• TABLE OF CONTENTS
HIDE
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Abstract
 Introduction
 Hillside farming system in...
 The hedgerow intercropping...
 Organization of the study
 Hedgerow/crop competition
 Land and household characteristics...
 Conclusions and recommendation...
 Appendices
 References
 Biographical sketch














Title: Dynamics of farmer adoption, adaptation, and management of soil conservation hedgerows in Haiti
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Permanent Link: http://ufdc.ufl.edu/UF00097372/00001
 Material Information
Title: Dynamics of farmer adoption, adaptation, and management of soil conservation hedgerows in Haiti
Physical Description: 1 online resource (xiv, 235 leaves) : ill. ;
Language: English
Creator: Bannister, Michael E
Publisher: s.n.
Place of Publication: Gainesville FL
Publication Date: 2001
Copyright Date: 2001
 Subjects
Subject: Soil conservation -- Haiti   ( lcsh )
Windbreaks, shelterbelts, etc -- Haiti   ( lcsh )
Hill farming -- Haiti   ( lcsh )
Genre: bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (Ph. D.)--University of Florida, 2001.
Bibliography: Includes bibliographical references (leaves 218-234).
General Note: Printout.
General Note: Vita.
General Note: Description based on print version record.
Statement of Responsibility: by Michael E. Bannister.
 Record Information
Bibliographic ID: UF00097372
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 004744249
oclc - 465403427

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Table of Contents
    Title Page
        Page i
        Page i-a
    Acknowledgement
        Page ii
    Table of Contents
        Page iii
        Page iv
    List of Tables
        Page v
        Page vi
        Page vii
        Page viii
        Page ix
    List of Figures
        Page x
        Page xi
        Page xii
    Abstract
        Page xiii
        Page xiv
    Introduction
        Page 1
        Page 2
        Page 3
    Hillside farming system in Haiti
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    The hedgerow intercropping system
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
    Organization of the study
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
    Hedgerow/crop competition
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
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    Land and household characteristics in relation to adoption and management of hedgerows
        Page 108
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    Conclusions and recommendations
        Page 179
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    Appendices
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    References
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    Biographical sketch
        Page 235
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Full Text










DYNAMICS OF FARMER ADOPTION, ADAPTATION. AND MANAGEMENT
OF SOIL CONSERVATION HEDGEROWS IN HAITI















By

MICHAEL E. BANNISTER


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2001


















UNIVERSITY OF FLORIDA
3 1II262 I086 32
3 1262 08666 372 0
i "06.1 g


160













ACKNOWLEDGMENTS

I wish to thank my graduate advisor, Dr. P.K.R. Nair, for his unflagging

encouragement and guidance throughout a long period of research and writing and Dr.

Peter Hildebrand for providing my Farming Systems assistantship from 1987 through

1989. My other committee members, Dr. Mary Duryea, Dr. Jerry Murray, and Dr. Ken

Buhr also provided valuable insights and assistance. The untiring work of the Pan

American Development Foundation (PADF) Haitian technical staff during data collection

and the encouragement and financial support of the PADF home office during my

sabbatical were essential to this dissertation, as was the cooperation of a multitude of

Haitian farmers. Deserving of special mention are PADF Haiti Country Representative

Lee Nelson for his key support of my sabbatical and Agronomist Jn-Charlot Bredy for

data collection on farms near Lascahobas. Data collection for the Leucaena/maize study

could not have been completed without the assistance of technicians Duverger Veris and

Rodini St-Juste. Finally, I thank my beloved wife Mojdeh for her essential care of my

sometimes-fragile psyche during this trying time.














TABLE OF CONTENTS

pages

LIST OF TABLES ...................................................... v

LIST OF FIGURES .................................................... x

ABSTRACT .............. ................... .................... xiii

CHAPTERS

1 INTRODUCTION .................................................. 1

2 HILLSIDE FARMING SYSTEM IN HAITI .......... ..............4

Land .............................................................5
Crops ............................................................ 7
Labor .............................................. 9
Farmer Development Groups and Local NGOs ........................... 10

3 THE HEDGEROW INTERCROPPING SYSTEM ........................ 13

Developm ents in the Tropics ......................................... 13
Developments of Hedgerow Intercropping in Haiti ........................ 18
Hedgerow Intercropping and Soil Conservation .......................... 22
Conclusions ...................................................... 26

4 ORGANIZATION OF THE STUDY ................................. 27

Justification .......................................................27
Hypotheses ...................................................... 33
General Description of Hypothesis-Testing Procedures ..................... 34

5 HEDGEROW/CROP COMPETITION ................................ 36

Introduction .................................................... 36
On-Station Studies: Effect of Root Barriers on the Growth of Maize and
Leucaena ....................................................39
On-Farm Study: Maize Growth at Varying Distances from Hedgerows ....... 100








6 LAND AND HOUSEHOLD CHARACTERISTICS IN RELATION TO
ADOPTION AND MANAGEMENT OF HEDGEROWS ................ 108

Introduction and Objectives ......................................... 108
Materials and Methods ................ ........................... 119
Results and Discussion ............... .......................... 127
Summary and General Discussion .................................... 166
Conclusions ..................................................... 175

7 SYNTHESIS AND CONCLUSIONS ................................ 179

APPENDICES

A POT STUDY OF SOIL WATER DEPLETION VS. MAIZE LEAF WATER
POTENTIAL .................................................. 186

B ROOT DISTRIBUTION OF A LEUCAENA LEUCOCEPHALA
HEDGEROW .................................................. 188

C P-VALUES OF ANOVAS PERFORMED ON STATION ................. 191

D HOUSEHOLD QUESTIONNAIRE ................................. 198

E GARDEN PLOT QUESTIONNAIRE ............................... 201

F SOIL NUTRIENTS, ORGANIC CARBON STATUS, AND pH
OF 175 HILLSIDE GARDENS .................................... 211

REFERENCES ................. ..................................... 218

BIOGRAPHICAL SKETCH ................ ........................... 235













LIST OF TABLES


Table page

5-1: Soil texture and organic carbon at the trial site .......................... 43

5-2: Effect of trenching on the production of maize biomass ................... 60

5-3: Effect of fertilizer on the production of maize biomass .................... 61

5-4: Soil water at three depths below the surface ......................... .. 62

5-5: Maize grain weight, number of plants, and number of ears ................. 65

5-6: Stem and leaf biomass harvests and daily growth increments of Leucaena
hedgerows ..................................................... 66

5-7: Height above a 50 cm stump and daily growth increments of Leucaena
hedgerows prior to the second root trenching, 33 and 65 DAS; Spring
1994 ............................ .................... ..........67

5-8: Maize biomass in trenched and nontrenched plots ....................... 69

5-9: Maize leaf water potential in trenched and nontrenched plots over four
distances from the hedgerows, 42 DAS; fall 1994 ........................ 71

5-10: Soil water in trenched and nontrenched plots by depth and distance ......... 73

5-11: Maize grain weight, number of plants, and number of ears at four
distances from the hedgerows and as a total per hectare, with p-values for
the differences between distances, Fall 1994 ............................ 75

5-12: Stem and leaf biomass harvests and daily growth increments of Leucaena
hedgerows after the second root trenching, Fall 1994 ..................... 76

5-13: Height above a 50 cm stump and daily growth increments of Leucaena
hedgerows after the second root trenching. Fall 1994 ..................... 77

5-14: Maize height in trenched and nontrenched plots at four distances from
hedgerows. 40 DAS; Spring 1995..................................... 79








5-15: Maize biomass in trenched and nontrenched plots at four distances from
the hedgerow, 47 and 54 DAS; Spring 1995. ........................... 82

5-16: Soil water in trenched and nontrenched plots by depth and distance from
the hedgerow, 26 and 61 DAS; Spring 1995 ............................ 86

5-17: Maize grain weight, number of plants, and number of ears ................. 89

5-18: Stem and leaf biomass harvests and daily growth increments of Leucaena
hedgerows .......................................... ............ 90

5-19: Height above a 50 cm stump and daily growth increments of Leucaena
hedgerows ................................................... 90

5-20: Maize yield in three soil conservation practices and control at 116 DAS on
four farm s, spring 1997 ........................................... 105

6-1: Age distribution by gender of members of 1,540 farm households
interviewed in the four PADF/PLUS project areas in Haiti, 1996. .......... 128

6-2: Number of years of school by gender in seven age classes of 1,540
households participating in the PADF/PLUS project, 1996 ............... 129

6-3: Percent of female and male members of 1,540 project households who
participated in various economic activities during 1995-1996 ............. 130

6-4: Percent of female and male members of 1,540 project households who
participated in various economic activities during 1995-1996, by age
class......................................................... .131

6-5: Percent of female and male members of 1.540 households who
participated in PLUS project activities during 1995-1996 ................. 132

6-6: Percent of female and male members of 1,540 project households who
participated in PLUS project activities during 1995-1996, by age class ...... 133

6-7: Average total area of three categories of plots held by 1,540 project
households based on the relative distance from the plots to the residence .... 134

6-8: Mean plot area of three categories of plots held by 1,540 project
households during 1995, based on the relative distance from the plots to
the residence ................................................... 134

6-9: Mean plot area of three categories of plots held by 1,540 project
households during 1995 in four PLUS project regions, based on the
relative distance from the plots to the residence ........................ 135








6-10: Percent of three categories of plots held by 1,540 project households
during 1995 under various modes of access ........................... 136

6-11: Area of 5,660 plots held by 1,540 households during 1995, by mode of
access ........................................................ 137

6-12: Percent of plots held by 1,540 households during 1995 in eight mode of
access categories by slope position .................................. 137

6-13: Percent of all plots held by 1,540 households during 1995 in eight modes
of access categories by slope steepness ............................... 138

6-14: Distance from residence of plots having project agroforestry practices held
by 1,540 households during 1995 in the five most common mode of
access categories ................................. ........... 139

6-15: Area of plots having project agroforestry practices held by 1,540
households during 1995 in the five most common mode of access
categories ................................................... 140

6-16: Elevation of plots having project agroforestry practices held by 1,540
households during 1995 in seven mode of access categories .............. 140

6-17: Slope of plots having project agroforestry practices held by 1,540
households during 1995 in seven mode of access categories .............. 141

6-18: Percent of 2,295 surveyed plots with and without three kinds of
agroforestry practice held under secure (purchased or inherited/divided) or
not secure (all other) tenure ..................................... 147

6-19: Percent of 2,295 surveyed plots with and without three kinds of
agroforestry practice held under secure (purchased or inherited/divided) or
not secure (all other) tenure ..................................... . 147

6-20: Percent of 2,295 surveyed plots with and without three kinds of
agroforestry practice having fertile or not fertile soil .................... 147

6-21: Percent of 2,295 surveyed plots with and without three kinds of
agroforestry practice having fertile or not fertile soil .................... 148

6-22: Percent of 2,295 surveyed plots with and without three kinds of
hedgerows held under secure (purchased or inherited/divided) or not
secure (all other) tenure ............... ......................... .149

6-23: Percent of 2,295 surveyed plots with and without three kinds of
hedgerows having fertile or not fertile soil ............................ 149








6-24: Number of all trees larger than 10 cm diameter on PLUS plots, by plot
tenure ..................................................... 150

6-26: Soil fertility and hedgerow management quality ......................... 154

6-27: PADF/PLUS field region and hedgerow management quality .............. 156

6-28: Soil fertility and crop band management quality ........... ... ......... 157

6-29: PADF/PLUS field region and crop band management quality .............. 158

6-30: Soil fertility and rock wall management quality ......................... 159

6-31: PADF/PLUS field region and rock wall management quality .............. 160

6-32: Percent of 1,362 plots where potential benefits of hedgerows (fuel,
charcoal, construction wood, fodder, soil fertility, soil conservation, and
crop production) were classified according to importance by farmers on a
five-point scale, 1=not important, 5=very important. .................... 161

6-33: Percent of hedgerows classified as well-managed by technicians in 1,362
plots where potential benefits of hedgerows (fuel, charcoal, construction
wood, fodder, soil fertility, soil conservation, and crop production) were
classified according to importance by farmers on a five-point scale, l=not
important, 5=very important. ...................................... 162

6-34: Percent of hedgerows classified as poorly-managed by technicians in
1,362 plots where potential benefits of hedgerows (fuel, charcoal,
construction wood, fodder, soil fertility, soil conservation, and crop
production) were classified according to importance by farmers on a five-
point scale, l=not important, 5=very important. ....................... 163

6-35: Number of breaches per 100 m of hedgerow counted by technicians in
1,362 plots where potential benefits of hedgerows (fuel, charcoal,
construction wood, fodder, soil fertility, soil conservation, and crop
production) were classified according to importance by farmers on a five-
point scale, l=not important, 5=very important. ........................ 164

6-36: Percent of gardens where hedgerow breaches were repaired or not repaired
for three potential benefits of hedgerows. .......................... 165

6-37: Percent of 1,362 plots where potential problems of hedgerows (shade,
reduced space, water competition, reduced ability to picket animals,
weediness, and labor cost) were classified according to importance by
farmers on a five-point scale, l=not important, 5=very important .......... 165








6-38: Percent of gardens where hedgerow breaches were repaired or not repaired
for three potential problems of hedgerows. ............................ 166

6-39: Estimated relative costs, benefits, and risk of agroforestry practices ........ 171














LIST OF FIGURES

Figure page

5-1: Layout of the Leucaena/maize hedgerow trial on Operation Double
Harvest property near Croix des Bouquets, Haiti ........................ 45

5-2: Diagram of one plot showing relative positions of a Leucaena hedgerow
and the adjacent rows of maize at four distances. ........................ 46

5-3: Rainfall, Leucaena and maize growth, and agronomic inputs; spring 1994
maize cropping season ................ ........................... 51

5-4: Rainfall, Leucaena and maize growth, and agronomic inputs; fall 1994
maize cropping season ............................................ 51

5-5: Rainfall. Leucaena and maize growth, and agronomic inputs; spring 1995
maize cropping season ................ ........................... 52

5-6: Maize biomass yields at 50, 100, 150, and 200 cm from the hedgerows at
four times after sowing during the spring 1994 season .................... 59

5-7: Growth stage of maize at four distances from hedgerows .................. 61

5-8: Yield of maize grain per six meters at four distances from the hedgerows ..... 64

5-9: Number of maize plants per eight hills at four distances from the
hedgerows ..................................................... 64

5-10: Number of maize ears per eight hills at four distances from the hedgerows .... 65

5-11: Trenched and nontrenched plots at 50, 100, 150, and 200 cm from the
hedgerows. 78 DAS; fall 1994 ............... ...................... 69

5-12: Maize leaf water potential in trenched and nontrenched plots ............... 70

5-13: Soil water in trenched plots (and difference between T+ and T- plots) at
42 DAS, fall 1994 .............................................. 72

5-14: Maize grain yield in trenched (T+) and nontrenched (T-) plots .............. 74








5-15: Maize height trenched and nontrenched at four distances from the
hedgerow, 40 DAS; Spring 1995 .................................... 79

5-16: Maize biomass in trenched and nontrenched plots at four distances from
the hedgerow, 47 DAS, Spring 1995 .................................. 81

5-17: Maize biomass in trenched and nontrenched maize weight at four
distances from the hedgerow, 54 DAS, Spring .......................... 81

5-18: Trenched and nontrenched maize growth stage at four distances from the
hedgerow, 68 DAS; Spring 1995. .................................... 83

5-19: Trenched and nontrenched maize growth stage at four distances from the
hedgerow, 75 DAS; Spring 1995. ....................................83

5-20: Soil water percent in trenched plots (and difference between T+ and T-
plots) at 26 DAS, Spring 1995 ....................................... 85

5-21: Soil water percent in trenched plots (and difference between T+ and T-
plots) at 61 DA S, Spring 1995 ....................................... 85

5-22: Maize grain weight from trenched and nontrenched plots at four distances
from the hedgerows, 131 DAS; Spring 1995. ........................... 87

5-23: Number of maize plants from trenched and nontrenched plots at four
distances from the hedgerows, 131 DAS; Spring 1995. ................... 88

5-24: Number of ears from trenched and nontrenched plots at four distances
from the hedgerows, 131 DAS; Spring 1995 ........................ 88

5-25: Number of very fine root (<2mm) intersections with a 10 by 100 cm plane
parallel to the trenched hedgerows at five distances and 10 depths, with
the difference between the trenched and nontrenched hedgerows shown in
parentheses ................ ................................... 92

5-26: Number of fine root (2-5 mm) intersections with a 10 by 100 cm plane
parallel to the trenched hedgerows at five distances and 10 depths, with
the difference between the trenched and nontrenched hedgerows shown in
parentheses. ..................................................... 92

5-27: Number of medium root (5-10 mm) intersections with a 10 by 100 cm
plane parallel to the trenched hedgerows at five distances and 10 depths,
with the difference between the trenched and nontrenched hedgerows
shown in parentheses ...................................... ...... 93








5-28: Number of large root (>10 mm) intersections with a 10 by 100 cm plane
parallel to the trenched hedgerows at five distances and 10 depths, with
the difference between the trenched and nontrenched hedgerows shown in
parentheses .................................................... 93

5-29: Leucaena small stem and leaf biomass from trenched and nontrenched
plots, May 1991 through September 1995 .............................. 98

5-30: Maize development in three soil conservation practices and control at four
times during the growing season on four farms during Spring 1997 ......... 104

6-1: Relative importance of four plot characteristics to the decision to install
six agroforestry practices ............... ......................... 168













Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

DYNAMICS OF FARMER ADOPTION, ADAPTATION, AND MANAGEMENT
OF SOIL CONSERVATION HEDGEROWS IN HAITI

By

Michael Bannister

May 2001

Chair: P. K. Ramachandran Nair
Major Department: School of Forest Resources and Conservation

Understanding the conditions under which hillside farmers in Haiti adopt soil

conservation practices helps programs to develop technologies that increase farmer

revenue and stabilize or improve soil and water resources. Three studies were done in

Haiti that examined biophysical and socioeconomic aspects of contour hedgerows, an

agroforestry practice with the potential of stabilizing soil, conserving water for crops,

increasing soil fertility, and producing wood and fodder.

An on-station study of soil water competition between Leucaena leucocephala

(Lan.) de Wit hedgerows and adjacent maize (Zea mays L.) over three cropping cycles

found that substantial maize yield reduction was caused by the hedgerow trees because of

soil water competition. Polyethylene barriers between the hedges and the first row of

maize improved maize yield in two subsequent seasons by 18% and 77% over plots

without barriers. The percent increase in maize yield was highest during a season of very

poor rainfall; but it was lowest in a season of adequate rainfall. Barrier installation








reduced Leucaena biomass production by about 1,500 kg/ha over seven months, but this

effect was temporary. An examination of the distribution of Leucaena roots after the

final maize harvest showed that the hedgerow roots in the plots with barriers had grown

under the hedgerows and developed more fine roots at 200 cm from the hedges than plots

without barriers.

An on-farm study comparing maize development in two kinds of hedgerows, rock

wall terraces, and an untreated control was unable to detect differences in the rate of

maize growth with respect to position within the alleys or with respect to position on the

overall slope. However, the maize in the hedgerows developed more slowly than in the

rock wall terraces or the control plot, indicating competitive interactions between maize

and hedgerow plants. There were no differences in maize grain yield among treatments.

An on-farm questionnaire-based survey of 1,540 Haitian farmers showed that

they considered plot characteristics, including mode of tenure, soil fertility, distance from

the residence, and slope in their decisions to install different agroforestry practices.

Tenure security and soil fertility appeared to be the most important plot characteristics in

the decision to install, although it was not possible to separate them. Hedgerows were

more likely to be installed in plots having less secure tenure and less fertile soil; the

opposite was true for other agroforestry practices. Farmers' qualitative assessments of

soil fertility were positively correlated with management quality of hedgerows.













CHAPTER 1
INTRODUCTION

The research presented here focuses on agroforestry technologies, which could

contribute to increasing the revenue of small farms on the hillsides of Haiti in a

sustainable, environmentally friendly way. This is a formidable goal, because Haiti is

primarily a mountainous country long since shorn of its natural vegetative cover. Its

once-rich soils are badly eroded, and their productive capacity severely diminished.

Haiti is densely populated by very poor people who generally lack formal education or

access to a functioning legal system. It has a long history of political instability that

continues to this day. At best, agriculture is difficult in such a setting. But, Haitian

farmers regularly experiment with new techniques.

This dissertation investigates the biological and adoption aspects of hedgerow

intercropping, an agroforestry practice that involves growing food crops in the

interspaces between rows of densely planted trees or shrubs. Two types of studies are

included. One focuses on competition for growth resources between trees and crops

while the other focuses on the factors that influence farmers' adoption of the technology.

However, these different studies are linked together, because both social and biological

aspects of agroforestry practices must be understood for providing efficient extension

services to farmers.

The dissertation is presented in seven chapters. Chapter 1 briefly explains the

background of the research and states its objectives. Chapter 2 describes Haitian








smallholder farms, the population of interest to the research. Following a definition of

hedgerow intercropping, the agroforestry practice that is the subject of the research.

Chapter 3 reviews its development in the tropics and in Haiti and examines how it is used

as a soil conservation technique. Chapter 4 justifies the research, presents the hypotheses

to be tested, and describes the studies used to test the hypotheses. The next chapter

(Chapter 5) presents the two studies examining competition between hedgerows and

adjacent crops. The first is done on station, the second on farm. The questionnaire-based

survey of farmers who adopted soil conservation practices promoted by the PLUS project

is the subject of Chapter 6. Finally, Chapter 7 synthesizes the previous chapters.

and presents the overall conclusions of the dissertation.

The research was done while the author was employed by the Pan American

Development Foundation (PADF) in Haiti. The PADF implements a U.S. Agency for

International Development (USAID) project called Productive Land Use Systems

(PLUS). The PADF/PLUS has worked with about 170,000 hillside farmers in soil

conservation, tree planting and grafting, has improved food crop distribution and

marketing, and has been strengthening local farmer organizations between 1992 and

1999. The on-farm study of maize (Zea mays L.) production between soil conservation

structures discussed in Chapter 5 and the questionnaire-based study discussed in Chapter

6 were done as PLUS monitoring and evaluation exercises by PADF staff. The author

designed the questionnaires and trained staff in their use.

The overall objective of this research is to understand how characteristics of

Haitian farm families, their plots, and agroforestry practices affect the adoption and

management of those practices. The purpose is not to use the data gathered in the course

of this research to define and predict adopters so that nonadopters can be excluded from








extension efforts. It is rather an effort to understand how appropriate practices can

evolve and be extended more rapidly.

In particular, the objectives of the three studies that comprise this dissertation are

to determine, in the relatively controlled environment (for a research station),
whether the competition for soil water between trees in hedgerows and
adjacent maize is significant and can be reduced by the use of plastic root
barriers,

to understand whether tree-crop competition in farmers' steeply sloping fields
is similar to that observed in the flat controlled environment of the research
station, and

to examine the factors (e.g., land tenure, perceived tree/crop competition, plot
slope, soil fertility of the plot, distance from the residence to the plot, previous
experience of the farmer, and the availability of other farm resources) that
influence farmer adoption, adaptation, and management of hedgerow
intercropping.













CHAPTER 2
HILLSIDE FARMING SYSTEM IN HAITI

Haiti is mainly hilly, with 20% of the land area below 185 m elevation and 40%

above 450 m-about 75% highlands, 22% lowlands (Weil et al. 1973). The most

common "life zones," according to Holdridge's (1945) classification, are subtropical

moist forest and subtropical dry forest, but subtropical wet and rain forest zones are

common in the middle and upper elevations. Limestone substrate underlies 80% of the

land area; the rest is basaltic or alluvial (Ehrlich et al. 1985). According to Ehrlich et al.

(1985) estimates, 1.3 million hectares (of 2.7 million total for the country) were under

agricultural production; six times the area classified as "good agricultural land." The

practice of annual agriculture on steeply sloping plots causes severe losses of arable soil

due to erosion, estimated to be about 37 million tons annually in 1994 (UNDP, 1996).

Haitians have been practicing agriculture on small, privately held plots in the hills

since the 1840s. as the large plantations and public domain lands were divided (de Young

1958. Leyburn 1941). Haitian peasants are not subsistence farmers in the strict sense that

they do not live off the land self-sufficiently and independently, but rather produce for,

and are linked closely to, the market (Murray 1981). Most farm families have some

nonagricultural income and are net food buyers (Locher 1996). De Young (1958)

describes the economic organization of Haitian farms as "horticultural" rather than

agricultural, and gives the following characteristics that still hold true today:

They are market directed, not subsistence directed.








They give more importance to perennial rather than annual crops.

The farm units are small parcels, and the land is used intensively.

They are capital saving rather than labor saving. Farmers own only a few
hand tools, have little invested in storage or farm buildings, and rarely use
plows and animal traction.

The farm animals are used mainly for transport to market.

Reducing risk is as important to most farmers as increasing production, and to

this end they manage a network of ties to relatives and other farmers as social capital that

can be leveraged in order to gain access to scarce land, labor, and capital (Smucker et al.

2000). Haitian families also spread out risk by diversifying human and economic

resources via selective migration, emigration, and off-farm economic enterprises (Locher

1996). Therefore, not only is any one particular crop not the sole interest of a farm

family, but agriculture is not the only domain of economic activity. It is quite likely that

other activities, such as nonagricultural marketing or remittances from relatives overseas,

bring in more cash.

Land

Haitian hillside farms are small and complex. Farm families usually manage or

cultivate several parcels of land at any given time, held under a mix of land tenure

arrangements (e.g., owned, tenancy, usufruct) (Bloch et al. 1987, Locher 1996) and often

on sites differing in their physical characteristics (hillside, plain, irrigated, rainfed) and in

distance from the residence. This is done as a purposeful strategy to reduce risk of

harvest loss and to spread out crop harvest over the year (McLain and Stienbarger 1988,

Murray 1981, Zuvekas 1979). Plot sizes are small and fallow periods are short. Plots are

worked and then abandoned when yield decreases below the farmer's economical limits.

Declining soil fertility, soil loss due to erosion, large variation in the timing of rainfall,








and the inability of traditional agricultural practices to harvest and store water in the soil

limit agricultural production. Residences tend to be physically disbursed in the mountain

regions instead of concentrated (Friedman 1955).

Two intertwining land tenure systems operate in Haiti, one official and the other

customary (Smucker et al. 2000). created by disenfranchised peasants to protect

themselves against loss of land via a corrupt justice system and government abuse. The

land market is active. Most farmers own most of their land, but the majority of the

transactions are done without recourse to expensive official processes (Smucker et al.

2000, Zuvekas 1979). The customary system provides farmers relatively secure access to

land, but some tenure classes are more stable over time than others so mixed tenure

configurations that change over time are the norm (Locher 1996). Zuvekas (1979)

reviewed data from 12 studies done in Haiti and found that the percentage of farmers

owning (by purchase or inheritance) at least part of their land ranged from 58 to 100%.

Secondary modes of access to land include rental from private owners, lease, and

sharecropping. Usufruct rights to land are also obtained from relatives or by acting as

caretaker for an absentee landowner

Information about farm size is available from several studies related to

agroforestry projects from various parts of the country (Lea 1994a, Lea 1996, Swanson

et al. 1993a, 1993c, White 1992a). The total size of all farm plots ranges from less than

one to about three hectares. The average farm family works two or three plots (Zuvekas

1979) that vary in size from about one half to just over one hectare each.

Haitian laws of inheritance have French antecedents and require that all siblings

inherit; therefore, land holdings are, in general, getting smaller. In 1950, 39% of

households held less than 1.3 hectares; by 1971 this proportion had increased to 71%








(Murray 1981). Brochet (1993) compared the average size of home gardens in one area

of Haiti over fifty years, and found that the average holding that was one hectare per

family in 1910 had decreased to 500 m2 (0.05 ha) by 1970. This study was done in an

area mined for bauxite by Reynolds Aluminum, so sale of land to the mining company

may have accelerated the rate of decrease, but in general average sizes of holdings grow

smaller as the population increases. One strategy adopted by Haitian families to ensure

that a plot is large enough to harvest a crop worth planting is to bequeath land to children

undivided, but this may discourage investing in improvements to the plot if the siblings

are contentious. Older farmers are likely to own a larger proportion of their holdings

(Lundahl 1997, McLain and Stienbarger 1988).

Other types of land tenure found in Haiti include purchased, inherited but

separated, rented from private owners, and rented from the state. Usufruct rights to land

also are obtained by sharecropping (on land owned by the sharecropper as well as on land

owned by another) and by acting as caretaker for an absentee landowner. A recent

survey of 5000 fields across the country (USAID. 1996) showed the following pattern of

land tenure: purchased 39%, inherited/divided 20%, inherited/undivided 14%, rented

12%, share cropped 5%. gift 1%. and other 9%.

Crops

Since small and scattered plots must provide food, fuel, building material, animal

fodder, and other household necessities, agroforestry has traditionally been practiced.

The farm plots, except the plot containing the residence and surrounding tree and

medicinal crops (sometimes called the home garden), are spatially dominated by cereal

grains and grain legumes (pulses), but income from roots, tubers, tree crops, and animals

is probably more important economically, and is able to shield farmers against variations








in rainfall better than grains and pulses. Home gardens include many tree crops such as

mango (mangifera indica L.), breadfruit (Artocarpus altilis [Parkinson] Fosberg), citrus

(Citrus spp.), royal palm (Roystonia borinquena), and coconut (Cocos nucifera L.).

Timber and fuelwood trees are planted or tended where they sprout around property

perimeters, scattered throughout plots, or as small woodlots. Trees are considered to be a

crop. and are managed as a savings account, to be harvested when cash or building

materials are needed (Murray 1981, Smucker and Timyan 1995). Fuelwood and animal

fodder are in short supply in many parts of the country.

Many different combinations of crops are grown. These vary with the season.

land tenure, distance from the residence, market demand, availability of seed, and the

rainfall and soil characteristics. The most common grain crops are maize (Zea mays L.)

and sorghum (Sorghum bicolor (L.) Moench) on the hillsides, and rice (Oryza sativa L.)

in the few irrigated plains. Pulses include beans (Phaseolus vulgaris L.), pigeon pea

(Cajanus cajan (L.) Millsp.), and peanuts (Arachis hypogaea L.). It is common for the

spring maize crop to fail, because of poor rainfall. Beans are able to generate important

income for farmers, but also fail often--rain is insufficient, or rain falls during flowering

(eliminating pod formation), or rain falls before seeds are dry causing them to germinate

in the pods. Root and tuber crops include yams (Diascora spp.), cassava (Manihot

esculenta Crantz), and cocoyam (Xanthosoma sagittifolium (L.) Schott). Plantains (Musa

spp.) are commonly grown in ravines and near the home. Living fences surround the

property where the house is located, and are commonly built of plants serving protective

functions due to the presence of spines or poisonous sap, such as bayonette (Yucca

aloifolia L.). pencilbrush (Euphorbia tirucalli L.), raquette (Euphorbia lactea Haw.), and

penguin (Bromelia pinguin) (Ashley 1986).








A 1996 USAID survey of 6,900 fields during a single spring planting season

(USAID, 1996) found that 27% of the plots had crops growing in association (two or

more crops present simultaneously in the same field for part or all of the cropping cycle),

and 21% in monoculture. There were 16 main maize associations and 98 minor (<5000

ha. each) ones. In addition, there were 12 important associations of other crops, 134

minor ones, and 14 main kinds of monocrops. This does not include the many different

kinds of tree and medicinal crops, crops found during the fall growing season, or animals.

The most commonly seen grain crop in the fall season is sorghum, usually intercropped

with pigeon pea. The USAID study notes only the physical presence of the crops, not

their relative economic importance.

Labor

Households function as separate economic units, but the members participate in

labor and food exchanges with other farmers (Murray 1981, Smucker and Dathis 1998).

The family itself provides the labor for most agricultural activities. This labor pool is

expanded periodically according to seasonal demands for land clearing, working the soil,

planting, weeding, and harvesting crops. Labor is a scarce resource, and has been more

difficult to supply and afford as the deteriorating social and economic situation in Haiti

has forced many rural inhabitants into political refuge or into taking jobs in the

neighboring Dominican Republic (Balzano 1997, Smucker and Dathis 1998). Farmers

form groups to exchange farm labor, earn cash, or to save money to attain a future goal.

However, this communal pooling is restricted to labor, not to the sharing of land or

produce (Murray 1991). Access to labor is crucial because working steep slopes is labor

intensive, and frequently must be done on short notice because rainfall varies so much

over short distances in the mountains. Crops must be planted as soon as the first rains








arrive. Farmers without access to labor at the right time will suffer. Work groups

generally consist of 3 to 15 members from the same socioeconomic level, and can be

permanent or formed for a single task (Murray 1991, Smucker and Dathis 1998, Swanson

et al. 1993a, 1993b 1993d, 1993e). The names given to labor groups differ from place to

place within Haiti, and even from farmer to farmer (Smucker and Thomson 1999). The

two main kinds of groups are those that are for labor exchange only and those that are

formed to work for cash. Client farmers paying cash for labor are generally not group

members, and are better off economically. A wealthy farmer may join a labor exchange

group just for the purpose of gaining access to the labor. Another kind of work party is

called the koumbit, where the host farmer provides one or two meals and sometimes

alcohol to other farmers invited to clear or prepare a field (Swanson et al. 1993a). It is

not possible to control the number of participants, the length of time they stay, or the

quality of the work done, and for this reason the koumbit is becoming rare (Swanson et

al. 1993e). Finally, individual farmers also are engaged by others to do specific tasks.

This is referred to as a djob (job).

Typically, men form labor exchange groups for agriculture while women form

mutual credit supply groups that permit them to engage in commerce. Women have

always participated in some aspects of agricultural labor, and this appears to be on the

rise because of the out-migration of men during times of political and economic troubles

mentioned above (Smucker and Dathis 1998).

Farmer Development Groups and Local NGOs

Indigenous development groups are of interest because, since the early 1980s,

most donor-financed development work, including agroforestry extension, has been done

through them. This happened because of the difficulty in controlling the use of funds








disbursed through the Haitian government, which has always been a predatory structure

serving the interests of the urban elite to the exclusion of the rural majority (Smucker and

Thomson 1999).

Smucker and Dathis (1998) give a comprehensive description of these groups, on

which the rest of this section is based. These groups vary widely in origin and

composition, ranging from community organizations, cooperatives, youth groups,

women's groups, work exchange groups, traditional groups, and religious groups.

Agricultural cooperatives began in the 1930s and expanded in number in the 1950s. The

community council movement began in the 1950s and was politicized by the Duvalier

regime in the 1970s. The Catholic Church created nonhierarchical farmer development

groups beginning in the 1960s that became known as groupement and eventually stood in

opposition to the community councils. After the fall of the Duvaliers in 1986 the

numbers of groups based on the groupement model increased dramatically; but they were

persecuted, and they went underground after the 1991 coup d'etat. All of the groups

have economic survival objectives, but are not limited to that. They look for more

control over the factors of production, including agricultural inputs, credit, grain storage,

more control over export crops, and investment in soil conservation and trees. They are

now experiencing growing pains as their membership increases and they take on more

objectives, without the legal recognition that would permit them to defend their interests

and open bank accounts. These difficulties increase as their growth pushes them to

depart from the basic characteristics of the traditional local groups, which are direct

participation, small size with common interests, hope of tangible profits, direct

investment of members' resources, and links of reciprocity and rotation. Farmers would

be better able to invest in necessary agroforestry practices if these groups were stronger.






12

For example, a group with juridical personality, basic accounting skills, and a bank

account would be more likely to succeed in negotiating crop sales to large buyers.

Profits from sales would allow them to buy labor to protect the plots that produce the

crops being sold.













CHAPTER 3
THE HEDGEROW INTERCROPPING SYSTEM

Developments in the Tropics

Definition

Hedgerow intercropping, also known as alley cropping and alley farming (Rao

et al. 1998), has been suggested as an approach to address decreasing soil fertility and for

controlling erosion (Kang et al. 1990). It is an agroforestry practice consisting of closely

planted and regularly spaced rows of fast-growing. repeatedly pruned trees, usually N2-

fixing legumes, with short cycle agricultural crops cultivated in the alleys or spaces

between the hedges (Kang et al. 1990). It is classified as a simultaneous (trees and crops

present in the field at the same time) and zonal (trees are concentrated in the field rather

than dispersed) agroforestry practice (Nair 1993). The hedges and crops are managed

together for a common purpose, and there are significant above- and below-ground

ecological interactions between them (Sinclair 1999). The most common objective of

hedgerow intercropping is to increase crop production in the alleys by applying the

pruned tops of the hedgerow trees to the soil as a green manure to improve soil fertility.

This objective is pursued by attempting to balance the facilitative and competitive effects

inherent in the practice (Vandermeer 1998). The more leaf biomass harvested from the

trees, the more green manure available to improve soil conditions and thereby increase

crop yield. However, more leaf biomass is obtained by increasing the number of

hedgerows and this reduces the space available to crops. It also increases the area of








tree-crop interface (Ong and Leakey 1999) and therefore creates more possible

competitive interactions (shading, soil water competition, nutrient competition) with the

crops, potentially depressing yield (Vandermeer 1998). Hedgerows fulfill other purposes

as well, including soil erosion control and production of fodder and fuel.

Origins

Hedgerow intercropping developed independently both in the western humid

lowlands of Africa and in southeast Asia. In Nigeria, traditional farmers have for several

generations planted and managed hedges of a shrub, Dactyladenia barteri (Hook f. ex

Oliver), for the purposes of contributing nutrients to crops. controlling weeds, and

production of fodder and stakes (Kang et al. 1984). Looking for a way to respond to soil

impoverishment due to the shortening cycle of traditional slash and burn agriculture,

researchers began investigating similar ways to use trees. The principles suggesting

intercropping plants with complementary root systems occupying different soil regions

(Weaver 1920) and the possibility of tree roots capturing nutrient resources out of the

reach of crops (Nye and Greenland 1960) were familiar, but had not yet been applied

systematically to agroforestry associations by nonfarmer researchers. The International

Institute for Tropical Agriculture (IITA). based in Ibadan, Nigeria. began trying woody

species to improve the fertility of low-activity clay soils. This led to the development of

alley cropping (also referred to as hedgerow intercropping), avenue cropping, and alley

farming if fodder production was a main objective (Kang and Wilson 1987). The first

alley cropping trial at IITA began in 1976; on-farm trials were established in the 1980s

(Tripathi and Psychas 1992).

An earlier start was made in Indonesia. Development of hedgerow intercropping

in this region appears to be related to the introduction of Leucaena spp. to the Philippines








and Indonesia by the Spanish from Mexico (Dijkman 1950) and its promotion by the

Dutch as a shade tree for coffee (Coffea arabica L.), cacao (Theobroma cacao L.), tea

(Camelia sinensis (L.) Kuntze), and tobacco (Nicotiana tabacum L.) in the 18th century

(Wirjodarmodjo and Wiroatodjo 1983). Dutch journal articles from the 1930s report the

use of Leucaena contour hedges to support bench terraces on slopes (Dijkman 1950).

Tacio (1993) cites a traditional ruling in the 1930s obliging all farmers in a region of

Timor, Indonesia to plant contour hedges of Leucaena 3 m apart in cropped areas.

Metzner (1976) notes Leucaena thickets were promoted by the Indonesian government in

the 1930s to recuperate nonarable lands, but farmers did not do it because they feared the

weedy qualities of Leucaena. By the 1950s, Leucaena was commonly used in the Pacific

as contour hedges for erosion control (Dijkman 1950). Hernandez (1961), cited in Benge

(1980), discusses results of Indonesian hedgerow intercropping research done in 1953.

The hedgerows decreased erosion and improved maize yield by 380% on the treated

plots, compared to traditional cultivation. Extension of hedgerows to farmers, supported

by the Indonesian government and religious groups, expanded greatly during the 1970s

(Metzner 1976, Tacio 1993, Wirjodarmodjo and Wiroatodjo 1983).

The Rise and Fall of Alley Cropping

Research on alley cropping in West Africa in the 1980s generated widespread

interest (Kang and Wilson 1987) and led to trials and extension in many parts of the

world. In trials examining their technical performance, hedgerows had positive effects

on the yield of adjacent food crops through the application of tree prunings as green

manure (Tonye and Titi-Nwel 1995), increased rainwater infiltration into the soil (Kiepe

1995), and reduced soil erosion when installed on sloping land (Paningbatan et al. 1995).

Some economic analyses indicated that alley cropping, in spite of its high labor








requirement, can be profitable under certain environmental conditions (Ehui 1988).

Based on these initial results, project based extension of hedgerow intercropping to

farmers in developing countries grew quickly (Ongprasert and Turkelboom 1995,

Sanchez 1995, Scherr 1994).

However, after a few years many came to believe that alley cropping had been

oversold and had much less applicability than previously thought, and that its potential

for adoption was limited to certain niche areas (Carter 1995, Sanchez 1995). Based on a

review of hedgerow trials covering some of the possible biophysical conditions and

hedgerow configurations, Sanchez (1995) lists the conditions where alley cropping is

most likely to succeed: areas having fertile soils with no major nutrient limits, adequate

rainfall during the cropping season, sloping land with erosion hazard, ample labor and

scarce land, and secure land tenure. In spite of the apparent productive advantages

discovered in controlled studies and the enthusiasm of project extension technicians,

adoption among farmers remained generally low. This has been observed in many

regions, including Indonesia and the Philippines (Fujisaka 1991, Nelson et al. 1997),

Thailand (Ongprasert and Turkelboom 1995). Central America (Kass et al. 1995), West

Africa (Lawry et al. 1994), and East Africa (Mutsotso and Gicheru 1995). Several

reasons for poor adoption of hedgerows are given, including damage by grazing animals

(Fujisaka and Cenas 1993, Mutsotso and Gicheru 1995), land tenure issues (Fujisaka et

al. 1995, Lawry et al. 1994), and competing farm and off-farm activities (Fujisaka 1993,

Ongprasert and Turkelboom 1995), but by far the most common reasons are the high

costs of labor for installation and management (David 1995. Fujisaka et al. 1995, Kass et

al. 1995, Mutsotso and Gicheru 1995, Nelson et al. 1997, Ongprasert and Turkelboom








1995, Stark 1996) and farmers' need for short-term economic returns from their plots

(Fujisaka 1993, Ongprasert and Turkelboom 1995, Steiner and Scheidegger 1994).

Initial positive results from alley cropping trials were eventually modified by later

studies that showed decreased crop production from alley cropping in certain biophysical

settings or prohibitive costs of installation and management to farmers in certain

socioeconomic settings. The claims made for the potential of alley cropping. it was felt.

were exaggerated. But criticisms of alley cropping, summarized in a review written by

Sanchez (1995), have also been exaggerated due in part to its having been tested in

limited and inappropriate situations (Nair 1998). and may have caused an unwarranted

backlash among researchers (Vandermeer 1998).

Rao et al. (1998) reviewed 29 hedgerow intercropping trials that had been

conducted for four or more years, mostly on small plots, over a wide range of soils and

climates, but no studies done on sloping land were included. They found both positive

(15 studies indicated positive results for cereals. 8 trials showed positive results for

noncereal crops) and negative (13 trials showed negative results for cereals, 1 showed

negative results for noncereal crops) effects of hedgerow intercropping on crop yields

across the tropics. Including only the studies showing crop yield increases in hedgerow

systems greater than 15% (assuming this would be a minimum level to interest farmers),

positive effects on crop yield were found in only 2 of 10 studies in semiarid (<1000 mm

rainfall) regions. and 7 of 11 studies in subhumid (1000 to 1600 mm) regions where soils

were either inherently fertile or supplemented. In 4 out of 8 trials in the humid tropics

(>2000 mm) maize and taro (Colocasia esculenta (L.)Schott) did not benefit from

hedgerow intercropping, but bean and cowpea yields did. The authors conclude that the







18

hedgerow intercropping system is location specific and sensitive to management, and that

generalizations are difficult to make.

One can understand the caveats attached to prescribing or proscribing hedgerow

intercropping as a general solution; however, a more balanced approach to both research

and extension of hedgerow intercropping is now emerging. There is a growing

recognition that its success or failure depends on many site-specific factors including the

type of crops grown, the species of plants used as the structural component of the

hedgerows, rainfall amount and distribution, soil type, and a host of socioeconomic

variables (land and tree tenure, labor costs, etc.), including equity issues, extension

approaches, and allowance for adaptation of the practice over time to optimize its

economic returns to farmers (Mercer and Miller 1998, Nair 1998, Rao et al. 1998.

Sanchez 1995, Scherr and Current 1997).

Developments of Hedgerow Intercropping in Haiti

Hedgerow intercropping using Leucaena leucocephala (Lam.) de Wit was tried

on a small scale in Haiti for the first time in the early 1980s, but there are earlier

examples of vegetation-based soil conservation structures. Mintz (1962) notes that

Haitian farmers have been building seasonal crop stover barriers staked roughly on the

contour to harvest water and soil since the 1950s. These structures, known as ranp pay in

Creole, are still being built in some parts of the country. They last only a single planting

season. Some farmers say that stover barriers provide habitat for rats and insects, and so

they prefer to burn the crop residue. Contour structures have been promoted by

development projects since the 1950s. A UNESCO project in the community of Marbial

paid people to plant sisal (Agave sisalana Perrine ex Engelm.) on the contour to control

soil erosion in the early 1950s, and a FAO project near the town of Les Cayes in the late








1960s promoted contour hedges of napier grass (Penisetum purpuremn K. Schumach.).

lemon grass (Cymbopogon citratus (DC.) Stapf). vetiver (Vetiveria zizanioides (Linn.)

Nash), and guinea grass (Panicum maximum Jacq.) (G. Brice, personal communication:

1998). These were done by farmers who were paid stipends based on the number of

hedges installed, and they were not always appropriately designed. The napier grass

hedgerows were planted on shallow, drought soils. Many eventually grew taller than

their shallow roots could support, and toppled over. This also happened to some of the

sisal, a crop that is traditionally planted up and down the slope so that farmers harvesting

the sharply pointed leaves do not injure themselves if they fall.

In contrast to the historically widespread nonadoption of soil conservation

strategies designed by technicians, there is an example of a successful practice designed

by Haitian farmers responding to a particular market opportunity. This involves the

yearly, labor-intensive construction of contour soil bunds (tram) to conserve expensive

chemical fertilizers used to produce high-value vegetables in a small region close to the

capital city (Murray 1980).

Initial interest in tree-based hedgerow intercropping was stimulated by reports of

developments in West Africa, Indonesia, and the Philippines, and by the general interest

in the use of Leucaena leucocephala as a fuelwood tree. There is a variety of Leucaena

native to Haiti, known locally as delen, oriman, ti movye, or i pingi. This variety is not

suited to hedgerow construction because it is extremely invasive and does not produce

sufficient biomass, and is therefore very unpopular among farmers. To promote the use

of Leucaena, USAID introduced seeds of productive varieties to Haiti in 1978 (Benge

1985). Seeds ofLeucaena K8, K28, and K67 from trees grown in the Philippines were

distributed, and later seeds from Flores, Indonesia were introduced. In 1979, a USAID






20

agronomist also introduced the concept of using Leucaena in hedgerows, and re-wrote an

existing paper on Leucaena hedgerows especially for Haiti (M. Benge. personal

communication: 1995).

The number of hedgerows reported by PADF as built by farmers participating in

PLUS and its two predecessor projects probably represents the largest percent of the

hedgerows in Haiti. During the seven-year period from 1985 through 1991. 848 km of

hedgerows were reported (PADF 1990). The number of hedgerows installed has been

much greater under the PLUS project, with over 12,000 km. having been installed from

1993 through mid-1999 (PADF 1999). If the number of hedgerows ever installed by

farmers working with all aid projects in Haiti is estimated at 15,000 lineal km, and if

there is an average of 5 meters between rows, then approximately 7,500 hectares of

hillside gardens have had hedgerows. Although this represents less than one-half of a

percent of the total land area, it is a significant figure for a new technique whose

management is still being developed.

Hedgerows have been recommended as a potentially appropriate agroforestry

technology and are commonly promoted in Haiti as part of project or government-based

soil conservation and natural resource strategies (Bannister and Nair 1990). Garrity and

Van Noordwijk (1995) note three paradigm shifts in hillside conservation management:

(1) an engineering approach using rock and earthworks in contour structures has

increasingly given way to vegetative structures; (2) top-down prescriptive watershed

management has evolved to a bottom-up, participative approach; and (3) tree-based alley

cropping has diversified to include a wider array of economically interesting plant

materials as structural components of contour hedgerows. All three of these shifts have

occurred in Haiti. Early attempts at erosion control promoted by projects in Haiti were








mainly based on rock walls constructed across the contour, but these were poorly

maintained because they did not respond to farmers' economic situation and the

extension approach was inappropriate (Murray 1980). The increasing emphasis on

vegetative barriers happened during the 1980s, as noted above, along with as-yet

incomplete attempts to manage natural resources participatively.

However, the ideotype of contour hedgerows is not static in Haiti. Farmers

continually modify the structural composition and management of hedgerows according

to their household needs, their ability to invest resources, their experience with

hedgerows. and changing marketing opportunities for crops and products derived from

hedgerow trees. Leucaena leucocephala was originally the predominant hedgerow

species, but that is changing. During 1995, PADF reported hedgerows made with 22

different tree, perennial food crop, grasses, and other perennial species planted in 54

different combinations. Leucaena was present in only 46% of the hedgerows. In

addition, hedgerows are evolving into perennial crop contour bands in some areas. These

bands, called bann manje (a play on words-either "band of food" or "a lot of food")

consist of rows of food crops planted across the contour, with a dimension up and down

the slope of more than one meter. Perennial crops such as pineapple (Ananas comosus

(L.) Merr.) or sugar cane (Sacharum officinarum L.) serve as the structural components,

but annuals such as yam and sweet potato (Lpomoea batatas (L.) Lam.) are also planted

within the band. Field crops are planted in the interspaces, as in hedgerows. During

1999. 20 different combinations of nine species of perennial food crops, trees, and other

perennials were used in crop contour bands (PADF 1999). This evolution is based on

farmers' needs for short-term cash return. The structural crops, such as pineapple,

respond directly to a marketing opportunity-a quintessentially Haitian strategy (Murray






22

1991), and one found in indigenous agroforestry associations in other cultures (Khaleque

and Gold 1993). This reinforces the notion that hedgerow intercropping should be

considered as a seed technology (Sumberg and Atta-Krah 1988. Wiersum 1994). to be

adapted and modified by farmers as a matter of course to fit into their unique agricultural

systems as they discover (or not) its as-yet unknown economic possibilities.

The cycle of enthusiastic promotion of hedgerow intercropping followed by

disappointment has a parallel in Haiti, although it is not documented apart from some

protest about the widespread promotion of Leucaena hedgerows in the early 1990s

(Swanson et al. 1993d, 1993e). It mainly takes the form of disappointment, informally

expressed by officials of donor agencies, that hedgerows do not yet cover every garden in

Haiti. More often the criticism of nonadoption has been aimed at the extension

methodology rather than the practice per se (Sieder 1994,Villanueva 1993). This has

been due, in part, to the development-driven agenda mentioned by Nair (1998) resulting

in the promotion of large numbers of an untested practice by donor-funded projects.

Reasons for farmer adoption, adaptation, or rejection of hedgerows are not well studied

in Haiti. The best available studies were done in a small region of the central plateau

near the town of Maissade (White 1992b), which noted farmers' reasons for nonadoption

of hedgerows as lack of time (39%), don't own land (21%). and land not appropriate

(17%). Vaval (1997) studied the same project area later, and documented the

disadvantages of hedgerows as expressed by adopting farmers as the time required for

management and loss of crop land due to the presence of hedgerows.

Hedgerow Intercropping and Soil Conservation

Because of the greater risk of soil erosion, performance of hedgerows on sloping

lands is not identical to their performance on flat land. Three kinds of biophysical








differences to consider include (1) the overall effect of hillside contour hedgerows on

crop production and soil erosion. (2) the gradients of soil accumulation/loss, soil physical

properties, tree/crop competition, and crop yield across the overall slope from the top

hedgerow to the bottom one, and (3) the same gradients within the alleys.

The concerns about the poor performance of alley cropping summarized by

Sanchez (1995) did not extend to hedgerow intercropping on sloping land. In part, this is

due to the proven ability of contour hedgerows to control soil erosion. Sanchez (1995)

stated that the hypothesis that contour hedgerows can substantially reduce soil erosion

has been definitively proven. This has been shown in many areas of the world, for

example a review often years of research in Thailand concluded that hedgerows

controlled erosion in areas of 18 to 55% slopes (Ongprasert and Turkelboom 1995); in

Rwanda on 23% slopes hedgerows reduced erosion to less than 2% of the runoff from

unprotected plots (Roose and Ndayizigiye 1993); in Malawi on 44% slopes hedgerows

reduced soil erosion to 2 t/ha compared to 80 t/ha on maize-only plots (Banda et al.

1994); in India on 9% slopes hedgerows significantly reduced soil erosion compared to

cassava-only plots or bare fallow (Ghosh et al. 1989); and in the Philippines there are

many examples of hedgerows substantially reducing erosion on sloped land (Agus et al.

1999, Comia et al. 1994, Paningbatan et al. 1995. Tacio 1993). The studies cited cover a

range of soil types from sandy loams (Banda et al. 1994) to gravelly sandy clays (Ghosh

et al. 1989) to heavy clays (Comia et al. 1994).

However, in spite of their proven ability to control erosion, in many cases

researchers have not been able to show crop yield improvements in hedgerow plots

compared to traditional systems. The principal reason for this appears to be the same on

slopes as it is in flat land alley cropping systems--the tradeoff between the production of








biomass for mulch or green manure needed to increase crop yield, and the loss of

cropping space caused by the presence of the hedgerows that produce the biomass

(Vandermeer 1998). The inter-row spacing required for the crops does not allow enough

biomass production from the hedgerows to improve soil fertility, so maize yield, for

example. is not improved unless inorganic fertilizer is applied (Ongprasert and

Turkelboom 1995, Roose and Ndayizigiye 1993). On steep slopes the Soil Changes

under Agroforestry (SCUAF) model (Young and Muraya 1990) predicts this might be

explained by high rates of leaching and organic matter decomposition, despite reductions

in the rate of erosion (Nelson et al. 1998). Crop yield declines are especially important in

newly established hedgerows as biomass application will not have yet contributed much

to soil improvement, although cropping space will have been reduced. Data taken from

89 hedgerow plots planted with maize on sloping plots in the Philippines showed a

decrease in maize yield in new hedgerows due to the loss of cropping space. The same

study estimated 8 years would be required for soil improvements caused by hedgerows to

compensate for loss in maize yield at a 5 m inter-row spacing (Shively 1998). In some

cases, however, soil conditions are improved by hedgerows sufficiently to maintain a

stable, if low, level of maize production on slopes compared to traditional cultivation,

where maize yield falls off over time (Banda et al. 1994, Comia et al. 1994). There are

also examples where crop yields in hedgerows on slopes were significantly greater and

more stable than those in unprotected control plots, as in a four-year study in Costa Rica

on farms having relatively fertile soils (Kass et al. 1995).

Gradients of soil water, soil physical properties, and crop yield have been

documented in alley cropping systems, as noted earlier in this chapter. For example,

infiltration rate and number of soil macropores were greater under the hedgerow trees






25

than in the middle of the alleys on a 14% slope in Kenya (Kiepe 1995). Competition for

light, water, and nutrients between hedgerow plants and adjacent crops is also noted on

slopes. Rice yield was depressed in the first two rows away from hedgerows on 15%

slopes in the Philippines, but the depression varied with different hedgerow species; it

was greatest near grass (Penisetum purpurenm) hedgerows (Garrity and Mercado 1994).

It has also been found that food crops in the alleys can restrict the growth of adjacent

hedgerow trees (Ghosh et al. 1989).

But as the slope increases a redistribution of soil fertility across the alley is often

seen that differs from that of flat plots (Garrity 1994, Ongprasert and Turkelboom 1995).

Increases in soil macropores near Calliandra callothrysus hedgerows in Reunion were

greater on the uphill side of the hedges than on the downhill side (Tassin et al. 1995). A

study done in the Philippines on 22 to 30% slopes found that average mid-alley maize

yields were greater than yields near hedgerows of Gliricidia sepium, Paspalum

conjugatum. and Penisetum pwupureum; and that the Ap soil horizon was thicker on the

lower part of the alleys (Agus et al. 1999). Garrity (1996) reviewed this phenomenon,

and noted that it was caused in a large part by the displacement of soil during crop

tillage. He has pointed out that on unprotected slopes there is often no net loss of soil

from the mid-slope area because any soil loss is replaced by soil eroding from the upper

portion of the hillside. The presence of hedgerows prevents a net accumulation of

upslope soil into the alleys, but the same displacement effect occurs within the alleys on

a smaller scale. Crop yield response on sloped hedgerow plots skews after a few years of

cultivation because scouring due to tillage displaces soil from the upper part of the alley

to the lower part, changing the soil profile, slope length, soil depth, and hydrological

properties. These changes combine with competitive interactions between the crop and

the hedgerows. The result is lower crop yields on the upper parts of the alleys and higher






26

yields on the lower middle part, with a slight decrease again as crops approach the lower

alley near the next hedge. The net yield curve across the alley is due to a combination of

soil scouring and competition with hedgerow trees. The effect of soil scouring on yield

is usually more important than that of tree/crop competition. Solera (1993), cited in

Garrity (1996) put in 50 cm plastic barriers between Gliricidia sepium hedgerows and

adjacent upland rice on a 20% slope, and found that the across-alley yield response was

unchanged by the barriers, and so was not due to competition between the hedgerows and

crop. Yield in the upper rows was 50% lower than that in the lower rows within the

alleys. The effects of slope on hedgerows are important because in wide alleys the soil

displaced from the upper position may lead to long-lasting crop yield depression in that

area, and because invalid comparisons between yield in hedgerows are often made

against an adjacent no-hedgerow control plot in the mid-slope area that has thicker soil

(Garrity 1996).

Conclusions

Hedgerow intercropping is an evolving technology meant to address the

increasingly rapid destruction of soil resources in developing countries. The defining

paradox in its history is that researchers and extension agents initially addressed it as a

technical solution, whereas farmers looked at it primarily as a potential economic

solution. Crop yield improvements due to hedgerow intercropping in certain regions of

the world justify continuing research. However, it has not yet been widely adopted even

in those regions, mainly due to high initial costs of installation and adaptation and farmer

need for short-term returns in the face of the probability of a yield loss in hedgerow plots

during the first few years after installation. Both the technical and socioeconomic

aspects of hedgerow intercropping must be resolved in order for adaptation and adoption

to increase.













CHAPTER 4
ORGANIZATION OF THE STUDY

This study is presented in three parts, beginning with an on-station study of

competitive interactions between hedgerows and adjacent maize, followed first by an on-

farm study of the performance of maize in hedgerows on sloping plots, and then by an

extensive field survey of the biophysical characteristics of plots and socioeconomic

characteristics of farmers who have constructed hedgerows and other soil conservation

practices with the PADF/PLUS project. The hypotheses to be tested correspond to some

of the biophysical and socioeconomic hypotheses referred to by Sanchez (1995) as being

fundamental to agroforestry, namely, biophysical hypothesis number 16: competition for

water in agroforestry systems can be reduced by modifying the spatial arrangement of

trees; and socioeconomic hypotheses numbers 1, 3, and 4:

the identification of key driving socioeconomic and ecological processes
within land-use typologies permits the spatial delineation of target and
recommendation domains for agroforestry interventions;

the adoptability of a new agroforestry practice is determined by 5 principal
components-the farmers' natural resource base, their resource endowment,
degree of market integration, cultural preferences and perceived benefits; and

at the farming systems scale, agroforestry adoption has different impacts for
different classes of farmers, such as their gender.

Justification

Declining farm productivity is a major problem confronting Haitian hillside

farmers. It is caused and exacerbated by a number of factors. Important among these are

soil degradation as a consequence of erosion. and farmers' difficulty in making capital








investments to support improvement of lost soil fertility and farm productivity.

Traditional agroforestry systems such as home gardens, shade coffee, and living fences

have not been able to cope with the degradation of soil resources on hill slopes as

population increased. Although rural migration to the cities has steadily increased

(Locher 1996), there is no reason to suppose that this will result in a significant decrease

in the population density in the mountains. Haiti's population might already have

exceeded the ecological carrying capacity of the land (Ewel 1977). Two decades ago, the

Haitian landscape was described as the victim of mismanagement: "the ruthless

application by the rural population of ecologically inappropriate and catastrophic lumber

extraction and gardening techniques which have transformed the once lush landscape of

entire regions into grim, denuded savannas" (Murray 1980, page 3). In addition to

decreasing productivity of individual hillside plots, inappropriate farming practices also

led to other local and regional environmental problems, including transport of rock

overburden that covers productive soil of farms on lower slopes and plains, reduction in

the water supply from springs, road washouts, and destruction of houses by water and

debris flows.

Hedgerow intercropping has gone through a cycle of research, widespread

promotion based on expected positive performance. extension by governments and

funded development projects, mounting criticism when expected performance was not

achieved, a resulting waning interest on the part of researchers and projects, and a

concern that alley cropping might be rejected due to inadequate identification of the

biophysical and socioeconomic conditions where it might succeed. This point was

discussed in more depth in Chapter 3.








Consequent to the reported promise and potential of hedgerow intercropping

technology in other parts of the tropics in the 1980s (Kang et al. 1984). it was introduced

in Haiti in the middle 1980's through externally funded development projects (Murray

1997. PADF 1986). As with most project-driven interventions, hedgerow intercropping

has had varying degrees of success. Several reasons could be attributed to this, both

biophysical and socioeconomic. They might include inappropriate extension approaches.

mismatch between farmer objectives and project objectives, inappropriate choice of

hedgerow species, competition between hedgerows and adjacent crops, high cost of

hedgerow establishment and management relative to the resulting effect on crop yield,

and farmers' and technicians' ignorance of the costs and benefits of hedgerows. But the

list of relevant factors contributing to hedgerow success or failure is poorly understood.

Indeed, farmers, extension agents, technicians, and project administrators have varying

definitions and perceptions of success and failure. The same cycle of widespread interest

followed by disappointment seen on the international level has been repeated on a

smaller scale in Haiti, where hedgerow intercropping has sometimes been labeled a

failure by consultants and donors who tend to observe the practice at an early stage of

development, in a small number of locations, or without a complete understanding of

important nontechnical parameters of the practice.

During the period 1984 to 1999, hedgerow intercropping technology has been

installed on approximately 10,000 hectares by farmers working with various funded

projects in Haiti (PADF 1990. PADF 1999). This is a significant coverage for a

development activity involving a relatively new and evolving technology. The rate of

hedgerow construction appears to have surpassed the level of understanding of how and

why they are installed and managed.








A number of studies have been published regarding various aspects of

hedgerow intercropping in Haiti. These include the effect of hedgerows on soil erosion

(Cunard and Lorcy 1990, Regis 1990), financial analysis of some of the benefits of

hedgerows (Bellerive 1991, Lea 1993. White and Quinn 1992). choice of hedgerow

species (Isaac and Shannon 1994, Shannon and Isaac 1993. Toussaint 1989. Treadwell

and Cunard 1992). management of hedgerow tree biomass (Isaac et al. 1995). farmer

adoption (Chary 1990, Emmanuel 1990, Lea 1994a. 1994b. Villanueva 1993. White

1992a), and farmer adaptation and management (Lea 1995, Pierre et al. 1995. Swanson et

al. 1993a, 1993b, 1993c, 1993d, 1993e. White 1992b).

Of the nine papers cited above reporting adaptation and management of hedgerow

intercropping in Haiti, only the one by Pierre et al. (1995) was specifically designed to

study how farmers manage hedgerows. They studied at 105 hedgerow gardens installed

before March 1994 in one region of southwestern Haiti. Although the study reported a

number of valuable observations on the management and performance of hedgerows, it

did not correlate the management quality indicator (the number of unrepaired breaches)

with other factors. Furthermore, the observations were based only on hedgerows

constructed of Leucaena leucocephala in a limited area of project intervention.

Another major study on hedgerows in Haiti was the series of qualitative,

questionnaire-based diagnostic surveys (Swanson 1993, Swanson et al. 1993a. 1993b.

1993c. 1993d. 1993e,) done just after the first field season of the PLUS project at the

request of PADF and Cooperative for American Relief Everywhere (CARE), the

implementing organizations. These studies were targeted at the whole farming

environment, not particularly at hedgerows. The diagnostic team visited over 200

farmers in fifteen small watersheds, interviewing individual farmers in their plots and






31

speaking with groups of farmers. The majority of the hedgerow gardens seen by the team

were installed under the Agroforestry II (AFII) project (1990-1991). The number of

hedgerow gardens visited was not stated, and the survey did not attempt to link hedgerow

management to specific conditions on the farms. Several useful observations were made

regarding hedgerows, however both the composition and management of hedgerows have

evolved since that time. and the number of hedgerows installed by farmers has increased

dramatically. In addition, an evaluation of the PLUS project monitoring and evaluation

system done in 1995 (Romanoff et al. 1995) suggested that the sampling areas used were

not representative of the whole project. They recommended that project impact be

measured over the whole area of intervention.

Competition between hedgerow trees and adjacent crop plants for soil water has

been the subject of an increasing number of studies in recent years (Chirwa et al. 1994a,

Govindarajan et al. 1996, Korwar and Radder 1994, 1997, Ong et al. 1991, Rane et al.

1995, Schroth et al. 1995a, Schroth and Zech 1993, Ssekabembe et al. 1994). This is

potentially a problem in Haitian hedgerow gardens because of the highly variable timing

of seasonal rainfall and the inability of eroded soils on steeply sloping land to absorb and

store water. Ewel (1977) referred to this as pseudo-drought, a condition that results from

a decrease in the water-holding capacity of the soil rather than from decreased rainfall.

The literature on hedgerow-crop soil water competition shows that, under some

conditions, hedgerows compete to the disadvantage of adjacent crops (Fernandes et al.

1993), (Govindarajan et al. 1996. Kamasho 1994. Korwar and Radder 1994, Ong et al.

1991. Salazari et al. 1993, Singh et al. 1986) and under other conditions, they do not

(Bohringer and Leihner 1997, Chirwa et al. 1994a. Haggar and Beer 1993, Jeanes et al.

1996, Schroth and Zech 1993).








One possible influence on farmer adaptation and management of hedgerows is

farmers' perception of the importance of soil water competition between the hedgerow

species and the interplanted crops. Experience in Haiti shows that maize (Zea mays) and

bean (Phaseolus vulgaris) crops, even without hedgerows, very often fail because of

drought conditions. Therefore, hedgerow trees are likely to compete with interplanted

crops for soil water at some time during the cropping cycle. The degree of competition

may also vary according to the position of the crop on the slope relative to the hedgerows

(Garrity 1996). However, it is not clear if farmers consider this competition as more or

less important than other perceived problems caused by hedgerows. Do farmers modify

hedgerow structure and management to compensate for perceived soil water

competition? Neither competition for soil water between crops and hedgerows. nor crop

yield relative to slope position and /or relative to hedgerows have been studied in Haiti.

Since intensive agriculture is practiced on small steeply sloping plots, it is

necessary to look for economically rational ways to maintain the soil's ability to sustain

crop production and to protect the local environment. Development of new agroforestry

systems that build upon traditional practices is needed. Hedgerow intercropping has been

shown to produce desirable results under certain circumstances. However, adoption or

lack of adoption may depend on factors extraneous to the characteristics of the

technology itself, including the socioeconomic status of farm families and the kinds of

land they access for agriculture. The extremely degraded condition of Haitian natural

resources makes it necessary to try any practice that could improve the economic

condition of Haitian farmers. Because of experience gained from agroforestry projects

operating in Haiti since the 1980s, there is reason to believe that adaptations of hedgerow

intercropping may increase farm stability and productivity in some areas of the country.






33
This study will help inform decision makers regarding the potential for use of hedgerow

intercropping in Haiti, and possibly avoid premature decisions to discontinue the effort to

adapt the technology.

Thus, hedgerow intercropping, a rapidly evolving and yet unproven technology.

has been extended in Haiti without the necessary supporting studies and documentation.

Development and extension resources could be used more efficiently by responding to

two documented shortcomings of agroforestry research that seem particularly appropriate

to the Haitian situation: that there is an inadequate understanding of below-ground

biophysical interactions in hedgerow systems; and that socioeconomic and biophysical

research must be linked, as adoption of the appropriate agroforestry practice depends

upon both (Rao et al. 1998).

Hypotheses

On-station Study

Leucaena hedgerows reduce the amount of soil water available to adjacent
maize, thereby causing a reduction in maize growth and yield.

Root barriers installed next to Leucaena hedgerows increase the amount of
soil water available to adjacent maize, thereby causing an increase in maize
growth and yield.

Cutting the roots of Leucaena hedgerows affects the production of tree
biomass.

On-Farm Study

*The pattern of competition between hedgerow trees and adjacent crops is
different on slopes vs. flat land, and maize growth varies with regard to the
position of the crop within the alleys and on the slope.

On-Farm Survey

SFamily characteristics influence the adoption and management of hedgerow
intercropping.







Plot characteristics influence the adoption and management of hedgerow
intercropping.

Problems and benefits with hedgerow intercropping as perceived by the
adopting farmer influence management quality.

General Description of Hypothesis-Testing Procedures

The study of soil water competition between Leucaena hedgerows and adjacent

maize was done on an NGO-operated research station located near Port au Prince. Four

treatment combinations were tested in nine replications: hedgerows with and without root

barriers between the trees and the adjacent row of maize, and maize fertilized or not

fertilized. Data for three maize seasons are reported, including gravimetric soil water:

maize height, leaf width, growth stage, leaf water potential, and final harvest: and

Leucaena height and biomass production. A pre-study examination of the distribution of

Leucaena hedgerow roots at a different location was done, and a post study count of the

distribution of Leucaena roots in hedgerows with and without barriers was done on-

station. A pot study of the correspondence between soil water percent and maize leaf

water potential was done as well.

The small on-farm study was an attempt to relate the on-station findings on flat

land under "controlled" conditions to sloping land managed by farmers. The study

collected maize growth and yield data for one season from four farms having previously

established trials of Leucaena hedgerows, crop contour bands, rock wall terraces, and

traditional cultivation. Maize growth data were collected by position in the alleys and on

the slopes. The four farm plots had been a part of an abandoned PLUS project research

effort previously carried out by the Southeast Consortium for International Development

(SECID)/Auburn University in conjunction with PADF. The author designed the data

collection protocol and performed the analysis.






35
A large list-frame questionnaire-based study was conducted, which provided on-

farm data about households adopting agroforestry soil conservation practices (including

hedgerows), how they were managed, and the characteristics of the plots where they were

installed. The study was undertaken by the author with the help of PADF PLUS

technicians as part of project monitoring during the early part of 1996. We visited 1.540

PLUS project agroforestry adopters and collected information regarding all plots

controlled by the family, and information regarding family members. We then visited

2.295 plots where farmers had installed at least one PLUS project agroforestry practice.

Data were collected on the biophysical parameters of the plots, the amount and condition

of the agroforestry practices installed on the plot, and the opinions of the farmers

regarding problems and benefits of the practices. Because farmers' assessment of soil

fertility appeared to influence where hedgerows were installed, soil samples were

collected from 175 farms. These were analyzed for percent organic carbon and soil

nutrients, and compared to farmers' classification of soil fertility.

Details of data collection and analysis for the on-station and on-farm

hedgerow/crop competition studies are reported in Chapter 5. Those for the on-farm

survey are reported in Chapter 6.













CHAPTER 5
HEDGEROW/CROP COMPETITION

Introduction

This chapter looks at competitive interactions between hedgerows and adjacent

maize on station and on farm. Competition is important because it is a key consideration

in designing agroforestry practices, it is difficult to measure, and farmers make adoption

and adaptation decisions based on its perceived severity. Competition is a central issue

in agroforestry because of the potential advantage in combining plants in such a way that

they capture more growth resources in combination than they would growing separately,

thereby producing greater physical yields (Cannell et al. 1996). The cost of the positive

effects of facilitation gained by growing plants in close proximity is the negative effects

of competition. In hedgerow intercropping in particular, the competitive characteristics

of the trees (they take up space, light, soil water, nutrients) must be balanced with their

facilitative characteristics (they impede soil erosion, capture soil water and nutrients out

of reach of the crops, improve soil fertility through biomass additions, improve the

microclimate, improve soil physical properties) (Vandermeer 1998). It is hard to develop

a hedgerow system that attains that balance because so many combinations of plants.

physical environments, and socioeconomic situations are possible. It is also difficult to

measure competition and to identify the processes that contribute to it because

competitive interactions change as the environment changes (Anderson and Sinclair

1993), and the hedgerows themselves change the environment-indeed, that is their






37

function. The way hedgerows and adjacent crops interact varies according to the age of

the hedgerows, relative size of the crops and hedgerows, population density, and the

supply of and access to limiting growth resources (Ong and Leakey 1999).

Farmers make adoption decisions based on competition between hedgerows and

crops. For example, farmers in the Philippines eliminated napier grass as a hedgerow

component because it was too competitive with crops grown in the alleys (Fujisaka et al.

1995), where it decreased maize yield by 86% by the second year after establishment

(Garrity and Mercado 1994). Therefore. competitive characteristics are important

considerations in the design of hedgerow systems.

Leucaena has characteristics that make it an aggressive competitor for growth

resources, including rapid growth and roots that occupy approximately the same soil

depth as that of maize (Jonsson et al. 1988), the crop of interest in this research. It was

noted several decades ago in Southeast Asia that Leucaena used as shade trees in

plantations rarely competed with the crop plants; but did so in times of drought, when

signs of water competition with coffee and rubber were reported (Dijkman 1950). In

more recent alley cropping studies, competition is a frequent subject of investigation, but

results vary with the specific site and plant components. Leucaena has been shown to

compete for soil nutrients to the detriment of rice (Salazari et al. 1993) and grasses

(George et al. 1996). In the semiarid tropics especially it has been shown to reduce the

amount of soil water available to pigeon pea, but less so for sorghum and millet

(Pennisetum glaucum L.) (Singh et al. 1986). In other areas of the semiarid tropics,

however, yields of both sorghum (Korwar and Radder 1997) and millet (Ong et al. 1991)

were significantly reduced in Leucaena hedgerows.








The on-station and on-farm studies reported on here both have maize planted in

the interspaces between Leucaena hedgerows. This combination has produced both

positive (Akonde et al. 1996, Banda et al. 1994, Hauser and Kang 1993, Hernandez 1961,

Mugendi et al. 1999, Mureithi et al. 1994) and negative (Chirwa et al. 1994b.

Govindarajan et al. 1996, Jama et al. 1995, Kamasho 1994) results. The positive results

in the cited studies ranged from maintaining the existing maize yield (versus a decrease

without hedgerows) to increases of 26%. 44%, 50%, and 400% in grain yield compared

to traditional cultivation. Positive results tended to be from subhumid or humid areas

with soils of moderate or better fertility, and from sloping areas. The negative results

ranged from 16% to 20% decreases in maize yield. These tended to be from semiarid,

moisture limiting, low fertility sites.

Effects of competition between maize and Leucaena are noted in several studies,

even where the overall effects of hedgerows are positive. In an early report of alley

cropping research in Ghana, Balasubramanian (1983) mentioned that soil water

competition with Leucaena might be a partial explanation of yield depression in adjacent

maize. Later hedgerow studies have attributed yield depression in adjacent crops to

competition for soil water (Govindarajan et al. 1996, Korwar and Radder 1997, Ong et al.

1991. Ssekabembe et al. 1994), nutrients (Chirwa et al. 1994b, Livesley et al. 1997,

Mureithi et al. 1994). or light (Kang et al. 1981. Lal 1989, Tilander et al. 1995, Welke et

al. 1995. Zoschke et al. 1990). Some studies claim all three resources are competed for

(Gaddanakeri et al. 1994). It is difficult to use these location-specific results to make

predictions about the probable success of a hedgerow intercropping system in another

location. However. Rao et al. (1998) have drawn some general conclusions: (1) In water

limiting areas, low yield of hedgerow prunings and competition for water between

hedgerows and adjacent crops were the major reasons for the negative results.








Inadequate water limited the response of crops even though hedgerows improved soil

fertility in certain sites of the semiarid tropics. (2) In poor soils, low yield of hedgerow

prunings and competition for nutrients were responsible for negative results. (3) The

advantages of hedgerow intercropping are more common on relatively fertile. N-deficient

soils in subhumid and humid environments, in areas where hedgerows produce a large

quantity of prunings, and where there is adequate water for both hedge and crop growth.

They also note that if competition is substantially reduced, even in semiarid climates.

hedgerows may be able to increase crop yields even where relatively small fertility

contributions are made by the hedges-but the cost of managing the hedges could be too

high to be practical.

Much of Haiti is subhumid, and there are still soils having a little remaining

fertility, on sloping land where hedgerows may be appropriate. The discussion to be

presented in this chapter will focus on the biophysical aspects of hedgerows and so will

necessarily be incomplete, lacking the socioeconomic elements, which will be discussed

in Chapter 6.

On-Station Studies: Effect of Root Barriers on the Growth of Maize and Leucaena

The objectives of this experiment were to test whether or not permanent root

barriers placed on either side of Leucaena leucocephala hedgerows affect the production

of maize grown in the alleys and the production of Leucaena leucocephala biomass. The

hypotheses were that the barriers will reduce competition for soil water between

Leucaena and adjacent maize, thereby increasing maize yield; and that production of

Leucaena will not be adversely affected by the barriers. If maize yield were to be

increased significantly an appropriate modification of the barrier could then be devised

for use on-farm, or a less competitive tree could be sought to construct hedgerows.






40

Crop yield depression close to trees is common. It has been reported for mustard

growing under Acacia nilotica in semiarid central India, where a yield depression of 54%

extending up to 8 m from the tree was correlated with increasing shallowness of the tree

roots (Yadav et al. 1993). Yield depression of maize and soybean near Siberian elm

(Ulnmus pumila) and eastern cottonwood (Populus deltoides) windbreaks in Nebraska was

significantly relieved by plowing parallel to the trees (Rasmussen and Shapiro 1989). A

study done in the savanna region of Kenya reported that Acacia tortilis trees competed

more intensely with understory grasses and herbs in wetter sites where the tree roots

terminated near the crown region, than in drier sites where the roots extended farther into

the grassland (Belsky 1994). Yield depression in millet extended significantly beyond

the area shaded by eucalyptus shelterbelts in Nigeria, corresponding to the area of tree

root growth (Ojyewotu et al. 1994). Nadagouda et al. (1994) found that severing the

roots of eucalyptus trees in India improved yield of adjacent maize.

Unless effective experimental controls are put into place, it is difficult to separate

the effects of above- from below-ground competition, and the effects of competition for

water from those of nutrients. Corlett et al. (1992b) describe a study done in the semiarid

tropics of India in which millet was grown alone and in Leucaena hedgerows. either with

or without barriers between the tree and crop roots. Millet yield was the same in the sole

crop and in the hedgerows with root barriers, but was 36% less in the hedgerows without

barriers. The authors proposed that, although one might have concluded that the yield

difference was due solely to below-ground competition. a better explanation was that the

millet adjacent to hedges with barriers grew taller because it had access to more soil

water than millet in hedgerows without barriers, and avoided light competition with the

Leucaena. There was an interaction between above- and below-ground processes.








Common methods used for studying the effects of below-ground competition in

alley cropping research include root pruning (Fernandes et al. 1993, Korwar and Radder

1994, Sitompul et al. 1992), trenching (Schroth et al. 1995b) or the installation of

permanent plastic barriers between the hedgerow trees and the crops (Corlett et al. 1992b.

Hauser and Gichuru 1994, Ong et al. 1991, Schroth et al. 1995a, Schroth and Lehmann

1995, Schroth and Zech 1993, Solera 1993c, Ssekabembe et al. 1994). The usual practice

is to open a narrow trench to a depth of 50 to 100 cm between the hedgerow trees and the

first crop row, install plastic awning or polyethylene sheeting, and then fill in the trench.

Studies using plastic barriers have produced results specific to the characteristics

of the site, species of hedgerow tree and crop. alley width, planting density and distance

between the hedgerow and crop, and the top-pruning regime (height and timing of cut)

used on the hedgerow. Ong et al. (1991) showed that yield of millet in hedgerows

without barriers was 40% less than yield in sole-cropped millet in semiarid India, but

where barriers were parallel to hedgerows the yield was the same as that in sole cropping.

They also showed that the barriers did not affect the production of the Leucaena

hedgerows. but the barriers did cause a redistribution of the Leucaena roots. Schroth and

Lehman (1995) found in subhumid Togo that barriers increased the yield of maize in

Calliandra callothyrsus hedgerows, but when the hedgerow species were Senna siamea

or Gliricidia sepium the presence of barriers was associated with a decrease in maize

yield. They concluded that Calliandra was relatively competitive compared to the other

trees, and that the barriers reduced the volume of exploitable soil available to the roots of

the other two species. The results obtained by studies using plastic barriers between trees

and crops do not always show competition for soil water. Two studies done in the West

African humid tropics put plastic barriers to 90 cm between Gliricidia hedgerows and








adjacent crops of rice, maize, and peanut. They showed crop yield improvement in

hedgerows compared to the sole cropping controls, but crop yield in hedgerows was not

affected by the presence of barriers (Schroth et al. 1995a, Schroth and Zech 1993). A

study done in the United States was able to isolate the effect of Robinia pseudoacacia

hedgerows on soil water at two sites having different soil characteristics (Ssekabembe et

al. 1994). The plots were irrigated, no crops were grown in the alleys between the

hedges, and the soil was covered with plastic to reduce evaporation. At the site having a

higher soil organic carbon content, hedgerows without barriers reduced soil water content

of the alleys by about 8%. At the second site, where higher gravel content impeded the

growth of tree roots, hedgerows without barriers reduced soil water content by 32%. and

there was significantly less water in alleys without barriers.

Materials and Methods

The experiment was carried out over a period of six years, from the spring of

1990 through the spring of 1995. During this period data collection was interrupted

several times by civil unrest in Haiti,' so although six maize crops and one sorghum crop

were planted only three successive maize crops from spring 1994 though spring 1995 are


'There was a coup d'etat in September 1991, which resulted in several missed
observations due to curfews. A night guard at the Operation Double Harvest (ODH) site,
where the experiment was installed, was killed by soldiers during that period, preventing
pre-dawn leaf moisture potential measurements. I was evacuated to the U.S. in October
1991 and returned to Haiti in September of the following year. By that time. the
Direction of ODH had changed hands, requiring that I obtain permission to continue my
work on the plot. This took several months, and the removal of a leaking irrigation line
installed next to the plots was necessary. During the regime of the defacto military
government (September 1991 to September 1994). fuel shortages were common because
of an international embargo, again interrupting data collection. Farmers with friends in
the local police station let donkeys into my plots, ruining the Fall 1993 harvest. Farm
workers bathing in the plots behind the screen provided by the Leucaena also prevented
soil moisture observations from being taken at least twice. The U.S military intervention
in September 1994 made adequate data collection difficult during that period as well.







discussed. Data available from the three maize crops were not identical, again due to

civil unrest and equipment problems. The spring 1991 data are used only for the

discussion of the effect of trenching on Leucaena height and biomass.

Trial site

The trial site was located at 18033' north latitude 721l 1' west longitude, with an

elevation of 80 m above sea level on property owned by Operation Double Harvest

(ODH), a nongovernmental organization (NGO) operating a farm and tree nursery in the

Cul de Sac plain, 30 minutes northeast of Port au Prince near the town of Croix des

Bouquets, Haiti. The soil was a vertisol of zero slope. From observations made in a soil

pit near the trial plots, heavy texture predominated to a depth of 1.1 m, where there was

an abrupt change to sandy, unconsolidated limestone to at least 1.7 m, the depth of the

pit. Soil texture from the surface to 30 cm depth was silty clay, changing to silty clay

loam in the 30-45 cm depth. Table 5-1 shows texture and organic carbon content for the

trial site.


Table 5-1: Soil texture and organic carbon at the trial site.

% Organic
Depth % Sand % Silt % Clay Carbon Texture
0-15 cm 8.4 49 42.6 1.71 silty clay
15-30 cm 7.2 41 51.8 1.10 silty clay
30-45 cm 7.2 53 39.8 1.0 silty clay loam


A pot study was established in January 1994 to determine how soil water

depletion at the ODH site correlated with plant water stress (Appendix A). When soil

water percent in the root zone decreased below about 25%, leaf water pressure passed






44

below 10 bars. Maize plants began to exhibit signs of drought stress at this point. Field

capacity at the site was reached at 41% soil water content.

Average annual rainfall based on data collected by ODH staff since 1977 was 968

mm per year. Distribution is bimodal, with most of the spring rains falling from April

through June. and the fall rains from August through November. The total annual rainfall

since 1977 varied from a low of 670 mm to a high of 1.301 mm. but in most years

rainfall was at least 900 mm. The trial site was located to the north of a small-container

tree nursery, and was previously used for tractor cultivation of hybrid sorghum. The area

to the east was used for composting sugarcane bagasse. A low earth barrier separated the

trial area from the composting area, to prevent water used for composting from entering

the trial.

Trial design

The trial design was a 2 by 2 factorial randomized complete block having 11

hedgerows of Leucaena leucocephala variety K636 planted at a within-row density of 10

trees per meter and a between row spacing of 5 meters. Each block consisted of a

hedgerow 22 meters long running through the center of four maize plots, to which were

randomly assigned the four treatment combinations. The hedgerows were laid out

exactly on an east-west axis. with hedgerow (block) 1 on the north end of the site and

hedgerow (block) 11 on the south side (Figure 5-1). The symbol T+ denotes a trenched

plot. T--a nontrenched plot: the symbol F+ denotes a fertilized plot. F--a nonfertilized

plot. All plots received the designated treatments throughout the three seasons of the

study. Figure 5-2 shows the layout of one of the plots within a block.

Each plot was centered on the hedgerow, and included four rows of maize on the

north side and four on the south side at 50, 100, 150, and 200 cm distances from the












2 m buffers


BLOCK

1



2



3



4



5



6



7



8



9



10



11


-- 3m --


5m

T-F+ T+ F-


T-F+ T+F- T+F+ T-F-


T-F-


T-F+


T+F+ I FT-F- T+F- T-F+



T+F- T-F+ __ T+F+ I T-F-I



T+F+I T-F+ I T-F- T+F-



T+F- T-F+ T+F+ T-F-



T+F- T-F+ T-F- T+F+



T-F+ T+F+ T+F- T-F-




ST+F- T-F- T+F+ T-F+


w


Hedgerow


IT+F+~


Layout of the Leucaena/maize hedgerow trial on Operation
Double Harvest property near Croix des Bouquets, Haiti


lI-.


T+F-


T-F-


I


Figure 5-1:


I i


a

















200 cm crop row



200 cm crop row

150 cm crop row

100 cm crop row

50 cm crop row

Leucaena Hedgerow

50 cm crop row

100 cm crop row

150 cm crop row

200 cm crop row

B

200 cm crop row


|4 3m --___ _|


Buffer crop row

Net plot A


uffer crop row


Diagram of one plot showing relative positions of a
Leucaena hedgerow and the adjacent rows of maize at four
distances.


Figure 5-2:







hedgerow, respectively. Buffer rows of maize were planted at 250 cm from the

hedgerows, marking the middle of the alley between hedgerows. Two-meter buffers

separated the plots within the blocks. Rows 1 and 11 were borders from which no data

were collected. Hedgerow experiments have been criticized for producing invalid results

because the no-hedgerow controls (sole crop plot) have been exploited by hedgerow roots

growing into adjacent plots, thereby over-estimating the benefits of hedgerow

intercropping (Hauser and Gichuru 1994). Some more recent studies have compensated

for this by digging trenches between hedgerow plots and control plots (Chamshama et al.

1998. Mugendi et al. 1999). Although the study reported here does not have sole crop

plots, and a two-meter buffer was left between plots, it is possible that Leucaena roots in

plots both with and without barriers exploited the soil in adjacent plots. This could not

be confirmed in this experiment.

Treatment installation

The hedgerow trees, grown in the ODH nursery, were planted out in April 1990

as one-year-old seedlings. The trees were cut to 50 cm stumps on 23 March 1991. In

April 1991, two randomly selected plots in each block were trenched to a depth of 30 cm

at a distance of 20 cm from each side of the hedgerows. The trenching was done with

picks, severing all roots. Plastic sheeting was put into the trenches to inhibit root re-

growth; the small canals created during root cutting were backfilled with soil. Trenching

extended for one meter beyond each side of the net plot boundaries, halfway into the two-

meter buffer between each plot. The decision to cut the roots to a depth of 30 cm was

based on a preliminary study of Leucaena roots done at a location off-station

(Appendix B). That study indicated 70% to 96% of the very fine roots (< I mm

diameter) were found in the top 30 cm of the soil, the lowest percent being found 150 cm








and 200 cm uphill from the hedgerow. A lesser percent of the fine roots (1-5 mm

diameter) were found in the top 30 cm (20 to 83%), with the least (20%) at the 200 cm

uphill position. Very few medium and large roots were found, but of those that were.

50% or more were deeper than 30 cm. Studies in semiarid India also found the majority

of Leucaena hedgerow root biomass in the top 30 cm of soil (Ong et al. 1991, Singh et al.

1996).

Due to my forced absence after the spring 1991 maize season the Leucaena

hedgerows in the main experiment were not top pruned between October 1991 and

September 1993. By that time, the hedgerow trees had grown to basal diameters of up to

10 cm. They were then cut back to a 50 cm stump height. Because the Spring 1994

maize harvest indicated the effect of trenching had almost disappeared, the plots were re-

trenched to a depth of 50 cm in August 1994 before the fall maize planting. Plastic

barriers were buried as before. The plastic barriers from the first root pruning were still

in place, but were missing or stiff and degraded in spots. In some places, soil had

covered the top of the barriers during cultivation, and Leucaena roots had grown over the

barriers into the alleys.

A selected local maize variety, known as chicken corn, was planted between the

hedgerows. The within-row spacing for maize hills was 75 cm, with 50 cm between

rows. Hill positions were laid out precisely using nylon cord with flagging tied at 75 cm

intervals. Maize was planted by hand three seeds per hill, and later thinned to two plants

per hill. The maize density of the interspaces at full stocking was then 53,333 plants per

hectare. If the space occupied by the hedgerows is included, maize plant density was

48,000 plants per hectare. Observations of 28,000 and 40,000 maize plants per hectare

were made on two farms in the south of Haiti at harvest time (after substantial mortality








during the season) in plots without hedgerows. Farmer interviews in one region of

northern Haiti indicated a higher density at planting, 62,500 plants per hectare (Swanson

et al. 1993a).

The fertilizer was to have been applied according to recommendations of the

Ministry of Agriculture, Haiti (MARNDR 1990): an initial broadcast application of 15-

15-15 (NPK) of 175 kg/ha at seeding followed by two applications of banded urea at 50

kg per hectare. In practice, however, due to the timing of rainfall and political instability

delaying travel to the site, only the spring 1995 maize crop received the complete

fertilizer treatment. The spring 1994 crop received only the initial application of 15-15-

15, and the fall 1994 crop received the 15-15-15 and the first urea application. Once a

given plot had been designated as fertilized, it remained a fertilized plot throughout the

three seasons reported here.

Operations by maize season

The spring 1994 maize crop was planted on 30 April. There had been 51 mm of

rain during the previous 7 days, 93 mm during the previous 14 days. Most of the rain

during the growing season fell between 11 and 21 DAS, with only one substantial rain

event after that, 23 mm at 67 DAS. A total of 206 mm of rain fell between sowing and

final harvest. The stand was thinned to two plants per hill at 28 DAS, and was weeded

once at 16 DAS. Insecticide was applied twice during the season. Fertilizer was applied

at a rate of 175 kg/ha at planting only; no urea was applied. Leucaeana top pruning was

done 35 days before sowing, then at 33 DAS (when trees were about 2.3 m high,

including the stump), and 65 DAS (when trees were about 1.8 m high). Figure 5-3 shows

the amount and timing of the rainfall in relation to the growth of Leucaena and maize,

and the timing of the agronomic interventions made to the plots during the spring 1994








season. The fall 1994 maize crop was planted on 10 September; two weeks after the

hedgerows were re-trenched to a depth of 50 cm (Figure 5-4). No measurable rain fell

during the 7 days preceding sowing, but 49 mm fell during the previous 14 days.

Tropical Storm Gordon passed over Haiti on 14 November (65 DAS) and dropped over

150 mm of rain in a 24-hour period on the trial site. This surpassed the capacity of the

rain gauge, so an accurate measurement was not recorded. This was the rainiest season

of the three, with at least (because of the inaccurate measurement during Tropical Storm

Gordon) 374 mm measured between sowing and final harvest. Most of the seeds had

germinated and had attained a height of 10 cm by 21 DAS, when they were weeded and

thinned to two plants per hill. Insecticide and urea (50 kg/ha) were applied at 26 DAS,

when the maize was about 25 cm tall. Because the effect of trenching was weak during

the previous season, the hedgerows were re-trenched to a 50 cm depth on 27 August

1994, 14 days before sowing the maize. Fewer measurements were made this season

than in others due to the U.S. military intervention in Haiti on 19 September, and the

events preceding and subsequent to it. Figure 5-4 shows the amount and timing of the

rainfall in relation to the growth of Leucaena and maize, and the timing of the agronomic

interventions made to the plots during the fall 1994 season.

The spring 1995 maize was planted initially on 26 March, but this planting failed

due to lack of rain. A new planting was done on 22 May. During the seven days before

sowing. 20 mm of rain had fallen, for a total of 39 mm during the 14 days before sowing.

After planting no rain was recorded until the 34th day, then 171 mm fell between 34 and

73 DAS. However, because the technician responsible for recording rainfall was on

vacation between the planting date and 36 DAS, two or three rainfall events were not

recorded. No additional rain fell before final harvest. I applied 15-15-15 at sowing and










Rain (mm) 49 0.8

(-4


67 83 49

rCIr? r"7


174+

r-S-


Total rain 0-114 DAS: 374+ mm Height (cm)
-250
200

-150

1 100
rrn


applied wedei urea 0
15-15-15 /inned insecticide

Avg. maize Avg. maize
height 10 cm height 25 cm


+ Leucaena topped, 28 & 126 DAS

* Maize biomass harvest, 78 DAS


Figure 5-3:


St Maize har


Most maize in Maize height
anthesis, silk up to 300 cm


+ Maize leaf w ater stress, 42 DAS

* Soilw ater content, 42 DAS


Rainfall. Leucaena and maize growth, and agronomic
inputs; spring 1994 maize cropping season


Rain (mm) 93 27 154

(-1- FJ--f


Leucaena height



DAS -20


20 1 40
I + 4


60


23 4 Total rain 0-91 DAS: 206 mm Height (cm)
-250
-200

-150

-100

50
80 100 120 140
,I I I o


ed
15-15-15

SAvg. maize
heiht 20 cm


weeded thinned,\ M' I Maize harvest, 91 DAS
insecticide insectici

Avg. maize _J Some maize \ Most maize in Maize leaf ma
height 100 cm in tassel anthesis, silk fired, soil has


+ Leucaena topped, 33 & 65 DAS

* Maize biomass harvest, 42, 49, 63, & 70 DAS


Figure 5-4:


rgins
1" cracks


+ Maize growth stage, 56 DAS

* Soil water content, 56 & 70 DAS


Rainfall, Leucaena and maize growth, and agronomic
inputs; fall 1994 maize cropping season


i


I ~ ~ [ -- d I





' "'






52

banded urea at 12 and 37 DAS. The maize was thinned to two plants per hill at 12 DAS.

The plots were weeded four times during the growing season; insecticide was applied

twice. Figure 5-5 shows the amount and timing of the rainfall in relation to the growth of

Leucaena and maize, and the timing of the agronomic interventions made to the plots

during the spring 1995 season.




Rain (mm) 83 1 40 41 91 Total rain 0-131 DAS: 171+ mm Height (cm)
rL- -250
200
Leucaena height -150

-- 100

DAS -20 0 20 40 60 80 100 120 140 50
+ + + +
applied thinned needed ulea weeded Maize harvest, 131 DAS
15-15-15 ure insecticide

Maize height 10-30 Maize height up to 95 Some maize
cm, leaf curl crm poor close to in tassel
hedgerow s in T-

+ Leucaena topped, 19, 57 & 130 DAS A Maize height, 40 DAS + Maize growth stage, 68 & 75 DAS
Maize biomass harvest, 47 & 54 DAS % Soil water content, 26 & 61 DAS


Figure 5-5: Rainfall. Leucaena and maize growth, and agronomic
inputs; spring 1995 maize cropping season


Measurements recorded

The following observations and measurements were made during the three maize

cropping seasons:

Maize height. This was done only for the spring 1995 season. Height to the top

of the highest fully open leaf of the tallest plant in each hill in blocks 2, 4, 6, and 8 was

measured at 40 days after sowing. Analysis was done on the mean height of eight plants

in each of the four hills to the north and four hills to the south of the hedgerow at a given






53
distance in each plot. If all plants in a hill had died. a height of zero was assigned for that

hill.

Maize growth stage. Growth stages of the plants were noted at 56 DAS in the

spring 1994 season, and at 68 and 75 DAS in the spring 1995 season. In the spring 1994

season, the scale was: 0=no maize plant present. 1= vegetative growth. 2=tassel.

3=anthesis, 4=silk. For the spring 1995 season, the scale was changed to include the

presence of ears: 0=no maize plant present, l=vegetative growth, 2=tassel/anthesis,

3=silk. 4=ear. Observations were made in blocks 2, 3. 5, 6, 8, and 9 on every maize plant

(2 plants per hill) in the spring 1994 season, and on only the most developed plant per

hill in the spring 1995 season.

Maize biomass during the growing season. For each of the four distances and in

each of the four plots in blocks 4, 7, and 10, the combined weight of one hill of maize on

the north side and one hill on the south side of the hedgerow was recorded. The plants

were cut at ground level, and then dried in a Watlow drying oven at 70 degrees C until a

constant weight was obtained.

Maize leaf water pressure. Predawn leaf water pressure was taken using a PMS

pressure chamber for one leaf at each distance in blocks 3, 6, and 9. A 2 cm by 10 cm

section was cut from the highest fully expanded leaf, one end was placed in a zip-lock

bag, and the sample was inserted into the pressure chamber. Compressed nitrogen gas is

normally used in the chamber, but as this was not available in Haiti compressed air was

used instead. This measurement was to have been done periodically throughout each

maize season, but was done only once because of the security problems discussed in the

footnote on page 44.








Maize yield. Grain yield. number of plants, and number of ears were measured

from blocks 2. 3, 5, 6, 8, and 9 at 91 DAS for the spring 1994 harvest. 114 DAS for the

fall 1995 harvest, and 131 DAS for the spring 1995 harvest. At each of the four distances

(50, 100. 150, and 200 cm), plants were harvested from a 3-meter length on the north and

south sides of the hedgerows, for a total of 6 meters (8 hills, or 16 plants maximum)

harvested in each plot at each distance. Because the grain moisture meter ceased to

function correctly, field dry grain weights are shown in the tables and figures. Harvests

for all treatments were made at the same time. and all samples were weighed at the same

time. Final harvest measurements are converted to per hectare equivalents by dividing

the sample weight or count for a given distance from the hedgerows by six (six meters

per plot were sampled) and multiplying by 4,500 (each distance represented 4,500 meters

per hectare given a 50 cm row spacing). The per-hectare contributions of the rows at

each distance were then summed to give a total per hectare figure, which included the

2,000 m occupied by the hedgerows.

Soil water percent. Soil cores were taken using a JMC Back-saver corer. Each

core was divided into three sections. 0-15 cm, 15-30 cm. and 30-45 cm. Four cores for

each depth and distance were combined for each measurement. The samples were

weighed wet in the field and dried in an oven at 70 degrees C until a constant weight was

obtained. Soil water content was determined gravimetrically by dividing the weight of

water lost in drying by the dry weight of the sample. The range of soil water content that

could be sampled at this site was narrow due to the heavy texture of the vertisol. When

the soil was very dry, the 0-15 cm depth often was not retained in the sampling tube, and

when the soil was wet, the end of the tube plugged and did not allow soil to enter. For

the calculation of field capacity, a large-diameter hammer-driven corer was used. This is








a slow procedure and the large-diameter corer could not be used under normal

circumstances due to the necessity of completing 192 cores in a single day each time

sampling was done. Soil water content was sampled twice during the spring 1994

growing season, at 56 and 70 DAS. The first, at 56 DAS. was done on blocks 3 and 6

only because the corer shaft broke. All subsequent samplings were done on blocks 3, 6.

and 9. A single sample was taken in fall 1994 at 42 DAS, and two were taken in spring

1995 at 26 and 61 DAS. An additional attempt was made to measure soil water content

at 54 DAS, but this was not successful because the soil was too wet and the corer

jammed.

Leucaena small stem and leaf biomass and height. Leucaena tops were cut back

to a 50 cm stump height using a machete. Leaves were not separated from stems; they

were weighed together in the field with a spring scale. Sub-samples were taken and dried

in a Watlow oven at 70 degrees C until a constant weight was obtained. Height above the

stump of the tallest stem in each plot was measured with a fiberglass tape. All leaves and

stems were removed from the site after harvest.

Leucaena root intersections in trenched and nontrenched hedgerows. After the

spring 1995 maize harvest was completed, numbers of Leucaena roots were counted in

trenched and nontrenched hedgerows to discover what influence plastic barriers had on

root distribution. Transects perpendicular to the hedgerows were excavated through rows

4, 5, and 6 (Figure 5-1). where there happened to be three trenched plots adjacent to three

nontrenched plots. Work began on 13 January 1996, 105 days after the maize harvest.

The plots were weeded three times during that period to keep out roots of grasses and

weeds. Thirty sections 1.2 m wide by 1 m deep parallel to the trenched hedgerows and

an equal number parallel to the nontrenched hedgerows were mapped, at 20, 50, 100,








150, and 200 cm distances. A Plexiglas plate inscribed with a 10 by 10 cm grid was

pinned to each cut surface. The positions of the roots were marked on plastic sheets

clipped over the Plexiglas plate, a separate symbol was used for each of four diameter

classes: very fine (10 mm).

Statistical analysis

Statistical analysis was done using the SPSS version 9.0 univariate GLM

ANOVA procedure. The model used for the dependent variables Leucaena leaf and

small stem biomass and height above the stump was as follows:

y,jk, = p + block, + t + f + t*fj + error,,,
where: y=dependent variable, t=trenching, f=fertilizer

i=2, 3, 4, 5, 6, 7, 8, 9, 10

j=0, 1 where 0=not trenched and =trenched

k=0, 1 where 0=no fertilizer applied andl=fertilizer applied

For each kind of field measurement taken at the four fixed distances and/or the

three soil depths, three levels of analysis were done-an overall ANOVA (referred to as

the complete model throughout the text) that included all the main effects and their

interactions, ANOVAs done separately for trenched and nontrenched plots that included

all other effects, and ANOVAS done separately for each distance from the hedgerows

that included only trenching and fertilization factors and their interaction. For percent

soil water, separate ANOVAs were done for each combination of distance from the

hedgerows with each of the three depths (0-15 cm, 15-30 cm. 30-45 cm). If there were

significant trenching by fertilization interactions produced by the ANOVAs done

separately for each distance and depth, contrast statements were run to determine at

which levels the interactions were significantly different.








The following example shows the complete ANOVA model used for the

dependent variables: maize biomass taken during the growing season, maize height.

maize leaf water pressure, maize grain at final harvest, number of maize plants at final

harvest, and number of maize ears at final harvest.

yji.k, = p + block, + t ,+ f, + t*f j + d, + t*d + f*d ,j + t*f*d 4, + error ,l,,,

where: y=dependent variable, t-trenching, f=fertilizer. d=distance

i=2, 3, 5, 6, 8. 9 (blocks used varied for each dependent variable)

j=0, 1 where 0=not trenched and 1-trenched

k=-, 1 where 0=no fertilizer applied andl=fertilizer applied

1=50, 100, 150, 200 cm distance from hedgerows

The overall mean square error was used to test the effect of distance and its

interactions. However, because measurements were taken at fixed distances and depths,

giving a split-plot characteristic to the experimental design. an "error a" term was

computed by adding sums of squares for the interactions of blocks with trenching and

fertilizer. This was used to test the effects of trenching and fertilizer and their

interaction.

The complete model for the percent soil water ANOVAs was:

ykl,,,, = p + block, + t + f + t *fjk + d, + t *d + f*dj/ + t *f*djk
+ dp,,, + t dp ,,, + f dpk,,, + d dp,,, + t f dpk,,, + error,k,,,,,

where: y=dependent variable, t=trenching, f=fertilizer, d=distance

i=3. 6. 9

j=0. 1 where O=not trenched and l=trenched

k=-, 1 where 0=no fertilizer applied andl=fertilizer applied

1=50. 100, 150, 200 cm distance from hedgerows

m=0-15, 15-30, 30-45 cm depth from soil surface






58

In addition to the "error a" term computed and applied as above, for the soil water

ANOVAs an "error b" term was computed to test the effects of distance and its

interactions with trenching and fertilizer. Sums of squares for the interactions of blocks

with distance and its interactions with trenching and fertilizer were added to compute this

term. The overall error term was used to test the effects of depth and its interactions.

"Error a" and "error b" and the corresponding F values were computed by hand;

SAS version 7.0 was used to compute the appropriate p-values. Soil water was expressed

as a percent, however the range of values was narrow (13% to 39%) and not extremely

high or low, so an arcsin transformation to stabilize the variances was not applied before

running the ANOVAs (Ott 1992).

Not all of the interactions that resulted in significant tests were meaningful due to

the very low numerical values of the differences. P-values for all factors and their

interactions are shown in Appendix C for all of the ANOVAs and contrasts.

Paired t-tests were used to detect significant differences in the numbers of root

intersections between trenched and nontrenched plots. This was possible because each

pair of measurements at each distance and depth were taken from physically adjacent

positions.

Results and Discussion

Results for each maize season are presented separately in this section, followed

by the results of the root distribution study and a general discussion.

Spring 1994 season

Two factors made this season differ from the two subsequent ones-the 30 cm

root barriers installed in the trenched plots in 1991 apparently no longer presented an

effective obstacle to the passage of Leucaena roots from the hedgerow into the alleys,

and the rainfall was poorly distributed.








Rainfall was 206 mm for the growing season and there was good soil water at

planting (51 mm fell in the 7 days prior to planting). However, most of the rain during

the growing season fell between 11 and 21 DAS (154 mm), and then no rain fell until 67

DAS (23 mm), which was the last effective rainfall event before final harvest. The plants

had reached about 20 cm height by 14 DAS. At 35 DAS the height was about 1 m, but

the soil was dry and cracking. Maize was always shorter than Leucaena until the 33

DAS hedgerow pruning; at that time the maize was about one meter high and the

hedgerows 50 cm. Maize tasseling began about 42 DAS, with most of the plants in

anthesis or silk by 50 DAS. The plants showed increasing signs of stress as the season

progressed. Many of the plants had fired leaf margins, and soil cracks opened to about

2.5 cm after 60 DAS.

Maize biomass production. Aboveground biomass production during the growing

season was not affected significantly by trenching or by fertilizer application, but the

amount of biomass did differ with distance from the hedgerows. The four

measurements of maize biomass are shown together in Figure 5-6.



a 300
N b
c
E 250 ---- c
4 b DC
8 200 50 cm
I, c C
E b E 100 cm
.2 o 150 b
"0 4 [ 150 cm
c 100 a a a 200 cm

0, w
5, 0 -- a

42 49 63 70
Days after sowing


Figure 5-6: Maize biomass yields at 50, 100, 150, and 200 cm from the hedgerows at
four times after sowing during the spring 1994 season






60

For the ANOVA model that included distance, there were no significant effects of

fertilization (o=.05 or =. 10) on the weight of maize biomass, and only one case where

trenching was significant (p = .085) at 63 DAS. P-values for the effect of distance on

maize biomass were <.001 at all four observations. The weight of maize biomass

produced was always significantly lower at 50 cm from the hedgerows. It appeared to

peak at 150 cm for the first three observation periods, although that distance was

significantly greater than the others only at 49 DAS (Figure 5-6). At 70 DAS, the weight

of biomass peaked at 200 cm. Competition between the maize and the trees clearly

extended to 100 cm at 42 DAS, and to 50 cm thereafter.

When the analyses were done separately at each distance, the effect of trenching

was significant only at 50 cm from the hedgerows at 42 DAS and at 63 DAS (Table 5-2).

In these two cases, the amount of maize biomass produced in trenched plots was at least

double that produced in nontrenched plots.


Table 5-2: Effect of trenching on the production of maize biomass 50
cm from the hedgerows at 42 and 63 DAS; spring 1994.

42 DAS 63 DAS
Trenched biomass (g) 50 93
Nontrenched biomass (g) 25 37
p-value .039 .039


There were also four instances when the effect of fertilizer was significant. More

maize biomass was produced in the nonfertilized (F-) plots at 49 DAS at both the 50 cm

and 100 cm distance from the hedgerows (Table 5-3). At both 42 and 49 DAS there was a

significant interaction of fertilizer and trenching at the 150 cm distance from the

hedgerows, in both cases more maize biomass was produced in trenched (T+) plots








(Table 5-3). However, at 42 DAS this effect was seen only between trenched and

nontrenched plots that were also fertilized, while at 49 DAS the effect was seen only

between plots that were not fertilized.


Table 5-3: Effect of fertilizer on the production of maize biomass 50. 100, and 150 cm
from the hedgerows at 42 and 49 DAS; spring 1994.

49 DAS 42 DAS 49DAS
50 cm 100 cm 150 cm F+ 150 cm F-
Maize (g) F+ 50 168 Maize (g) T+ 196 238
Maize (g) F- 62 209 Maize (g) T- 163 174
p-value .063 .002 p-value .055 .010


Maize growth stage. Numerical values corresponding to maize growth stages

were assigned at 56 DAS using the scale 0=absent, 1= vegetative growth, 2-tassel,

3=anthesis, 4=silk. On average, the plants at 50 cm were in the vegetative stage, all

others were in tassel or anthesis (Figure 5-7).



anthesis
3


tassel
2 ___





0



50 100 150 200
Distance from the hedgerow (cm)

Figure 5-7: Growth stage of maize at four distances from hedgerows, 56 DAS; spring
1994.








Soil water content. This was measured twice during this season, at 56 and 70

DAS. The ANOVAs that included both distance and depth in the model did not reveal

any differences in soil water due to trenching, fertilization, or distance from the

hedgerows. There were differences among depths below the surface, as shown in Table

5-4. At 70 DAS the surface 15 cm had more soil water than the deeper layers, probably

because 23 mm of rain fell just three days before the measurement. This was the first

rain since 21 DAS. At 56 DAS the water content of the soil increased steadily with

depth. The water content of the 30-45 cm layer was the same for both observations.


Table 5-4: Soil water at three depths below the surface at 56 and 70
DAS; spring 1994.

Soil Water %-Gravimetric
56 DAS 70 DAS
0-15 cm 15.0 a 24.0 c
15-30 cm 21.6 b 22.2 a
30-45 cm 23.5 c 23.4 b
p-value <.001 <.001


The complete model also indicated significant soil water interactions between

trenching and fertilizer (p = .081) at 56 DAS. and between trenching and distance (p =

.020) and fertilizer and distance (p = .007) at 70 DAS. When ANOVAs were done

separately for each depth and distance, with trenching and fertilizer as the only

independent variables, there were no significant differences in soil water percent between

the two trenching treatments at any distance or depth. In only two cases were the

differences between the two fertilizer treatments significant: at 56 DAS 100 cm distance

in the 30-45 cm depth the fertilized plots had 23.1% soil water vs. 24.2% for the

unfertilized plots (p = .004), and at 70 DAS 200 cm distance in the 15-30 cm depth






63

fertilized plots had 21.1% soil water vs. 23.1% for the unfertilized plots (p = .027). At 56

DAS there was a significant interaction at the 100 cm distance from the hedgerows: at the

0-15 cm depth trenched plots had less soil water than nontrenched plots where no

fertilizer was applied (p = .067); the reverse was true in the fertilized plots (p = .034).

The meaning of these interactions is not clear, since fertilizer was not significant as a

main effect. P-values for all interactions are listed in Appendix C, but not all will be

discussed as they are too numerous and add little to the understanding of the treatment

effects.

Maize yield. Grain yield for this season was very low, with no significant

differences due to trenching or fertilizer. A per-hectare equivalent corresponding to the

average values per six-meters as shown in Figure 5-8 is 182 kg/ha maize grain, with only

5.2 kg/ha of the total contributed by the 50 cm rows. As with maize biomass and sexual

development, grain yield was affected only by distance from the hedgerows. In addition,

the peak production in grain yield and number of ears appeared at 150 cm from the

hedgerows, then declined slightly at 200 cm. This is also similar to the pattern observed

in biomass production and sexual development, with a decline between 150 cm and 200

cm, although it was only statistically significant at 49 and 56 DAS.

Apparently, competition between maize and hedgerows affected the survival of

maize plants differently than grain yield or number of ears. There were significantly

fewer surviving plants at harvest time in the row closest to the Leucaena, but in the other

three more distant rows maize plant survival was the same, and did not decrease between

150 and 200 cm (Figure 5-9). Full stocking for each distance depicted in Figure 5-9

would have been 16 plants (per 6 m, or per 8 hills), equal to 12,000 plants per hectare at

each distance, totaling 48,000 plants per hectare if all had survived. Maize plant survival






64

with distance from the hedgerow was 48%, 84%, 87%, and 80% at 50 cm. 100 cm. 150

cm, and 200 cm from the hedgerows, respectively.

Figure 5-8: Yield of maize grain per six meters at four distances from the hedgerows;


b





a

50cm 100lcm


S150cm


Distance from hedgerow


spring 1994.


50cm


100 cm 150 cm
Distance from the hedgerow


200 cm


Figure 5-9: Number of maize plants per eight hills at four distances from the hedgerows;
spring 1994.


200 cm






65

Since the number of ears did not differ significantly between 100 and 150 cm

(Figure 5-10) and the grain yield did differ, the implication is that grain yield per ear was

lower at 100 cm than at 150 cm. This was the case, with the grain weight (g) per ear for

the four distances being, respectively, 3.5, 10.8, 13.0. and 9.7.





bc
o5 -- -
6-


E
3 .
z a
2
01-1

50 100 150 200
Distance from the hedgerow

Figure 5-10: Number of maize ears per eight hills at four distances from the hedgerows;
spring 1994.


Table 5-5 shows the data presented in Figures 5-8, 5-9, and 5-10 on a per hectare

basis.


Table 5-5: Maize grain weight, number of plants, and number of ears at
four distances from the hedgerows and as a total per hectare,
with p-values for the differences between distances.

Distance (cm) Grain (kg) No. of plants No. of ears
50 5.2 a 5,813 a 1,500 a
100 56.9 b 10,031 b 5,281 bc
150 75.3 c 10,406 b 5.813 c
200 44.6 b 9,563 b 4,594 b
Total/ha 182.0 35,813 17,188
p-value <.001 <.001 <.001






66

Leucaena biomass-production and height. The four Leucaena harvests discussed

in conjunction with the spring 1994 maize season are those made after my post-coup

d'etat-retur to Haiti, but before the hedgerows were re-trenched prior to the fall 1994

maize season. The 20 November 1993 harvest was the first re-growth after the

overgrown trees were cut back to 50 cm stumps. but this was before the first application

of fertilizer to a maize crop so the F+ and F- designations are not meaningful for this

harvest. Table 5-6 shows the weight of biomass harvested and Table 5-7 shows the

height above the stump for the four treatment combinations. The 33 and 65 DAS

harvests were taken during the spring 1994 maize season.


Table 5-6: Stem and leaf biomass harvests and daily growth increments of Leucaena
hedgerows 33 and 65 DAS; Spring 1994.

20 Nov 93 2 Jun 94 4 Jul 94 20 Aug 94
Biomass Increment Biomass Increment Biomass Increment Biomass Increment
(kg/m) (g/m/d) (kg/m) (g/m/d) (kg/m) (g/m/d) (kg/m) (g/m/d)
T+F+ 1.1 17.8 0.9 12.4 0.4 11.5 0.5 10.0
T+F- 1.2 18.3 0.9 12.6 0.3 10.4 0.4 9.1
T-F+ 1.4 21.7 1.0 14.1 0.4 12.2 0.5 10.2
T-F- 1.2 18.9 0.9 12.5 0.4 11.3 0.5 10.9
p-value T .074 .139 .300 .283
p-value F .358 .224 .187 .941
p-value TxF .198 .091 .994 .400
DSPHa 63 69 32 47
RSPH (mm)b 162 312 0 53
DAS 42c 33 65 between crops

a: Days since previous hedgerow harvest
b: Rainfall since previous hedgerow harvest
c: DAS (days after sowing) is reported because a fall 1993 maize crop was growing in the
plots at this time. This maize season is not reported here, as it was lost due to animal
damage.


It appears that the effect of the initial trenching on Leucaena biomass production

did not last beyond 20 November 1993, when there was a small reduction in biomass








production in the trenched plots (p = .074). Trenched plots produced 1.15 kg/m. while

nontrenched plots produced 1.3 kg/m. A five-meter spacing means there are 2.000

meters of hedgerow per hectare, so this amounts to a reduction of 300 kg/ha due to

trenching. There was no significant trenching effect in the subsequent three harvests, nor

did fertilizer application to the maize influence Leucaena production. The reduction in

Leucaena daily growth rate beginning in July and continuing in August was probably a

response to less rainfall during that period.


Table 5-7: Height above a 50 cm stump and daily growth increments of Leucaena
hedgerows prior to the second root trenching. 33 and 65 DAS; Spring 1994.

20 Nov 93 2 Jun 94 4 Jul 94 20 Aug 94
Height Increment Height Increment Height Increment Height Increment
(m) (cm/d) (m) (cm/d) (m) (cm/d) (m) (cm/d)
T+F+ 2.1 3.3 1.8 2.6 1.2 3.8 1.4 3.0
T+F- 2.1 3.3 1.8 2.6 1.3 4.1 1.4 3.0
T-F+ 2.0 3.2 1.8 2.6 1.2 3.8 1.4 3.0
T-F- 2.2 3.5 1.7 2.5 1.2 3.8 1.5 3.2
p-value T .725 .462 .095 .403
p-value F .076 .840 .393 .640
p-value TxF .129 .329 .160 .640
DSPHa 63 69 32 47
RSPH (mm)b 162 312 0 53
DAS 42c 33 65 between crops

a: Days since previous hedgerow harvest
b: Rainfall since previous hedgerow harvest
c: DAS (days after sowing) is reported because a fall 1993 maize crop was growing in the
plots at this time. This maize season is not reported here, as it was lost due to animal
damage.


Leucaena height growth is a less precise measure than the biomass yield, and was

taken to the nearest 10 cm. Neither trenching nor fertilizer application appeared to affect

height growth during the four harvests shown in Table 5-7. The p-value of .076 for the

effect of fertilizer on 20 November 1993 is difficult to explain, because this was before








the first fertilizer application to the maize crop. The significant (p = .095) effect of

trenching on 4 July is associated with a very small numerical height advantage in the

trenched, nonfertilized plots. It is interesting to note that while daily Leucaena biomass

increment decreased after 2 June (Table 5-7), daily height growth rate increased. The

July and August cutting intervals were shorter than the previous two, so this may mean

that Leucaena puts on stem height first, then adds stem diameter, leaf biomass, or new

stems later in the cycle.

Fall 1994 season

The fall 1994 season was the best of the three in terms of maize production,

because it had the highest rainfall and the best rainfall distribution through the growing

season. After the Leucaena was pruned at 28 DAS, the maize quickly gained a height

advantage over the hedgerow trees and maintained it throughout the rest of the season in

both the trenched and nontrenched plots, including the rows closest to the trees. Most of

the plants were in flower (tassel and silk) by the time tropical storm Gordon passed at 65

DAS. By 70 DAS the maize was about 3 m tall, taller by about 1 m than the Leucaena

hedgerows.

Maize biomass production. Maize biomass production was measured only once

during the season, at 78 DAS. The ANOVA for the complete model (including distance)

was significant for trenching (p = .018) and distance from the hedgerow (p = .023).

ANOVAs separate by distance showed that only at the 50 cm distance from the

hedgerows was trenching a statistically significant factor (p = .037). At all other

distances trenched plots produced more maize biomass than nontrenched plots, but the

difference was not significant (Figure 5-11). The complete model also indicates an

interaction between trenching and fertilizer at the 150 cm distance (p = .093). There was






69

significantly more biomass produced in trenched (509 g) than nontrenched plots (307 g)

where they were not fertilized, but the difference was not significant in fertilized plots.



600 -
/ ~ns
500 -ns-
N a ns
M 400 -
0 OT+
m 300 T
E b IT-
'j 200 -
N
'c 100 -

0
50 100 150 200
Distance from the hedgerow

Figure 5-11: Trenched and nontrenched plots at 50, 100, 150, and 200 cm from the
hedgerows, 78 DAS; fall 1994.


ANOVAs run separately for trenched and nontrenched hedgerows showed that

distance was a significant factor only for nontrenched hedgerows, with the 50 cm

distance producing less biomass than the other distances. This was not the case for

trenched hedgerows, where no significant difference in biomass production was detected

over the four distances (Table 5-8).


Table 5-8: Maize biomass in trenched and nontrenched plots over four
distances from the hedgerows, 78 DAS; fall 1994.

Trenched Nontrenched
Distance (cm) (g/2 hills) (g/2 hills)
50 412.6 a 249.2 a
100 501.9 a 389.1 b
150 475.5 a 416.4 b
200 400.6 a 356.2 b
p-value .485 0.001








Maize leaf water potential. The complete ANOVA model did not show any

significant leaf water potential differences among factor levels for any factor. However.

when the ANOVAs were run separately for each distance, maize plants in trenched plots

indicated less leaf water pressure than did those in nontrenched plots (p = .081) at the 50

cm distance from the hedgerows (Figure 5-12). Differences were not significant at the

other distances.





S3.0
r ns
2.5 -
b ns ns
2.0
P i E T+
S1.5 E T-
a
1.0

N 0.5

0.0
50 100 150 200
Distance from the hedgerow (cm)



Figure 5-12: Maize leaf water potential in trenched and nontrenched plots at four
distances from the hedgerow. 42 DAS; fall 1994.


Similarly, when ANOVAs were run separately for trenched and nontrenched

plots, there was no significant difference in maize leaf water potential among the four

distances for the nontrenched plot. For the trenched plots, however, the leaf water

potential in the 50 cm plots was significantly lower (p = .008) than in the other three

distances (Table 5-9).








Table 5-9: Maize leaf water potential in trenched and nontrenched plots
over four distances from the hedgerows, 42 DAS; fall 1994.

Distance (cm) Trenched (bars) Nontrenched (bars)
50 1.1 a 2.0 a
100 2.5 b 1.7 a
150 1.8 b 2.0 a
200 2.1 b 2.1 a
p-value .008 .917


Soil water content. Soil water was measured on the same day as maize leaf water

potential. Figure 5-13 shows the soil water percent for trenched plots at all

combinations of distance and depth. The differences in soil water percent between

trenched and nontrenched plots are shown in parentheses. The overall model indicated

that trenching (p = .042), distance from the hedgerow (p < .001). and depth below the

surface (p < .001) were significantly affecting soil water content. The effect of fertilizer

was not significant (p = .352). Separate ANOVAs for each combination of distance and

depth were not significant for either trenching or fertilizer in the 0-15 cm depth. There

were significant differences due to trenching in the lower depths. In the 15-30 cm layer,

soil water percent was higher in trenched plots at the 50 cm (p = .033) and 150 cm (p =

.095) distances from the hedgerow. In the 30-45 cm layer, soil water percent was higher

in trenched plots at the 50 cm (p = .002) and 100 cm (p = .014) distance from the

hedgerow.

The effect of distance from the hedgerows was significant in trenched plots at the

15-30 cm (p = .004) and the 30-45 cm depths (p < .001), with more soil water present

close to the hedgerows. In the surface layer distance was significant for trenched plots at

the a=. 10 level, with more soil water at the 50 cm distance than the 150 distance (p =

.078). In Figure 5-13, cells having the same letter, in a given row, are not significantly








different. Soil water percent in nontrenched plots did not differ significantly with

distance from the hedgerow in any of the three depths.





Distance from Hedgerow (cm))

50 100 150 200
A I I I I
Soil Depth (cm) Soil Water (%, Gravimetric)
0-15 27.8 (1.4) 24.6 (1.5) 23.6 (1.4) 24.5 (3.6)

r a ab bc c
15-30 129.9 (3.5)i 27.2 (1.6) 25.1 (1.2) 23.5 (-3.2)
r a b c c
30-45 132.5 (4.9) 29.7 (3.4)1 25.6 (0.1) 26.7 (-0.6)




Figure 5-13: Soil water in trenched plots (and difference between T+ and T- plots) at
42 DAS, fall 1994. Cells with solid border (a=.05) or dashed border
(a=. 10) indicate significantly greater soil water in trenched plots than in
the corresponding nontrenched plots at that position. Letters indicate
differences between distances within a depth for trenched plots (a=.05).


Soil water percent increased with depth differently in trenched plots than in

nontrenched plots. In the trenched plots (Table 5-10), soil water increased with depth at

the 50 cm distance (p = .066) and the 100 cm distance (p = .020), with the deepest layer

having significantly more water than the surface layer. However, there were no

significant differences in soil water with depth at the 150 and 200 cm distances. In

contrast, the nontrenched plots had significantly more soil water with depth at the 100

cm. 150 cm, and 200 cm distances, but did not show significantly more soil water with

depth at the 50 cm distance.






73
Table 5-10: Soil water in trenched and nontrenched plots by depth and distance from the
hedgerow, 42 DAS; Fall 1994.

Distance (cm) Depth (cm) Trenched (%) Nontrenched (%)
0-15 27.8 a 26.4
50 15-30 29.9 ab 26.3
30-45 32.5 b 27.6
p-value .066 .820
0-15 24.6 a 23.1 a
100 15-30 27.2 ab 25.6 ab
30-45 29.7 b 26.3 b
p-value .020 .075
0-15 23.6 22.2 a
150 15-30 25.0 23.9 ab
30-45 23.6 25.5 b
p-value .368 .012
0-15 24.4 20.8 a
200 15-30 23.5 26.7 b
30-45 26.7 27.3 b
p-value .502 .048


Maize yield. The complete model for maize grain was significant for the effect of

trenching (p = .009) and distance from the hedgerows (p = .076), but not for the effect of

fertilizer (p = .385). The complete models for number of plants and for number of ears

were not significant for any of those factors. ANOVAs done separately at each distance

showed that maize grain from trenched plots was significantly greater (ao=. 10) than that

from nontrenched plots at the 50 cm (p = .071) and 100 cm (p = .068) distances from the

hedgerows (Figure 5-14). There was also a statistically significant difference between

the numbers of plants in trenched plots vs. nontrenched plots at the 100 cm distance (p =






74

.020), with the nontrenched plots having about one more plant per six-meter sample at

that distance.



1000
900 a
E a ns ns
C5 800 b
700
S-I b
S600 -
"l OT+
500
C ET-
400 --
a 300
S200 --
100
0
50 100 150 200
Distance from the hedgerow (cm)


Figure 5-14: Maize grain yield in trenched (T+) and nontrenched (T-) plots at four
distances from the hedgerow, Fall 1994.


Final harvest is presented on a per-hectare basis in Table 5-11. Although there

were differences in grain yield between trenched and nontrenched plots at 50 and 100 cm

from the hedgerows (cr=.10, Figure 5-14 above), there was no significant difference in

grain, number of plants or number of ears over distance from the hedgerows, for either

trenched or nontrenched plots.

In general, there were no strong differences in yield parameters this season,

probably due to the adequate, well-distributed rainfall partially negating the potential

advantages of the root barriers. If only the differences in grain weight at 50 cm and 100

cm are accepted as significant, then trenching made a difference of 252 kg maize








grain/ha, an increase of 12% over the nontrenched plots. However, since the effect of

trenching for the complete model was significant (p = .009), then the advantage of

trenching increased to 360 kg/ha (2,382 kg-2,022 kg), an increase of 18% over the

nontrenched plots. Since there were no differences in the numbers of plants or ears, the

advantage of trenching was manifested in more grain weight per ear in trenched plots.

especially at the 50 and 100 cm distances.


Table 5-11: Maize grain weight, number of plants, and number of ears at four
distances from the hedgerows and as a total per hectare, with p-values for
the differences between distances, Fall 1994.

Grain (kg) No. plants No. ears
Distance (cm) T+ T- T+ T- T+ T-
50 563.1 423.1 10,563 10,625 11,250 10,313
100 648.1 535.6 10,188 11,125 10.750 11,313
150 601.3 561.3 11,188 10,813 11,313 11,688
200 569.4 501.9 10,938 10,875 10,688 10,750
Total/ha 2,382 2,022 42,875 43,438 44,000 44,063
P-value .488 .103 .152 .637 .869 .314


Leucaena biomas-production and height. Four Leucaena harvests are presented

in Tables 5-12 and 5-13-the first was done during the fall 1994 maize season at 28

DAS, the others were done after the fall maize harvest but before the spring 1995 maize

was sown. The reaction of Leucaena to the re-trenching to 50 cm depth done in August

1994 is clear. In every case, the trenched plots produced less biomass than the

nontrenched plots. The loss of small stem and leaf biomass due to the effect of trenching

was 532, 452. 422. and 154 kg per hectare for the four pruning dates in Table 5-12.

respectively, for a total loss over this seven-month period of 1,561 kg per hectare. The






76

relatively slow growth rate between the 8 October and 14 January harvests in spite of the

plentiful rainfall was probably due to insect damage (species not identified) in the

southeast quarter of the trial site, in blocks 6-10. The damage affected trenched and

nontrenched plots equally. Fertilizer application on the adjacent maize did not affect

Leucaena biomass or height growth. The significant trenching by fertilization interaction

at the 6 May harvest does not appear to be important in magnitude.


Table 5-12: Stem and leaf biomass harvests and daily growth increments of Leucaena
hedgerows after the second root trenching, Fall 1994.

8 Oct 94 14 Jan 95 16 Mar 95 6 May 95
Biomass Increment Biomass Increment Biomass Increment Biomass Increment
(kg/m) (g/m/d) (kg/m) (g/m/d) (kg/m) (g/m/d) (kg/m) (g/m/d)
T+F+ 0.3 6.8 0.4 3.8 0.5 8.5 0.4 7.1
T+F- 0.3 6.5 0.4 3.6 0.5 8.6 0.3 5.9
T-F+ 0.6 12.0 0.5 5.3 0.7 11.3 0.4 7.3
T-F- 0.6 12.2 0.7 6.8 0.8 13.0 0.4 8.7
p-value T <.001 .005 <.001 .013
p-value F .985 .401 .301 .919
p-value TxF .745 .255 .358 .033
DSPHa 49 98 61 51
RSPHb (mm) 174 320+ 56 76
DAS 28 between crops between crops between crops

a: Days since previous hedgerow harvest
b: Rainfall since previous hedgerow harvest


Trenching significantly reduced Leucaena height growth only for the first two

harvests following re-trenching (Table 5-13). Height difference between trenched and

nontrenched plots was not significant during the third harvest, even though the difference

in small stem and leaf biomass was significant.








Table 5-13: Height above a 50 cm stump and daily growth increments of Leucaena
hedgerows after the second root trenching, Fall 1994.

8 Oct. 94 14 Jan. 95 16 Mar. 95 6 May 95
Height Increment Height Increment Height Increment Height Increment
(m) (cm/d) (m) (cm/d) (m) (cm/d) (m) (cm/d)
T+F+ 1.3 2.7 1.9 1.9 1.5 2.5 1.4 2.7
T+F- 1.4 2.9 1.8 1.8 1.5 2.5 1.3 2.5
T-F+ 1.5 3.1 2.2 2.2 1.6 2.6 1.5 2.9
T-F- 1.5 3.1 2.2 2.2 1.6 2.6 1.5 2.9
p-value T .005 .038 .113 .311
p-value F 1.000 .945 .633 .311
p-value TxF .471 .331 .447 .030
DSPH 49 98 61 51
RSPH (mm) 174 320+ 56 76
DAS 28 between crops between crops between crops
a: Days since previous hedgerow harvest
b: Rainfall since previous hedgerow harvest


Spring 1995 season

This season had less rainfall during the growing season than fall 1994, but the

distribution was better than that during the spring 1994 season. Germination initially

appeared to be good, with the tallest plants 20 cm tall at 19 DAS. However, at 26 DAS it

was evident that germination at the 50 cm distance was poor. Maize height was up to 30

cm at that time, but some plants were showing leaf curl. Flowering began at 47 DAS; by

54 DAS most of the plants were flowering. At this time there appeared to have been an

underground leak in the irrigation system (used in the nearby tree nursery) that might

have increased soil water content in the east side of blocks 9 and 10. The only

measurement that might have been influenced was the maize biomass harvest done at 54

DAS. Since maize was cut in blocks 4, 7, and 10 and the eastern-most plot in block 10








was a nontrenched plot. an inadvertent increase in soil water content in that plot only

strengthens the result of the ANOVA that showed a significant difference in maize

biomass due to trenching.

The effect of trenching on maize development and yield was more pronounced

than during the other two seasons. However, even though this was the only season for

which the complete amount of fertilizer recommended by the Ministry of Agriculture

(MARNDR 1990)was applied, there were no significant effects of fertilizer on any of the

parameters measured for the complete ANOVA models.

All the ANOVAs run using the complete model for maize growth and yield

during this season produced very significant p-values for the effects of trenching, with

trenched plots producing more than nontrenched plots, especially close to the hedgerows.

All but the two maize biomass harvests were significant for distance from the hedgerow

and the trenching by distance interaction (Appendix C). Much of the difference was due

to the poor survival of maize plants in the nontrenched plots, especially in the two rows

closest to the trees.

Maize height. Figure 5-15 shows a significant maize height advantage at 40 DAS

in trenched plots at all four distances from the hedgerows (p < .001). Missing plants

were assigned values of zero because the mortality was attributed to competition with the

hedgerows. There were more missing plants in nontrenched plots than in trenched plots:

at the 50 cm distance 84% of the hills in nontrenched plots had no surviving plants vs.

20% for trenched plots; at the 100 cm distance the corresponding numbers were 25% in

the nontrenched plots and 4% in the trenched plots.









45 a
40 -a .. a
40 5 ------- ---------a-- -----
E a
5030 100 150 200
Ds 25 m te hw T+
2 hedg0 -40 DAS; Spg 19-b T-
N 15
Z 10
5 t

50 100 150 200
Distance from the hedgerow (cm)

Figure 5-15: Maize height trenched and nontrenched at four distances from the
hedgerow, 40 DAS; Spring 1995.


Distance from hedgerows was significant for both trenched and nontrenched

plots, but not in the same way. Maize height in trenched plots reached a maximum at

100 cm, and then decreased (although not significantly) at 150 and 200 cm. Maize height

in nontrenched plots was minimum at 50 cm, and then increased progressively with

distance but never attained the height as maize in trenched plots (Table 5-14).


Table 5-14: Maize height in trenched and nontrenched plots at four distances from
hedgerows, 40 DAS; Spring 1995.

Distance (cm) Trenched (cm) Nontrenched (cm)
50 30.0 a 2.2 a
100 40.6 b 13.5 b
150 36.1 ab 16.8 b
200 36.5 b 23.9 c
p-value .009 <.001


Maize height was less than Leucaena height until the hedgerows were pruned at

60 DAS (Figure 5-5). This raises the question of whether the maize on the north side of








the hedgerows experienced a shade regime different from that on the south side. No

direct measurements of light were done, but maize height at 40 DAS was analyzed for the

effect of aspect. Neither the complete model (including distance as a factor) nor the

separate models for each distance showed orientation with respect to the hedgerows to be

a significant influence on maize height (data not shown).

The effect of fertilizer on maize height was significant only at the 50 cm distance

from the hedgerows and only in the trenched plots (p = .035), where fertilized maize was

10 cm shorter than nonfertilized maize.

Maize biomass production. Differences between maize biomass harvested in

trenched and nontrenched plots at 47 and 54 DAS were similar, and continued the pattern

of differences in maize height discussed above. However, the statistical tests produced

higher p-values than did those for height, probably due to smaller samples sizes and high

variability caused by three outliers in block 10 at the 50 and 100 cm distances. The

irrigation system leak causing water contamination in blocks 9 and 10, discussed above,

was probably responsible. The complete model ANOVA at 47 DAS was significant for

trenching (p = .035), but not for fertilizer or distance from the hedgerow. The 54 DAS

complete model was significant only for trenching at a=.10 (p = .085).

At 47 DAS, ANOVAs done separately for each distance showed that trenched

plots produce significantly more biomass at all four distances from the hedgerows

(Figure 5-16). P-values for trenching are = .030, .096, .016, and .017 for the four

distances. At 54 DAS, the difference due to trenching is significant only at the 50 cm

distance (p = .072). The difference between trenched and nontrenched plots at the 100

cm distance shown in Figure 5-17 was numerically large, but because of the outliers

discussed above, did not result in a significant difference.
















OT+
ST-


50 100 150 200


Distance from the hedgerow (cm)


Figure 5-16:


Maize biomass in trenched and nontrenched plots at four distances from
the hedgerow, 47 DAS, Spring 1995.


ST+
mT-


100 150
Distance from the hedgerow


Figure 5-17:


Maize biomass in trenched and nontrenched maize weight at four
distances from the hedgerow, 54 DAS, Spring.






82

The changes in biomass over distance were similar for both observation dates. In

neither case were there significant differences over distance for trenched plots. In both

cases, maize biomass in nontrenched plots was less in the two rows closest to the

hedgerows than in the more distant rows (Table 5-15).


Table 5-15: Maize biomass in trenched and nontrenched plots at four distances from
the hedgerow, 47 and 54 DAS; Spring 1995.

47 DAS 54 DAS
Distance (cm) T+ (g) T- (g) T+ (g) T- (g)
50 25.9 1.6 a 61.9 1.3 a
100 43.7 5.3 ab 77.9 6.0 a
150 30.4 9.2 b 36.1 18.8 b
200 25.0 6.5 b 21.3 18.3 b

p-value .232 .010 .118 .007



Maize growth stage. Maize in trenched plots had attained a more advanced stage

of development than maize in nontrenched plots at both 68 and 75 DAS. Competition

with the trees retarded development of maize plants growing in nontrenched plots

increasingly as they neared the hedgerows. This was not the case for maize plants

growing in trenched plots-development was most advanced at 100 cm from the

hedgerows.

Figures 5-18 and 5-19 use different scales to indicate maize growth stage (see

Materials and Methods). A four-number scale was used at 68 DAS: 0=missing.

l=vegetative growth, 2=tassel/anthesis, 3=silk, and 4=ear. At 75 DAS a five-number

scale was used: 0=missing, l=vegetative, 2=tassel, 3=anthesis, 4=silk, and 5=ear.

















3
Silk


^2

o T





0 -


Figure 5-18:


Trenched and nontrenched maize growth stage at four distances from the
hedgerow, 68 DAS; Spring 1995.


Ear

4.0
Silk


3.0 -
A

o 2.0

1.0
Ve

0.0 -







Figure 5-19:


iithesis

assel

(etative


I I


ET+
MT-


100 150
Distance from the hedgerow (cm)


200


Trenched and nontrenched maize growth stage at four distances from the
hedgerow, 75 DAS; Spring 1995.


100 150 200
Distance from the hedgerow (cm)


O T+
mT-








As was the case with maize biomass production. growth stage changed with

distance from the hedgerows differently for plants in trenched plots than for those in

nontrenched plots. Plants in trenched plots were most advanced at 100 cm from the

hedgerows, and identical at the other three distances. There was no retardation in the 50

cm row, and conditions for maize development appear to have been enhanced at 100 cm

due to the presence of hedgerows. Maize plants in the nontrenched plots were least

developed in the 50 cm row, and progressively more developed as distance increased.

Soil water content. The complete ANOVA models for soil water at 26 and 61

DAS did not produce significant p-values for trenching, fertilizer, or distance from the

hedgerow. Only depth was significant (p < .001) on both dates. ANOVAs run separately

for each distance and depth were also not significant for trenching or fertilizer, with the

exception of a significant p-value (.016) for fertilizer at 150 cm distance, 15-30 cm depth

at 26 DAS. The nonfertilized plots in that position had only 0.5% more soil water than

did fertilized plots, so this difference is probably meaningless. Figures 5-20 and 5-21

show the percent soil water for the various positions in the trenched plots, with the

difference between trenched and nontrenched plots in parentheses. None of these

differences were significant.

When ANOVAs were run separately for trenched and nontrenched plots for each

depth, there were no significant differences in soil water between distances from the

hedgerow for either trenched or nontrenched plots, with one exception. At 61 DAS in the

nontrenched plots in the 0-15 cm depth, the 50 cm distance had about 1.5% more soil

water than the other three more distant positions (p = .002). Soil water increased with

depth for both trenched and nontrenched plots at all distances from the hedgerows, at

both observation periods (Table 5-16).












t i Distance from Hedgerow (cm)

50 100 150 200
_k__ I


Soil depth (cm)

0-15 cm


15-30 cm


30-45 cm <


II


Figure 5-20:


26.4 (0.7)


28.5 (1.0)


28.8 (-0.3)


Soil Water (%, Gravimetric)

24.7 (0.5) 24.4 (1.4)


27.6 (0.6) 27.2 (=)


29.2 (0.4) 29.2 (-0.2)


24.1 (0.6)


27.0 (0.1)


29.6 (0.7)


Soil water percent in trenched plots (and difference between T+ and T-
plots) at 26 DAS, Spring 1995.


Figure 5-21: Soil water percent in trenched plots (and difference between T+ and T-
plots) at 61 DAS, Spring 1995.




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