 29.24 21.38a mdpa 213.85 C. ensiformis 0-5 1.53 0.31 31.24 55.33 10.33a 394.76ab 288.85 C. macrocarpum 0-5 0.94 0.15 31.27 41.99 24.42a 213.40 193.58 C. mucunoides 0-5 1.24 0.01 41.53 29.26 11.51a mdp 278.07 C. repens 0-5 1.25 0.17 36.08 42.79 11.54a mdp 239.20 Control 0-5 0.82 0.14 34.05 39.28 32.90b 184.43b 177.49 Fertilized 0-5 2.93 0.59 45.79 66.21 22.27a 357.40 272.35 A. pintoi 5-15 0.54 0.01 20.02 32.18 33.32 mdp 188.13aa C. ensiformis 5-15 0.59 0.04 25.93 34.66 16.50 339.93a 247.74 C. macrocarpum 5-15 0.64 0.15 28.99 27.98 16.50 231.28 204.41 C. mucunoides 5-15 0.40 0.02 17.84 28.40 24.85 mdp 255.66b C. repens 5-15 0.52 0.05 39.17 44.39 28.89 mdp 190.64a Control 5-15 0.42 0.09 25.01 30.07 24.55 227.35b 202.49 Fertilized 5-15 0.98 0.12 44.46 51.63 21.76 312.77 265.07 A. pintoi 15-30 0.73 0.01 17.87 27.84 30.28 mdp 190.74 C. ensiformis 15-30 0.53 0.02 19.82 22.64 27.22 251.79a 274.10 C. macrocarpum 15-30 0.52 0.01 23.43 27.12 21.70 251.78 226.27 C. mucunoides 15-30 0.44 0.01 20.76 27.07 9.91 mdp 203.04 C. repens 15-30 0.49 0.45 29.53 22.01 17.26 mdp 193.97 Control 15-30 0.52 0.02 27.50 31.92 13.82 292.99b 209.45 Fertilized 15-30 0.66 0.03 22.87 23.54 24.06 304.98 227.49 a Mean values followed by different letters indicate significant differences at the P < 0.05 level. b mdp indicates a missing data point

PAGE 60

60 Table 3-7. Phosphorus content of cover crop foliar tissue. Treatment Block P Mean P Mean P % % kg ha-1 Arachis pintoi 1 0.12 0.11 0.0013 Arachis pintoi 2 0.11 Arachis pintoi 3 0.11 Calopogonium mucunoides 1 0.16 0.10aa 0.0006 Calopogonium mucunoides 2 0.07 Calopogonium mucunoides 3 0.07 Callisia repens 1 0.11 0.09a 0.0003 Callisia repens 2 0.08 Callisia repens 3 0.08 Cannavalia ensiformis 1 0.18 0.20b 0.0014 Cannavalia ensiformis 2 0.17 Cannavalia ensiformis 3 0.25 Centrocema macrocarpum 1 0.09 0.10 0.0015 Centrocema macrocarpum 2 0.12 Centrocema macrocarpum 3 0.11 a Mean values followed by different letters indicate significant differences at the P < 0.05 level.

PAGE 61

61 Table 3-8. Soil organic matter, potassium, cation ex change capacity, cations, and base saturation averaged data. Treatmenta Depth SOM CEC Ca2+ Mg2+ K+ Al3+ + H+ Base Sat cm % cmol/kg cmol/kg cmol/kg cmol/kg cmol/kg % Control 0-20 1.90 5.97 2.03 3.04 0.15 0.75 87.44 Fertilizer 0-20 2.20 7.13 3.01 3.25 0.19 0.68 90.46 C. repens 0-20 2.20 4.86 3.12 0.87 0.23 0.65 86.83 C. mucunoides 0-20 2.00 4.25 2.69 0.69 0.26 0.61 85.65 C. macrocarpum 0-20 2.00 6.27 2.25 3.07 0.24 0.71 88.68 C. ensiformis 0-20 2.10 3.92 2.33 0.69 0.29 0.61 84.44 A. pintoi 0-20 1.90 6.04 2.06 3.14 0.25 0.58 90.40 a data provided courtesy of Instituto de Cultivos Tropicales (Baligar et al. 2008).

PAGE 62

62Table 3-9. Extractable phosphorus expre ssed in kilograms per hectare. Treatment Depth Water [Pi] NH4Cl [Pi] NaOH [Pi] NaOH [TP] 0.5 M HCL [Pi] 6 M HCl Air Dried Soil [Pi] Mehlich [Pi] Mehlich [Po] Mehlich [TP] cm kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha A. pintoi 0-5 0.63 0.07 13.99 21.93 16.04 160.39 nda nd nd C. ensiformis 0-5 1.14 0.24 23.43 41.50 7.75 208.55 nd nd nd C. macrocarpum 0-5 0.71 0.12 23.45 31.49 18.32 179.40 nd nd nd C. mucunoides 0-5 0.93 0.01 31.15 21.94 8.63 145.19 nd nd nd C. repens 0-5 0.94 0.13 27.06 32.09 8.66 216.64 nd nd nd Control 0-5 0.61 0.11 25.54 29.46 24.68 204.26 nd nd nd Fertilized 0-5 2.19 0.44 34.34 49.66 16.70 133.12 nd nd nd A. pintoi 5-15 0.81 0.01 30.03 48.27 49.98 282.20 nd nd nd C. ensiformis 5-15 0.88 0.06 38.90 51.98 24.74 383.49 nd nd nd C. macrocarpum 5-15 0.96 0.23 43.48 41.97 24.75 285.96 nd nd nd C. mucunoides 5-15 0.60 0.03 26.76 42.60 37.28 306.62 nd nd nd C. repens 5-15 0.79 0.08 58.75 66.59 43.34 371.61 nd nd nd Control 5-15 0.64 0.14 37.51 45.10 36.82 397.61 nd nd nd Fertilized 5-15 1.47 0.18 66.69 77.44 32.64 303.74 nd nd nd A. pintoi 15-30 1.63 0.02 40.21 62.65 68.12 444.53 nd nd nd C. ensiformis 15-30 1.20 0.04 44.60 50.94 61.25 552.58 nd nd nd C. macrocarpum 15-30 1.16 0.03 52.72 61.01 48.81 467.87 nd nd nd C. mucunoides 15-30 0.98 0.02 46.71 60.92 22.30 468.20 nd nd nd C. repens 15-30 1.10 1.00 66.44 49.52 38.83 608.02 nd nd nd Control 15-30 1.18 0.04 61.88 71.82 31.09 573.68 nd nd nd Fertilized 15-30 1.49 0.07 51.46 52.96 54.14 442.08 nd nd nd

PAGE 63

63Table 3-9 Continued Treatment Depth Water [Pi] NH4Cl [Pi] NaOH [Pi] NaOH [TP] 0.5 M HCL [Pi] 6 M HCl Air Dried Soil [Pi] Mehlich [Pi] Mehlich [Po] Mehlich [TP] cm kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha A. pintoi 0-15 1.44 0.08 44.03 70.20 66.01 442.58 4.57 14.19 18.76 C. ensiformis 0-15 2.02 0.30 62.32 93.48 32.49 592.04 7.07 24.50 31.57 C. macrocarpum 0-15 1.67 0.35 66.93 73.46 43.07 465.36 6.27 19.42 25.70 C. mucunoides 0-15 1.52 0.04 57.91 64.54 45.91 451.80 8.83 27.35 36.18 C. repens 0-15 1.72 0.20 85.81 98.68 51.99 588.25 5.71 17.68 23.38 Control 0-15 1.25 0.24 63.04 74.56 61.50 436.85 5.56 17.23 22.79 Fertilized 0-15 3.67 0.62 101.03 127.10 49.34 601.87 8.70 26.95 35.65 a nd indicates no data for that depth.

PAGE 64

64 Figure 3-1. Map of Peru, with an arrow indicat ing the location of Tara poto, the outskirts of which is the location of this research.

PAGE 65

65 Figure 3-2. Experimental design consisted of three randomized blocks, each containing one replicate each of seven ground cover types in the understory of a cacao agroforestry system. Each number indicates the placement of ground cover type as follows: 1 = A. pintoi 2 = Control, 3= C. mucunoides 4 = C.ensiformis 5 = C. repens 6 = C. macrocarpum and 7= Fertilized. 1 2 3 5 6 7 4 1 2 3 4 5 6 7 1 2 3 4 5 6 7 45 m 2 m 10 m Block 1 Block 2 Block 3

PAGE 66

66 Figure 3-3. Sequence for the fractionation of soil phosphorus pools. Adapted from (Nair et al. 1995). 6M HCl Digest Quantify [P] Soil Air dried <2mm fraction H2O Deionized 20 mL Shake 2 1M NH4Cl 20 mL Shake 2 hours 0.1M NaOH 20 mL Shake 17 0.5M HCl 20 mL Shake 24 hours HCl Supernatant Quantify [P] Quantify [P] H2O Supernatant NH4Cl Supernatant NaOH Supernatant Quantify [P] Kjeldahl Digest NaOH Supernatant Quantify [P] Residual Soil Quantify [P]

PAGE 67

67 Figure 3-4. Significant correlati ons between cover crop tissue and soil extracted phosphorus pools. A. A significant linear regression between cover crop foliar phosphorus and Mehlich 1 soil extractable phosphorus (R2 = 0.41, P = 0.026). B. A significant linear regression between cover crop foliar phosphorus and water extractable soil phosphorus (R2 = 0.44, P = 0.018) in the 0-5 cm depth. -0.30 -0.28 -0.26 -0.24 -0.22 -0.20 -0.18 -0.16 -0.14 -0.12 -0.10 95100105110115120125 -0.30 -0.28 -0.26 -0.24 -0.22 -0.20 -0.18 -0.16 -0.14 -0.12 -0.10 -1.50-1.00-0.500.000.501.001.50A. B.Box-Cox transformed water extractable [Pi] Box-Cox transformed Mehlich 1 extractable [Pi]Box-Cox transformed foliar phosphorus (%)

PAGE 68

68 Figure 3-5. Physical symptoms of aluminum toxi city expressed in the mature leaves of cacao plants at Instituto de Culti vos Tropicales. A. Yellowing of the interveinal regions of the distal end of a mature leaf. B. Progressi on of leaf tip scorch. C. Leaf tip scorch in conjunction with interveinal yellowing. A B C

PAGE 69

69 APPENDIX A UNTRANSFORMED DATA Table A-1. Soil sam ple collection co-ordinates. Block Replicate Width ordinate Length ordinate m m 1 1 7.0 19.5 1 1 4.9 12.5 1 1 5.10.4 1 1 6.534.9 1 1 7.514.7 1 1 3.81.5 1 1 2.922.0 1 1 3.637.8 1 1 5.237.4 1 1 1.212.3 1 2 4.412.9 1 2 2.99.5 1 2 5.33.7 1 2 4.029.8 1 2 2.018.3 1 2 5.119.1 1 2 4.16.8 1 2 4.58.3 1 2 6.826.9 1 2 3.627.6 1 3 6.312.4 1 3 2.915.0 1 3 8.08.2 1 3 7.117.0 1 3 5.627.5 1 3 0.129.2 1 3 7.230.4 1 3 6.87.3 1 3 5.010.6 1 3 2.116.7 1 4 1.05.3 1 4 5.424.1 1 4 4.226.9 1 4 2.934.0 1 4 3.02.2 1 4 6.214.3

PAGE 70

70 Table A-1 Continued Block Replicate Width ordinate Length ordinate m m 1 4 3.4 24.7 1 4 1.3 25.2 1 4 1.217.3 1 4 2.913.7 1 5 1.54.5 1 5 3.834.4 1 5 2.013.9 1 5 3.815.5 1 5 0.724.8 1 5 1.839.0 1 5 2.517.6 1 5 5.239.1 1 5 4.529.8 1 5 3.62.7 1 6 1.219.6 1 6 3.522.3 1 6 6.420.8 1 6 3.632.4 1 6 0.625.5 1 6 5.941.1 1 6 0.241.4 1 6 2.442.5 1 6 3.417.8 1 6 1.530.2 1 7 7.340.1 1 7 1.333.7 1 7 3.721.2 1 7 0.427.8 1 7 0.71.5 1 7 5.138.8 1 7 2.718.5 1 7 6.38.3 1 7 2.11.0 1 7 4.635.1 2 1 7.019.5 2 1 4.912.5 2 1 5.10.4 2 1 6.534.9

PAGE 71

71 Table A-1 Continued Block Replicate Width ordinate Length ordinate m m 2 1 7.5 14.7 2 1 3.8 1.5 2 1 2.922.0 2 1 3.637.8 2 1 5.237.4 2 1 1.212.3 2 2 4.412.9 2 2 2.99.5 2 2 5.33.7 2 2 4.029.8 2 2 2.018.3 2 2 5.119.1 2 2 4.16.8 2 2 4.58.3 2 2 6.826.9 2 2 3.627.6 2 3 6.312.4 2 3 2.915.0 2 3 8.08.2 2 3 7.117.0 2 3 5.627.5 2 3 0.129.2 2 3 7.230.4 2 3 6.87.3 2 3 5.010.6 2 3 2.116.7 2 4 1.05.3 2 4 5.424.1 2 4 4.226.9 2 4 2.934.0 2 4 3.02.2 2 4 6.214.3 2 4 3.424.7 2 4 1.325.2 2 4 1.217.3 2 4 2.913.7 2 5 1.54.5 2 5 3.834.4

PAGE 72

72 Table A-1 Continued Block Replicate Width ordinate Length ordinate m m 2 5 2.0 13.9 2 5 3.8 15.5 2 5 0.724.8 2 5 1.839.0 2 5 2.517.6 2 5 5.239.1 2 5 4.529.8 2 5 3.62.7 2 6 1.219.6 2 6 3.522.3 2 6 6.420.8 2 6 3.632.4 2 6 0.625.5 2 6 5.941.1 2 6 0.241.4 2 6 2.442.5 2 6 3.417.8 2 6 1.530.2 2 7 7.340.1 2 7 1.333.7 2 7 3.721.2 2 7 0.427.8 2 7 0.71.5 2 7 5.138.8 2 7 2.718.5 2 7 6.38.3 2 7 2.11.0 2 7 4.635.1 3 1 7.019.5 3 1 4.912.5 3 1 5.10.4 3 1 6.534.9 3 1 7.514.7 3 1 3.81.5 3 1 2.922.0 3 1 3.637.8 3 1 5.237.4 3 1 1.212.3

PAGE 73

73 Table A-1 Continued Block Replicate Width ordinate Length ordinate m m 3 2 4.4 12.9 3 2 2.9 9.5 3 2 5.33.7 3 2 4.029.8 3 2 2.018.3 3 2 5.119.1 3 2 4.16.8 3 2 4.58.3 3 2 6.826.9 3 2 3.627.6 3 3 6.312.4 3 3 2.915.0 3 3 8.08.2 3 3 7.117.0 3 3 5.627.5 3 3 0.129.2 3 3 7.230.4 3 3 6.87.3 3 3 5.010.6 3 3 2.116.7 3 4 1.05.3 3 4 5.424.1 3 4 4.226.9 3 4 2.934.0 3 4 3.02.2 3 4 6.214.3 3 4 3.424.7 3 4 1.325.2 3 4 1.217.3 3 4 2.913.7 3 5 1.54.5 3 5 3.834.4 3 5 2.013.9 3 5 3.815.5 3 5 0.724.8 3 5 1.839.0 3 5 2.517.6 3 5 5.239.1

PAGE 74

74 Table A-1 Continued Block Replicate Width ordinate Length ordinate m m 3 5 4.5 29.8 3 5 3.6 2.7 3 6 1.219.6 3 6 3.522.3 3 6 6.420.8 3 6 3.632.4 3 6 0.625.5 3 6 5.941.1 3 6 0.241.4 3 6 2.442.5 3 6 3.417.8 3 6 1.530.2 3 7 7.340.1 3 7 1.333.7 3 7 3.721.2 3 7 0.427.8 3 7 0.71.5 3 7 5.138.8 3 7 2.718.5 3 7 6.38.3 3 7 2.11.0 3 7 4.635.1

PAGE 75

75 Table A-2. Soil total nitrogen, total carbon, pH, and carbon to n itrogen ratio unaltered data. Treatment Block Depth N C C/N pH # cm % % Arachis pintoi 1 0-5 0.162.6716.32 5.62 Arachis pintoi 2 0-5 0.112.0517.89 5.47Arachis pintoi 3 0-5 0.112.5923.01 5.56Arachis pintoi 1 5-15 0.101.2312.32 5.24Arachis pintoi 2 5-15 0.071.0415.40 5.16Arachis pintoi 3 5-15 0.050.8618.58 5.04Arachis pintoi 1 15-30 0.050.6714.15 5.09Arachis pintoi 2 15-30 0.060.7513.13 5.16Arachis pintoi 3 15-30 0.070.8512.92 5.04Callisia repens 1 0-5 0.192.9715.25 6.04Callisia repens 2 0-5 0.121.8114.76 5.37Callisia repens 3 0-5 0.071.4219.19 5.26Callisia repens 1 5-15 0.141.9613.66 5.28Callisia repens 2 5-15 0.081.1113.54 5.14Callisia repens 3 5-15 0.081.3716.88 5.11Callisia repens 1 15-30 0.091.0811.75 4.97Callisia repens 2 15-30 0.060.7611.73 5.10Callisia repens 3 15-30 0.050.9018.46 4.92Calopogonium mucunoides 1 0-5 0.162.1513.25 5.37Calopogonium mucunoides 2 0-5 0.091.2613.82 5.06Calopogonium mucunoides 3 0-5 0.061.1017.52 5.36Calopogonium mucunoides 1 5-15 0.081.1213.48 5.15Calopogonium mucunoides 2 5-15 0.071.1916.37 5.06Calopogonium mucunoides 3 5-15 0.060.8415.11 5.05Calopogonium mucunoides 1 15-30 0.091.1512.97 4.84Calopogonium mucunoides 2 15-30 0.070.9413.56 5.14Calopogonium mucunoides 3 15-30 0.050.7313.42 5.08Cannavalia ensiformis 1 0-5 0.162.0112.78 5.41Cannavalia ensiformis 2 0-5 0.172.6915.62 5.50Cannavalia ensiformis 3 0-5 0.111.9917.71 5.42Cannavalia ensiformis 1 5-15 0.141.6712.20 5.15Cannavalia ensiformis 2 5-15 0.101.5115.23 5.13Cannavalia ensiformis 3 5-15 0.071.4119.66 5.00Cannavalia ensiformis 1 15-30 0.060.7712.39 5.00Cannavalia ensiformis 2 15-30 0.070.8311.08 5.22Cannavalia ensiformis 3 15-30 0.050.7816.43 4.97Centrosema macrocarpum 1 0-5 0.141.9714.29 5.43Centrosema macrocarpum 2 0-5 0.131.8714.88 5.47

PAGE 76

76 Table A-2 Continued Treatment Block Depth N C C/N pH # cm % % Centrosema macrocarpum 3 0-5 0.142.2916.53 5.38 Centrosema macrocarpum 1 5-15 0.081.0713.07 5.13Centrosema macrocarpum 2 5-15 0.070.9713.98 5.11Centrosema macrocarpum 3 5-15 0.070.8912.40 4.92Centrosema macrocarpum 1 15-30 0.060.8314.00 4.97Centrosema macrocarpum 2 15-30 0.070.7710.32 5.21Centrosema macrocarpum 3 15-30 0.040.7917.60 4.83Control 1 0-5 0.121.5812.75 5.26Control 2 0-5 0.081.3517.21 5.24Control 3 0-5 0.101.7617.81 5.04Control 1 5-15 0.091.3115.13 5.09Control 2 5-15 0.071.1015.77 5.13Control 3 5-15 0.071.0114.66 5.15Control 1 15-30 0.091.2914.34 5.09Control 2 15-30 0.050.7814.77 5.02Control 3 15-30 0.080.9511.98 4.94Fertilized 1 0-5 0.152.1714.18 5.65Fertilized 2 0-5 0.081.7320.61 5.35Fertilized 3 0-5 0.152.1614.82 5.30Fertilized 1 5-15 0.091.5817.62 5.40Fertilized 2 5-15 0.151.227.95 5.20Fertilized 3 5-15 0.121.5312.44 5.09Fertilized 1 15-30 0.050.9517.76 5.09Fertilized 2 15-30 0.050.8217.01 5.13Fertilized 3 15-30 0.160.845.23 4.91

PAGE 77

77 Table A-3. Loss on ignition unaltered data. Treatment Block Depth Sample Volumetric Soil Volumetric + soil Post ignite volumetric + ash Post ignite ash Loss on ignition # cm # g g g g g % A. pintoi 1 0-5 1 29.42 0.21 29.63 29.60 0.18 3.91 A. pintoi 1 5-15 2 31.67 0.21 31.88 31.87 0.20 3.85 A. pintoi 1 15-30 3 31.59 0.22 31.81 31.82 0.22 0.46 A. pintoi 2 0-5 4 30.82 0.24 31.05 31.06 0.23 0.43 A. pintoi 2 5-15 5 28.37 0.23 28.60 28.61 0.23 0.43 A. pintoi 2 15-30 6 28.62 0.21 28.83 28.84 0.20 4.76 A. pintoi 3 0-5 7 28.66 0.22 28.88 28.88 0.22 0.77 A. pintoi 3 5-15 8 28.66 0.23 28.88 28.89 0.23 0.04 A. pintoi 3 15-30 9 28.77 0.21 28.98 28.99 0.21 0.49 C. repens 1 0-5 10 28.81 0.20 29.01 29.01 0.20 1.82 C. repens 1 5-15 11 29.20 0.21 29.41 29.40 0.20 5.61 C. repens 1 15-30 12 28.55 0.20 28.75 28.74 0.19 5.39 C. repens 2 0-5 13 28.60 0.22 28.82 28.81 0.22 3.15 C. repens 2 5-15 14 30.94 0.23 31.17 31.15 0.21 6.55 C. repens 2 15-30 15 29.18 0.21 29.39 29.38 0.21 2.19 C. repens 3 0-5 16 28.98 0.22 29.20 29.19 0.21 2.50 C. repens 3 5-15 17 29.68 0.20 29.88 29.87 0.20 3.37 C. repens 3 15-30 18 28.76 0.22 28.98 28.97 0.21 2.33 C. mucunoides 1 0-5 19 29.91 0.22 30.12 30.11 0.20 5.12 C. mucunoides 1 5-15 20 30.90 0.21 31.11 31.10 0.20 6.54 C. mucunoides 1 15-30 21 28.75 0.21 28.96 28.95 0.20 5.27 C. mucunoides 2 0-5 22 28.67 0.23 28.89 28.88 0.21 5.96 C. mucunoides 2 5-15 23 28.80 0.22 29.02 29.01 0.21 4.91 C. mucunoides 2 15-30 24 32.00 0.22 32.22 32.21 0.21 3.49 C. mucunoides 3 0-5 25 28.71 0.22 28.92 28.92 0.21 1.57

PAGE 78

78 Table A-3 Continued Treatment Block Depth Sample Volumetric Soil Volumetric + soil Post ignite volumetric + ash Post ignite ash Loss on ignition # cm # g g g g g % C. mucunoides 3 5-15 26 28.72 0.21 28.93 28.92 0.20 4.05 C. mucunoides 3 15-30 27 31.73 0.22 31.94 31.94 0.21 1.40 C. macrocarpum 1 0-5 28 28.60 0.21 28.81 28.80 0.20 7.02 C. macrocarpum 1 5-15 29 30.83 0.20 31.03 31.03 0.20 0.88 C. macrocarpum 1 15-30 30 30.89 0.21 31.11 31.10 0.21 2.47 C. macrocarpum 2 0-5 31 32.13 0.21 32.34 32.32 0.20 7.76 C. macrocarpum 2 5-15 32 31.08 0.24 31.32 31.31 0.23 2.34 C. macrocarpum 2 15-30 33 30.57 0.24 30.81 30.80 0.23 4.55 C. macrocarpum 3 0-5 34 29.22 0.21 29.43 29.42 0.20 4.40 C. macrocarpum 3 5-15 35 30.95 0.24 31.19 31.19 0.24 1.91 C. macrocarpum 3 15-30 36 28.65 0.21 28.86 28.85 0.20 2.72 C. ensiformis 1 0-5 37 30.53 0.23 30.76 30.74 0.22 7.61 C. ensiformis 1 5-15 38 30.78 0.21 30.99 30.98 0.20 4.29 C. ensiformis 1 15-30 39 28.71 0.23 28.94 28.93 0.22 3.86 C. ensiformis 2 0-5 40 29.92 0.23 30.16 30.14 0.22 6.92 C. ensiformis 2 5-15 41 31.21 0.20 31.41 31.40 0.19 5.42 C. ensiformis 2 15-30 42 31.74 0.21 31.96 31.95 0.21 2.48 C. ensiformis 3 0-5 43 29.90 0.22 30.11 30.10 0.20 6.19 C. ensiformis 3 5-15 44 31.03 0.21 31.24 31.23 0.20 4.81 C. ensiformis 3 15-30 45 28.52 0.23 28.75 28.74 0.22 2.78 Control 1 0-5 46 31.35 0.23 31.58 31.57 0.22 4.47 Control 1 5-15 47 28.86 0.21 29.08 29.07 0.21 3.36 Control 1 15-30 48 28.72 0.24 28.95 28.94 0.22 5.85 Control 2 0-5 49 32.18 0.20 32.39 32.38 0.20 3.27 Control 2 5-15 50 28.73 0.20 28.93 28.92 0.19 4.90

PAGE 79

79 Table A-3 Continued Treatment Block Depth Sample Volumetric Soil Volumetric + soil Post ignite volumetric + ash Post ignite ash Loss on ignition # cm # g g g g g % Control 2 15-30 51 31.01 0.21 31.22 31.21 0.20 2.88 Control 3 0-5 52 30.96 0.21 31.17 31.16 0.20 4.44 Control 3 5-15 53 31.15 0.22 31.37 31.36 0.22 2.27 Control 3 15-30 54 28.68 0.20 28.88 28.88 0.20 1.38 Fertilized 1 0-5 55 29.79 0.20 29.99 29.98 0.19 5.88 Fertilized 1 5-15 56 31.91 0.22 32.13 32.12 0.21 6.24 Fertilized 1 15-30 57 28.49 0.21 28.70 28.69 0.20 3.12 Fertilized 2 0-5 58 31.26 0.23 31.49 31.48 0.22 2.63 Fertilized 2 5-15 59 28.68 0.21 28.89 28.88 0.20 3.00 Fertilized 2 15-30 60 28.92 0.20 29.12 29.11 0.19 4.51 Fertilized 3 0-5 61 30.15 0.21 30.35 30.34 0.19 6.63 Fertilized 3 5-15 62 28.81 0.23 29.04 29.03 0.22 4.24 Fertilized 3 15-30 63 28.67 0.21 28.87 28.87 0.20 1.51

PAGE 80

80 Table A-4. Soil concentration of calcium, pot assium, iron, aluminum, and magnesium unaltered data. Depth Ca K Fe Al Mg cm mg kg-1 mg kg-1 mg kg-1 mg kg-1 mg kg-1 0-5 1.83 4.4144.8150.921.55 0-5 1.12 4.1640.1268.981.42 0-5 1.76 2.0536.8451.660.91 5-15 1.11 3.6339.3356.591.38 5-15 0.97 4.8252.3984.421.49 5-15 0.70 2.6252.6084.840.93 15-30 1.50 3.4636.4559.641.34 15-30 1.63 4.7864.93103.111.43 15-30 0.44 3.6177.42133.041.08

PAGE 81

81 Table A-5. Mehlich I extraction of i norganic phosphorus unaltered data. Treatment Block Sample Soil Mehlich Total Murphy & Riley Sample in Murphy & Riley Spectrophotometer [P] Calculated [Pi] # # g ml ml ml mg kg-1 mg kg-1 A. pintoi 1 0 5.09 20.5 25.0 6.0 0.15 2.47 A. pintoi 1 1 5.29 20.5 25.0 6.0 0.15 2.35 A. pintoi 2 2 5.33 20.5 25.0 6.0 0.13 2.04 A. pintoi 2 3 5.14 20.5 25.0 6.0 0.12 2.03 A. pintoi 3 4 5.16 20.5 25.0 6.0 0.11 1.75 A. pintoi 3 5 5.42 20.5 25.0 6.0 0.10 1.57 C. repens 1 6 5.11 20.5 25.0 6.0 0.25 4.11 C. repens 1 7 5.03 20.5 25.0 6.0 0.26 4.47 C. repens 2 8 5.14 20.5 25.0 6.0 0.17 2.89 C. repens 2 9 5.23 20.5 25.0 6.0 0.17 2.78 C. repens 3 10 5.25 20.5 25.0 6.0 0.21 3.34 C. repens 3 11 5.16 20.5 25.0 6.0 0.21 3.50 Control 1 12 5.08 20.5 25.0 6.0 0.05 0.89 Control 1 13 5.0 20.5 25.0 6.0 0.06 1.06 Control 2 14 5.2 20.5 25.0 6.0 0.20 3.23 Control 2 15 5.09 20.5 25.0 6.0 0.19 3.16 Control 3 16 5.02 20.5 25.0 6.0 0.19 3.28 Control 3 17 5.2 20.5 25.0 6.0 0.20 3.21 C. ensiformis 1 18 5.04 20.5 25.0 6.0 0.15 2.53 C. ensiformis 1 19 5.12 20.5 25.0 6.0 0.15 2.50 C. ensiformis 2 20 5.05 20.5 25.0 6.0 0.43 7.29 C. ensiformis 2 21 5.22 20.5 25.0 6.0 0.31 5.06 C. ensiformis 3 22 5.09 20.5 25.0 6.0 0.18 3.05 C. ensiformis 3 23 5.17 20.5 25.0 6.0 0.19 3.11 Fertilized 1 24 5.02 20.5 25.0 6.0 0.24 4.08

PAGE 82

82 Table A-5 Continued Treatment Block Sample Soil Mehlich Total Murphy & Riley Sample in Murphy & Riley Spectrophotometer [P] Calculated [Pi] # # g ml ml ml mg kg-1 mg kg-1 Fertilized 1 25 5.13 20.5 25.0 6.0 0.23 3.82 Fertilized 2 26 5.05 20.5 25.0 6.0 0.31 5.17 Fertilized 2 27 5.27 20.5 25.0 6.0 0.31 5.02 Fertilized 3 28 5.2 20.5 25.0 6.0 0.19 3.11 Fertilized 3 29 5.14 20.5 25.0 6.0 mdpa mdp C. macrocarpum 1 30 5.13 20.5 25.0 6.0 0.12 2.01 C. macrocarpum 1 31 5.04 20.5 25.0 6.0 0.11 1.95 C. macrocarpum 2 32 5.02 20.5 25.0 6.0 0.14 2.32 C. macrocarpum 2 33 5.08 20.5 25.0 6.0 0.14 2.33 C. macrocarpum 3 34 5.15 20.5 25.0 6.0 0.12 2.00 C. macrocarpum 3 35 5.23 20.5 25.0 6.0 0.13 2.05 C. mucunoides 1 36 5.17 20.5 25.0 6.0 0.28 4.57 C. mucunoides 1 37 5.07 20.5 25.0 6.0 0.27 4.49 C. mucunoides 2 38 5.04 20.5 25.0 6.0 0.16 2.64 C. mucunoides 2 39 5.05 20.5 25.0 6.0 0.17 2.86 C. mucunoides 3 40 5.04 20.5 25.0 6.0 0.12 1.96 C. mucunoides 3 41 5.05 20.5 25.0 6.0 0.12 1.99 a mdp indicates a missing data point.

PAGE 83

83 Table A-6. Mehlich I extraction of total phosphorus unaltered data. Treatment Block Sample Soil Mehlich Pi total Digest total Mehlich in digest Murphy & Riley total Digest in Murphy & Riley Spec. Conc. Calculated [TP] # # g ml ml ml ml ml mg kg-1 mg kg-1 A. pintoi 1 0 5.09 20.0 35.0 5.0 25.0 10.0 0.15 10.14 A. pintoi 1 1 5.29 20.0 35.0 5.0 25.0 10.0 0.15 9.65 A. pintoi 2 2 5.33 20.0 35.0 5.0 25.0 10.0 0.13 8.34 A. pintoi 2 3 5.14 20.0 35.0 5.0 25.0 10.0 0.12 8.31 A. pintoi 3 4 5.16 20.0 35.0 5.0 25.0 10.0 0.11 7.18 A. pintoi 3 5 5.42 20.0 35.0 5.0 25.0 10.0 0.10 6.43 C. repens 1 6 5.11 20.0 35.0 5.0 25.0 10.0 0.25 16.84 C. repens 1 7 5.03 20.0 35.0 5.0 25.0 10.0 0.26 18.31 C. repens 2 8 5.14 20.0 35.0 5.0 25.0 10.0 0.17 11.83 C. repens 2 9 5.23 20.0 35.0 5.0 25.0 10.0 0.17 11.40 C. repens 3 10 5.25 20.0 35.0 5.0 25.0 10.0 0.21 13.70 C. repens 3 11 5.16 20.0 35.0 5.0 25.0 10.0 0.21 14.34 Control 1 12 5.08 20.0 35.0 5.0 25.0 10.0 0.05 3.65 Control 1 13 5.00 20.0 35.0 5.0 25.0 10.0 0.06 4.36 Control 2 14 5.20 20.0 35.0 5.0 25.0 10.0 0.20 13.24 Control 2 15 5.09 20.0 35.0 5.0 25.0 10.0 0.19 12.93 Control 3 16 5.02 20.0 35.0 5.0 25.0 10.0 0.19 13.45 Control 3 17 5.20 20.0 35.0 5.0 25.0 10.0 0.20 13.14 C. ensiformis 1 18 5.04 20.0 35.0 5.0 25.0 10.0 0.15 10.36 C. ensiformis 1 19 5.12 20.0 35.0 5.0 25.0 10.0 0.15 10.25 C. ensiformis 2 20 5.05 20.0 35.0 5.0 25.0 10.0 0.43 29.88 C. ensiformis 2 21 5.22 20.0 35.0 5.0 25.0 10.0 0.31 20.75 C. ensiformis 3 22 5.09 20.0 35.0 5.0 25.0 10.0 0.18 12.51 C. ensiformis 3 23 5.17 20.0 35.0 5.0 25.0 10.0 0.19 12.73

PAGE 84

84 Table A-6 Continued Treatment Block Sample Soil Mehlich Pi total Digest total Mehlich in digest Murphy & Riley total Digest in Murphy & Riley Spec. Conc. Calculated [TP] # # g ml ml ml ml ml mg kg-1 mg kg-1 Fertilized 1 24 5.02 20.0 35.0 5.0 25.0 10.0 0.24 16.70 Fertilized 1 25 5.13 20.0 35.0 5.0 25.0 10.0 0.23 15.66 Fertilized 2 26 5.05 20.0 35.0 5.0 25.0 10.0 0.31 21.17 Fertilized 2 27 5.27 20.0 35.0 5.0 25.0 10.0 0.31 20.59 Fertilized 3 28 5.20 20.0 35.0 5.0 25.0 10.0 0.19 12.74 Fertilized 3 29 5.14 20.0 35.0 5.0 25.0 10.0 mdp a mdp C. macrocarpum 1 30 5.13 20.0 35.0 5.0 25.0 10.0 0.12 8.22 C. macrocarpum 1 31 5.04 20.0 35.0 5.0 25.0 10.0 0.11 7.98 C. macrocarpum 2 32 5.02 20.0 35.0 5.0 25.0 10.0 0.14 9.52 C. macrocarpum 2 33 5.08 20.0 35.0 5.0 25.0 10.0 0.14 9.54 C. macrocarpum 3 34 5.15 20.0 35.0 5.0 25.0 10.0 0.12 8.18 C. macrocarpum 3 35 5.23 20.0 35.0 5.0 25.0 10.0 0.13 8.42 C. mucunoides 1 36 5.17 20.0 35.0 5.0 25.0 10.0 0.28 18.72 C. mucunoides 1 37 5.07 20.0 35.0 5.0 25.0 10.0 0.27 18.40 C. mucunoides 2 38 5.04 20.0 35.0 5.0 25.0 10.0 0.16 10.81 C. mucunoides 2 39 5.05 20.0 35.0 5.0 25.0 10.0 0.17 11.73 C. mucunoides 3 40 5.04 20.0 35.0 5.0 25.0 10.0 0.12 8.02 C. mucunoides 3 41 5.05 20.0 35.0 5.0 25.0 10.0 0.12 8.15 a mdp indicates a missing data point.

PAGE 85

85 Table A-7. Water extraction of i norganic phosphorus unaltered data. Treatment Depth Spec. Conc. ABS Blank mean Tube Soil Tube + Soil Tube + Soil + H2O H2O H2O [P] Remaining H2O in tube [P] in remaining H2O cm mg kg-1 mg kg-1 g g g g g mg kg-1 g mg kg-1 A. pintoi 0-5 0.07 0.05 0.00 10.382.55 12.9332.85 19.920.62 4.50 0.00 A. pintoi 5-15 0.04 0.03 0.00 10.322.18 12.5032.46 19.960.42 3.73 0.00 A. pintoi 15-30 0.05 0.03 0.00 10.342.01 12.3532.40 20.050.55 2.58 0.00 A. pintoi 0-5 0.12 0.08 0.00 10.292.04 12.3332.35 20.021.35 3.47 0.00 A. pintoi 5-15 0.05 0.03 0.00 10.232.03 12.2632.17 19.910.53 2.90 0.00 A. pintoi 15-30 0.07 0.05 0.00 10.372.00 12.3732.55 20.180.84 3.55 0.00 A. pintoi 0-5 0.05 0.04 0.00 10.362.28 12.6432.66 20.020.54 3.63 0.00 A. pintoi 5-15 0.06 0.04 0.00 10.362.19 12.5532.51 19.960.68 3.01 0.00 A. pintoi 15-30 0.08 0.05 0.00 10.382.22 12.6032.57 19.970.79 2.37 0.00 C. repens 0-5 0.26 0.17 0.00 10.312.03 12.3432.35 20.012.94 4.30 0.01 C. repens 5-15 0.07 0.05 0.00 10.282.07 12.3532.48 20.130.79 3.20 0.00 C. repens 15-30 0.06 0.04 0.00 10.322.08 12.4032.35 19.950.70 3.12 0.00 C. repens 0-5 0.03 0.02 0.00 10.232.38 12.6132.65 20.040.32 3.28 0.00 C. repens 5-15 0.02 0.02 0.00 10.362.05 12.4132.43 20.020.27 2.56 0.00 C. repens 15-30 0.02 0.02 0.00 10.312.07 12.3832.50 20.120.26 2.54 0.00 C. repens 0-5 0.05 0.03 0.00 10.362.27 12.6332.84 20.210.50 3.23 0.00 C. repens 5-15 0.05 0.03 0.00 10.352.16 12.5132.63 20.120.51 2.18 0.00 C. repens 15-30 0.04 0.03 0.00 10.261.99 12.2532.35 20.100.51 4.73 0.00 C. mucunoides 0-5 0.30 0.20 0.00 10.252.22 12.4732.65 20.183.15 2.69 0.01 C. mucunoides 5-15 0.05 0.03 0.00 10.272.29 12.5632.58 20.020.50 3.10 0.00 C. mucunoides 15-30 0.03 0.02 0.00 10.332.07 12.4032.44 20.040.33 2.25 0.00 C. mucunoides 0-5 0.02 0.01 0.00 10.282.06 12.3432.49 20.150.22 4.91 0.00 C. mucunoides 5-15 0.02 0.02 0.00 10.342.04 12.3832.45 20.070.26 2.51 0.00 C. mucunoides 15-30 0.05 0.03 0.00 10.222.11 12.3332.48 20.150.49 2.66 0.00

PAGE 86

86 Table A-7 Continued Treatment Depth Spec. Conc. ABS Blank mean Tube Soil Tube + Soil Tube + Soil + H2O H2O H2O [P] Remaining H2O in tube [P] in remaining H2O cm mg kg-1 mg kg-1 g g g g g mg kg-1 g mg kg-1 C. mucunoides 0-5 0.03 0.02 0.00 10.132.11 12.2432.44 20.200.33 1.74 0.00 C. mucunoides 5-15 0.04 0.03 0.00 10.282.34 12.6232.67 20.050.44 4.15 0.00 C. mucunoides 15-30 0.05 0.03 0.00 10.322.20 12.5232.59 20.070.48 3.67 0.00 C. macrocarpum 0-5 0.11 0.07 0.00 10.352.03 12.3832.43 20.051.25 3.55 0.00 C. macrocarpum 5-15 0.04 0.03 0.00 10.272.07 12.3432.39 20.050.46 3.01 0.00 C. macrocarpum 15-30 0.04 0.03 0.00 10.342.01 12.3532.37 20.020.51 3.95 0.00 C. macrocarpum 0-5 0.09 0.06 0.00 10.112.02 12.1332.27 20.140.98 3.79 0.00 C. macrocarpum 5-15 0.04 0.03 0.00 10.372.04 12.4132.51 20.100.45 2.41 0.00 C. macrocarpum 15-30 0.06 0.04 0.00 10.312.28 12.5932.58 19.990.60 3.05 0.00 C. macrocarpum 0-5 0.05 0.04 0.00 10.332.03 12.3632.44 20.080.60 4.28 0.00 C. macrocarpum 5-15 0.09 0.06 0.00 10.342.01 12.3532.53 20.181.02 3.19 0.00 C. macrocarpum 15-30 0.04 0.03 0.00 10.342.01 12.3532.46 20.110.45 2.78 0.00 C. ensiformis 0-5 0.06 0.04 0.00 10.222.02 12.2432.44 20.200.68 2.28 0.00 C. ensiformis 5-15 0.06 0.04 0.00 10.382.02 12.4032.43 20.030.68 2.65 0.00 C. ensiformis 15-30 0.04 0.02 0.00 10.282.03 12.3132.53 20.220.42 2.11 0.00 C. ensiformis 0-5 0.23 0.15 0.00 10.262.05 12.3132.46 20.152.62 2.32 0.01 C. ensiformis 5-15 0.05 0.03 0.00 10.342.02 12.3632.50 20.140.57 1.85 0.00 C. ensiformis 15-30 0.05 0.03 0.00 10.352.12 12.4732.67 20.200.57 2.76 0.00 C. ensiformis 0-5 0.11 0.07 0.00 10.312.04 12.3532.55 20.201.28 2.83 0.00

PAGE 87

87 Table A-7 Continued Treatment Depth Spec. Conc. ABS Blank mean Tube Soil Tube + Soil Tube + Soil + H2O H2O H2O [P] Remaining H2O in tube [P] in remaining H2O cm mg kg-1 mg kg-1 g g g g g mg kg-1 g mg kg-1 C. ensiformis 5-15 0.05 0.03 0.00 10.322.05 12.3732.44 20.070.51 1.77 0.00 C. ensiformis 15-30 0.05 0.04 0.00 10.342.07 12.4132.71 20.300.61 3.01 0.00 Control 0-5 0.11 0.07 0.00 10.372.00 12.3732.48 20.111.23 3.11 0.00 Control 5-15 0.04 0.03 0.00 10.232.07 12.3032.36 20.060.49 2.97 0.00 Control 15-30 0.05 0.04 0.00 10.352.07 12.4232.54 20.120.59 3.23 0.00 Control 0-5 0.04 0.03 0.00 10.272.07 12.3432.50 20.160.43 2.61 0.00 Control 5-15 0.04 0.03 0.00 10.362.07 12.4332.71 20.280.43 2.82 0.00 Control 15-30 0.06 0.04 0.00 10.352.06 12.4132.57 20.160.67 2.33 0.00 Control 0-5 0.07 0.05 0.00 10.342.02 12.3632.50 20.140.78 5.12 0.00 Control 5-15 0.03 0.02 0.00 10.362.00 12.3632.46 20.100.36 2.81 0.00 Control 15-30 0.03 0.02 0.00 10.342.03 12.3732.52 20.150.32 3.17 0.00 Fertilized 0-5 0.43 0.29 0.00 10.302.01 12.3132.38 20.074.93 2.47 0.01 Fertilized 5-15 0.08 0.05 0.00 10.272.01 12.2832.47 20.190.89 2.78 0.00 Fertilized 15-30 0.03 0.02 0.00 10.382.00 12.3832.68 20.300.39 1.86 0.00 Fertilized 0-5 0.15 0.10 0.00 10.342.03 12.3732.59 20.221.66 2.43 0.00 Fertilized 5-15 0.05 0.03 0.00 10.312.09 12.4032.64 20.240.54 2.78 0.00 Fertilized 15-30 0.10 0.07 0.00 10.312.06 12.3732.50 20.131.17 3.52 0.00 Fertilized 0-5 0.19 0.13 0.00 10.322.04 12.3632.51 20.152.19 3.78 0.01 Fertilized 5-15 0.13 0.09 0.00 10.352.00 12.3532.49 20.141.52 2.86 0.00 Fertilized 15-30 0.04 0.03 0.00 10.252.06 12.3132.63 20.320.43 2.60 0.00 Blank ndpa 0.00 0.00 0.00 10.300.00 10.30ndp 22.29ndp 0.15 ndp Blank ndp 0.00 0.00 0.00 10.390.00 10.39ndp 22.15ndp 0.06 ndp Blank ndp 0.00 0.00 0.00 10.360.00 10.36ndp 22.18ndp 0.06 ndp a ndp indicates that there is no data point.

PAGE 88

88 Table A-8. One molar NH4Cl extraction of inorganic phosphorus unaltered data. Treatment Depth Spec. conc. ABS Blank mean Tube Soil Tube + soil NH4Cl NH4Cl [P] Remain NH4Cl P remaining in NH4Cl Final NH4Cl [P] cm mg kg-1 mg kg-1 g g g g mg kg-1 ml mg kg-1 mg kg-1A. pintoi 0-5 0.01 0.01 0.00 10.38 2.55 12.9320.26 0.12 2.12 0.00 0.12 A. pintoi 5-15 0.00 0.00 0.00 10.32 2.18 12.5020.26 0.01 2.09 0.00 0.01 A. pintoi 15-30 0.00 0.00 0.00 10.34 2.01 12.3520.43 0.01 1.67 0.00 0.01 A. pintoi 0-5 0.01 0.01 0.00 10.29 2.04 12.3320.33 0.15 2.34 0.00 0.15 A. pintoi 5-15 0.00 0.00 0.00 10.23 2.03 12.2620.35 0.01 1.43 0.00 0.01 A. pintoi 15-30 0.00 0.00 0.00 10.37 2.00 12.3720.27 0.01 1.9 0.00 0.01 A. pintoi 0-5 0.00 0.00 0.00 10.36 2.28 12.6420.39 0.01 2.44 0.00 0.01 A. pintoi 5-15 0.00 0.00 0.00 10.36 2.19 12.5520.34 0.01 1.32 0.00 0.01 A. pintoi 15-30 0.00 0.00 0.00 10.38 2.22 12.6020.41 0.01 1.2 0.00 0.01 C. repens 0-5 0.04 0.03 0.00 10.31 2.03 12.3420.37 0.49 1.85 0.00 0.49 C. repens 5-15 0.01 0.01 0.00 10.28 2.07 12.3520.34 0.09 1.3 0.00 0.09 C. repens 15-30 0.11 0.07 0.00 10.32 2.08 12.4020.33 1.23 1.46 0.00 1.22 C. repens 0-5 0.00 0.00 0.00 10.23 2.38 12.6120.33 0.01 1.51 0.00 0.01 C. repens 5-15 0.00 0.00 0.00 10.36 2.05 12.4120.26 0.01 1.59 0.00 0.01 C. repens 15-30 0.00 0.00 0.00 10.31 2.07 12.3820.39 0.04 1.49 0.00 0.04 C. repens 0-5 0.00 0.00 0.00 10.36 2.27 12.6320.34 0.01 2.06 0.00 0.01 C. repens 5-15 0.00 0.00 0.00 10.35 2.16 12.5120.51 0.05 1.57 0.00 0.05 C. repens 15-30 0.01 0.01 0.00 10.26 1.99 12.2520.42 0.08 1.01 0.00 0.08 C. mucunoides 0-5 0.00 0.00 0.00 10.25 2.22 12.4720.29 0.01 1.39 0.00 0.01 C. mucunoides 5-15 0.00 0.00 0.00 10.27 2.29 12.5620.44 0.03 2.09 0.00 0.03 C. mucunoides 15-30 0.00 0.00 0.00 10.33 2.07 12.4020.33 0.01 1.46 0.00 0.01 C. mucunoides 0-5 0.00 0.00 0.00 10.28 2.06 12.3420.26 0.02 1.78 0.00 0.02 C. mucunoides 5-15 0.00 0.00 0.00 10.34 2.04 12.3820.32 0.01 2.01 0.00 0.01 C. mucunoides 15-30 0.00 0.00 0.00 10.22 2.11 12.3320.33 0.01 1.87 0.00 0.01 C. mucunoides 0-5 0.00 0.00 0.00 10.13 2.11 12.2420.32 0.01 1.3 0.00 0.01

PAGE 89

89 Table A-8 Continued Treatment Depth Spec. conc. ABS Blank mean Tube Soil Tube + soil NH4Cl NH4Cl [P] Remain NH4Cl P remaining in NH4Cl Final NH4Cl [P] cm mg kg-1 mg kg-1 g g g g mg kg-1 ml mg kg-1 mg kg-1C. mucunoides 5-15 0.00 0.00 0.00 10.28 2.34 12.6220.14 0.01 1.42 0.00 0.01 C. mucunoides 15-30 0.00 0.00 0.00 10.32 2.20 12.5220.19 0.01 1.17 0.00 0.01 C. macrocarpum 0-5 0.02 0.01 0.00 10.35 2.03 12.3820.19 0.19 2.15 0.00 0.19 C. macrocarpum 5-15 0.00 0.00 0.00 10.27 2.07 12.3420.20 0.01 1.81 0.00 0.01 C. macrocarpum 15-30 0.00 0.00 0.00 10.34 2.01 12.3520.32 0.01 1.27 0.00 0.01 C. macrocarpum 0-5 0.02 0.01 0.00 10.11 2.02 12.1320.26 0.21 1.57 0.00 0.21 C. macrocarpum 5-15 0.00 0.00 0.00 10.37 2.04 12.4120.24 0.01 1.38 0.00 0.01 C. macrocarpum 15-30 0.00 0.00 0.00 10.31 2.28 12.5920.18 0.01 0.94 0.00 0.01 C. macrocarpum 0-5 0.00 0.01 0.00 10.33 2.03 12.3620.32 0.06 1.3 0.00 0.06 C. macrocarpum 5-15 0.04 0.03 0.00 10.34 2.01 12.3520.20 0.44 1.73 0.00 0.44 C. macrocarpum 15-30 0.00 0.00 0.00 10.34 2.01 12.3520.22 0.02 1.61 0.00 0.02 C. ensiformis 0-5 0.00 0.00 0.00 10.22 2.02 12.2420.30 0.02 1.97 0.00 0.02 C. ensiformis 5-15 0.00 0.00 0.00 10.38 2.02 12.4020.46 0.01 2.55 0.00 0.01 C. ensiformis 15-30 0.00 0.00 0.00 10.28 2.03 12.3120.27 0.01 1.76 0.00 0.01 C. ensiformis 0-5 0.05 0.03 0.00 10.26 2.05 12.3120.29 0.60 2.85 0.00 0.60 C. ensiformis 5-15 0.01 0.01 0.00 10.34 2.02 12.3620.38 0.10 1.34 0.00 0.10 C. ensiformis 15-30 0.00 0.00 0.00 10.35 2.12 12.4720.18 0.03 1.58 0.00 0.03 C. ensiformis 0-5 0.03 0.02 0.00 10.31 2.04 12.3520.12 0.33 2.54 0.00 0.33 C. ensiformis 5-15 0.00 0.00 0.00 10.32 2.05 12.3720.24 0.01 1.67 0.00 0.01 C. ensiformis 15-30 0.00 0.00 0.00 10.34 2.07 12.4120.36 0.01 1.5 0.00 0.01 Control 0-5 0.01 0.01 0.00 10.37 2.00 12.3720.17 0.07 1.27 0.00 0.07 Control 5-15 0.00 0.00 0.00 10.23 2.07 12.3020.25 0.00 1.34 0.00 0.00 Control 15-30 0.00 0.00 0.00 10.35 2.07 12.4220.16 0.03 1.5 0.00 0.03 Control 0-5 0.03 0.02 0.00 10.27 2.07 12.3420.37 0.29 2.86 0.00 0.29 Control 5-15 0.02 0.02 0.00 10.36 2.07 12.4320.28 0.26 3.02 0.00 0.26

PAGE 90

90 Table A-8 Continued Treatment Depth Spec. conc. ABS Blank mean Tube Soil Tube + soil NH4Cl NH4Cl [P] Remain NH4Cl P remaining in NH4Cl Final NH4Cl [P] cm mg kg-1 mg kg-1 g g g g mg kg-1 ml mg kg-1 mg kg-1Control 15-30 0.00 0.00 0.00 10.35 2.06 12.4120.22 0.01 1.31 0.00 0.01 Control 0-5 0.01 0.01 0.00 10.34 2.02 12.3620.27 0.06 1.81 0.00 0.06 Control 5-15 0.00 0.00 0.00 10.36 2.00 12.3620.17 0.01 1.62 0.00 0.01 Control 15-30 0.00 0.00 0.00 10.34 2.03 12.3720.30 0.01 1.81 0.00 0.01 Fertilized 0-5 0.06 0.04 0.00 10.30 2.01 12.3120.31 0.74 2.74 0.00 0.74 Fertilized 5-15 0.00 0.00 0.00 10.27 2.01 12.2818.35 0.05 1.35 0.00 0.05 Fertilized 15-30 0.00 0.00 0.00 10.38 2.00 12.3820.25 0.01 1.92 0.00 0.01 Fertilized 0-5 0.03 0.02 0.00 10.34 2.03 12.3720.35 0.33 1.33 0.00 0.33 Fertilized 5-15 0.00 0.00 0.00 10.31 2.09 12.4020.36 0.03 1.46 0.00 0.03 Fertilized 15-30 0.00 0.00 0.00 10.31 2.06 12.3720.34 0.01 1.29 0.00 0.01 Fertilized 0-5 0.06 0.04 0.00 10.32 2.04 12.3620.30 0.69 1.61 0.00 0.69 Fertilized 5-15 0.02 0.02 0.00 10.35 2.00 12.3520.18 0.28 1.61 0.00 0.28 Fertilized 15-30 0.01 0.01 0.00 10.25 2.06 12.3120.30 0.07 1.49 0.00 0.07

PAGE 91

91 Table A-9. One-tenth molar NaOH extraction of inorganic phosphor us unaltered data. Treatment Block Depth ABS Mean blank Y intercept Spec. conc. NaOH Digest solution Sample in digestion solution Murphy & Riley Sample in Murphy & Riley NaOH extractable [Pi] # cm mg kg-1 g g ml ml ml mg kg-1 A. pintoi 1 0-5 0.29 0 1.64 0.48 19.95 10.39 10.00 5.70 1.00 22.08 A. pintoi 1 5-15 0.19 0 1.64 0.32 19.99 10.39 10.00 5.70 1.00 17.35 A. pintoi 1 15-30 mdpa 0 1.64 mdp 20.12 10.39 10.00 5.70 1.00 mdp A. pintoi 2 0-5 mdp 0 1.64 mdp 19.86 10.39 10.00 5.70 1.00 mdp A. pintoi 2 5-15 mdp 0 1.64 mdp 20.07 10.39 10.00 5.70 1.00 mdp A. pintoi 2 15-30 mdp 0 1.64 mdp 19.90 10.39 10.00 5.70 1.00 mdp A. pintoi 3 0-5 0.18 0 1.64 0.29 20.15 10.39 10.00 5.70 1.00 15.23 A. pintoi 3 5-15 0.26 0 1.64 0.42 19.99 10.39 10.00 5.70 1.00 22.70 A. pintoi 3 15-30 0.20 0 1.64 0.33 20.13 10.39 10.00 5.70 1.00 17.87 C. repens 1 0-5 0.59 0 1.64 0.96 20.11 10.39 10.00 5.70 1.00 56.32 C. repens 1 5-15 0.64 0 1.64 1.05 20.25 10.39 10.00 5.70 1.00 60.65 C. repens 1 15-30 0.36 0 1.64 0.59 20.10 10.39 10.00 5.70 1.00 33.80 C. repens 2 0-5 0.38 0 1.64 0.62 19.99 10.39 10.00 5.70 1.00 30.64 C. repens 2 5-15 0.33 0 1.64 0.54 20.02 10.39 10.00 5.70 1.00 31.26 C. repens 2 15-30 0.30 0 1.64 0.49 20.17 10.39 10.00 5.70 1.00 28.46 C. repens 3 0-5 0.25 0 1.64 0.41 20.03 10.39 10.00 5.70 1.00 21.26 C. repens 3 5-15 0.28 0 1.64 0.46 20.19 10.39 10.00 5.70 1.00 25.60 C. repens 3 15-30 0.27 0 1.64 0.44 20.08 10.39 10.00 5.70 1.00 26.34 C. mucunoides 1 0-5 0.67 0 1.64 1.10 20.06 10.39 10.00 5.70 1.00 59.07 C. mucunoides 1 5-15 0.20 0 1.64 0.33 20.08 10.39 10.00 5.70 1.00 17.32 C. mucunoides 1 15-30 0.33 0 1.64 0.55 19.93 10.39 10.00 5.70 1.00 31.33 C. mucunoides 2 0-5 0.36 0 1.64 0.59 19.98 10.39 10.00 5.70 1.00 34.01 C. mucunoides 2 5-15 0.14 0 1.64 0.23 19.99 10.39 10.00 5.70 1.00 13.25 C. mucunoides 2 15-30 0.13 0 1.64 0.22 19.97 10.39 10.00 5.70 1.00 12.39

PAGE 92

92 Table A-9 Continued Treatment Block Depth ABS Mean blank Y intercept Spec. conc. NaOH Digest solution Sample in digestio n solution Murphy & Riley Sample in Murphy & Riley NaOH extractable [Pi] # cm mg kg-1 g g ml ml ml mg kg-1 C. mucunoides 3 0-5 0.34 0 1.64 0.56 20.12 10.39 10.00 5.70 1.00 31.51 C. mucunoides 3 5-15 0.28 0 1.64 0.45 19.99 10.39 10.00 5.70 1.00 22.95 C. mucunoides 3 15-30 0.21 0 1.64 0.34 20.07 10.39 10.00 5.70 1.00 18.55 C. macrocarpum 1 0-5 0.30 0 1.64 0.50 20.16 10.39 10.00 5.70 1.00 29.35 C. macrocarpum 1 5-15 0.30 0 1.64 0.49 20.13 10.39 10.00 5.70 1.00 28.31 C. macrocarpum 1 15-30 0.29 0 1.64 0.48 19.91 10.39 10.00 5.70 1.00 28.20 C. macrocarpum 2 0-5 0.42 0 1.64 0.69 20.09 10.39 10.00 5.70 1.00 40.53 C. macrocarpum 2 5-15 0.28 0 1.64 0.46 20.01 10.39 10.00 5.70 1.00 26.96 C. macrocarpum 2 15-30 0.27 0 1.64 0.44 19.86 10.39 10.00 5.70 1.00 22.50 C. macrocarpum 3 0-5 0.25 0 1.64 0.41 20.07 10.39 10.00 5.70 1.00 23.93 C. macrocarpum 3 5-15 0.33 0 1.64 0.54 20.08 10.39 10.00 5.70 1.00 31.70 C. macrocarpum 3 15-30 0.20 0 1.64 0.33 19.93 10.39 10.00 5.70 1.00 19.58 C.ensiformis 1 0-5 0.56 0 1.64 0.92 20.00 10.39 10.00 5.70 1.00 54.13 C.ensiformis 1 5-15 0.21 0 1.64 0.35 20.18 10.39 10.00 5.70 1.00 20.47 C.ensiformis 1 15-30 0.22 0 1.64 0.35 19.94 10.39 10.00 5.70 1.00 20.52 C.ensiformis 2 0-5 0.22 0 1.64 0.36 20.05 10.39 10.00 5.70 1.00 20.80 C.ensiformis 2 5-15 0.36 0 1.64 0.59 20.15 10.39 10.00 5.70 1.00 35.03 C.ensiformis 2 15-30 0.23 0 1.64 0.38 19.97 10.39 10.00 5.70 1.00 21.13 C.ensiformis 3 0-5 0.20 0 1.64 0.32 20.14 10.39 10.00 5.70 1.00 18.78 C.ensiformis 3 5-15 0.24 0 1.64 0.39 19.99 10.39 10.00 5.70 1.00 22.28 C.ensiformis 3 15-30 0.19 0 1.64 0.31 20.04 10.39 10.00 5.70 1.00 17.80 Control 1 0-5 0.63 0 1.64 1.04 19.97 10.39 10.00 5.70 1.00 61.26 Control 1 5-15 0.45 0 1.64 0.73 20.12 10.39 10.00 5.70 1.00 42.11

PAGE 93

93 Table A-9 Continued Treatment Block Depth ABS Mean blank Y intercep t Spec. conc. NaOH Digest solution Sample in digestion solution Murphy & Riley Sample in Murphy & Riley NaOH extractable [Pi] # cm mg kg-1 g g ml ml ml mg kg-1 Control 1 15-30 0.47 0 1.64 0.77 19.97 10.39 10.00 5.70 1.00 43.78 Control 2 0-5 0.13 0 1.64 0.21 20.10 10.39 10.00 5.70 1.00 12.27 Control 2 5-15 0.11 0 1.64 0.19 20.13 10.39 10.00 5.70 1.00 10.74 Control 2 15-30 0.28 0 1.64 0.47 20.12 10.39 10.00 5.70 1.00 26.97 Control 3 0-5 0.30 0 1.64 0.49 19.94 10.39 10.00 5.70 1.00 28.61 Control 3 5-15 0.23 0 1.64 0.38 19.88 10.39 10.00 5.70 1.00 22.17 Control 3 15-30 0.12 0 1.64 0.20 19.97 10.39 10.00 5.70 1.00 11.74 Fertilized 1 0-5 0.37 0 1.64 0.61 20.01 10.39 10.00 5.70 1.00 35.94 Fertilized 1 5-15 0.67 0 1.64 1.10 20.00 10.39 10.00 5.70 1.00 64.78 Fertilized 1 15-30 0.20 0 1.64 0.34 19.99 10.39 10.00 5.70 1.00 19.88 Fertilized 2 0-5 0.61 0 1.64 1.00 20.00 10.39 10.00 5.70 1.00 58.53 Fertilized 2 5-15 0.42 0 1.64 0.69 20.12 10.39 10.00 5.70 1.00 39.22 Fertilized 2 15-30 0.27 0 1.64 0.45 20.10 10.39 10.00 5.70 1.00 25.80 Fertilized 3 0-5 0.45 0 1.64 0.74 20.04 10.39 10.00 5.70 1.00 42.90 Fertilized 3 5-15 0.30 0 1.64 0.50 19.95 10.39 10.00 5.70 1.00 29.37 Fertilized 3 15-30 0.24 0 1.64 0.40 20.10 10.39 10.00 5.70 1.00 22.93 a mdp indicates a missing data point

PAGE 94

94 Table A-10. Digest of 0.1 M NaOH supernatan t for the quantification of total 0.1 M NaOH extractable phosphorus unaltered data. Treatment Depth 0.1 M NaOH Soil Sample Volume of H2O Total sample Dilute times Spec. conc. 0.1M NaOH extractable [TP] cm g g ml ml ml mg kg-1mg kg-1 A. pintoi 0-5 20.15 2.02 0.12 10.07 10.19 85.43 0.03 24.95 A. pintoi 0-5 20.15 2.04 0.12 10.07 10.19 85.43 0.02 17.72 A. pintoi 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.04 33.12 A. pintoi 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.04 31.02 A. pintoi 15-30 20.15 2.15 0.12 10.07 10.19 85.43 0.03 24.31 A. pintoi 15-30 20.15 2.06 0.12 10.07 10.19 85.43 0.03 25.05 A. pintoi 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.05 45.06 A. pintoi 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 48.48 A. pintoi 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.04 32.39 A. pintoi 5-15 20.15 2.12 0.12 10.07 10.19 85.43 0.04 30.62 A. pintoi 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.04 34.18 A. pintoi 15-30 20.15 2.00 0.12 10.07 10.19 85.43 0.02 21.42 A. pintoi 0-5 20.15 2.10 0.12 10.07 10.19 85.43 0.05 39.26 A. pintoi 0-5 20.15 2.07 0.12 10.07 10.19 85.43 0.04 35.73 A. pintoi 5-15 20.15 2.14 0.12 10.07 10.19 85.43 0.02 18.56 A. pintoi 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 22.56 A. pintoi 15-30 20.15 2.06 0.12 10.07 10.19 85.43 0.04 29.93 A. pintoi 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.04 32.76 C. repens 0-5 20.15 2.03 0.12 10.07 10.19 85.43 0.04 31.46 C. repens 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 55.55 C. repens 5-15 20.15 2.00 0.12 10.07 10.19 85.43 0.08 66.03 C. repens 5-15 20.15 2.01 0.12 10.07 10.19 85.43 0.05 40.10 C. repens 15-30 20.15 2.08 0.12 10.07 10.19 85.43 0.03 25.38 C. repens 15-30 20.15 2.03 mdpa mdp mdp mdp mdp mdp C. repens 0-5 20.15 2.11 0.12 10.07 10.19 85.43 0.05 41.35 C. repens 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 45.78 C. repens 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.03 27.05 C. repens 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 26.40 C. repens 15-30 20.15 2.12 0.12 10.07 10.19 85.43 0.02 18.48 C. repens 15-30 20.15 2.04 0.12 10.07 10.19 85.43 0.03 22.17 C. repens 0-5 20.15 2.08 0.12 10.07 10.19 85.43 0.05 38.93 C. repens 0-5 20.15 2.04 0.12 10.07 10.19 85.43 0.04 36.87 C. repens 5-15 20.15 2.04 0.12 10.07 10.19 85.43 0.03 28.33 C. repens 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.03 23.17 C. repens 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.03 22.42

PAGE 95

95 Table A-10 Continued Treatment Depth 0.1 M NaOH Soil Sample Volume of H2O Total sample Dilute times Spec. conc. 0.1M NaOH extractable [TP] cm g g ml ml ml mg kg-1mg kg-1 C. repens 15-30 20.15 2.07 0.12 10.07 10.19 85.43 0.02 13.49 C. mucunoides 0-5 20.15 2.08 0.12 10.07 10.19 85.43 0.02 12.49 C. mucunoides 0-5 20.15 2.08 0.12 10.07 10.19 85.43 0.04 30.45 C. mucunoides 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.04 31.16 C. mucunoides 5-15 20.15 2.07 0.12 10.07 10.19 85.43 0.04 33.97 C. mucunoides 15-30 20.15 2.06 mdp mdp mdp mdp mdp mdp C. mucunoides 15-30 20.15 2.02 0.12 10.07 10.19 85.43 0.01 5.19 C. mucunoides 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 44.84 C. mucunoides 0-5 20.15 2.14 0.12 10.07 10.19 85.43 0.05 44.03 C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.02 20.07 C. mucunoides 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.03 29.43 C. mucunoides 15-30 20.15 2.02 0.12 10.07 10.19 85.43 0.05 42.34 C. mucunoides 15-30 20.15 2.05 0.12 10.07 10.19 85.43 0.04 33.69 C. mucunoides 0-5 20.15 2.15 0.12 10.07 10.19 85.43 0.05 39.51 C. mucunoides 0-5 20.15 2.09 0.12 10.07 10.19 85.43 0.07 54.97 C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.05 38.59 C. mucunoides 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.04 32.48 C. mucunoides 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.03 28.85 C. mucunoides 15-30 20.15 2.09 0.12 10.07 10.19 85.43 0.04 29.16 C. macrocarpum 0-5 20.15 2.04 0.12 10.07 10.19 85.43 0.05 43.78 C. macrocarpum 0-5 20.15 2.02 mdp mdp mdp mdp mdp mdp C. macrocarpum 5-15 20.15 2.01 0.12 10.07 10.19 85.43 0.04 30.45 C. macrocarpum 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.04 31.90 C. macrocarpum 15-30 20.15 2.00 0.12 10.07 10.19 85.43 0.03 29.93 C. macrocarpum 15-30 20.15 2.08 0.12 10.07 10.19 85.43 0.04 30.93 C. macrocarpum 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.04 33.70 C. macrocarpum 0-5 20.15 2.14 0.12 10.07 10.19 85.43 0.06 48.49 C. macrocarpum 5-15 20.15 2.03 0.12 10.07 10.19 85.43 0.03 21.59 C. macrocarpum 5-15 20.15 2.14 0.12 10.07 10.19 85.43 0.03 24.20 C. macrocarpum 15-30 20.15 2.09 0.12 10.07 10.19 85.43 0.02 20.49 C. macrocarpum 15-30 20.15 2.13 0.12 10.07 10.19 85.43 0.03 23.48 C. macrocarpum 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 41.52 C. macrocarpum 0-5 20.15 2.03 0.12 10.07 10.19 85.43 0.05 43.95 C. macrocarpum 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.03 26.99 C. macrocarpum 5-15 20.15 2.07 0.12 10.07 10.19 85.43 0.04 29.05 C. macrocarpum 15-30 20.15 2.10 0.12 10.07 10.19 85.43 0.02 19.94

PAGE 96

96 Table A-10 Continued Treatment Depth 0.1 M NaOH Soil Sample Volume of H2O Total sample Dilute times Spec. conc. 0.1M NaOH extractable [TP] cm g g ml ml ml mg kg-1mg kg-1 C. macrocarpum 15-30 20.15 2.03 0.12 10.07 10.19 85.43 0.03 26.75 C. ensiformis 0-5 20.15 2.11 0.12 10.07 10.19 85.43 0.07 56.65 C. ensiformis 0-5 20.15 2.03 0.12 10.07 10.19 85.43 0.07 61.46 C. ensiformis 5-15 20.15 2.01 mdp mdp mdp mdp mdp mdp C. ensiformis 5-15 20.15 2.09 0.12 10.07 10.19 85.43 0.05 43.33 C. ensiformis 15-30 20.15 2.02 0.12 10.07 10.19 85.43 0.03 25.52 C. ensiformis 15-30 20.15 2.13 0.12 10.07 10.19 85.43 0.02 18.19 C. ensiformis 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 47.88 C. ensiformis 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.06 47.75 C. ensiformis 5-15 20.15 2.10 0.12 10.07 10.19 85.43 0.04 29.92 C. ensiformis 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.04 30.71 C. ensiformis 15-30 20.15 2.10 0.12 10.07 10.19 85.43 0.03 24.21 C. ensiformis 15-30 20.15 2.07 0.12 10.07 10.19 85.43 0.03 27.42 C. ensiformis 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.04 32.46 C. ensiformis 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 44.01 C. ensiformis 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.03 25.02 C. ensiformis 5-15 20.15 2.11 0.12 10.07 10.19 85.43 0.04 33.26 C. ensiformis 15-30 20.15 2.08 0.12 10.07 10.19 85.43 0.03 20.90 C. ensiformis 15-30 20.15 2.08 0.12 10.07 10.19 85.43 0.03 27.19 Control 0-5 20.15 2.09 0.12 10.07 10.19 85.43 0.05 42.49 Control 0-5 20.15 2.01 0.12 10.07 10.19 85.43 0.05 43.34 Control 5-15 20.15 2.06 0.12 10.07 10.19 85.43 0.04 31.16 Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.03 29.05 Control 15-30 20.15 2.13 0.12 10.07 10.19 85.43 0.05 37.44 Control 15-30 20.15 2.03 0.12 10.07 10.19 85.43 0.04 37.11 Control 0-5 20.15 2.14 0.12 10.07 10.19 85.43 0.04 32.02 Control 0-5 20.15 2.00 0.12 10.07 10.19 85.43 0.04 32.94 Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.04 29.99 Control 5-15 20.15 2.02 0.12 10.07 10.19 85.43 0.02 19.91 Control 15-30 20.15 2.14 0.12 10.07 10.19 85.43 0.03 21.21 Control 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.02 16.97 Control 0-5 20.15 2.02 0.12 10.07 10.19 85.43 0.03 22.98 Control 0-5 20.15 2.07 0.12 10.07 10.19 85.43 0.03 21.82 Control 5-15 20.15 2.13 0.12 10.07 10.19 85.43 0.03 28.17 Control 5-15 20.15 2.10 0.12 10.07 10.19 85.43 0.03 25.55 Control 15-30 20.15 2.11 0.12 10.07 10.19 85.43 0.04 30.94

PAGE 97

97 Table A-10 Continued Treatment Depth 0.1 M NaOH Soil Sample Volume of H2O Total sample Dilute times Spec. conc. 0.1M NaOH extractable [TP] cm g g ml ml ml mg kg-1mg kg-1 Control 15-30 20.15 2.03 0.12 10.07 10.19 85.43 0.04 37.74 Fertilized 0-5 20.15 2.05 0.12 10.07 10.19 85.43 0.09 77.91 Fertilized 0-5 20.15 2.06 0.12 10.07 10.19 85.43 0.09 72.44 Fertilized 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.08 69.87 Fertilized 5-15 20.15 2.09 0.12 10.07 10.19 85.43 0.06 45.66 Fertilized 15-30 20.15 2.00 0.12 10.07 10.19 85.43 0.03 23.54 Fertilized 15-30 20.15 2.02 0.12 10.07 10.19 85.43 0.05 44.68 Fertilized 0-5 20.15 2.14 0.12 10.07 10.19 85.43 0.06 48.29 Fertilized 0-5 20.15 2.03 0.12 10.07 10.19 85.43 0.06 50.95 Fertilized 5-15 20.15 2.09 0.12 10.07 10.19 85.43 0.05 39.35 Fertilized 5-15 20.15 2.01 0.12 10.07 10.19 85.43 0.04 37.45 Fertilized 15-30 20.15 2.01 0.12 10.07 10.19 85.43 0.04 34.93 Fertilized 15-30 20.15 2.02 0.12 10.07 10.19 85.43 0.05 41.34 Fertilized 0-5 20.15 2.06 0.12 10.07 10.19 85.43 0.04 32.18 Fertilized 0-5 20.15 2.07 0.12 10.07 10.19 85.43 0.04 35.94 Fertilized 5-15 20.15 2.06 0.12 10.07 10.19 85.43 0.03 23.47 Fertilized 5-15 20.15 2.05 0.12 10.07 10.19 85.43 0.02 18.42 Fertilized 15-30 20.15 2.04 0.12 10.07 10.19 85.43 0.02 18.46 Fertilized 15-30 20.15 2.05 0.12 10.07 10.19 85.43 0.02 14.38 Blank 20.15 0.00 0.12 10.07 10.19 85.43 0.00 mdp Blank 20.15 0.00 0.12 10.07 10.19 85.43 0.00 mdp Blank 20.15 0.00 0.12 10.07 10.19 85.43 0.00 mdp a mdp indicates a missing data point.

PAGE 98

98 Table A-11. Half molar HCl extraction of inorganic phosphorus unaltered data. Treatment Depth Spec. conc. ABS Y intercept Mean blank Soil HCl Murphy & Riley Sample in M&R HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml mg kg-1 A. pintoi 0-5 1.81 1.14 1.59 0.00 2.55 19.70 6.00 5.00 16.77 A. pintoi 0-5 2.06 1.30 1.59 0.00 2.04 19.70 6.00 5.00 23.85 A. pintoi 0-5 2.27 1.43 1.59 0.00 2.28 19.70 6.00 5.00 23.51 C. ensiformis 0-5 1.13 0.71 1.59 0.00 2.02 19.70 6.00 5.00 13.24 C. ensiformis 0-5 0.96 0.60 1.59 0.00 2.05 19.70 6.00 5.00 11.05 C. ensiformis 0-5 0.58 0.36 1.59 0.00 2.04 19.70 6.00 5.00 6.69 C. macrocarpum 0-5 0.99 0.63 1.59 0.00 2.03 19.70 6.00 5.00 11.57 C. macrocarpum 0-5 2.52 1.58 1.59 0.00 2.02 19.70 6.00 5.00 29.46 C. macrocarpum 0-5 2.77 1.74 1.59 0.00 2.03 19.70 6.00 5.00 32.23 C. mucunoides 0-5 1.59 1.00 1.59 0.00 2.22 19.70 6.00 5.00 16.89 C. mucunoides 0-5 1.43 0.90 1.59 0.00 2.06 19.70 6.00 5.00 16.43 C. mucunoides 0-5 0.11 0.07 1.59 0.00 2.11 19.70 6.00 5.00 1.22 C. repens 0-5 1.48 0.93 1.59 0.00 2.03 19.70 6.00 5.00 17.22 C. repens 0-5 0.76 0.48 1.59 0.00 2.38 19.70 6.00 5.00 7.59 C. repens 0-5 0.94 0.59 1.59 0.00 2.27 19.70 6.00 5.00 9.82 Control 0-5 2.38 1.50 1.59 0.00 2.00 19.70 6.00 5.00 28.14 Control 0-5 3.33 2.09 1.59 0.00 2.07 19.70 6.00 5.00 37.99 Control 0-5 2.78 1.75 1.59 0.00 2.02 19.70 6.00 5.00 32.58 Fertilized 0-5 1.36 0.85 1.59 0.00 2.01 19.70 6.00 5.00 15.96 Fertilized 0-5 2.62 1.65 1.59 0.00 2.03 19.70 6.00 5.00 30.54 Fertilized 0-5 1.75 1.10 1.59 0.00 2.04 19.70 6.00 5.00 20.31 A. pintoi 15-30 3.17 1.99 1.59 0.00 2.01 19.70 6.00 5.00 37.23 A. pintoi 15-30 3.22 2.03 1.59 0.00 2.00 19.70 6.00 5.00 38.10 A. pintoi 15-30 1.46 0.92 1.59 0.00 2.22 19.70 6.00 5.00 15.50 C. ensiformis 15-30 1.72 1.09 1.59 0.00 2.03 19.70 6.00 5.00 20.08

PAGE 99

99 Table A-11 Continued Treatment Depth Spec. conc. ABS Y intercept Mean blank Soil HCl Murphy & Riley Sample in M&R HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml mg kg-1 C. ensiformis 15-30 1.76 1.11 1.59 0.00 2.12 19.70 6.00 5.00 19.63 C. ensiformis 15-30 3.67 2.31 1.59 0.00 2.07 19.70 6.00 5.00 41.96 C. macrocarpum 15-30 0.59 0.37 1.59 0.00 2.01 19.70 6.00 5.00 6.94 C. macrocarpum 15-30 1.68 1.06 1.59 0.00 2.28 19.70 6.00 5.00 17.46 C. macrocarpum 15-30 3.46 2.18 1.59 0.00 2.01 19.70 6.00 5.00 40.68 C. mucunoides 15-30 1.67 1.05 1.59 0.00 2.07 19.70 6.00 5.00 19.11 C. mucunoides 15-30 0.67 0.42 1.59 0.00 2.11 19.70 6.00 5.00 7.54 C. mucunoides 15-30 0.29 0.18 1.59 0.00 2.20 19.70 6.00 5.00 3.08 C. repens 15-30 1.97 1.24 1.59 0.00 2.08 19.70 6.00 5.00 22.36 C. repens 15-30 1.40 0.88 1.59 0.00 2.07 19.70 6.00 5.00 15.96 C. repens 15-30 1.13 0.71 1.59 0.00 1.99 19.70 6.00 5.00 13.45 Control 15-30 1.60 1.01 1.59 0.00 2.07 19.70 6.00 5.00 18.32 Control 15-30 0.21 0.13 1.59 0.00 2.06 19.70 6.00 5.00 2.36 Control 15-30 1.78 1.12 1.59 0.00 2.03 19.70 6.00 5.00 20.77 Fertilized 15-30 2.66 1.68 1.59 0.00 2.00 19.70 6.00 5.00 31.47 Fertilized 15-30 1.73 1.09 1.59 0.00 2.06 19.70 6.00 5.00 19.82 Fertilized 15-30 1.82 1.15 1.59 0.00 2.06 19.70 6.00 5.00 20.90 A. pintoi 5-15 2.78 1.75 1.59 0.00 2.18 19.70 6.00 5.00 30.14 A. pintoi 5-15 3.03 1.91 1.59 0.00 2.03 19.70 6.00 5.00 35.27 A. pintoi 5-15 3.20 2.01 1.59 0.00 2.19 19.70 6.00 5.00 34.54 C. ensiformis 5-15 1.84 1.16 1.59 0.00 2.02 19.70 6.00 5.00 21.57 C. ensiformis 5-15 0.70 0.44 1.59 0.00 2.02 19.70 6.00 5.00 8.20 C. ensiformis 5-15 1.71 1.08 1.59 0.00 2.05 19.70 6.00 5.00 19.71 C. macrocarpum 5-15 0.48 0.30 1.59 0.00 2.07 19.70 6.00 5.00 5.44 C. macrocarpum 5-15 2.39 1.51 1.59 0.00 2.04 19.70 6.00 5.00 27.75

PAGE 100

100 Table A-11 Continued Treatment Depth Spec. conc. ABS Y intercept Mean blank Soil HCl Murphy & Riley Sample in M&R HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml mg kg-1 C. macrocarpum 5-15 1.39 0.87 1.59 0.00 2.01 19.70 6.00 5.00 16.32 C. mucunoides 5-15 1.14 0.72 1.59 0.00 2.29 19.70 6.00 5.00 11.76 C. mucunoides 5-15 mdpa mdp 1.59 0.00 2.04 19.70 6.00 5.00 mdp C. mucunoides 5-15 3.55 2.24 1.59 0.00 2.34 19.70 6.00 5.00 35.91 C. repens 5-15 2.35 1.48 1.59 0.00 2.07 19.70 6.00 5.00 26.88 C. repens 5-15 1.34 0.84 1.59 0.00 2.05 19.70 6.00 5.00 15.46 C. repens 5-15 4.05 2.55 1.59 0.00 2.16 19.70 6.00 5.00 44.33 Control 5-15 1.61 1.02 1.59 0.00 2.07 19.70 6.00 5.00 18.43 Control 5-15 3.11 1.96 1.59 0.00 2.07 19.70 6.00 5.00 35.50 Control 5-15 1.67 1.05 1.59 0.00 2.00 19.70 6.00 5.00 19.72 Fertilized 5-15 2.14 1.35 1.59 0.00 2.01 19.70 6.00 5.00 25.21 Fertilized 5-15 1.66 1.04 1.59 0.00 2.09 19.70 6.00 5.00 18.76 Fertilized 5-15 1.80 1.14 1.59 0.00 2.00 19.70 6.00 5.00 21.32 Blank 0.00 0.00 1.59 0.00 mdp 19.70 6.00 5.00 mdp Blank 0.00 0.00 1.59 0.00 mdp 19.70 6.00 5.00 mdp Blank mdp mdp 1.59 0.00 mdp 19.70 6.00 5.00 mdp a mdp indicates a missing data point.

PAGE 101

101 Table A-12. Six molar HCl digest an d extraction of inorganic phosphorus from residual soil unaltered data. Treatment Depth ABS. Mean blank Y intercept of R2 Spec. conc. Glass Soil Post digest solution volume Colormetric solution Sample in colormetric solution 6 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 A. pintoi 0-5 mdpa 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp A. pintoi 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. repens 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 5-15 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp

PAGE 102

102 Table A-12 Continued Treatment Depth ABS. Mean blank Y intercept of R2 Spec. conc. Glass Soil Post digest solution volume Colormetric solution Sample in colormetric solution 6 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 C. mucunoides 15-30 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 0-5 mdp 0 1.75 mdp mdp mdp 50 11.4 5 mdp C. mucunoides 5-15 0.23 0 1.75 0.40 28.80 0.22 50 11.4 5 203.29 C. mucunoides 15-30 0.42 0 1.75 0.73 31.63 0.21 50 11.4 5 402.49 C. macrocarpum 0-5 0.21 0 1.75 0.36 30.06 0.23 50 11.4 5 181.61 C. macrocarpum 5-15 0.18 0 1.75 0.32 28.74 0.21 50 11.4 5 176.85 C. macrocarpum 15-30 0.19 0 1.75 0.32 29.18 0.22 50 11.4 5 170.61 C. macrocarpum 0-5 0.33 0 1.75 0.57 28.73 0.22 50 11.4 5 293.86 C. macrocarpum 5-15 0.31 0 1.75 0.53 28.67 0.21 50 11.4 5 292.99 C. macrocarpum 15-30 0.31 0 1.75 0.55 31.40 0.21 50 11.4 5 299.02 C. macrocarpum 0-5 0.18 0 1.75 0.32 29.02 0.22 50 11.4 5 164.73 C. macrocarpum 5-15 0.23 0 1.75 0.41 31.27 0.21 50 11.4 5 224.00 C. macrocarpum 15-30 0.31 0 1.75 0.54 31.03 0.21 50 11.4 5 285.70 C. ensiformis 0-5 0.49 0 1.75 0.85 31.85 0.20 50 11.4 5 476.16 C. ensiformis 5-15 0.63 0 1.75 1.10 28.56 0.22 50 11.4 5 559.50 C. ensiformis 15-30 0.29 0 1.75 0.50 30.58 0.24 50 11.4 5 240.00 C. ensiformis 0-5 0.43 0 1.75 0.75 28.62 0.21 50 11.4 5 410.05 C. ensiformis 5-15 0.18 0 1.75 0.31 31.15 0.22 50 11.4 5 162.05 C. ensiformis 15-30 0.23 0 1.75 0.40 28.47 0.21 50 11.4 5 222.30 C. ensiformis 0-5 0.33 0 1.75 0.57 28.62 0.22 50 11.4 5 298.09 C. ensiformis 5-15 0.31 0 1.75 0.55 31.55 0.21 50 11.4 5 298.26 C. ensiformis 15-30 0.34 0 1.75 0.60 30.75 0.23 50 11.4 5 293.08 Control 0-5 0.16 0 1.75 0.28 28.76 0.22 50 11.4 5 149.36

PAGE 103

103 Table A-12 Continued Treatment Depth ABS. Mean blank Y intercept of R2 Spec. conc. Glass Soil Post digest solution volume Colormetric solution Sample in colormetric solution 6 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 Control 5-15 0.17 0 1.75 0.29 28.63 0.23 50 11.4 5 148.52 Control 15-30 0.25 0 1.75 0.44 28.50 0.22 50 11.4 5 226.87 Control 0-5 0.34 0 1.75 0.59 30.69 0.24 50 11.4 5 284.66 Control 5-15 0.34 0 1.75 0.59 28.69 0.23 50 11.4 5 292.60 Control 15-30 0.33 0 1.75 0.58 28.70 0.22 50 11.4 5 304.36 Control 0-5 0.14 0 1.75 0.24 28.69 0.23 50 11.4 5 119.28 Control 5-15 0.29 0 1.75 0.50 30.95 0.24 50 11.4 5 240.93 Control 15-30 0.39 0 1.75 0.67 28.92 0.22 50 11.4 5 347.73 Fertilized 0-5 0.61 0 1.75 1.07 32.21 0.22 50 11.4 5 553.02 Fertilized 5-15 0.40 0 1.75 0.70 28.28 0.22 50 11.4 5 366.99 Fertilized 15-30 0.36 0 1.75 0.62 28.55 0.22 50 11.4 5 318.36 Fertilized 0-5 0.24 0 1.75 0.43 30.53 0.22 50 11.4 5 224.69 Fertilized 5-15 0.22 0 1.75 0.39 29.79 0.20 50 11.4 5 217.63 Fertilized 15-30 0.39 0 1.75 0.68 28.73 0.24 50 11.4 5 324.79 Fertilized 0-5 0.32 0 1.75 0.56 28.76 0.22 50 11.4 5 294.49 Fertilized 5-15 0.37 0 1.75 0.65 29.08 0.21 50 11.4 5 353.71 Fertilized 15-30 0.29 0 1.75 0.50 28.61 0.21 50 11.4 5 271.77 a mdp indicates a missing data point.

PAGE 104

104 Table A-13. Six molar HCl digest and extraction of inorganic phosphorus fr om air-dried soil unaltered data. Treatment Depth ABS Mean blank Y Intercept Spec. conc. Glass Soil Post digest solution Murphy & Riley Sample in M&R 6.0 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 A. pintoi 0-5 0.27 0.00 1.75 0.47 29.42 0.21 50.00 11.40 5.00 251.11 A. pintoi 5-15 0.21 0.00 1.75 0.37 31.67 0.21 50.00 11.40 5.00 203.16 A. pintoi 15-30 0.16 0.00 1.75 0.28 31.59 0.22 50.00 11.40 5.00 149.33 A. pintoi 0-5 0.23 0.00 1.75 0.41 30.82 0.24 50.00 11.40 5.00 196.84 A. pintoi 5-15 0.21 0.00 1.75 0.37 28.37 0.23 50.00 11.40 5.00 183.79 A. pintoi 15-30 0.22 0.00 1.75 0.38 28.62 0.21 50.00 11.40 5.00 205.30 A. pintoi 0-5 0.21 0.00 1.75 0.37 28.66 0.22 50.00 11.40 5.00 193.61 A. pintoi 5-15 0.20 0.00 1.75 0.35 28.66 0.23 50.00 11.40 5.00 177.44 A. pintoi 15-30 0.23 0.00 1.75 0.39 28.77 0.21 50.00 11.40 5.00 217.60 C. repens 0-5 0.44 0.00 1.75 0.78 28.81 0.20 50.00 11.40 5.00 434.34 C. repens 5-15 0.33 0.00 1.75 0.58 29.20 0.21 50.00 11.40 5.00 308.52 C. repens 15-30 0.41 0.00 1.75 0.72 28.55 0.20 50.00 11.40 5.00 401.80 C. repens 0-5 0.26 0.00 1.75 0.46 28.60 0.22 50.00 11.40 5.00 234.55 C. repens 5-15 0.25 0.00 1.75 0.43 30.94 0.23 50.00 11.40 5.00 213.47 C. repens 15-30 0.23 0.00 1.75 0.40 29.18 0.21 50.00 11.40 5.00 218.95 C. repens 0-5 0.21 0.00 1.75 0.38 28.98 0.22 50.00 11.40 5.00 197.66 C. repens 5-15 0.22 0.00 1.75 0.39 29.68 0.20 50.00 11.40 5.00 221.24 C. repens 15-30 0.22 0.00 1.75 0.38 28.76 0.22 50.00 11.40 5.00 201.54 C. mucunoides 0-5 0.25 0.00 1.75 0.43 29.91 0.22 50.00 11.40 5.00 229.87 C. mucunoides 5-15 0.22 0.00 1.75 0.39 30.90 0.21 50.00 11.40 5.00 205.28 C. mucunoides 15-30 0.29 0.00 1.75 0.50 28.75 0.21 50.00 11.40 5.00 267.19 C. mucunoides 0-5 0.24 0.00 1.75 0.41 28.67 0.23 50.00 11.40 5.00 208.01 C. mucunoides 5-15 0.25 0.00 1.75 0.43 28.80 0.22 50.00 11.40 5.00 221.26 C. mucunoides 15-30 0.22 0.00 1.75 0.39 32.00 0.22 50.00 11.40 5.00 204.17 C. mucunoides 0-5 0.16 0.00 1.75 0.27 28.71 0.22 50.00 11.40 5.00 142.84

PAGE 105

105 Table A-13 Continued Treatment Depth ABS Mean blank Y Intercept Spec. conc. Glass Soil Post digest solution Murphy & Riley Sample in M&R 6.0 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 C. mucunoides 5-15 0.20 0.00 1.75 0.35 28.72 0.21 50.00 11.40 5.00 186.69 C. mucunoides 15-30 0.22 0.00 1.75 0.39 31.73 0.22 50.00 11.40 5.00 207.47 C. macrocarpum 0-5 0.27 0.00 1.75 0.48 28.60 0.21 50.00 11.40 5.00 257.40 C. macrocarpum 5-15 0.19 0.00 1.75 0.33 30.83 0.20 50.00 11.40 5.00 183.10 C. macrocarpum 15-30 0.20 0.00 1.75 0.35 30.89 0.21 50.00 11.40 5.00 188.55 C. macrocarpum 0-5 0.23 0.00 1.75 0.41 32.13 0.21 50.00 11.40 5.00 220.04 C. macrocarpum 5-15 0.22 0.00 1.75 0.38 31.08 0.24 50.00 11.40 5.00 183.24 C. macrocarpum 15-30 0.23 0.00 1.75 0.41 30.57 0.24 50.00 11.40 5.00 189.67 C. macrocarpum 0-5 0.25 0.00 1.75 0.44 29.22 0.21 50.00 11.40 5.00 240.15 C. macrocarpum 5-15 0.25 0.00 1.75 0.43 30.95 0.24 50.00 11.40 5.00 205.58 C. macrocarpum 15-30 0.21 0.00 1.75 0.37 28.65 0.21 50.00 11.40 5.00 203.69 C. ensiformis 0-5 0.42 0.00 1.75 0.73 30.53 0.23 50.00 11.40 5.00 356.09 C. ensiformis 5-15 0.33 0.00 1.75 0.57 30.78 0.21 50.00 11.40 5.00 308.23 C. ensiformis 15-30 0.20 0.00 1.75 0.35 28.71 0.23 50.00 11.40 5.00 175.36 C. ensiformis 0-5 0.33 0.00 1.75 0.58 29.92 0.23 50.00 11.40 5.00 281.74 C. ensiformis 5-15 0.22 0.00 1.75 0.38 31.21 0.20 50.00 11.40 5.00 211.01 C. ensiformis 15-30 0.24 0.00 1.75 0.42 31.74 0.21 50.00 11.40 5.00 225.64 C. ensiformis 0-5 0.21 0.00 1.75 0.37 29.90 0.22 50.00 11.40 5.00 196.38 C. ensiformis 5-15 0.26 0.00 1.75 0.46 31.03 0.21 50.00 11.40 5.00 247.73 C. ensiformis 15-30 0.24 0.00 1.75 0.42 28.52 0.23 50.00 11.40 5.00 208.12 Control 0-5 0.28 0.00 1.75 0.49 31.35 0.23 50.00 11.40 5.00 242.69 Control 5-15 0.23 0.00 1.75 0.40 28.86 0.21 50.00 11.40 5.00 211.87 Control 15-30 0.24 0.00 1.75 0.42 28.72 0.24 50.00 11.40 5.00 202.76 Control 0-5 0.13 0.00 1.75 0.22 32.18 0.20 50.00 11.40 5.00 123.69 Control 5-15 0.21 0.00 1.75 0.36 28.73 0.20 50.00 11.40 5.00 203.53

PAGE 106

106 Table A-13 Continued Treatment Depth ABS Mean blank Y Intercept Spec. conc. Glass Soil Post digest solution Murphy & Riley Sample in M&R 6.0 M HCl extractable [P] cm mg kg-1 mg kg-1 g g ml ml ml mg kg-1 Control 15-30 0.22 0.00 1.75 0.38 31.01 0.21 50.00 11.40 5.00 206.41 Control 0-5 0.17 0.00 1.75 0.30 30.96 0.21 50.00 11.40 5.00 166.09 Control 5-15 0.21 0.00 1.75 0.37 31.15 0.22 50.00 11.40 5.00 192.08 Control 15-30 0.22 0.00 1.75 0.39 28.68 0.20 50.00 11.40 5.00 219.16 Fertilized 0-5 0.38 0.00 1.75 0.66 29.79 0.20 50.00 11.40 5.00 367.74 Fertilized 5-15 0.35 0.00 1.75 0.61 31.91 0.22 50.00 11.40 5.00 313.19 Fertilized 15-30 0.22 0.00 1.75 0.39 28.49 0.21 50.00 11.40 5.00 216.78 Fertilized 0-5 0.28 0.00 1.75 0.48 31.26 0.23 50.00 11.40 5.00 240.33 Fertilized 5-15 0.25 0.00 1.75 0.44 28.68 0.21 50.00 11.40 5.00 236.58 Fertilized 15-30 0.21 0.00 1.75 0.37 28.92 0.20 50.00 11.40 5.00 209.39 Fertilized 0-5 0.22 0.00 1.75 0.38 30.15 0.21 50.00 11.40 5.00 208.96 Fertilized 5-15 0.28 0.00 1.75 0.49 28.81 0.23 50.00 11.40 5.00 245.42 Fertilized 15-30 0.26 0.00 1.75 0.46 28.67 0.21 50.00 11.40 5.00 256.30

PAGE 107

107 LIST OF REFERENCES Alexander D B 1998 Bacteria and Archaea. In Principles and Applicati ons of Soil Microbiology, Eds D M Sylvia, J J Fuhrm ann, P G Hartel and D A Zuberer. pp 44-71. Prentice Hall, New Jersey, NJ. Alvim R and Nair P K R 1986 Combin ation of cacao with other plantation crops: an agroforestry system in Southeast Bahia, Brazil. Agroforestry Systems 4, 3-15. Appiah M R, Sackey S T, Ofori-Frimpong K and Afrifa A A 1997 The consequences of cacao production on soil fertility in Ghana: A revi ew. Ghana Journal of Agricultural Science 30, 183-190. Baligar V C, Elson M K and Meinhardt W L 2008 Cover crops useful for improving soil productivity under cacao. In Theobroma cacao: Biology, Chemistry and Human Health., Eds A B Bennett, C Keen and H Shapiro. Wile y Publishers, Beltsville, MD. In press. Baligar V C, Fageria N K, Eswaran H, Wilson M J and He Z 2004 Nature and Properties of Red Soil of the World. In The Red Soils of China: Their Na ture, Management and Utilization, Eds M J Wilson, Z He and X Yang. pp 7-27. Kluwer Academic Publishers, Beltsville, MD. Barber S A 1995 Nutrient Absorption by Plant Roots. In Soil Nutrient Bioavailability: A Mechanistic Approach, Ed S A Barber. pp 49-84. John Wiley & Sons, Inc., New York, NY. Basamba T A, Barrios E, Amezquita E, Rao I M and Singh B R 2006 Tillage effects on maize yield in a Colombian Savanna oxisol: Soil organic matter and P fractions. Soil and Tillage Research, In Press. Berkelaar E 2001 The effect of aluminum in acidic soils on plant growth. ECHO Development Notes 71, 1-3. Brady N C and Weil R R 1999 The Nature and Prope rties of Soils. Prenti ce-Hall, Inc. 881 p. Bridges T 2006 New road aims to turn farmers away from coca. In World. Knight Ridder Newspapers, Kansas City, KS. Bright C 2001 Chocolate Could Bring the Forest Back. World Watch, 17-28. Carter M E, Gamez R and Gliessman S 1993 Sustai nable Agriculture and the Environment in the Humid Tropics. National Academ y Press, Washington D.C. Chang S C and Jackson M L 1957 Fractionation of soil phosphorus. Soil Science Society of America Journal 84, 133-144. Chapin F S, Matson P A and Mooney H A 2002 Pr inciples of Terrestri al Ecosystem Ecology. Springer, New York, NY.

PAGE 108

108 Davidson E A, Carvalho C J R, Figueira A M, Ishida F Y, Ometto J P H B, Nardoto G B, Saba R T, Hayashi S N, Leal E C, Vieira I C G and Martinelli L A 2007 Recuperation of nitrogen cycling in Amazonian forests followi ng agricultural aba ndonment. Nature 447. Dinesh R, Suryanarayana M A, Chaudhuri S G and Sheeja T E 2004 Long-term influence of leguminous cover crops on the biochemical pr operties of a sandy clay loam Fluventic Sulfaquent in a humid tropical region of India. Soil and Tillage Research 77, 69-77. Duguma B, Gockowski J and Bakala J 2001 Smallholder Cacao (Theobroma cacao Linn.) cultivation in agroforestry systems of West and Central Africa challenges and opportunities. Agroforestry Systems 51, 177-188. Elrashidi M A 2006 Selection of an Appropriate Phosphorus Test for Soils, Ed U N R a C Service. Soil Survey Laboratory. Evans H C, Krauss U, Rutz R R, Acosta T Z an d Arevalo-Gardini E 1998 Cacoa in Peru. Cocoa Growers Bulletin No. 51, 7-51. Ewel J J 1986 Designing Agricultural Ecosystems for the Humid Tropics. Annual Review of Ecology and Systematics 17, 245-271. F.A.O 2005 Global Forest Resources Assessm ent. Food and Agriculture Organization. Fageria N K, Baligar V C and Bailey B A 2005 Ro le of Cover Crops in Improving Soil and Row Crop Productivity. Communications in Soil Science and Plant Analysis 36, 2733-2757. Graetz D A and Nair V D 1999 Inorganic Forms of Phosphorus in Soils and Sediments. In Phosphorus Biogeochemistry in Subtropical Ecosystems, Eds K R Reddy, G A O'Connor and C L Schelske. pp 171-186. Lewis Publishers, Gainesville, FL. Hall H unpublished data Informal interviews wi th cacao agroforesters in San Martin, Peru, Tarapoto. Hall H 2006 pH determination of cacao agroforestry soils in San Martin, Peru. University of Florida. Hartemink A E 2005 Nutrient Stoc ks, Nutrient Cycling, and Soil Changes in Cocoa Ecosystems: A Review. In Advances in Agronomy. pp 227-253. ISRIC-CABI Publishing, Wallingford, CT. Hedley M J, Stewart J W B and Chauman B S 1982a Changes in Inorganic and Organic Soil Phosphorus Fractions Induced by Cultivation Pr actices and by Laboratory Incubations. Soil Science Society of America Journal 46, 970-976.

PAGE 109

109 Hedley M J, White R E and Nye P H 1982b Plant-induced changes in the rhizosphere of Rape ( Brassica napus var. Emerald) seedlings. III. Changes in L Value, Soil Phosphate Fractions and Phosphatase Activit y. The New Phytol ogist 91, 45-56. Heiri O, Lotter A F and Lemcke G 2001 Loss on ignition as a method for estimating organic and corbonate content in sediments: reproducibility and comparability of results. Journal of Paleolimnology 25, 101-110. Hieltjes A H M and Lijklema L 1980 Fractionation of Inorganic Phosphates in Calcareous Sediments. Journal of Environmental Quality 9, 405-407. Hinsinger P 2001 Bioavailability of soil inorganic P in the rhizosphere as affected by rootinduced chemical changes: a review. Plant and Soil 237, 173-195. Hopkins W G and Huner N P A 2004 Introduction to Plant Phys iology. John Wiley and Sons, Inc., New York, NY. I.C.T. 2007 Instituto de Cultivos Tropical es Home Page. I.C.T., Tarapoto, Peru. Jonasson O 1951 Potential Areas of Cacao Cultiva tion in South America: A Review. Economic Geography 27, 90-93. Kuo S 1996a Extraction with Dilute Concentration of Strong Acids. In Methods in Soil Analysis. Part 3. Chemical Analysis. pp 893-894. Soil Society of America and American Society of Agronomy, Madison, WI. Kuo S 1996b Phosphorus. In Methods of Soil Analysis. Part 3. Chemical Methods, Ed S S S o A a A S o Agronomy. pp 869-919. Soil Science So ciety of America and American Society of Agronomy, Madison, WI. Levy E T and Schlesinger W H 1999 A comparison of fractionation methods for forms of phosphorus in soils. Biogeochemistry 47, 25-38. Li L, Li S-M, Sun J-H, Zhou L-L, Bao X-G, Zhang H-G and Zhang F-S 2007 Diversity enhances agricultural productivity via rhizosphere phosphorus facil itation on phosphorus-deficient soils. PNAS 104, 11192-11196. Mafongoya P L, Giller D E, Odee D, Gathumbi S, Nduga S K and Sitompul S M 2004 Benefiting from N2-Fixation and Managing Rhizobia. In Below-ground Interactions in Tropical Agroecosystems. pp 227-242. CAB International. McGrath D A, Smith C K, Gholz H L and Oliveira F d A 2001 Effects of Land-Use Change on Soil Nutrient Dynamics in Amazonia. Ecosystems 4, 625-645.

PAGE 110

110 Miller R W and Gardiner D T 2001a Acidic Soils. In Soils in Our Envirnoment, Ed D Yarnell. pp 242-258. Prentice Hall, New Jersey, NJ. Miller R W and Gardiner D T 2001b Organisms and Their Residues. In Soils in Our Environment, Ed D Yarnell. pp 164 -203. Prentice Hall, New Jersey, NJ. Miller R W and Gardiner D T 2001c Plant Nu trients: Nitrogen, Phosphorus, and Potassium. In Soils in Our Environment. pp 302-30 9. Prentice Hall, New Jersey, NJ. Nair V D, Graetz D A and Portier K M 1995 Forms of Phosphorus in Soil Profiles from Dairies of South Florida. Soil Science So ciety of America Journal 59, 1244-1249. Nelson D W and Sommers L E 1996a Loss-On-Ignition Method. In Methods of Soil Analysis. Part 3. Chemical Methods. pp 1004-1005. Soil Science Society of America and American Society of Agronomy, Madison, WI. Nelson D W and Sommers L E 1996b Walkley-Black Method. In Methods of Soil Analysis. Part 3. Chemical Methods. SSSA Book Series no. 5., Ed J M Bartels. pp 995-996. Soil Science Society of America and American Society of Agronomy, Madison, WI. NOAA 2007 Climate and Dayli ght Chart for Tarapoto, Pe ru. ClimateCharts.com. Paul E A and Clark F E 1989 Soil Microbiology and Biochemistry. Academic Press, Inc. Peoples M B and Baldock J A 2001 Nitrogen dynamic of pastures: nitrogen fixation inputs, the impact of legumes on soil nitrogen fertility, a nd the contributions of fixed nitrogen to Australian farming systems. Australian J ournal of Experimental Agriculture 41, 327-346. Phiri S, Barrios E, Rao I M and Singh B R 2001 Changes in soil organic matter and phosphorus fractions under planted fallow and a crop ro tation system on a Colombian volcanic-ash soil. Plant and Soil 231, 211-223. Russell S E J 2002a The Composition of Soil Organic Matter. In Soil Conditions & Plant Growth. pp 255-285. Biotech Books, New Dehli, India. Russell S E J 2002b The Effect of Soil Ac idity and Alkalinity on Plant Growth. In Soil Conditions & Plant Growth, Ed E W Russe ll. pp 473-481. Biotech Books, New Delhi, India. Ryan P and Delhaize E 2001 Function and Mechan ism of Organic Anion Exudation from Plant Roots. Annual Review of Plant Physio logy & Plant Molecular Biology 52, 527-560. S.A.S. 2007 JMP Statistical So ftware. S.A.S Institute. Sample E C, Soper R J and Racz G J 1976 Reaction of Phosphate Fertilizers in Soil. In The Role of Phosphorus in Agriculture, Alabama, 1976.

PAGE 111

111 Sanchez P A 2000 Linking climate change research with food security and poverty reduction in the tropics. Agriculture, Ecos ystems & Environment 82, 371-383. Schactman D P, Reid R J and Ayling S M 1998 Phos phorus uptake by plants: From soil to cell. Plany Physiology 116, 447-453. Schroth G, Teixeira W G, Seixas R, Silva L F d, Schaller M, Macedo J L V and Zech W 2000 Effect of five tree crops and a cover crop in multi-strata agroforestry at two fertilization levels on soil fertility and soil solution ch emistry in central Amazon. Plant and Soil 221, 143-156. Silva I R, Smyth T J, Moxley D F, Carter T E, Allen N S and Rufty T W 2000 Aluminum Accumulation at Nuclei of Cells in the Root Tip. Fluorescence Detection Using Lumogallion and Confocal Laser Scanni ng Microscopy. Plant Physiology 123, 543-552. Sylvia D M, Fuhrmann J J, Hartel P G and Zuberer D A 1998 Fungi. In Principles and Applications of Soil Microbiology, Ed D M Sylvia. pp 72-93. Prentice Hall, Inc., New Jersey, NJ. Szulczewski M D and Li Y unpublished Phosphorus Fractions in Calcareous Soils from the Southern Everglades and Nearby Farmlands. University of Florida. Thomas G W 1996 Determination-pH in water. In Methods of Soil Analysis. Part 3. Chemical Methods. pp 487. Soil Science Society of Amer ica and American Society of Agronomy, Madison, WI. Tiessen H, Cuevas E and Chacon P 1994 The role of soil organic matter in sustaining soil fertility. Nature 371, 783-785. Tiessen H and Moir J O 1993 Characterization of Available P by Sequential Extraction. In Soil Sampling and Methods of Analysis, Ed M R Carter. pp 75-86. Canadian Society of Soil Science. Uehara G and Gillman G 1981 The Mineralogy, Ch emistry, and Physics of Tropical Soils with Variable Charge Clays. Westview Press. USDA 2007 ARS Office of International Research Programs. USDA and ARS 2007 Fighting a fungal siege on cacao farms. In New & Events, Ed USDA. USDA ARS. Vitousek P M, Cassman K, Cleveland C, Crew s T, Field C B, Grimm N B, Howarth R W, Marino R, Martinelli L, Ra stetter E B and Sprent J I 2002 Towards an ecological understanding of biological nitrogen fixation. Biogeochemistry 57/58, 1-45.

PAGE 112

112 Vitousek P M and R.L. Sanford J 1986 Nutrient Cycling in Moist Tropical Forest. Annual Review of Ecology and Systematics 17, 137-167. W.C.F. 2007 Encouraging Sustainable, Respons ible Cocoa Growing. Wo rld Cacoa Foundation. Wang Q R, Li Y C and Klassen W 2007 Changes in Soil Microbial Biomass Carbon and Nitrogen with Cover Crops and Irrigation in a Tomato Field. Journal of Plant Nutrition 30, 623-639. Weintraub M N, Scott-Denton L E, Schmidt S K and Monson R K 2007 The effects of tree rhizodeposition on soil exoenyme activiti y, dissolved organic carbon, and nutrient availability in a subalpine forest ecosystem. Oecologia 154, 327-338. Wessel M 1971 Fertilizer Requirements of Cacao ( Theobroma cacao L.) in South-western Nigeria. Department of Agricultural Research of the Royal Tropical Institute, Amsterdam. Wood G A R 1975 Cocoa. Longman Group Limited, Great Britian. Wood G A R and Lass R A 2001 Co coa. Blackwell Science. Wortmann C S, McIntyre B D and Kaizzi C K 2000 Annual soil improving legumes: agronomic effectiveness, nutrient uptake, nitrogen fixation and water use. Field Crops Research 68, 75-83. Young A 1997 Soil Organic Matter and Physical Properties. In Agroforestry for Soil Management. pp 98-110. CABI Publishing. Zuberer D A 1998 Biological Dini trogen Fixation: Symbiotic. In Principles and Applications of Soil Microbiology, Eds D M Sylvia, J J Fuhr mann, P G Hartel and D A Zuberer. pp 322345. Prentice Hall, New Jersey, NJ.

PAGE 113

113 BIOGRAPHICAL SKETCH The author began her studies in soil scien ce throu gh lectures, la boratories, and field excursions while fulfilling the requirement of a Bachelor of Science (BS) in the Rangeland Resource Management program at Humboldt State University (H SU) in northern California. Believing soils to provide the f oundation of life on the planet a nd aiming to secure a career allowing the inclusion of this spectrum of ecosyst em components to solve resource use issues the author has been diligent in her efforts to include plants, people, and water in her studies of soil science. To this end, the author supplemented her Rangeland Resources program at HSU with a minor in botany, and an option in wildland soil science, and several in ternship and volunteer activities. A one-year Co-Direc torship of the Campus Center for Appropriate Technology at HSU fostered the development of teamwork and project management skills while maintaining an educational forum from which th e authors community could learn to reduce their consumption of natural resources. A summer internship work ing on the big island of Hawaii with the Natural Resource Conservation Service as a soil conservation technician allowed the author to gain exposure to the resource conservation issues a ssociated with agricultural production in the tropics, and experience taxonomically describing soils. In a second summer internship, the author worked as a Biological Technician for th e National Forest Service in the Sierra Nevada Mountain Range of California. This work allowed the author to use her skills in soil science to assess the impact of cattle grazing on the physical ch aracters of meadow soils. In a third summer internship, working as a research assistant for pl ant ecologist Dr. Eric Jules, the author and a dendro-chronologist collected soil and tree age data from spruce forests throughout the Redwoods State and National Parks in an effort to map the historic grassl and range as it existed under Native North American management. After completing her BS degree at HSU the author

PAGE 114

114 took a 1-year hiatus from academia to implem ent watershed restoration technologies throughout the Mattole River watershed in Northern Califor nia before moving to Gainesville, Florida to pursue a Master of Science degree from the Soil and Water Science Department. At the University of Florida, the author worked under the guidance of her academic committee to investigate the influence of cover crops on phos phorus fractions and soil fertility in a cacao agroforestry system located in the Peruvian Amazon. Having completed her Masters of Science degree requirements the author wi ll continue in the Soil and Water Sciences department to pursue a PhD program as part of a National Science Foundation funded Integrated Graduate Education and Research Traineeship focused on using Adaptive Management theories for the wise use of water.