• TABLE OF CONTENTS
HIDE
 Front Cover
 About IITA
 Title Page
 Table of Contents
 Board of trustees
 Foreword
 Farming systems program






Group Title: Annual report, International Insitute if Tropical Agriculture
Title: Annual report
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00053869/00001
 Material Information
Title: Annual report
Alternate Title: International Institute of Tropical Agriculture annual report
Physical Description: 8 v. : ill. ; 23-28 cm.
Language: English
Creator: International Institute of Tropical Agriculture
Publisher: The Institute
Place of Publication: Ibadan Nigeria
Frequency: annual
regular
 Subjects
Subject: Agriculture -- Periodicals -- Tropics   ( lcsh )
Tropical crops -- Periodicals   ( lcsh )
Genre: international intergovernmental publication   ( marcgt )
 Notes
Statement of Responsibility: International Institute of Tropical Agriculture.
Dates or Sequential Designation: Began in 1974; ceased in 1981.
General Note: Description based on: 1977; title from cover.
Funding: Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
 Record Information
Bibliographic ID: UF00053869
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: aleph - 002203897
oclc - 03806543
notis - ALE3829
lccn - 82642611 //r85
 Related Items
Preceded by: Report
Preceded by: Report
Preceded by: Report
Preceded by: Report
Succeeded by: IITA annual report

Table of Contents
    Front Cover
        Front Cover
    About IITA
        Unnumbered ( 2 )
    Title Page
        Page i
        Page ii
    Table of Contents
        Page iii
        Page iv
    Board of trustees
        Page v
    Foreword
        Page vi
    Farming systems program
        Page 1
        Introduction
            Page 1
        Baseline data collection
            Page 1
            IITA general weather conditions
                Page 1
                Page 2
            Agroclimatic analysis
                Page 3
                Page 4
            Soil and land characterization and evaluation
                Page 5
                Page 6
            Socio-economic analysis
                Page 7
                Page 8
                Page 9
        Land and soil management
            Page 10
            Land clearing and development
                Page 10
            Tillage systems and small tools development
                Page 11
                Page 12
                Page 13
                Page 14
                Page 15
                Page 16
                Page 17
                Page 18
                Page 19
                Page 20
            Management of kaolintic alfisols
                Page 21
                Page 22
                Page 23
                Page 24
                Page 25
                Page 26
                Page 27
            Management of siliceous ultisols
                Page 28
                Page 29
                Page 30
                Page 31
        Cropping systems
            Page 32
        Intercropping agronomy and meso/micro-climatic studies
            Page 32
            Page 33
            Page 34
            Page 35
            Alley cropping
                Page 36
                Page 37
                Page 38
                Page 39
                Page 40
                Page 41
            Live mulch systems
                Page 42
            Weed biology and herbicide research
                Page 43
            Plantain improvement
                Page 44
                Page 45
                Page 46
                Page 47
            Eastern Cameroon farming systems project
                Page 48
            Small farms systems research (Atebubu district, Ghana)
                Page 49
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1980
ANNUAL REPORT
INTERNATIONAL INSTITUTE OF
TROPICAL AGRICULTURE


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Contents


v Board of Trustees

vi Foreword

1 Farming Systems Program

1 Introduction

1 Baseline data collection and analysis
1 General weather conditions
3 Agroclimatic analysis
5 Soil and land characterization and evaluation
7 Socio-economic analysis

10 Land and soil management
10 Land clearing and development
11 Tillage systems and small tools development
21 Management of kaolintic Alfisols
28 Management of siliceous Ultisols

32 Cropping systems
32 Intercropping agronomy and meso/micro-climatic studies
36 Alley cropping
^k 42 Live mulch systems
43 Weed biology and herbicide research
44 Plantain improvement
48 Eastern Cameroon Farming Systems Project
49 Small farms systems research (Atebubu District, Ghana)

51 Root and Tuber Improvement Program

5.1 Introduction

51 Cassava
51 Genetic improvement
54 Entomology
59 Pathology
61 Nematology
62 Tissue culture and virus indexing
62 Zaire's National Manioc Program (PRONAM)
64 Cameroon National Root Crops Improvement Program (CNRCIP)

64 Yam
65 Genetic improvement
66 Pathology
70 Nematology
72 Quality evaluation
72 Tissue culture and virus indexing
72 Cameroon National Root Crops Improvement Program (CNRCIP)

72 Sweet Potato
73 Genetic improvement
74 Entomology
76 Nematology
77 Quality evaluation
78 Tissue culture and virus indexing
80 Cameroon National Root Crops Improvement Program (CNRCIP)

83 Cocoyam
83 Genetic improvement
83 Agricultural economics
84 Cameroon National Root Crops Improvement Program (CNRCIP)








85 Cereal Improvement Program
85 Introduction

85 Maize
86 Genetic improvement
95 Entomology
96 Semi-Arid Food Grains Research and Development Project (SAFGRAD)
100 Rice
100 Genetic improvement
109 Pathology
109 Physiology

117 Grain Legume Improvement Program

117 Introduction
117 Cowpea
117 Genetic improvement
124 Entomology
130 Upper Volta Food Legumes Program
131 Semi-Arid Food Grains Research and Development Project (SAFGRAD)
134 Tanzania Food Crops Research
137 Brazil Cowpea Program

137 Soybean
137 Genetic improvement
143 Entomology
149 Agronomy
155 Tanzania Food Crops Research

155 Microbiology

161 Training Program

163 Research Support
163 Introduction
163 High-rainfall substation
163 Research station operations
163 Screenhouses and the plant growth facilities
163 Genetic Resources Unit
166 Virology Unit
171 Analytical Services Laboratory
171 Biometrical Unit
171 Conference Center
171 Library and Documentation Center
172 Communications and Information Office

173 Special Projects
173 Introduction
174 Training and collaborative research projects
174 Core supplementing projects

175 Personnel

177 Collaborators and Training

180 Publications

182 Conference and Seminar Papers

185 Major Seminars


























Board of Trustees


Mr. Guy Vallaeys (Chairman)
Institute de Recherches Agronomiques Tropicales et de
Cultures Vivrieres (IRAT), Paris, France

Mr. D. lyamabo (Vice Chairman)
Ministry of Science and Technology, Ibadan, Nigeria

Dr. R. C. McGinnis
Dean of Agricultute, University of Manitoba, Winnipeg,
Canada

Dr. Hidetsugu Ishikura
Director General, Institute of Environmental Toxicology,
Tokyo, Japan

Alhaji M. Liman
Federal Ministry of Agriculture, Lagos, Nigeria

Dr. E. H. Hartmans
Director General, IITA, Ibadan, Nigeria


Dr. Willi Ehman
Ministry of Economic Cooperation, 53 Bonn 12,
Germany

Prof. R. J. Olembo
Div. of Ecosystems and Natural Resources, UNEP,
Nairobi, Kenya

Citoyen Mukendi Mbuyi Tshingoma
FAO, Bamako, Mali

Dr. F. F. Hill
Ford Foundation, Ithaca, New York 14850

Dr. John J. McKelvey, Jr.
Associate Director, Agricultural Sciences, The
Rockefeller Foundation, New York, N.Y. 10036

Prof. C. A. Onwumechili
Vice Chancellor, University of Ife, Ile-lfe, Nigeria


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Foreword


T he year 1980 was one of financial uncer-
tainty for the International Institute of
Tropical Agriculture. A high rate of infla-
tion, a doubling of the minimum wage, and a
strengthening of the Nigerian naira against
the American dollar had a very serious and
negative impact on the real research capac-
ity of IITA. : '. .- ...
Research program budgets and staff had to
be reduced, and a general belt tightening left
the remaining scientists with insufficient sup-
porting staff and operating allocations to en-
ab!*them to work in a fully effective and
productive manner.
It was through a very generous special con-
tribution of 1 million naira, equivalent to 1.9
million U.S. dollars, by the Federal Republic
of Nigeria in December 1980 that this precar-
i ous financial situation could be redressed.
Despite.. the disruptive economic condi-
tions, IITA's research community produced a
scientific product of commendable quality
and quantity as reflected in this Annual
Report.
As in previous years, the 1980 Annual Re-
port is a compendium of salient, research
conducted in cereal, root, tuber, and grain
legume improvement programs, and in farm-
ing systems for the humid and subhumid
tropics. This report and its sister publication,
1980 Research Highlights, together provide a
comprehensive summary of findings for both
the scientist and the generalist.
This year also marks the first time the An-
nual Report is being published in French.
Long overdue, we are confident it will
be enthusiastically received by our French-
speaking colleagues.
The structure of the Institute's .research
program remained unchanged in 1980, but
the focus of the work was somewhat
modified.


Farming systems research was reorganized
to focus on three major components-land
clearance and development, post-clearance
management, and cropping systems. The
maize improvement program included some
exploratory work on the development of hy-
brids. The development of lowland rice vari-
eties and the problems of production in
central and eastern Africa were given greater
emphasis. Breeding for resistance to insect
pests of cowpeas was intensified, and cas-
sava research was concentrated on host
plant resistance to the green spider mite and
mealybug. -
In the resolution of the etiology of virus dis-
eases, techniques of indexing the presence
of sweet potato virus was developed. As a
result, it is now possible to export virus-free
sweet potato clones in tissue culture form
internationally.
Previously, the Institute's research was al-
most exclusively pointed toward the small,
traditional, resource-poor African farmer. But
because of increasing interest in commercial
farming in many African countries, the Insti-
tute is devoting a greater share of its re-
search effort toward the solution of problems
encountered by medium and large-scale
farming enterprises.
We are sure you will find this Annual Report
informative, and we will be pleased to re-
spond to all requests for additional informa-
tion about on-going research at the Institute.
A listing of journal articles and IITA's sci-
entific staff is appended to this report to
assist you.




Dr. E. H. Hartmans
Director General




















Farming Systems Program




Introduction


A primary goal of the Farming Systems Program is
the development of methods of land use and crop
management that will enable efficient, economic
and sustained production of food crops for the humid
and subhumid tropics. Research is directed primarily at
problem solving the constraints of small farmers, many
of whom still rely on bush fallow systems for producing
the bulk of the food in the humid and subhumid tropics
of Africa and elsewhere. Emphasis is given to developing
technologies that are scale neutral so that they can be
used by a range of farmers.
Because of the wide range of farming system forms in
the humid and subhumid tropics, the program will not
develop specific local blueprints for improved methods
of land, soil and crop management; rather, the program's
concern is to develop and make available preliminary
technologies and subsystems that can be modified and
adapted by national and regional organizations to the
agronomic and economic as well as political conditions
of their own areas. Considering the diversity of the farm-
ing systems in the Institute's mandate area, baseline data
collection and analysis are undertaken to better deline-
ate the major benchmark areas with relevant bioclimatic
and soil parameters in relation to prevailing cropping
systems. The benchmark sites will be used for determin-
ing typologies and testing principles of land and soil
management and cropping systems.
The research emphasis of the program is on assisting
farmers in the move from the subsistence shifting culti-
vation and particularly bush fallow systems, to more con-
tinuous and productive systems of cultivation with
appropriate land and soil management practices, which
will maintain soil productivity and minimize soil erosion
and soil degradation.
To achieve more impact in the immediate future, the pro-
gram focused its activities in the following research
areas: baseline data collection and analysis, land and
soil management and cropping systems.
Cooperative programs have been established in Came-
roon and Ghana. Reports of these projects are included
in cooperative projects, and individual reports are avail-
able from the respective organizations.


Baseline data collection
and analysis

Research on baseline data collection and analysis in-
cludes the following areas: agroclimatology, soil and
land characterization and evaluation and socioeconomic
analysis.
Research in 1980 emphasized crop water requirements
as well as the development of a soil evaluation system
for highly weathered soils in West Africa and studies of
soil erodibility. Socioeconomic analyses included food
crop and agro-forestry farming systems surveys.


IITA general weather conditions
The nonoccurrence of the late July-August dry season
was the dominant feature of the weather in 1980. As with
similar cases in 1973 and 1979, the only other 2 of the
decade, this feature was again associated with a general
shift in rainfall pattern; the second rather than the first
season constituted the major rainy season. There were
consonant departures in isolation, the heavy rainfall pe-
riod generally receiving less than normal global radia-
tion. The mean temperatures were comparatively high
along with the mean relative humidity while the evapo-
rative demand was lower than the long-term mean. A
summary of the main variables is given in Table 1.

Rainfall and evaporation. A streak of rainless days
extending back to November, 1979, was broken with a
26.2 mm rain on 14 February. There were 4 other rains
before the end of March (Table 1, Fig. 1), and the first
quarter of the year was, thus, marked by a pronounced
moisture deficit with a -44 percent departure in cumu-
lative rainfall in conjunction with a -7 percent differ-
ence in cumulative evaporation.
No rain of substance fell in April, and total rainfall was
fully 66 percent below normal. It was a clear case of a
"false start" in the rains, causing most of the late March
plantings to succumb to drought stress (Fig. 2). Favor-
able water balance was first established at the beginning


__




















Farming Systems Program




Introduction


A primary goal of the Farming Systems Program is
the development of methods of land use and crop
management that will enable efficient, economic
and sustained production of food crops for the humid
and subhumid tropics. Research is directed primarily at
problem solving the constraints of small farmers, many
of whom still rely on bush fallow systems for producing
the bulk of the food in the humid and subhumid tropics
of Africa and elsewhere. Emphasis is given to developing
technologies that are scale neutral so that they can be
used by a range of farmers.
Because of the wide range of farming system forms in
the humid and subhumid tropics, the program will not
develop specific local blueprints for improved methods
of land, soil and crop management; rather, the program's
concern is to develop and make available preliminary
technologies and subsystems that can be modified and
adapted by national and regional organizations to the
agronomic and economic as well as political conditions
of their own areas. Considering the diversity of the farm-
ing systems in the Institute's mandate area, baseline data
collection and analysis are undertaken to better deline-
ate the major benchmark areas with relevant bioclimatic
and soil parameters in relation to prevailing cropping
systems. The benchmark sites will be used for determin-
ing typologies and testing principles of land and soil
management and cropping systems.
The research emphasis of the program is on assisting
farmers in the move from the subsistence shifting culti-
vation and particularly bush fallow systems, to more con-
tinuous and productive systems of cultivation with
appropriate land and soil management practices, which
will maintain soil productivity and minimize soil erosion
and soil degradation.
To achieve more impact in the immediate future, the pro-
gram focused its activities in the following research
areas: baseline data collection and analysis, land and
soil management and cropping systems.
Cooperative programs have been established in Came-
roon and Ghana. Reports of these projects are included
in cooperative projects, and individual reports are avail-
able from the respective organizations.


Baseline data collection
and analysis

Research on baseline data collection and analysis in-
cludes the following areas: agroclimatology, soil and
land characterization and evaluation and socioeconomic
analysis.
Research in 1980 emphasized crop water requirements
as well as the development of a soil evaluation system
for highly weathered soils in West Africa and studies of
soil erodibility. Socioeconomic analyses included food
crop and agro-forestry farming systems surveys.


IITA general weather conditions
The nonoccurrence of the late July-August dry season
was the dominant feature of the weather in 1980. As with
similar cases in 1973 and 1979, the only other 2 of the
decade, this feature was again associated with a general
shift in rainfall pattern; the second rather than the first
season constituted the major rainy season. There were
consonant departures in isolation, the heavy rainfall pe-
riod generally receiving less than normal global radia-
tion. The mean temperatures were comparatively high
along with the mean relative humidity while the evapo-
rative demand was lower than the long-term mean. A
summary of the main variables is given in Table 1.

Rainfall and evaporation. A streak of rainless days
extending back to November, 1979, was broken with a
26.2 mm rain on 14 February. There were 4 other rains
before the end of March (Table 1, Fig. 1), and the first
quarter of the year was, thus, marked by a pronounced
moisture deficit with a -44 percent departure in cumu-
lative rainfall in conjunction with a -7 percent differ-
ence in cumulative evaporation.
No rain of substance fell in April, and total rainfall was
fully 66 percent below normal. It was a clear case of a
"false start" in the rains, causing most of the late March
plantings to succumb to drought stress (Fig. 2). Favor-
able water balance was first established at the beginning


__




















Farming Systems Program




Introduction


A primary goal of the Farming Systems Program is
the development of methods of land use and crop
management that will enable efficient, economic
and sustained production of food crops for the humid
and subhumid tropics. Research is directed primarily at
problem solving the constraints of small farmers, many
of whom still rely on bush fallow systems for producing
the bulk of the food in the humid and subhumid tropics
of Africa and elsewhere. Emphasis is given to developing
technologies that are scale neutral so that they can be
used by a range of farmers.
Because of the wide range of farming system forms in
the humid and subhumid tropics, the program will not
develop specific local blueprints for improved methods
of land, soil and crop management; rather, the program's
concern is to develop and make available preliminary
technologies and subsystems that can be modified and
adapted by national and regional organizations to the
agronomic and economic as well as political conditions
of their own areas. Considering the diversity of the farm-
ing systems in the Institute's mandate area, baseline data
collection and analysis are undertaken to better deline-
ate the major benchmark areas with relevant bioclimatic
and soil parameters in relation to prevailing cropping
systems. The benchmark sites will be used for determin-
ing typologies and testing principles of land and soil
management and cropping systems.
The research emphasis of the program is on assisting
farmers in the move from the subsistence shifting culti-
vation and particularly bush fallow systems, to more con-
tinuous and productive systems of cultivation with
appropriate land and soil management practices, which
will maintain soil productivity and minimize soil erosion
and soil degradation.
To achieve more impact in the immediate future, the pro-
gram focused its activities in the following research
areas: baseline data collection and analysis, land and
soil management and cropping systems.
Cooperative programs have been established in Came-
roon and Ghana. Reports of these projects are included
in cooperative projects, and individual reports are avail-
able from the respective organizations.


Baseline data collection
and analysis

Research on baseline data collection and analysis in-
cludes the following areas: agroclimatology, soil and
land characterization and evaluation and socioeconomic
analysis.
Research in 1980 emphasized crop water requirements
as well as the development of a soil evaluation system
for highly weathered soils in West Africa and studies of
soil erodibility. Socioeconomic analyses included food
crop and agro-forestry farming systems surveys.


IITA general weather conditions
The nonoccurrence of the late July-August dry season
was the dominant feature of the weather in 1980. As with
similar cases in 1973 and 1979, the only other 2 of the
decade, this feature was again associated with a general
shift in rainfall pattern; the second rather than the first
season constituted the major rainy season. There were
consonant departures in isolation, the heavy rainfall pe-
riod generally receiving less than normal global radia-
tion. The mean temperatures were comparatively high
along with the mean relative humidity while the evapo-
rative demand was lower than the long-term mean. A
summary of the main variables is given in Table 1.

Rainfall and evaporation. A streak of rainless days
extending back to November, 1979, was broken with a
26.2 mm rain on 14 February. There were 4 other rains
before the end of March (Table 1, Fig. 1), and the first
quarter of the year was, thus, marked by a pronounced
moisture deficit with a -44 percent departure in cumu-
lative rainfall in conjunction with a -7 percent differ-
ence in cumulative evaporation.
No rain of substance fell in April, and total rainfall was
fully 66 percent below normal. It was a clear case of a
"false start" in the rains, causing most of the late March
plantings to succumb to drought stress (Fig. 2). Favor-
able water balance was first established at the beginning


__




















Farming Systems Program




Introduction


A primary goal of the Farming Systems Program is
the development of methods of land use and crop
management that will enable efficient, economic
and sustained production of food crops for the humid
and subhumid tropics. Research is directed primarily at
problem solving the constraints of small farmers, many
of whom still rely on bush fallow systems for producing
the bulk of the food in the humid and subhumid tropics
of Africa and elsewhere. Emphasis is given to developing
technologies that are scale neutral so that they can be
used by a range of farmers.
Because of the wide range of farming system forms in
the humid and subhumid tropics, the program will not
develop specific local blueprints for improved methods
of land, soil and crop management; rather, the program's
concern is to develop and make available preliminary
technologies and subsystems that can be modified and
adapted by national and regional organizations to the
agronomic and economic as well as political conditions
of their own areas. Considering the diversity of the farm-
ing systems in the Institute's mandate area, baseline data
collection and analysis are undertaken to better deline-
ate the major benchmark areas with relevant bioclimatic
and soil parameters in relation to prevailing cropping
systems. The benchmark sites will be used for determin-
ing typologies and testing principles of land and soil
management and cropping systems.
The research emphasis of the program is on assisting
farmers in the move from the subsistence shifting culti-
vation and particularly bush fallow systems, to more con-
tinuous and productive systems of cultivation with
appropriate land and soil management practices, which
will maintain soil productivity and minimize soil erosion
and soil degradation.
To achieve more impact in the immediate future, the pro-
gram focused its activities in the following research
areas: baseline data collection and analysis, land and
soil management and cropping systems.
Cooperative programs have been established in Came-
roon and Ghana. Reports of these projects are included
in cooperative projects, and individual reports are avail-
able from the respective organizations.


Baseline data collection
and analysis

Research on baseline data collection and analysis in-
cludes the following areas: agroclimatology, soil and
land characterization and evaluation and socioeconomic
analysis.
Research in 1980 emphasized crop water requirements
as well as the development of a soil evaluation system
for highly weathered soils in West Africa and studies of
soil erodibility. Socioeconomic analyses included food
crop and agro-forestry farming systems surveys.


IITA general weather conditions
The nonoccurrence of the late July-August dry season
was the dominant feature of the weather in 1980. As with
similar cases in 1973 and 1979, the only other 2 of the
decade, this feature was again associated with a general
shift in rainfall pattern; the second rather than the first
season constituted the major rainy season. There were
consonant departures in isolation, the heavy rainfall pe-
riod generally receiving less than normal global radia-
tion. The mean temperatures were comparatively high
along with the mean relative humidity while the evapo-
rative demand was lower than the long-term mean. A
summary of the main variables is given in Table 1.

Rainfall and evaporation. A streak of rainless days
extending back to November, 1979, was broken with a
26.2 mm rain on 14 February. There were 4 other rains
before the end of March (Table 1, Fig. 1), and the first
quarter of the year was, thus, marked by a pronounced
moisture deficit with a -44 percent departure in cumu-
lative rainfall in conjunction with a -7 percent differ-
ence in cumulative evaporation.
No rain of substance fell in April, and total rainfall was
fully 66 percent below normal. It was a clear case of a
"false start" in the rains, causing most of the late March
plantings to succumb to drought stress (Fig. 2). Favor-
able water balance was first established at the beginning


__







Table 1. Summary of climatic data (IITA, 1980).
Total Total Solar Temperature Relative humidity
rain- evapo- radiation *C %
fall ration G"-call
Month mm mm cm2/day Min. Mean Max. Min. Mean Max.
Jan. 0 121.22 391.90 23.3 27.8 32.2 46 71 96
Feb. 26.2 150.51* 504.14 23.8 28.9 33.9 39 68 39
Mar. 52.0 174.22 513.70 24.3 28.7 33.0 46 72 98
Apr. 50.1 164.70* 490.16 23.8 28.4 33.0 49 72 95
May 193.0 126.17* 401.85 23.3 26.7 30.1 61 79 97
June 132.2 129.50 421.16 23.2 26.3 29.4 64 80 95
Jul. 203.8 88.04* 318.53 22.2 24.6 27.0 72 84 96
Aug. 367.8 -- 92.07* 325.16 22.4 24.9 27.3 73 85 97
Sept. 248.9 104.10* 384.56 22.3 25.5 28.7 67 83 98
Oct. 208.4 107.88 418.96 22.5 26.0 29.4 64 81 97
Nov. 66.7 107.10* 408.28 22.5 26.3 30.0 56 76 97
Dec. 0 117.58 386.25 20.1 25.3 30.5 41 67 92
*Values adjusted for days with missing data.


-x IITA, 19
e-- University
average


of Ibadan 20-year


O---O RAINFALL
- -- EVAPORATION


TIME
Weekly mean rainfall and evaporation (IITA,


TIME
Fig. 1. Mean monthly rainfall.


of May, about a full month later than normal (Fig. 2) with
a corresponding delay in the start of the first cropping
season.
Precipitation remained quite regular through the first 2
weeks of June but tapered off again in the last third of
the month and continued so through the first of July.


This spell of moisture deficit was followed by a period of
excessive and persistent rainfall, which culminated in
the highest monthly peak for the year and the third high-
est on record (367.8 mm for August). A singular rain in-
cidence on 31 August resulted in an unprecedented and
catastrophic flood in the general area.
With the failure of the 'normal' August break in the rains,
first-season crops, with potential yields already de-
pressed, suffered further damages through lodging, im-
proper drying and delayed harvesting. The excessive
moisture also caused considerable delay in land prepa-
ration and second season planting and persisted
through September and October. The rainy season
ended in early November. The cumulative total for the
year was 1,549 mm or 22 percent above the long-term
mean. Pan evaporation, on the other hand, was 7 percent
less than its mean, totalling 1,483.09 mm.

Sky conditions and solar radiation. January and Febru-
ary were unusually cloudy, but solar radiation (Table 1,
Fig. 3) was higher than normal. Cloudiness increased,
particularly in the second half of April, in spite of the
limited rainfall.


Fig. 2.
1980).














S350
.1

, 31-

250'
S200-
1 O-
6w


WEEKLY MEAN
-- MONTHLY MEAN


50
I Fl J AN I FB I yIAY I Jun I aJ IAUG ISEP I OCT INOV IDEC I
TIME
Fig. 3. Weekly and monthly mean solar radiation (IITA,
1980).


During the period May through August, which in effect
covers the first cropping season, incident radiation
dropped to a mean of 363.7 g-cal cm-2 day-1 or 6 percent
less than the multiannual mean for these 4 months. The
rest of the year, except for the month of November, saw
a return to higher than normal insolation regimes.
Temperature and relative humidity. Higher tempera-
tures prevailed on the average, mainly as a result of
higher night-time temperatures, an apparent result of the
more humid and cloudier conditions (Fig. 4). Monthly
average minimum temperatures were record-high in
many cases.



40


o.30-

20-
SMAXIMUM
.a.. -MEAN
Ow MINIMUM
I-.


I JAN I FEB I MAR IAPR I MAY IJUN IJUL I AUG I SEP OCT INOV I DEC I
TIME

Fig. 4. Weekly mean, maximum, and minimum mean air
temperature (IITA, 1980).

Daytime hours were by contrast cooler. The only above-
average maximum temperature occurred in April (depar-
ture: +0.60CY, a month of subnormal rainfall. With the
delay in the onset of the rains, soil temperatures re-
mained rather high well into the month of April with a
mean maximum of 41.30C at 5 cm.
Observed relative moisture contents of air were also
higher than normal, except for April (Fig. 5). These
higher humidities evidently account, in part, for the
lower values of evaporative demand.
An unusual prevalence of southerly and southwesterly
winds in January and February constituted the basis for
the observed cloudiness noted earlier. In general, wind
speeds also remained above average throughout the
year. The incidences of gusts during the wet period, par-
ticularly in late July and in August, account for the con-


0 0 MAXIMUM
.----... MEAN
-- MINIMUM


JAN I FB IR IAPR 1 MAY I JUN IJUL I AUG I SEP I OCT I NOV I DEC

Fig. 5. Mean, maximum, and minimum relative humidity
(IITA, 1980).

siderable lodging and stalk breaking observed during the
period.
Dew/light precipitation. The contribution of dew to the
water budget was much less than in the previous year.
This is not surprising in view of the record high minimum
temperatures and the high incidence of rainfall. The
measured total for the year was 11.59 mm, ranging from
a monthly maximum of 1.57 mm in November to 0.48 mm
in August.


Agroclimatic analysis

Agroclimatic zones of West Africa
To provide a uniform framework for research to facilitate
the choice of priority areas and determine the range of
applicability of research results, an agroclimatic zona-
tion of West Africa was undertaken. It is based on the
concept of water-balance and Franguin's method of in-
terception of rainfall potential evapotranspiration cure.
Months of positive water balance were defined as
months with rainfall greater than or equal to potential
evapotranspiration. On the basis of the number of the
months determined for the network of approximately 88
stations over the region, 7 generalized agroclimatic
zones were defined (Fig. 6).
Commonly used terminologies were retained in describ-
ing these zones. It is believed that the basic definition
used in this classification is not only more meaningful
from the cropping point of view but also avoids complex
indices and is, thus, easier for the user to follow.


Crop water requirements.
There is a scarcity of research information regarding the
water requirements for tropical food crops. It is impor-
tant, therefore, to define the optimum water require-
ments of these crops to maximize their productivity
under different ecological conditions.
Evapotranspiration and cowpea yields. Many studies on
a variety of crops have tended to show a linear relation-
ship between actual evapotranspiration and, more par-
ticularly, actual transpiration and yield. Using cowpea,
TVu 3629 and TVu 4557, yield figures from a series of


--
---. ;-









LEGEND 20 ." .

- PERHUMID:(PWETp for Bmonths or more)- -.
HUMID: (P2ETp for period between 6-8montns) ..
TRANSITION HUMID/SUBHUMID: (P ETp for .. -~s- 1
period 5-6 months)
SUBHUMID:(PETp for period between 4-5 3
months)
SEMI-ARID:(P_>ETp for period between 2- 4

ARID:(P>ETp for period between 1-2 ION 2
months)
DESERT:(PETp for period less thonone 7 ..
month)
NATIONAL BOUNDARIES
ISOLINES OF NUMBER OF HUMID (P-ETp) 5N 4 5rj
MONTHS
BOUNDARY OF BIMODAL RAINFALL/CROPP- tOE8 7
ING AREA
* STATIONS


Fig. 6. Generalized agroclimatic map of West Africa.
(Source: T. L. Lawson, IITA, 1979).


previous sequential planting experiments (IITA Annual
Report, 1976), a preliminary attempt was made to model
cowpea yield using estimated evapotranspiration.

Evapuiranspiration estimates were obtained by assum-
ing that the potential evapotranspiration is equal to Class
A pan evaporation, and the actual mean weekly evapo-
transpiration is proportional to the ratio of the actual
available soil moisture to the available soil moisture at
field capacity. The 1976 results show a much better rela-
tionship than the 1977 results between the estimated
evapotranspiration and cowpea yields (Figs. 7 and 8).


2000.


1800


1600


1400


1200


S1000.
> 800o
S0oo


0
1976 PLANTING SEASON x
VARIETY I, ISt 10 weeks ---
VARIETY 2. I -10 weeks ---















0 /

O 0
,/ o
/ '

/ r


Pest and disease problems are believed to be partly re-
sponsible for this. Possible inaccuracies in the evapo-
transpiration estimates may be equally important.


(I r 1


0 20 40 60 80 100 120 140 160 180 200 220240 260
TOTAL EVAPOTRANSPIRATION ( ET )

Fig. 7. Cowpea yield vs. evapotranspiration (1976).


1977 PLANTING SEASON
VARIETY I"- 10 WEEKS *---
VARIETY2 I -IOWEEKS i--..


20 40 60 80 100 120 140
TOTAL EVAPOTRANSPIRATION (SET)


160 180 200


Fig. 8. Cowpea yield vs. evapotranspiration (1977).


Dry season evaporative demand and cassava yields.
Cassava planted in a given year normally grows through
the dry season and is harvested at the beginning of the
rains the following year or thereafter. Although the plant
reduces its canopy during the intervening dry season, no
sign of wilting is observed on the leaves of the remaining
foliage. On the hypothesis that the plants probably
achieve this only by drawing on reserve resources, it
would appear that yields might tend to decline in propor-
tion to the length and severity of the dry season. Using
cumulative Class A pan evaporation (Ep) as a measure of
the intensity of the dry season, an analysis was made to
relate the reported decline in the average yield of the 10


15E


I


15W low 5W 0O








most promising cassava clones at IITA between 1973/
1974 and 1977/1978 (IITA Annual Report 1977). The re-
sults, indeed, show a negative and highly significant lin-
ear relationship between the cumulative pan evaporation
from 1 December through 28 and 29 February (the dry
season for IITA) and the cassava yield. The relevant equa-
tion is as follows: Y = 176.69-0.3421, r = -.978*, where

Y is the yield of cassava and I = (Ep) (1 = Dec., n =

Feb. 28/29). This relationship could prove useful in esti-
mation of the performance of cassava across climatic
zones.


Soil and land characterization and
evaluation

Technical soil evaluation system based
on soil mineralogy
Two distinctive approaches have evolved in recent years
regarding the management of tropical soils for higher
agricultural productivity. The high-energy input, exten-
sive food and cash crop production systems are well
suited for the fine-textured oxidic Oxisols, Alfisols, Ulti-
sols and Inceptisols; whereas, agroforestry and low-en-
ergy input, food crop production systems are more
suitable for the kaolinitic and siliceosis Alfisols, Ultisols
and Inceptisols.
A key factor differentiating these 2 major categories of
soils and their response to agricultural exploitation is
soil mineralogy. A technical soil evaluation system using
mineralogical characteristics as the main criterion is
being developed at IITA with the primary objective to
provide agricultural planners in the tropics with a set of
simple guidelines for agricultural soil utilization. It is in-
tended to provide supplementary information to the es-
tablished soil classification systems with special
reference to agricultural soils in which variable charge
colloids dominate. Vertisols, Alfisols, Ultisols and Incep-
tisols dominating in high activity clays or constant
charge minerals are excluded from this system since the
agricultural soil evaluation systems for such soils are
well established for the temperate and subtropical re-
gions.
The proposed system may be briefly summarized as fol-
lows:

'Condition modifiers
(or soil fertility
limitation)
Soil group Sub-group Physical Chemical
Kaolinitic soils Eutric w, r, c t*, (m*)
Dystric w, r, c t, k, a, (m)
Siliceous soils Eutric w, c t*, k*, (m*)
Dystric w, c t, k, a (m)
Oxidic soils Eutric w i
Dystric w i, t, k, a
Allophanic soils Eutric i
Dystric -i, t, k
The eutric subclass refers to high "base" status, and dys-
tric to low "base" status. The soil fertility limitations in


the last 2 columns refer to:
Physical condition modifiers:
w -low available water reserve
r -high soil erosion hazard
c -high soil compaction hazard
Chemical condition modifiers:
k -low potassium reserve
i -high phosphate fixation
t -secondary/micronutrient deficiencies and/or imbal-
ances
a -aluminum toxicity for most legume crops
m -manganese toxicity to most legume crops
-potential soil toxicity and/or secondary and micro-
nutrient deficiencies and imbalance due to contin-
uous cultivation with conventional chemical fertil-
ization.
Tentative quantitative limits of the "soil condition modi-
fiers" have been defined, and refinement of these can be
introduced in the future on the basis of further research
information.
It is proposed to integrate this soil evaluation system in
the land types and agroclimatic information so as to es-
tablish comprehensive guidelines for land clearing and
management for different regions of the tropics. Close
collaboration with FAO and other development agencies
and interested national soils research institutions will be
fruitful in further development of the system.

Soil erodibility characterization
Field experiments have been established to directly mon-
itor soil erodibility at 3 locations in Nigeria-Onne, Ikom
and Jos. In addition, soil detachability and transportabil-
ity measurements on 20 soils collected from different
parts of Nigeria are being made with a laboratory rainfall
simulator. The accumulative infiltration measured for 3
locations prior to establishing the runoff plots are de-
scribed by the following equations:
I = 30.8t/2 + 26.1t ... Onne
I = 16.0t/2 + 93.3t...Ikom
I = 2.1t/2 + 6.3t .. Jos
Where I is the accumulative infiltration in centimeters,
and t is the time in minutes.

Field measurements of soil bulk density for 20 soils indi-
cated a range of 0.70g cm-3 for Ikom to 1.5g cm-3 for
Bakura and Tumu, Nigeria. Similarly, the soil-water
transmissivity ranged from 236 cm/hr for Ikom to 1.4 cm/
hr for Samaru, Nigeria. A plot of the accumulative infiltra-
tion vs. time for some Nigerian soils is shown in Fig. 9.
Estimates of erodibility for some Nigerian soils by using
the USDA Nomogram indicate a range of 0.05 t/acre/foot-
ton for Ikom to 0.56 t/acre/foot-ton for steep lands near
Abakaliki, Nigeria. A majority of the soils, however, have
a low erodibility of about 0.1.


Hydromorphic soils in West Africa
A study was carried out to assess the quality and distri-
bution of hydromorphic soils in various wetland areas in
West Africa and their suitability and limitations for
rainfed and irrigated rice production.
Hydromorphic soils could be defined simply as those
soils where water can gather in sufficient volume and
time to produce the effects of gleying or reducing re-












o 3 9. BA CHI.
,. SAMARU ////.. /




3 ^u
2.








I 2 5 6 76B90 20 30 40 5060 80 00 200 400 600 a8 000
TIME (MN)
Fig. 9. Accumulative infiltration for some Nigerian soils.

gime. While hydromorphic soils mean the same to all soil
scientists in terms of morphological and chemical prop-
erties, the different soil classification systems are still
not very interchangeable because their respective con-
cepts are based on different premises.
According to U.S. Soil Taxonomy, hydromorphic soils
have an aquic soil moisture regime, and they appear
under the suborder as well as the subgroup levels of
classification. The FAO/UNESCO soil classification em-
phasizesthe concept of gleization, and Gleysols and the
"gleyic" subunits constitute the major hydromorphic
soils of the "FAO Soil Map of the World." For both the
French and Belgian classification systems, the pro-
cesses of gley and pseudogley play prominent parts in
the definition of hydromorphism. Moreover, Vertisols in
West Africa are also subjected to seasonal waterlogging
(pseudogley) and should come under the realm of hydro-
morphic soils. From the agronomic viewpoint, wherever
excess soil moisture is the most important feature in land
use for crop production, soils in such areas will come
underthe realm of hydromorphicsoils.
An approximate correlation of the hydromorphic soils
among the 3 international soil classification systems has
been prepared at IITA.
A preliminary inventory of some chemical and physical
properties of hydromorphic soils from Nigeria, Sierra
Leone and Liberia may be summarized as follows:

Forest zone (Liberia, Sierra Leone and southern Ni-
geria). Hydromorphic soils occur in coastal, fresh-water
swamps, inland swamps and small river valleys. Some
areas are subject to deep flooding during the rainy sea-
son.
Approximately 80 percent of the hydromorphic soils (ex-
cluding acid sulfate soils in this region) are acidic (pH
below 5.0) and coarse-textured (loamy sand and sandy
loam) with low P and K reserves and low clay activity
(Tables 2 and 3). Such soils would require high fertilizer


inputs and good water control for intensive wetland rice
production. More fertile rice soils in terms of soil-texture
and nutrient status comprise about 15-20 percent of the
37 soils studied (Tables 2 and 3). Wetland areas with
such soils may be developed into productive rice land.
More detailed and systematic soil surveys by national
organizations are needed in order to determine the ex-
tent and distribution of the more fertile wetlands and
their feasibility for rice production.

Table 2. Texture, organic C and pH of 37 hydromorphic
soils from the forest region of West Africa
(southern Nigeria, Sierra Leone and Liberia).

Properties Distribution, %
and range Surface soil Subsurface soil
pH(H20, 1:1)
4.0-5.0 78 73
5.1-5.5 14 22
5.6-6.0 8 5

Organic C, %
0.5-1.5 38 .97
1.6-2.5 24 3
2.6-5.0 30 0
> 5.0 8 0

Clay content, %
0-15 46 19
16-25 19 35
25-35 14 16
35-45 8 16
45-55 5 3
55-65 8 11

Silt content, %
0-10 16 24
11-20 22 24
21-30 16 14
31-40 24 19
41-50 12 14
51-80 10 5
Source of Data: IITA Soil Information Bank, Njala Univer-
sity College and University of Illinois Soil Survey Report
for Sierra Leone (1974), Ministry of Agriculture and
USAID Soil Survey Report for Liberia (1977), Manor River
Union Soil Survey Report, Liberia (1979).

Forest/savanna transition zone (southern Nigeria). Hy-
dromorphic soils in the forest/savanna transition zone
occur mainly in inland valleys and depressions. As the
region is characterized by a rolling topography and
quartzose-rich basement complex rocks, the wetland
valleys or depressions are generally small, and the soil
depths are shallow. All the same, they occupy about 10-
15 percent of the total land surface. Most of the hydro-
morphic land in this region presently is not used for food
crop cultivation.
An extensive study on the soil and land characteristics of
several inland valleys in the region was completed in
1979. In this study, groundwater regime throughout the
year was used as an important criterion for the hydro-
morphic land quality evaluation. N deficiency and Fe tox-
icity associated with groundwater or seepage water were








Table 3. Nutrient status of 37 hydromorphic soils from
the forest region of West Africa (southern Ni-
geria, Sierra Leone and Liberia).

Properties Distribution, %
and range Surface soil Subsurface soil
Exch. Ca, meq/100g
0-0.50 41 59
0.51-2.00 35 22
2.01-4.00 5 5
4.01-8.00 11 8
> 8.00 8 5

Exch. Mg, meq/100g
0-0.50 70 78
0.51-1.50 11 5
1.51-2.50 8 5
2.51-3.50 8 3
> 3.50 3 8

Exch. K, meq/100g
0-0.05 24 65
0.06-0.15 35 22
0.15-0.25 30 14
0.25-0.35 11 0

Extractable P (Bray 1), ppm
0-5 51 89
6-15 35 8
16-25 8 0
25-35 0 3
> 35 5 0
Source of Data: IITA Soil Information Bank, Njala Univer-
sity College and University of Illinois Soil Survey Report
for Sierra Leone (1974); Ministry of Agriculture and
USAID Soil Survey Report for Liberia (1977), Manor River
Soil Survey Report, Liberia (1979).

also stressed. Utilization of these lands at traditional and
improved levels of management for year-round crop pro-
duction using wetland rice as the main season crop was
proposed.
Further inventory of properties of 17 selected soils from
the region are given in Table 4. Again, the predominant
hydromorphic soils in this region are coarse and medium
textured, but their chemical quality is slightly better than
their counterpart in the high-rainfall region in terms of
available Ca, Mg and K in the surface horizons. Available
P status is invariably low although these soils have very
low P fixation capacity.
Savanna zone (central and northern Nigeria). Hydro-
morphic soils in the savanna zone occur in a wide range
of land forms such as inland depressions, river valleys
and ancient and recent flood plains. The sedimentary
plains of the Niger and Kaduna Rivers and their tribu-
taries comprise a significant portion of potential rice
land in central Nigeria, which is yet to be fully developed
and utilized.
The inventory of hydromorphic soils in this region is ex-
ploratory due to lack of soil survey information. A prelim-
inary inventory of soil properties of 10 selected sites in
central Nigeria (excluding Vertisols) is given in Table 4.
Hydromorphic soils at these locations show wide vari-
ability in texture, organic matter and soil reaction. Miner-
alogical studies showed that many hydromorphic soils in


Table 4. Properties of 27 hydromorphic soils from the
savanna zone and the forest/savanna transi-
tion zone of Nigeria.
Surface soil Subsurface soil
Properties Range Mean Range Mean
Forest/savanna transition zone (17 soils)
pH (H20, 1:1) 4.7-6.4 5.6 5.0-6.5 5.8
Organic C, % 0.37-1.96 0.91 0.07-1.36 0.42
Clay, % 4-68 15 3-70 21
Silt, % 4-51 21 5-53 18
Sand,% 13-89 64 10-84 61


Exch. cations, meq/100g
Ca 0.67-12.83 3.48 C
Mg 0.29-7.40 1.53
K 0.03-0.26 0.13
ECEC, meq/100g 1.51-23.60 5.99 1
Bray P1, ppm 2-14 5
Savanna zone (10 soils)
pH (H0O, 1:1) 4.2-6.1 5.3
Organic C, % 0.29-2.70 1.04
Clay, % 6-50 22
Silt, % 8-51 37
Sand.% 4-82 42


Exch. cations, meq/100g
Ca 0.55-7.94
Mg 0.20-3.36
K 0.04-1.92
ECEC, meq/100g 1.73-11.31
Bray, P1, ppm 2-39


C


).47-11.13
0.21-7.89
0.02-0.46
.06-21.26
0.2-4

4.6-7.4
0.07-0.75
5-70
6-55
5-89


0.40-6.84
0.06-3.25
0.04-0.29
).99-10.61
0.4-5


3.34
1.67
0.11
6.14
2

5.7
0.42
28
29
43


3.34
1.30
0.14
6.13
2


this region are montmorillonitic and, thus, of high clay
activity. Hydromorphic soils with more favorable clayey
and silty texture are found in some extensive areas in the
river basins of central Nigeria. But, because of generally
low nutrient status and seasonal flooding, effective water
management and fertilization are required in order to
develop such areas for rice production.
An estimate is being made of the distribution of hydro-
morphic soils of selected areas of West Africa using
LANDSAT imageries and a few large-scale soil maps that
are available. The selected study areas include the
wetland tracts along rivers of West Africa and inland
swamps, such as those in Liberia and Sierra Leone and
the wet sedimentary belts of southern Nigeria. Vertisols
and the vertic subgroups are widely scattered but not
fully documented on a national and regional basis.


Socio-economic analysis

Labor utilization
Literature was reviewed on labor utilization in cassava,
yam, maize and upland rice production. Additionally,
from short regional crop production surveys-prelimi-
nary labor utilization data were derived for cocoyam and
soybean production in Nigeria (Table 5).
In 1980, further progress was made in the collection of
time series data for food crop prices in West African
countries. In addition to food crop prices in Nigeria and
Cameroon, market prices were obtained from Ghana,
Ivory Coast and Togo.








Table 5. Estimated average labor utilization for differ-
ent food crops per operation in Nigeria.
From literature
sources From field surveys
Crop mandays/ha mandays/ha
Up-
Cas- land Coco- Soy-
Operation Maise Yam sava rice yam bean
Land preparation 24 95 40 55 36 35
Planting 10 35 13 30 14 15
Fert. application 15 15 5 12
Weeding 25 70 45 50 38 28
Harvesting 16 60 70 35 60 35
Totals 90 275 168 175 148 125


Agroforestry surveys
An agroforestry field survey was undertaken in southern
Nigeria to identify major types of landuse in traditional
farming systems and establish the degree of integration
between (a) forest and tree crop plantations and small
holder tree crop farming and (b) traditional arable crop
farming and livestock production systems. Economic
woody species, both cultivated and noncultivated, and
their association with traditional arable crop farming
received particular emphasis during the survey. The
6 survey locations-Ezzamgbo, Umudike, Onne, Ikom,
/opmkpa and Uyo-are in the humid tropical zone, ex-
cept Ezzamgbo, which is in the transition from the tropi-
cal wet to the tropical wet-and-dry climatic zone.
Landuse in traditional farming systems. Both traditional
agriculture and rural settlements are largely confined to
uplands with bottomlands seldom used for agriculture.
All farmers in the survey areas have rain-fed upland
farms. Only 23, 13 and 23 percent of the farmers in the
derived savanna, lowland forest and coastal lowlands,
respectively, have additional farms located in bottom-
lands. Permanent compound farm plots, common in the
central zone of the region and in the settlement sites, are
typically located on uplands or well-drained sites. The
most common type of settlement is the dispersed home-
stead type, which is also correlated with the prevalence
of permanent compound farms.
Major types of traditional systems of agriculture and


their landuse. The dominant and most widespread types
of traditional farming systems are permanent compound
farming, rudimentary sedentary agriculture (with or with-
out short fallow periods), bush fallow cultivation and
traditional permanent tree crop farming. Shifting
cultivation hardly exists, and taungya is hardly used in
the region. Livestock is relatively insignificant. The bush
fallow cultivation and the rudimentary sedentary agricul-
ture are the most widespread systems of land use. Per-
manent compound farming is comprised of tree and
arable crop farming enterprises with livestock as a third
and minor activity. Land allocation is essential for home-
steads, and tree and arable crop farming with livestock
is confined to homesteads and villages.
Outside the permanent compound farms, except for re-
tained (wild) economic tree crops such as oil palm,
planted tree crops and arable crop farming are not spa-
tially integrated. Hence, tree crops, once planted, occupy
the land permanently while the arable crops are largely
grown in the traditional bush fallow and/or rudimentary
sedentary agriculture with a land use factor for uplands
C+F
(L = -) ranging from 2.5 to 3.6 (Table 6). Thus, out-


C
side the permanent compound farms and traditional per-

manent tree crop farms, the land use ratio (R = C x

100) in eastern Nigeria is less than 34 percent for uplands
and 51 percent for bottomlands (Table 6).
In terms of land allocation, planted tree crops (including
plantains and bananas) accounted for about 67 percent
of the cultivated land; tree and arable crops mixture for
7 percent; and arable crops for only 25 percent (Table 7).
About 76 percent of the farmers had arable crop farms
under 4 ha, 45 percent of which were under 2 ha. Simi-
larly, about 56 percent of the farmers had tree crop farms
under 4 ha. Tree and arable crop mixtures were largely
confined to farmers with the smallest amount of culti-
vated land.
Cultivated areas devoted to the important tree and arable
crops grown were assessed for each survey location.
Tree and arable crops most frequently grown with con-
siderable acreage, in the order of importance for each
group, were (a) oil palm, cocoa, plantain/banana, kola,
rubber and citrus and (b) cassava, yam, maize and rice.


Table 6. Small holder land use in eastern Nigeria: Type of land cropped and cropping/fallow duration (1980).
Derived Savanna Lowland Forest Coastal Lowland
Ezzamgbo Ikom Umudike Akamkpa Onne Uyo
Bot- Bot- Bot- Bot- Bot- Bot-
Up- tom Up- tom Up- tom Up- tom Up- tom Up- tom .
land land land land land land land land land land land land
Enterprise/Farmer Yr. Yr. Yr. Yr. Yr. Yr. Yr. Yr. Yr. Yr. Yr. Yr.
Cropping year, average 2 1.5 1.8 2.20 1 2.10 1 2 1.3 2.15
Cropping year, range 1-5 1-8 1-3 1-3 1 2-3 1 1-3 2-8 2-3
Fallow year, average 3.2 1.3 5 4.9 1.25 4.9 1.35 4.9 1.3 4.1
Fallow year, range C + F' 2-5 1-3 3-7 5 6 3-7 1-5 2-7 1-8 2-7
Land use factor (L = ) 2.5 1.9 3.6 3.25 2.25 3.33 2.35 3.45 2.08 2.9
Frequency of upland and bottom
lands (% of farmers using) 100 35 100 100 5 100 20 100 50 100 5
'(See Okigbo and Greenland, 1977 for classification)








Table 7. Small holder land use in eastern Nigeria: Land allocation to enterprises per farmer (1979-80).
Derived Savanna Lowland Forest Coastal Lowland Row Total
Enterprise Ezzambgo Ikom Umudike Akamkpa Onne Uyo Av. %
Average No. of plots 4.5 3.7 5.20 4.95 4.45 5.50 4.91
Area under Tree Crops (ha)' 1.34 7.10 15.05 13.79 6.30 11.87 9.24 67.0
Area under Arable Crop (ha)' 3.00 4.43 2.30 2.47 5.00 3.78 3.50 25.0
Area under Tree/Arable
Crop (ha)' 0.12 1.01 0.56 0.81 3.03 0.51 1.01 7.0
Av. total Cult. land (ha)' 4.46 12.54 17.81 17.07 14.33 16.16 13.75
' Fallow periods are often short and contain some cassava resulting in some short fallows being considered as
cultivated plots by farmers. This has tended to put the total cultivated land slightly higher along with the problem of
double counting of same plots due to intercropping and relay cropping.


Small ruminant (goats and sheep) and poultry pro-
duction is common with a general trend of more small
ruminant production in areas of higher demographic
densities where goats are more common and important
in both humid and subhumid zones, while sheep and
poultry are more important in the subhumid (derived sa-
vanna) zone. The number of domestic animals kept by
each family is small.
Resource allocation to enterprises and production con-
traints. Family labor and arable land are the 2 principal
resources. Farmers are dependent on family labor and
only use hired labor during labor peak periods. A crop-
ping calendar of the 13 most important tree and 18 ara-
ble crops showed that upland tree and arable crop
farming, as parallel systems of production, compete for
farm labor during land clearing, preparing and weeding.
It was observed that there is a better utilization of family
labor by having both tree and arable food crops than by
either alone, and the 2 enterprises fulfill both cash and
food needs of the family. The competition for labor be-
tween the tree and arable food crop enterprises could be
reduced, if not eliminated, if both are integrated on the
same land and, when possible, simultaneously operated.
However, the practice of burning the bush in land prep-
aration induces the physical or spatial separation of the
2 enterprises and causes arable crops to be grown in
distant farms away from the homesteads (Table 7).
State of tree and arable crop farming. In general, there
appears to be less expansion of tree crops on new lands.
Any increase, especially in cocoa, kola and citrus, is due
to rehabilitation and an increase in density of tree crops.
Most farmers in the drier savanna and coastal lowlands,
particularly under high-population conditions, thought
tree crop farming to be declining. Major constraints to
tree crop replanting and expansion were credit and lack
of production inputs.
Farmers' view toward farming. Many traditional farmers
themselves view farming as a nonprofitable enterprise
and will abandon it if given other options. Eighty-six per-
cent of the farmers stated that they will continue farming.
Of these, 68 percent stated that they will continue be-
cause they have no other option available to them, 12
percent stated that they have great family responsibility
that requires them to continue farming and 6 percent
stated that they do not wish to buy foods from the mar-
ket. Only 14 percent stated that they will continue farm-
ing because it is profitable. Those wishing to discontinue
farming, especially arable crops farming, often gave old
age as their main reason.


Proposed agroecological regions of the survey area: a
synthesis. A map at a scale of 1:3,000,000 delineating
agroecological regions has been prepared using the data
of this survey (Fig. 10). Climate, geomorphology and
soils, agricultural land use (farming systems), demo-
graphic conditions (density and settlement patterns) and
the interaction of these have been considered in identi-
fying these regions.

Accordingly, 5 major agroecological regions were iden-
tified:

I. Basement complex (cocoa/forest) with 4 sub-
regions.
II. Sandstone and coastal sand complex (oil palm/
root crop) with 5 subregions.
III. Niger delta and coastal swamp complex with 2
subregions.
IV. Upland moist savanna complex with 4 subre-
gions.
V. Mangroves and coastal sand complex.

Region V was not surveyed, for it is considered a non-
agricultural zone. Similarly, region III was not included in
the survey because it is nonzonal in that land use is gov-
erned by the Niger River as the environmental factor.
Only the lower part of Region IV was included in the
survey, the derived savanna part, and this region, often
referred as the middle belt is agriculturally (crop and
livestock) important and is currently experiencing in-
creased agricultural developments with a corresponding
increase in population.
Region I and II are the most important for rain-fed tradi-
tional farming. The major distinction between these is
their difference in geology and soils. In general, soils of
Region I are geologically better soils (mostly Alfisols)
and can support both tree and arable crop farming. The
zone is currently used for cocoa, kola, citrus, etc., and a
great variety of food crops is grown. On the other hand,
Region II has soils that are chemically poor but with
good physical properties (mostly Ultisols) that make till-
age easy. Both soils are erodable and easily degradable
with intensive cropping, particularly soils of Region II
where the situation is already serious.
The agroforestry potentials (alley or strip cropping,
planted fallows or taungya, multi-storey farming and
agro-silvo-pastoral) are higher for Regions I and IV
where such new or improved systems of land use may
not be difficult to adopt. But, the same cannot be said
for Region II.

































Fig. 10. Agro-ecological regions in the humid and sub-humid zones of Nigeria.


, Basement Complex Regions (Cocoa/Forest)
IA Northern sub-humid zone (W. Nigeria)-pop.
high
IBa Central Humid, Sub-humid Uplands-(W. Ni-
geria)-pop. high.
IBb Eastern Humid Uplands (E. Nigeria) base-
ment complex/volcanic-low pop.
IC Southern Humid Lowlands (W. Nigeria)-
basement complex/coluvial, alluvial deposits
-high pop.

II. Sandstone and Coastal Sand (Oilpalm/Root Crops/
Forest Complex)
IIA S.W. Sub-humid lowlands-sandy lowlands
-medium pop.
IIB Lagos and Adjacent Lowlands-sedimentary
sands-high pop.
IlCa Benin Lowlands-Sedimentary sands-me-
dium to low pop.



Land and soil management

Research on land and soil management includes the fol-
lowing areas: land clearing and development, tillage sys-
tems and small tools development and management of
kaolinitic Alfisols and siliceous Ultisols.


Land clearing and development
Hydrological investigations and characterization of soil
physical properties as influenced by methods of land
clearing and post-clearing soil management were con-
tinued in 1980 for cassava planted in the 1979 second
season and harvested toward the end of 1980.


IICb Cross River Basin-sedimentary sands-low
pop.
IID (Coastal) Sedimentary Sandy Plains-(E. Ni-
geria)-high pop.

Ill. Niger Delta and Coastal Swamps
IIIA Middle-Upper Delta-medium to high pop.
IIIB Lower Delta and Coastal Swamps-low pop.

IV. Upland Moist Savanna
IVAa Western Moist Savanna-mostly Basement
Complex, medium-high pop.
IVAb Eastern Moist Savanna (sandstone hills)-
high pop.
IVAc Eastern Moist Savanna-medium pop.
IVB. North Eastern (Guinea) Savanna-Sand-
stone medium to low pop.

V. Mangroves/Coastal Sands



Effect on soil bulk density. Deforestation resulted in a
significant increase in soil bulk density (Table 8), and
there were slight differences in bulk density among var-
ious methods of land clearing. Maize, being an open-row
crop grown immediately after deforestation, increased
soil bulk density (data of 1979), while cassava, being a
close canopy crop, decreased soil bulk density. More-
over, tuber development just beneath the soil surface
may have contributed to decreasing the bulk density of
the layer above the tuber and increasing the bulk density
of the layer below the tubers. Differences in soil bulk
density were'also reflected in the infiltration rate and
penetrometer resistance.
Effect on total water yield. Water yield from the cleared
watershed treatment was 259 mm while the forested

































Fig. 10. Agro-ecological regions in the humid and sub-humid zones of Nigeria.


, Basement Complex Regions (Cocoa/Forest)
IA Northern sub-humid zone (W. Nigeria)-pop.
high
IBa Central Humid, Sub-humid Uplands-(W. Ni-
geria)-pop. high.
IBb Eastern Humid Uplands (E. Nigeria) base-
ment complex/volcanic-low pop.
IC Southern Humid Lowlands (W. Nigeria)-
basement complex/coluvial, alluvial deposits
-high pop.

II. Sandstone and Coastal Sand (Oilpalm/Root Crops/
Forest Complex)
IIA S.W. Sub-humid lowlands-sandy lowlands
-medium pop.
IIB Lagos and Adjacent Lowlands-sedimentary
sands-high pop.
IlCa Benin Lowlands-Sedimentary sands-me-
dium to low pop.



Land and soil management

Research on land and soil management includes the fol-
lowing areas: land clearing and development, tillage sys-
tems and small tools development and management of
kaolinitic Alfisols and siliceous Ultisols.


Land clearing and development
Hydrological investigations and characterization of soil
physical properties as influenced by methods of land
clearing and post-clearing soil management were con-
tinued in 1980 for cassava planted in the 1979 second
season and harvested toward the end of 1980.


IICb Cross River Basin-sedimentary sands-low
pop.
IID (Coastal) Sedimentary Sandy Plains-(E. Ni-
geria)-high pop.

Ill. Niger Delta and Coastal Swamps
IIIA Middle-Upper Delta-medium to high pop.
IIIB Lower Delta and Coastal Swamps-low pop.

IV. Upland Moist Savanna
IVAa Western Moist Savanna-mostly Basement
Complex, medium-high pop.
IVAb Eastern Moist Savanna (sandstone hills)-
high pop.
IVAc Eastern Moist Savanna-medium pop.
IVB. North Eastern (Guinea) Savanna-Sand-
stone medium to low pop.

V. Mangroves/Coastal Sands



Effect on soil bulk density. Deforestation resulted in a
significant increase in soil bulk density (Table 8), and
there were slight differences in bulk density among var-
ious methods of land clearing. Maize, being an open-row
crop grown immediately after deforestation, increased
soil bulk density (data of 1979), while cassava, being a
close canopy crop, decreased soil bulk density. More-
over, tuber development just beneath the soil surface
may have contributed to decreasing the bulk density of
the layer above the tuber and increasing the bulk density
of the layer below the tubers. Differences in soil bulk
density were'also reflected in the infiltration rate and
penetrometer resistance.
Effect on total water yield. Water yield from the cleared
watershed treatment was 259 mm while the forested













I


T!!alment
', :it!onal farming
'.'.inual clearing-no tillage
'..inual clearing-conventional tillage
Srear blade
Tree pusher-no tillage
Tree pusher-conventional tillage
,Mean of 25 replications.
1978 data prior to clearing.


1978' 1979 1980
0.64 1.06 1.07
0.68 1.14 1.05
0.68 1.20 1.29
0.70 1.19 1.37
0.66 1.25 1.37
0.53 1.22 1.32


Effect on surface runoff and erosion. Soil erosion and
.,ter runoff were lower for cassava than maize. More-
S:;.er. there were no significant differences among treat-
rents either for runoff or erosion, except for the tree
pusher-conventional tillage treatment. In spite of the
protective cover of the cassava canopy, this treatment
had 48 mm of water runoff and 4.2 t/ha/annum of soil
erosion (Table 9). In comparison to this, runoff and ero-
sion from the shear blade-no-tillage cassava was 5.0

Table 9. Effects of land clearing methods on surface
runoff and erosion (IITA, 1980)


Treatment
Traditional farming
Manual clearing-no tillage
Manual clearing-conventional tillage
Shear blade-no tillage
Tree ousher-no tillage
Tree pusher-conventional tillage


Run-
off,
mm


Ero-
sion,
t/ha


0
0.001
0.06
0.08
0.04
4.2


mm and 0.08 t/ha. On the contrary, runoff and erosion
from the shear blade-no-tillage maize treatment was 53
mm and 1.9 t/ha/annum, respectively. These results on
the effects of methods of land clearing and post-clearing
soil management have important practical agronomic
implications. It seems that, in the long run, post-clearing
soil management has the most important effect on soil
erosion, runoff and decline of soil physical and chemical
properties. This is not to say that the methods of land
clearing are not important because a combination of
harmful land clearing and post-clearing soil manage-
ment methods, such as land clearing with tree pusher/
root rake followed by conventional plowing and harrow-
ing, results in the most losses in water runoff and soil
erosion and in rapid degradation of soil physical and
chemical properties.


..,,:'-..nt was only 2 mm. Deforestation contributed to a
-.. :nt amount of seepage or ground water flow. The
:-,' ..'.en: stream with only traces of flow during pe-
eavv rains is now a perennial stream with mea-
t. .1 f.ow throughout the year. The maximum surface
S,.vas observed in September; the subsurface flow
:ar was almost equal to surface runoff. Continu-
-.. :. through the dry season also indicates the pos-
: cf sizeable ground water storage that may be
S!!ant at least in analyzing the hydrological balance
c .1 c:eared watershed.

Table 8. Effects of land clearing methods on soil bulk
density in g/cm3 for the 0-5 cm depth (IITA,
1978-80).


Effect on cassava growth and yield. Seedling mortality
was about 50 percent in these treatments because of
shading by trees in the traditionally managed plots and
by maise in the no-tillage plots (Table 10). Since cassava
was planted in no-tillage treatments through 6-8 week-
old maize, row spacing was often more than 1 m (some-
times 1.5 m), which also contributed to a low plant pop-
ulation. Cassava tuber yield varied by a factor of 2-2.5
among treatments with the lowest yield in the tradition-
ally managed plots. Conventional tillage plots were
planted at least 6 weeks later and harvested about a
month after no-tillage plots. Tuber yield in conventional
tillage plots would have been even more if they had been
harvested 2-3 months later. Nevertheless, tuber and stalk
yield from the no-tillage plots were comparable with
those from the plowed and ridged plots.

Table 10. Effects of land clearing methods on cassava
growth and yield (IITA, 1980)
Yield
Plants/ Tubers/ t/ha
Treatment ha ha Tubers Stalks
Traditional farming 4,540 31,570 7.7 14.6
Manual clearing-
no-tillage 5,230 36,640 15.0 22.4
Manual clearing-
conventional-tillage 4,850 36,180 11.7 26.1
Shear blade-
no-tillage 5,420 30,550 14.1 14.6
Tree pusher-
no-tillage 5,800 39,580 20.2 16.8
Tree pusher-
conventional-tillage 12,700 59,940 17.5 23.0


Tillage systems and small tools
development

Effects of tillage methods on maize production. No-
tillage methods with residue mulch have proven useful
for some row crops in kaolinitic Alfisols in the forest
zone of Western Nigeria. However, long-term studies at
IITA have indicated that soil compaction can be a prob-
lem in no-tillage plots within 3-4 years. Moreover, soil
compaction is more severe on mechanized than man-
ually cultivated plots. Crop residue mulch is needed for
many other uses (fodder, building houses and fences,
fuel, etc.) and, therefore, may not be always available in
the quantity required for effective soil and water conser-
vation. Chiseling in the row zone rather than plowing the
entire field, which makes the soil vulnerable to erosion,
may be an alternative to ameliorate the soil of the com-
paction hazard. Plowing at the end of the rainy season
may be another method. With this background, an exper-
iment was carried out at IITA with the following treat-
ments:
A. No-tillage with residue mulch.
B. No-tillage with chiseling in the dry season.
C. Moldboard plowing followed 2 harrowings (residue
plowed in).
D. Disc plowing (residue disced).
E. No-tillage with residue removed.
F. Moldboard plowing at the end of rainy season and
harrowing at planting.


I---- II C-








* G. Moldboard plowing followed by 2 harrowings (res-
idue on the surface).
H. Moldboard plowing followed by 2 harrowings, fol-
lowed by ridging (residue plowed in).
The effects of these treatments were investigated for soil
physical properties and crop response. Preliminary re-
sults indicated that for a sandy loam soil, tillage methods
had no significant effects on grain yield (Tables 11 and
12). However, it will be useful to conduct a similar study
for different soils and ecological conditions to provide
guidelines for appropriate tillage methods.


Table 11. Effects of tillage methods on grain and stover
yield (IITA, 1980 First season).
Grain yield Stover yield Harvest index
Treatment t/ha t/ha %
A 2.52 A 6.3 AB 39.8 A
B 2.00 A 5.2 B 39.8 A
C 2.69 A 7.7 A 35.0 AB
D 2.41 A 6.7 AB 36.0 AB
E 2.14 A 5.9 AB 36.2 AB
F 2.62 A 7.3 AB 36.5 AB
G 2.07 A 7.7 A 27.0 B
H 2.25 A 6.9 AB 33.0 AB
LSD (5%) 0.82 2.1 10.5


Table 12. Effects of tillage methods on grain and stover
yield (IITA, 1980 Second season).
Grain yield Stover yield Harvest index
Treatments t/ha t/ha %
A 2.40 A 4.80 A 51.8 A
B 1.81 A 4.32 A 43.5 A
C 2.00 A 3.65 A 53.3 A
D 2.12 A 3.53 A 60.2 A
E 1.80 A 4.22 A 42.3 A
F 1.81 A 3.58 A 49.9 A
G 1.97 A 4.54 A 43.6 A
H 2.05 A 4.27 A 49.3 A
LSD (5%) 1.01 1.81 17.7


Maize grain yield declined sharply in a field with its
twelfth continuous crop of maize (2 crops per year).
However, the rate of decline was much greater in con-
ventional than in no-tillage plots (Fig. 11). Soil erosion
has been a severe problem for yield decline in conven-
tional-tillage plots while soil compaction has been a se-
vere problem in no-tillage plots.


50
BLOCK 0
o-o NO TILLAGE UNTERRACED
X.- CONVENTIONAL TILLAGE-TERRACED

40



a
30


0
I




S20

to

101





1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR

Fig. 11. Maize grain yield (Cv TZPB) under conventional
and no tillage on a kaolinitic Alfisol cleared from sec-
ondary forest.


" ''" i ':


Maize planted at the same time as the conventionally
tilled maize, it has a good crop stand and compaction
was not severe enough to reduce infiltration.


Poor stand in conventionally tilled maize with water
standing for up to 2 weeks after rain because of com-
paction and low permeability.








E!,ect of tillage methods and mulches on crop produc-
.,on in heavy-textured soils in Zanzibar. In collaboration
:- :e University of Morogoro, Tanzania, tillage studies
7, 'c:ducted in Zanzibar to investigate the effects of
--, s .-cs of seedbed preparation and mulching on crop
%. ,.rI Different treatments investigated were black and
S~f,' colythene mulch, no tillage, ridges and bare flat
,l'.ace Differences in plant growth among different
:tr:ments were attributed to differences in soil temper-
..'.*e and moisture regimes. These soils have high clay
c-!ent and low permeability. High soil moisture content
a-:; :oor aeration were more serious in no-tillage and
-,.rcned lots during periods of frequent and heavy
S.-,. consequently, crops were more chlorotic than in
ccnventional-tillage plots. Effects of different treatments
on rc'n yield indicate that the highest maize yield was
c.tained under white polythene mulch treatments and
-, westt under no-tillage treatments (Table 13). These
c "elences in grain yield were attributed to the number
.' g;rains per row and the unit grain weight. The yields of
cc.uea and soybean also observed a similar trend.


Table 13. Effects of seedbed preparation on soybean
grain yields in Zanzibar.

Grain yield t/ha
Treatment 1979 1980
Lack polythene 0.8 1.1
White polythene 1.5 1.0
No-tillage 0.5 0.4
Ridges 0.6 0.5
Bare 0.8 0.6
LSD (506) 0.4 0.2



Effect of tillage on paddy rice production. In 1976, grain
yields of rice were similar in conventional and non-tillage
methods. Yields were significantly affected only by the
level of N application. The yields were not affected by the
tillage treatments for about 3 years. Since 1979, the plant
height, tillers and grain and straw yield have been less in
conventional-tillage than no-tillage for sandy soils (Table
14). In clayey soil, the differences due to tillage treat-
ments were not pronounced (Table 15). Comparisons of
rice yield in Tables 14 and 15 indicate that an optimum
level of N for rice for a clayey soil is about 60 kg N/ha;
whereas, the effect of N on rice yield in a sandy soil was
not significant. The adverse effect of no-tillage on rice
may be due to many factors, including nutrient imbal-
ance. In a sandy soil, leaching losses of applied fertilizer
on an untilled paddy may be more than in a puddled soil.



Table 14. Effects of tillage methods and N on rice grain
yield (IITA, 1980 First season).

Grain yield t/ha


Fertilizer No Tillage
With 2.50
Without 1.98
LSD (5%)


Conventional
Tillage


Table 15. Effects of tillage methods and N on rice grain
yield (IITA, 1980 Second season).
Grain yield t/ha
N rate Conventional
kg/ha No Tillage Tillage
0 1.99 3.75
30 2.94 4.79
60 3.59 4.54
90 4.02 5.05
LSD (5%) 0.82


Effects of tillage methods and mulches on yam produc-
tion. An experiment was initiated at Onne to investigate
the effects of tillage methods and mulches on yam pro-
duction. Treatments consisted of planting on either the
flat or ridge with and without residue mulch. Observa-
tions were made for soil temperature, moisture and bulk
density and root and shoot growth and tuber yield. Leaf
area was generally more in mulched than unmulched
plots with the least leaf area measured in the unmulched


No-till rice (top) had a poor stand and low yield after 6
consecutive crops compared to good stand and high
yield in conventionally puddled paddy (below).


-=~-









ridged treatment. Table 16 shows that 20 percent more
yam tubers were produced in mulched than unmulched
plots with least tuber yield measured in the unmulched
ridge treatment. The beneficial effects of residue mulch
may partly be attributed to favorable soil temperature
and moisture regimes. Observations on soil moisture
content made 40 and 90 days after planting indicated
that unmulched ridges had the least soil moisture re-
serves.

Table 16. Effects of tillage methods and mulches on
yam production (Onne, 1980).
Ridge Flat Ridge plus Flat plus
no mulch no mulch mulch mulch
Length of
tuber 20.7 20.7 23.5 21.7
cm
Diameter
of tuber 13.3" 13.9a 16.7b 17.lb
cm
Yield 14.1 16.3 19 18.9
t/ha


Effects of soil bulk density on root and shoot growth of
cassava. A root-box study was conducted to investigate
the effects of 3 soil bulk density treatments, 1.4, 1.6 and
1.8 gcm-3, on cassava root and shoot growth. Cassava
was grown in collapsable boxes 48 cm x 46 cm x 100 cm,
with sides that could be removed for monitoring root
growth at different stages. Measurements on root growth
were made for cassava cultivar TMS30572 at 48, 78, 108,
132 and 185 days after planting. Root density, measured
as length and dry weight, was not significantly affected
by the soil bulk density treatments investigated. Neither
were there significant differences in plant height, leaf
area nor shoot dry weight. Cassava can withstand soil
compaction more than grain crops such as maize, cow-
pea or soybean. Nevertheless, the shoot: root ratio was
generally higher at soil bulk density of 1.6 gcm 3 than
other densities (Table 17). The optimum density for the
high feeding: tuberous root ratio was 1.6 gcm-3. These
results imply that effects of soil compaction on cassava
may be highly dependent on soil texture as the latter
affects both the intensity and capacity factors for nu-
trient and water availability.

Effects of tillage methods and mulches on soil temper-
ature regime and its effects on crop production. Ther-
mal diffusivity, the ratio of thermal conductivity and


volumetric heat capacity, generally increases with an in-
crease in soil moisture content up to a certain value. The
exact relationship depends on soil texture. Thermal dif-
fusivity measurements were made for 20 different soils,
and the relationship between soil moisture content and
thermal diffusivity for some soils is shown in Fig. 12. In
general, thermal diffusivity is higher in coarse-textured
sandy soils than heavy-textured clayey soils. The regres-
sion equations between sand, silt and clay on thermal
diffusivity are given in Table 18.


WATER CONTENT, cm3cm3


Fig. 12. Thermal differsivity of various soils as a function
of the water content. Size of glass beads used 50-75 U.




Table 18. Regression equations relating thermal diffu-
sivity, D (cm2 sec-1) to percent sand, silt, clay
or organic matter in a soil sample.
Simple
1. D = 0.0103 0.000148 cl r = 0.788"
Multiple
2. D = 0.01182 01099 x 10-3 r =0.844"
cl 0.1680 x 10-2 cm
3. D = 0.0121 0.3066 x 10-4 r = 0.860"
Si 0.1104 x 10- 3ci 0.1479 x 10-2
Om
4. D = 0.001025 + 0.1104 x 10-3 r = 0.60"
Sa + 0.798 x 10 4 Si 0.1479 x 10-2
Om
Sa = Sand, Si = Silt, Cl = Clay, and Om = Organic
matter.


Table 17. Effects of soil bulk density on cassava's shoot: root ratio and feeding root: tuberous root ratio.
Bulk density Bulk density Bulk density
1.4 1.6 1.8
Root dry wt Root dry wt Root dry wt
Days after Shoot dry wt Tuber dry wt Shoot dry wt Tuber dry wt Shoot dry wt Tuber dry wt
planting Root dry wt x 10 Root dry wt x 10 4 Root dry wt x 10 '
48 134.72 58.89 50.00
77 188.24 84.53 258.89 305.08 126.04 185.90
106 140.13 67.47 128.55 70.40 110.4 98.81
134 150.17 .42.44 267.41 41.90 348.91 12.60
185 401.96 299.79 249.39 537.66 200.01 329.94








A knowledge of the thermal diffusivity is necessary in
predicting the temperature profile of a soil under differ-
ent systems of management. Soil temperature affects
crop growth directly as well as indirectly through its in-
teraction with soil moisture regime and its effects on root
growth, biotic activity and plant nutrients. Soil tempera-
ture measurements at different depths and times can be
cumbersome. With the knowledge of soil thermal prop-
erties, moisture regime and boundary conditions, the
temperature profile of a soil can be predicted with a rea-
sonable degree of accuracy. An attempt was made to
compare the measured soil temperature with that esti-
mated by the Fourier series solution and the Hanks
model. The initial and boundary conditions were mea-
sured for the following treatments: bare flat, flat mulched
with crop residue ( ut/ha, ridged and flat surface cov-
ered with transparent polythene.
Soil temperature measurements were made for maize,
cowpea and soybean. The predicted soil temperature at
20 cm depth under maize and cowpea was within 0.6C
of the measured soil temperature. Soil temperature can
also be predicted from the air temperature (Table 19).
The effect of canopy cover on diurnal fluctuations in soil
temperature at 29 and 37 days after planting for a sunny
and a cloudy day, respectively, is shown in Fig. 13. The
higher temperature under soybean compared to the
lower temperature under maize and cowpea is partly
attributed to poor stand because of a supraoptimal tem-
perature regime during the periods of seedling
g emergence and establishment.
The values of amplitude and phase angle for the first 3
harmonics of the temperature wave for different surface
conditions and crop covers are shown in Table 20. It is


52 .-
48-/ Rodiotion 590gm/Col cm2
44 ... Flat bore
Soybeon (1-96)
40 -i- Cowpea (1-80) X
36 -- Mize (1-41) -
X,
32


24 37 daysofter seeding
20 "--0-


II 8 2 16 20 24
Hour of the day
-- Soybean (0-37) x Radiation = 230
-x- Cowpeo (0-41) ,
-a- Maize (0-47) "





29 days after seeding
. -x-x-x-x-x'


g/Col cm-2


4 8 12 16 20 24

Fig. 13. Diurnal temperature variation at 5-cm depth in
a flat base soil under 3 crop canopies at 2 occasions
following seeding. Numbers in the brackets denote leaf
area index on the day of temperature measurements.


Table 19. Calculated and measured soil temperature in control (bare flat) treatment.
Air-
temperature
at 1-m Soil temperature (oC)
height
Soil (0C)
depth Maxi. Mini. Maximum Minimum Mean
Date (cm) Meas. Calc. Meas. Calc. Meas. Calc. Difference
4.12.80 1 34.3 22.9 44.2 47.8 26.7 26.0 35.4 36.9 1.5
15 35.5 34.2 29.5 30.0 32.5 32.1 0.4
8.12.80 1 35.5 23.2 45.8 49.2 27.2 26.3 36.5 37.7 1.2
15 35.6 34.4 29.6 30.3 32.6 32.3 0.3
Maxi. = maximum; Mini. = minimum; Meas. = Measured; Calc. = Calculated.


Table 20. Total variance (C) of the soil temperatures at various depths under different crops grown on bare flat,
mulched flat or bare ridged soil surface and its percentage accounted for by different harmonics.
Percentage of variance accounted for by the harmonic
Cover Crop-- No Crop Soybean Cowpea Maize
Harmonic Soil --
Number depth (cm) 5 20 35 5 20 35 5 20 35 5 20 35
BARE FLAT
Variance (oC) 115.53 19.90 4.45 140.83 28.75 6.45 19.30 3.49 0.56 18.12 3.20 0.57
1 94.8 95.6 92.6 93.2 96.0 93.3 92.3 94.0 91.1 94.4 95.3 89.5
2 3.8 2.1 4.5 5.3 1.7 4.2 4.4 4.3 5.4 3.2 2.5 7.0
3 0.5 0.7 0.7 0.6 0.8 0.5 1.3 0.3 0.4 0.9 0.9 1.2
Total
1 to 3 99.1 98.4 97.8 99.1 98.5 98.0 98.1 98.6 96.9 98.5 98.7 97.7


I








obvious that 90-95 percent of the variability in soil tem-
perature regime under bare, maize, cowpea and soybean
covers can be explained by the first harmonic while 97-
99 percent of the variability can be explained by the first
3 harmonics (Table 20). In general, the second and third
harmonics represented 1.2-7 percent and 0.1-3.8 percent
of the total variance, respectively. This implies that the
first 2 harmonics alone can explain the diurnal fluctua-
tion in soil temperature up to about a 30 cm depth. The
third harmonic explains about 1 percent of the total var-
iance.

Runoff and erosion under root crops. Table 21 shows
the effects of canopy cover of tropical root crops at dif-
ferent growth stages on runoff and erosion. Cassava, al-
though a closed canopy crop, takes a relatively longer
time to provide a complete ground cover than maize or
cowpea. Staked yams leave the ground surface exposed
to raindrop impact even when the canopy is fully devel-
oped and, therefore, renders the soil more susceptible to
erosion. Sweet potato, with quick and effective ground
cover, is a soil-conserving cover since it results in mini-
mal runoff and erosion compared to cassava and yam
(Table 21). Mixed croppings of maize with cassava, cas-
sava with melon and maize with yam resulted in a signif-
icant decrease in both runoff and erosion. Simultaneous
measurements of canopy cover made at different growth
stages will provide necessary information for computing
"C" values that can be used in the "Universal Soil Loss
Equation" for predictive purposes.



Weed control in no-tillage system
The effect of residue management and tillage on maize
production using chemical weed control was investi-
gated on a 1-year Eupatorium odoratum fallow. (Tables
22a and 22b). Maize yield was significantly lower in the
no-tillage plot than conventional (plow and harrow) and
reduced tillage (disc harrow) plot. Also, significantly
more weeds grew at 4 weeks after planting where the
residue was burnt off than where the residue was re-
tained or raked off. The method of weed control affected
grain yield but not lodging in maize. The maize yield was
significantly lower in the unweeded than weeded plots
(Table 23a). When plots were hand weeded, the crop
yield was identical in the 3 tillage practices. However,
when a preemergence herbicide was used for weed con-


Table 21. Effects of crop cover on runoff and erosion.


Crop cover
Maize with sweet potato
Cassava with melon
Yam with melon
Sweet potato
Maize
Melon
Weed fallow
Yam
Cassava with maize
Cassava


trol, the yield was significantly
than no-tillage plots (Table 23b).


Runoff
(mm)
154
380
314
223
197
303
251
186
457
462


Erosion
(t/ha)
2.2
3.7
4.0
4.4
4.4
6.3
4.4
2.0
9.2
8.0


higher in conventional


Weed control in conventional and no-tillage cassava was
evaluated in an Alfisol in a subhumid climate. The vege-
tation was a 2-year fallow consisting of perennial grass,
Panicum maximum; and broad leaves, Eupatorium odor-
atum, Alchornia laxiflora and Ficus spp. The fallow veg-
etation was first slashed in late February before the onset
of rains, and its regrowth was then sprayed in April with
3.0 kg glyphosate/ha a.i. In the conventional-tillage sec-
tion, the fallow vegetation was plowed under, and the
cassava was planted at 1.0 m x 1.0 m spacing on the flat
after harrowing. In the no-tillage section, the cassava
was planted directly into sprayed regrowth. Cassava


Table 22a. Effect of residue management and tillage
practices on maize yield and crop perfor-
mance (Ikenne, 1980).
Weed Grain
Management Plant Lodging F.W. Yield
practice Ht. cm % g/m2 t/ha
Residue present 81.4 33 a 6.1 2.06 a
Residue removed 81.7 29 a 6.7 2.06 a
Residue burnt 87.9 a' 35 a 12.2 a 1.98 a
Plow and harrow 86.7 a 41 a 8.5 ab 2.12 a
Disc harrow 89.8 a 34 a 11.4 a 2.20 a
No tillage 74.5 22 5.0 b 1.78
SMeans followed by the same letter in the same column
are not significantly different at the 5% level of Duncan's
New Multiple Range Test.


Table 22b. Effect of residue management and tillage practices on maize yield and crop performance (Ikenne, 1980)
Grain
Residue Tillage Plant ht. Lodging Weed F.W. Yield
Management Practice cm. % g/m2 t/ha
Residue present Plow and harrow 83.8 ab' 45 a 5.8 b 2.13 ab
Disc harrow 88.7 ab 31 abc 7.2 b 2.20 ab
No tillage 71.7 c 24 bc 5.2 b 1.84 ab
Residue removed Plow and harrow 87.0 ab 38 ab 8.8 b 2.17 ab
Disc harrow 86.3 ab 32 abc 7.0 b 2.34 a
No tillage 71.9 c 18 c 4.2 b 1.68 b
Residue burnt Plow and harrow 89.3 ab 41 ab 10.8 ab 2.07 ab
Disc harrow 94.3 a 39 ab 20.2 a 2.05 ab
No tillage 79.9 bc 25 bc 5.7 b 1.83 ab
'Means followed by the same letter in the same column are not significantly different at the 5% level of Duncan's New
Multiple Range Test.


---








Table 23a. Effect of tillage and weed control on maize
yield and crop performance (Ikenne, 1980).
Stand
count
(x 103 Lodging Grain yield
Treatment pl/ha) % t/ha
Plow and harrow 25 a' 40 a 1.91 ab
Disc harrow 25 a 37 a 2.06 a
No tillage 18 21 1.81 b
Herbicide 22 33 a 2.03 a
Hand weeding x 2 25 a 34 a 1.99 a
Unweeded check 20 32 a 1.76
'Means followed by the same letter in the same column
are not significantly different at the 5% level of Duncan's
New Multiple Range Test.

Table 23b. Effect of tillage and weed control on maize
yield and crop performance (Ikenne, 1980).
Stand
count Grain
Tillage Weed (x 103 Lodging yield
practice Control pl/ha) % t/ha
Plow and
harrow Herbicide 26 a' 41 a 2.12 a
Handweeding
x 2 27 a 40 a 1.96 abc
Weedy 22 bc 40 a 1.66 c
Disc harrow Herbicide 25 ab 34 a 2.20 a
Handweeding
x 2 27 a 39 a 2.08 ab
Weedy 22 bc 39 a 1.92 abc
No tillage Herbicide 16 e 22 b 1.78 bc
Handweeding
x 2 20 cd 23 b 1.94 abc
Weedy 18 de 19 b 1.71 c
'Means followed by the same letter in the same column
are not significantly different at the 5% level of Duncan's
New Multiple Range Test.

storage root yield was significantly depressed by tillage
(Tables 24a and 24b). However, preemergence herbi-
cides were more effective in conventional than no-tillage
cassava. Crop yield was significantly higher in the hand
weeded than in the chemically weeded plot under no-


tillage. The hand weed plot under no-tillage compared
favorably with the preemergence herbicide treatments
under conventional-tillage. This is an indication that
good cassava yield is possible under no-tillage condi-
tions provided that weeds are controlled. The best weed
control in cassava was obtained when a mixture of me-
tolachlor and fluometuron was used. This yield did not
differ significantly from that of the formulated mixture of
atrazine and metolachlor, which has previously been
shown to be safe for maize/cassava intercrops.


Table 24b. Effect of weed control on weed biomass
and cassava root yield in an Alfisol (IITA,
1980)
Cassava
Weed D. Wt. root yield
Weed control t/ha t/ha
Atrazine plus metolachlor 3.18a' 19.53 b
Fluometuron plus meto-
lachlor 3.88 a 20.89 b
Diuron plus paraquat 3.97 a 19.58 b
Weed free 0 31.79 a
Unweeded check 3.39 a 12.27 c
'Means followed by the same letter in the same column
are not significantly different at the 5% level of Duncan's
New Multiple Range Test.


Small tools development and evaluation
Rolling injection planter. The rolling injection planter
was modified to improve its performance in both the
conventional and no-tillage systems. First, it was pro-
vided with a small metal cover to hold the seed on the
metering wheel to prevent uneven distribution of seed.
This cover holds the seed in the metering wheel until the
seed is just over the opener, and the seed is dropped
almost directly on the ground through the opener (Fig.
14). Previously, the cutoff device on the rolling injection
planter had a tendency to pinch maize seeds in such a
way that the seeds jumped out of the seed hole in the
metering wheel. This happened just as the seed had al-
most completely passed under the cut-off device. Also,
the vibration of the machine had a tendency to shake
seeds out of the metering wheel prematurely. This


Table 24a. Effect of tillage and weed control on weed biomass and cassava root yield in an Alfisol (IITA, 1980).
Treatment Cassava root
Tillage Weed control Weed D. Wt. t/ha yield t/ha
Conventional tillage Atrazine + metolachlor 3.0 kg/ha 1.85 de' 25.08 b
Fluometuron + metolachlor 2.0 + 2.0 kg/ha 1.94 de 28.62 ab
Diuron + paraquat 3.0 kg/ha 2.71 bcd 27.27 b
Weed free 0 e 35.83 a
Unweeded check 2.13 cde 16.43 c
Mean 1.73 26.65
No tillage Atrazine + metolachlor 3.0 kg/ha 4.51 abc 13.98 cd
Fluometuron + metolachlor 2.0 + 2.0 kg/ha 5.81 a 13.17 cd
Diuron + paraquat 3.0 kg/ha 5.24 ab 11.90 cd
Weed free 0 e 27.75 b
Unweeded check 4.65 abc 8.10 d
Mean 4.04 14.98
'Means followed by the same letter in the same column are not significantly different at the 5% level of Duncan's New
Multiple Range Test.






























Fig. 14. Two-view drawing of the metering wheel cover
for the rolling injection planter.

caused increased numbers of seeds in some hills and
none in others. For crops requiring 3 or 4 seeds to be
planted per hill, the small metal plate is not necessary.
The seeds distribute themselves fairly evenly between
*0the hole openers giving good crop stands.
A simple guard was designed that covers the opening
between the opener lever and the injection wheel to pre-
vent trash from passing between. The guard does not
add significantly to the cost or weight of the machine.
Previously, the small pieces of wood left in the field after
clearing fallow were found to catch in the hole opener
lever and wedge between the injector wheel and the han-
dles. This makes the planter almost impossible to push.
The solution to the planter sinking in soft soil was to fit a
wider hole opener lever. This lever is 5 cm wide, adding
3 cm to the width of the previous hole opener lever. The
extra width provides for more contact with the soil, thus,
distributing the weight over a greater area and keeping
the planter from sinking. Finally, the requirement of
planting in the row at other than 250 mm spacing has
partially been solved. Seed rollers were made that give 2
and 3 seeds per revolution of the rolling injection wheel.
This will give seed spacing of 500 mm (3-hole roller) and
750 mm (2-hole roller). A single hole roller could be made
to give 1,500 mm spacing. This development brings a
much wider range of activities for the rolling injection
planter, giving it adaptability to various crops.
In an attempt to increase the rate of planting, different
configurations of planters and fertilizer band applicators
were also designed and tested as follows:
(a) A 2-row rolling injection planter was designed to
increase the field capacity and make a more stable
planter by eliminating the sideways tipping of the
machine.
(b) A 2-row rolling injection planter with a fertilizer
band applicator attached behind it acting as a
press wheel worked very well, but lumpy fertilizer
slows down the planting operation as the lumps
must be broken up before being used.


(c) A single-row rolling injection planter with a fertil-
izer band applicator attached behind it is too heavy
to balance.
(d) A single-row rolling injection planter with a fertil-
izer band applicator attached beside it acting as a
row marker as well as placing basal fertilizer works
very well and eliminates using strings or poles for
marking the rows. This system does not work well
on heavy mulch, which contains a lot of fine
grasses or weeds and hides the fertilizer.
Neither the single-row rolling injection planter with a fer-
tilizer band applicator nor the 2-row rolling injection
planter are able to work on traditionally cleared land that
has stumps left standing more than 15 cm in height. This
is because the amount of deviation from the row to be
able to go around the stump is too great.
The working rates of these machine combinations are
shown in Table 25. Table 26 gives the amount of time to
move row marker stakes when planting or spraying.


Table 25. Rate of work of planter combinations (IITA,
1980).
Machine Man-hr/ha*
Single row rolling injection planter 10
Single row rolling injection planter plus
fertilizer band applicator 13
2-row rolling injection planter 6
2-row rolling injection plus fertilizer band
applicator 9
Single row rolling injection with fertilizer
band applicator row marker 13
*These times to not include time to move row marking
stakes.


Table 26. Time for machine operator to move row
marker stakes per hectare (IITA, 1980).
Width of machine man-hr/ha
0.75 m 5
1.5 m 4
2.0 m* 3
*Estimate.


Guard on opener lever. Planter on right has guard in-
stalled.


18










.7


- -


,-: ',. opener lever. Planter on left has 50 mm wide lever,
.,j; er on right a 25 mm wide lever.


Single-row rolling injection planter with the fertilizer
band applicator attached.


Single-row rolling injection planter with fertilizer band
applicator row marker.


Two-row rolling injection planter.


Two-row rolling injection planter with the fertilizer band
applicator attached.







All machines were designed to either push or pull. Op-
erators generally chose to pull. When conditions made
penetration a problem, it was improved if the planter was
pushed. Other trials were carried out to judge the vari-
ability of the rolling injection planter in stand establish-
ment with no tillage. This variability may be caused by
the amount of mulch cover on the soil or by how well the
seeds are covered. To determine whether the planter was
covering seeds well enough, maize was planted with no
tillage. Ten pairs of rows were selected at random. One
of the pairs of rows was carefully dug up and the seeds
counted, then carefully replaced in their holes and cov-
ered with soil. The next row was left and not counted.
Out of the total number of rows tested, the average stand
count for the seeds dug up was 82 percent. The count
for the rows left alone was only 51 percent. It is clear
from this test that more work is required on seed cover-
ing. It was also noted that the heavier the mulch cover,
the lower the stand count when using the rolling injec-
tion planter. A test to determine the effect of the amount
of mulch cover on the effectiveness of the rolling injec-
tion planter was carried out on small plots with maize
and cowpea, separately, replicated 20 times.
Tables 27 and 28 show that there is a consistent reduc-
tion in stand establishment as the amount of mulch
cover increases for both maize and cowpea. This reduc-
tion in stand as mulch weight increased could be attrib-
uted to greater bird and rodent activity on the heavily
mulched fields and/or shading from the mulch.

Table 27. Percent stand of maize on varying mulch
weight per hectare (IITA, 1980).
Mulch t/ha Stand percent
0 (Control) 74.4'
0 47.4
4 35.2
6 32.4
8 23.2
10 22.1
'The control seeds were planted by hand and well cov-
ered between the rows planted and the rolling injection
planter.

Table 28. Percent stand of cowpeas on varying mulch
weight per hectare (IITA, 1980).


Mulch t/ha


Stand percent


0 (Control) 84.0*
0 84.4
4 59.7
6 52.9
8 51.5
10 41.1
*The control seeds were planted by hand and well cov-
ered between the rows planted by the rolling injection
planter.

In the cowpea plots, no mulch treatments were rotovated
before planting. The control seeds, which were well cov-
ered, had the same germination rate as the seeds planted
with the rolling injection planter. In the maize plots, the
no mulch treatments were not rotovated before planting.
The control seeds had 27 percent more germination than
the seeds planted with the rolling injection planter.


The results on the no mulch treatments for both maize
and cowpea support the conclusion of the earlier test on
covering of seed. When the seeds are well covered, there
is higher germination. During planting, it was noted that
seeds are covered better when planting on soil with con-
ventional than no-tillage. The soil falls back better onto
the seed with conventional than no-tillage. On no-tillage
planting, there is usually a small indentation above the
seed where the opener is inserted. This may allow birds
and rodents to find the seeds more easily and, thus, re-
duce the stand establishment. Further tests will be con-
ducted to determine the causes of lower stands.
The hole openers of the rolling injection planter were
tested to know the maximum speed for pushing before
seeds are left on the ground's surface and the advan-
tages and disadvantages of the different types of hole
openers. Table 29 shows the maximum speed for a
formed hole opener, a wedge hole opener and a split
type hole opener. (Also see Fig. 15.) Both wedge and the
split hole openers had a maximum speed of 3.4 kph while
the formed hole opener had only 2.6 kph. This lower
speed for the formed hole opener was because a small
cup near the end of the opener held the seed after it was
opened causing a delay before the seed was dropped.


m~V


Fig. 15. Side view of different hole openers for the roll-
ing injection planter; left to right, formed, wedge and
split.

Table 29. Performance test of 3 types of hole openers
at different speeds of planting.
% of Seed placement'
Wedge3 Split*
Kph Cup type2 Type Type Remarks
1.69 100 100 100
2.14 100 100 100
2.61 100 100 100
3.00 75.02 97.85 100
3.43 50.07 98.60 97.37 Limiting
4.00 37.42 80.66 83.31 speed
4.29 13.05 15.00 17.00
'Percentage (%) seeds deposited inside the hole.
2Formed hole opener carries the seed out, harder to pen-
etrate the soil; clogged with soil very often.
3Wedge hole opener frequently clogged with soil.
"Split hole opener; split opener squeezes out dirt.

CDA sprayer. A 2 head, hand-carried sprayer, which had
been built previously at IITA, was modified to give more
even flow between the heads. The original sprayer had 1
feed line from the bottle to the cross supporting the
heads. The tube had a T placed in it at the cross support
to feed each of the heads (Fig. 16). The combination of
low pressure in the spray bottle and the resistance to


----


=Y








S--- SPRAY BOTTLE


DELIVERY TUBE


FIRST DESIGN


SECOND DES


Fig. 16. Schematic diagram of delivery tubes
CDA sprayer.


DELIVERY TUBES C
E
u
C,

w


UJ
IGN



o
for 2 head I

0
a-


flow in the 6 mm tubing would at times allow 1 head to
take all the flow, leaving the other with no flow at all.
This would happen normally when 1 head was higher
than the other. This was mostly overcome by having a
separate tube for each head coming from the spray bot-
tle. The sprayer was set up with the spray heads 0.75 m
apart to match the row width when working on standing
maize stubble. This 2 head sprayer was used in conjunc-
tion with the 2-row planter with every other row of maize
stover knocked down. The time required for using the 2
heads was approximately 0.6 of the single head. This
increase in the rate of work would probably justify the
extra expense of the 2 head machine, approximately 1.5
times the price of a single head machine.


Management of Kaolinitic Alfisols
A long-term experiment established at IITA since 1972
shows that fallow remains a vital component in maintain-
ing the soil productivity of the highly erosive kaolinitic
Alfisols on a predominantly rolling topography in the for-
est/savanna transition zone of West Africa. This is, in
part, demonstrated by the alarming decline of some
chemical and physical properties of the soils after 8
years of continuous cropping compared to those under
natural and planted fallow.
Effect on soil chemical and physical properties. Contin-
uous cropping for 8 years with insufficient amounts of


w
CL


Paleustalt
IITA, Ibadan
After years



MAIZE RESIDUE


//

/1/


BUSH FALLOW


5 10 15 2
SOIL DEPTH, cm
Fig. 17. Penetrometer readings of the surface layers of
kaolinitic Alfisols under fallow and after 8 years of con-
tinuous cultivation.

crop residue return resulted in an increase in soil bulk
density and acidity and a decrease in soil organic matter
levels, and, consequently, a reduction in CEC and ex-
changeable Ca and Mg status in the soil (Table 30).
Penetrometer readings of the cropped plots after 8 years
indicated a severe compaction of the surface horizons
compared to the soils under grass and bush fallow (Fig.
17).
Continuous no-tillage maize with crop residue returned
as surface mulch twice a year was able to maintain soil
organic matter (i.e., total N) levels comparable to that of
bush fallow. But, the decline in soil pH, CEC, exchange-
able Ca and Mg levels and the increases in soil bulk
density and penetrometer readings were considerable


Table 30. Properties of surface soil (0-15 cm) under 8-year continuous cultivation and fallow after clearing of
secondary forest (Oxic Paleustalf, Egbeda Series, IITA, 1980).
Bulk density
Total (Fine earth)
pH N ECEC Exch. cations, meg/100g g/cm3
Treatment (H20) % meq/100g Ca Mg K 0-5 cm
Continuous cropping with minimum tillage
Maize, residue returned 5.0 0.18 3.23 2.19 0.41 0.35 1.20
Maize, residue removed 4.7 0.11 1.81 1.13 0.24 0.11 1.31
Maize/Cassava 5.6 0.15 3.40 2.04 0.42 0.32 1.25
Soybean, residue returned 5.0 0.11 3.05 1.65 0.42 0.28 1.23
Natural and planted fallow
Natural regrowth 6.5 0.19 5.14 3.53 0.91 0.41 0.88
Guinea grass 6.7 0.26 7.69 4.75 1.28 0.91 1.01
Pigeon pea 6.0 0.23 3.42 2.18 0.64 0.32 1.10








although to a much lesser extent compared to the no
crop residue plots (Table 30). Moreover, properties of
soils under continuous mulch, no-tillage maize for 8
years were by no means comparable to that under bush
and grass fallow. Planted fallows such as Lucaena with
both leaves and branches returned as surface mulch
compared favorably to that of natural bush fallow;
whereas, results of pigeon pea (bush type) were inferior.
The latter result is mainly due to severe disease problems
that cause the crop to die off after 1 year. Lack of effec-
tive ground cover during or before the reestablishment
of the new crop may have caused the loss of Ca, Mg and
K from the surface soil by eroding and leaching.

Effect on earthworm activity. There was a remarkable
difference in earthworm activity between the fallow and
cultivated plots. Earthworm activity monitored during a
4-day period in July, 1980 (Table 31), showed that the
natural bush fallow plot had a significantly higher Hyper-
iodillus activity (columnar casts) than the 2 planted fal-
low plots (Leucaena and Guinea grass). The extremely
low earthworm activity in the continuously cropped plots
(8.5 years) is apparently due to many factors. Soil com-
paction, continued use of pesticides and herbicides and
the decline in soil organic matter are probably among
the important ones. The results of Eudrillus activity
(granular casts) taken during the same period were less
indicative. Although the difference among the fallow and
cropped plots was not statistically significant, the Eudril-
lus activity under Leucaena was considerably greater
.Jan that under bush and Guinea grass as well as the
cropped plots (Table 31).

Role of crop residue mulch on maize yield under no-
tillage system. Respectable grain yields under a mulch-
no-tillage system on manually cleared land were main-
tained up to 4 years; but yield declined steadily, there-
after, despite adequate fertilization and plant protection
(Fig. 18). The reason for the yield decline is a complex
one. The decline in soil biomass activity due to cultiva-
tion, soil compaction and possible Mn toxicity due to soil
acidification are probably among the more important
growth-limiting factors that cannot be simply remedied
by conventional fertilization. The beneficial effect of crop
residue mulch in the no-tillage maize system is evident,
particularly in areas of ustic soil moisture regime and
frequent incidences of dry spells during the early crop-
ping season. These results suggest that to avoid perma-.
nent degradation of the "superficially" fertile Alfisols in
the forest/savanna transition zone of West Africa, culti-
vated land needs to be returned to an effective fallow or
resting period after 4-5 years of cropping under recom-
mended soil management practices, i.e., the mulch no-
tillage system.


No-Til stoerw Mulhed
* 718.37 .6667X- 110-2X2
R2. 07087O


No-7i. Stoer Removed
S. 6s29 s.S56X-6r-2X2 '
R2.o07599


1972 19 197 197 i7 78 879 o60

Fig. 18. Calculated yield curves of maize for a period of
9 years under no-tillage with and without stover mulch
on a kaolinitic Alfisol.


Mineralization of soil organic matter.
A small-scale, manual, land clearing project (0.25 ha)
was carried out to study the soil organic matter decom-
position and nutrient release after forest clearing. A sec-
ondary objective of the experiment was to demonstrate
whether improved soil and crop management practices
at the small farmer's level could, in fact, increase the
length of the period under cultivation before the land is
returned to bush fallow. The improved practices in-
cluded no burning, no tillage and the use of mulches,
fertilizers, preemergence herbicides, pesticides and an
improved crop variety. Soybeans were planted immedi-
ately after land clearing during the 1979 second season
followed by maize during the 1980 first season. Fertilizer
was not applied to either crop. Excellent growth of both
the soybean and maize was observed, and tissue analysis
indicated no nutrient deficiency. Results of weekly mon-
itoring of NOr-N and NH,-N in the surface (0-10 cm) soil
are given in Figure 19. Substantial amounts of soil or-
ganic N were mineralized during the onset of the rainy
season. These data further suggest that, in spite of risk-
ing a drought stress, early planting of maize is preferred
so that the crop can effectively utilize the high levels of
mineralized N in the soil during the second season, both


Table 31. Earthworm activity in fallow and cropped plots taken during a 4-day period in July, 1980 (IITA).
Hyperiodillus (columnar cast) Eudrillus (granular cast)
Treatment g/250 cm2 No./250 cm2 g/250 cm2 No./250 cm'
Natural bush 10.46 a 12.98 a 0.01 a 7.66 a
Guinea grass 7.83 ab 10.02 ab 0.04 a 3.22 a
Leucaena 3.98 bc 6.85 abc 2.36 a 29.30 a
Maize/Cassava 2.15 c 5.78 abc 0.01 a 8.48 a
Maize + residue 0.60 c 1.79 c 0.02 a 2.35 a
Maize residue 0.004 c 0.02 c 0.00 a 2.67 a









-s




r


NH4 N \ \ |i
Feb Mar Apr.l 1 y June July Ag Sep Oct Nov
MONTHS, 1980


Fig. 19. Seasonal fluctuation of nitrate and ammonium
-N in a newly cleared forest Alfisol (0-10 cm).

the NO,-N and NH,-N content in the soil were low, indi-
cating that a higher rate of N fertilization would be re-
quired for the second maize crop. There were significant
changes in soil organic C, N and P as well as bulk density
1 year after clearing (Table 32). The decline of soil or-
ganic C, N and P is primarily due to mineralization as soil
erosion and surface run-off on this carefully cleared plot
(64 subplots) are minimal. The second season maize,
however, suffered severe streak virus disease.
4 Grain and dry matter yields of soybean and first season
maize are given in Table 33. The grain yield of the first
season maize was considerably lower than would be pre-
dicted from its early growth condition. This is prob-
ably because of the long dry spell during the grain-filling
stage that severely affected the grain yield of the 1980
first season crop without supplementary irrigation.


LSD (5%)


III III


Table 32. Changes in soil properties of a forest Alfisol
1 year after forest clearing (0-10 cm) (IITA,
1979-80).
Property and At clearing After one year #
standard error (1979) (1980)
Bulk Density, g/cm 1.04 0.05 1.22 0.02
OrganicC,% 1.55 0.07 1.24 0.06
Total N, % 0.171 0.007 0.146 0.007
Organic P, ppm 1947 1607
#Crop residues were removed after each harvest.


Table 33. Average grain and dry matter yields of
soybean and maize from 32 subplots (IITA,
1979-80).
Grain Yield Dry Matter
(12% moisture) (Oven Dry)
Crop kg/ha kg/ha
Soybean (TGM 294)
(2nd season, 1979) 17595 4605202#
Maize (TZPB) 2639 183 4709 20"
#Total dry matter yield sampled at maturing stage.
*Stover yield only at harvest.



Continuous fertilization and cropping
The long-term fertility trials initiated in 1972 on an Alfisol
(Egbeda Series, Oxic Paleustalf) and Entisol (Apomu Se-
ries, Psammentic Usthorthent) to investigate the long
term N, P, K, Mg, S and Zn responses of these soils fol-
lowing land clearing were continued in 1980. Maize


LSD (5%)



'''''IT''


N2 P2 K2


N2 P2K
N2 P2Ko


EGBEDA SOIL
(OXIC PALEUSTALF)


N2 P2 KI

N2 P2K2
N2 P2 K0
APOMU SOIL
(PSAMMENTIC USTHORTHENT)


72 4 75 76 77 78


79 86


YEAR


73 73 7 75 76 7 78 79 60


YEAR


Fig. 20. Potassium response of maize grown on Egbeda and Apomu soils in long-term fertility trials at Ibadan,
Nigeria (K-rates; K, = 0; K, = 40 and K, = 80 kg K/ha).


U l-


I I I r I I 1 1 I . .







(main season crop) followed by cowpea (minor season
crop) annual rotation was practiced during the last 6
years. Though P and N responses on the sandy loam
Egbeda soil were observed, respectively, since the first
and third years following land clearing, a significant re-
sponse to K application on the maize crop was not ob-
served until 1980, the ninth year after land clearing (Fig.
20).
The significant response to an annual application of 40
kg K/ha was rather unexpected since the soil K-status
with this treatment at the start of the trial in 1980 was
more than adequate at 0.32 me K/100g soil (Fig. 21). This
may result from an early drought affecting the crop,
which may have less effect on the crop receiving the
higher K application.
On the sandy textured Apomu soil, where significant K
response was observed already in the fourth cropping
year, the main yield response was observed to be consis-
tently higher at 40 kg K/ha than 80 kg K/ha. Though no
definite explanation can be given for this observation, it
may in part be due to the higher acidity build up with the
higher K rate, which could have an indirect negative ef-
fect on the maize crop.


Data on the soil K-status with K application and cropping
showed significant changes on both soil types (Fig. 21).
The soil K-status showed faster depletion with continu-
ous cropping compared to a bare uncultivated treat-
ment, particularly on the Egbeda soil. Annual application
of 80 kg K/ha was able to maintain the soil K-status of the
Egbeda soil at a level comparable to that observed under
bush fallow. However, on the Apomu soil, the K-status
was observed to be lower than that observed under bush
fallow even with an annual application of 80 kg K/ha.
The effect of maize crop residue retention and removal
with and without fertilizer application in this long-term
trial, which initially did not show any particular trend on
the maize grain yield in the last few years began to result
in definite effects (Fig. 22). On the Egbeda soil, removal
of the maize residue, particularly without fertilizer appli-
cation, significantly reduced maize grain yield. On the
Apomu soil, removal of maize residue significantly re-
duced maize grain yield, particularly with fertilizer appli-
cation.
The detrimental effect of continuous removal of maize
*crop residue with continuous fertilizing and cropping
was observed to be more pronounced with the cowpea
crop. In 1980, the cowpea variety used in the experiment
was changed from VITA-4 to VITA-5. VITA-5 gave a lower
yield (Fig. 23) and is apparently more sensitive to Mn
toxicity. With continuous application of NPK fertilizers,
there was a significant soil pH depression with both the
Egbeda and Apomu soils. The lower pH resulted in
higher mobilization and extractable Mn levels, particu-
larly on the Apomu soil, resulting in lower cowpea yields
mainly due to Mn toxicity combined with K deficiency.

Plant residue management


Sr I.. Despite the importance of maintaining adequate soil or-
,E [ ganic matter under the traditional techniques of shifting
EL ..: cultivation or bush-fallowing, the plant residue during
So 1 seedbed preparation is commonly burnt off. The long-
I term effect of this practice compared to plant residue
L management has not been adequately studied. A trial
z was, therefore, initiated on an Alfisol at Ikenne, Nigeria,
S6 EGBEDA SOL to study the effects of burning and mulching of plant
o residue in relation to fertilizer application on the perfor-
o mance of maize. Results of the trials during 1978-80 are
05o q shown in Table 34. Though some responses to N and P
O were observed following land clearing from fallow, sig-
nificant responses to P and N were only observed, re-
0-4 spectively, in the second and third years following
04 = clearing. The main response was to P application.
o03 Though the mean maize grain yields do not show any
significant differences between burning and mulching of
Sthe plant residue during the 3 cropping years, some ef-
0- o fects were observed among the various fertilizer treat-
Sments. Without fertilizer application, PK, NP and NPK
4 s treatments combined with mulching gave a higher maize
0., yield, particularly in the third cropping year. However,
o 40 8s BARE BUSH with the NK treatment, burning gave a higher maize yield,
K-RATE, KG/HA SOIL FALLOW which may be attributed to a quick release of P from
burning of the plant residue.
Fig. 21. Changes In soil potassium status of Egbeda Nitrogen-tillage interaction on maize
(Oxic Paleustalf) and Apomu (Psammentic Usthorthent)gen-tage interaction on maize
soils in long-term fertility trials at Ibadan, Nigeria, with Despite the importance of no-tillage systems in soil con-
K application (K, = 0; K, = 40 and K, = 80 kg K/ha) and servation, little information is available on the best nu-
without cultivation, trient management aspects of the no-tillage system of





























Sg 2I Fi
*. t Lr inal





3.;
-.
:-*

43















-2


EGBEDA SOIL


72 73 74 75


N2 P2 KI R


76 77 78 9
YEAR


APOMU SOIL
No P0 Ko-R


72 73 74 75 76 77 78 7 80
YEAR


f'ect of continuous removal of maize crop residue and fertilizer application on maize grain yield in long-
on Egbeda (Oxic Paleustalf) and Apomu (Psammentic Usthorthent) soils.


LSD (5%)


C


0

0


LSD (5%)

1 I I I '


P2 KI- R

,N2 P2KI- R


N2 P2 K R

N2 P2K1+ R.


EGBEDA SOIL


No Po Ko f* R


APOMU SOIL


76 77 78 79 80
YEAR


76 77 78 79 80
YEAR


F,19 23. Effect of continuous removal of maize crop residue and fertilizer application on grain yield of cowpeas
', onqterm trial on Egbeda (Oxic Paleustalf) and Apomu (Psammentic Usthorthent) soils.


AU- b~~


LSD (5/%)

III


LSD (5%)

III


I -' I


APOMU SOIL


No Po Ko R








Table 34. Effect of plant residue management and fer-
tilizer application on main season grain yield
of maize variety TZPB grown on Alfisol (Oxic
Paleustalf), Ikenne, 1980.
1978 1979 1980
Fertilizer M* B** M B M B
treatment kg/ha
Control 4228 3706 2864 2675 2841 3055
PK 5069 4830 4493 4386 4341 4080
NK 4939 4812 3016 3385 3243 3601
NP 5205 4720 4360 4526 5378 4857
NPK 5327 5275 4454 4448 5289 4936
NPK Mg Zn 5838 5824 4316 4509 4968 4724
Mean 5101 4861 3852 3988 4343 4208
LSD (5%) (1)*" 835 612 567
(II) 822 536 802
(111) 738 764 1263
*M = Plant residue applied as mulch.
"B = Plant residue burnt before each cropping.
**LSD (I) = Between plant residue management
means.
LSD (II) = Between fertilizer treatments within resi-
due management.
LSD (111) = Between any two fertilizer treatments with
different residue management.










LSD (.05)
5-01 -


IKENNE
OXIC PALEUSTALF
1980


maize production. Most of the fertilizer trials carried out
in the tropics have dealt with conventional tillage. Stud-
ies were, therefore, carried out on an Alfisol (Alagba se-
ries, Oxic Paleustalf) at Ikenne and on an Entisol (Apomu
series, Psammentic Usthorthent) at Ogbomosho, Ni-
geria, to determine the N requirements for maize produc-
tion under conventional and no tillage. At both locations,
maize yields from the control plots without N application
were higher with conventional tillage than no tillage. this
was also observed during the first cropping year in 1979
(Fig. 24). However, maize yields with N application, par-
ticularly at high N rates, were higher with no tillage than
conventional tillage.

Planted fallow as an alternative N source
Use of Leucaena prunings. In looking at low cost alter-
natives to N sources, experiments were carried out using
Leucaena leuocephala top prunings. Leucaena not only
can serve as a potential N source but also can supply
fuel wood. In a trial carried out on an Apomu soil series
at IITA, the effects of rate and placement methods of the
Leucaena top prunings were compared to urea. Leu-
caena top prunings were banded or broadcasted once at
maize planting, while urea was banded twice, one-third
N at maize planting and two-thirds N at 4 weeks after
maize planting. Figure 25 shows that banding the Leu-
caena top prunings at 25 cm widths was most effective,
and banding at rates of 5t or 10t was, respectively, 52
and 67 percent as effective as urea. Though the prunings
can be used as an N source, application at planting time
only was apparently not too effective.




LSD (-05)


OGBOMOSHO
PSAMMENTIC
USTORTHENT
1980


-W- 30 6----- -


0 30 60 90 .120 150 0
N-RATE, KG N/HA

Fig. 24. Effect of tillage and N rates on maize grain yield.


30 60 90 120 150


< 4-0-




> 3.0


0:
w
N
2 2-0.




























0 50 o00 5 TONS 10 TONS
N RATE LEUCAENA RATE/HA
KG N/HA

Fig. 25. Effect of N and Leucaena rates and application
methods (A and B Leucaena tops banded at, respec-
tively, 25 and 50 cm width and C Leucaena tops broad-
l casted) on maize grain yield on Apomu soil series
(Psammentic Usthorthent).

In-situ mulch from cover crops and fertilizer levels on
maize yield. In-situ mulch from cover crop residue has
been found to be a feasible method of establishing
mulch for effective no tillage or mulch-conventional till-
age production. Using Mucuna utilis as the cover crop,
the effect of fertilizer and preemergence herbicide on
maize yield in mulch-conventional tillage was evaluated.
The design was a split plot in which main plots were (a)
no herbicide and (b) a basal application of 60 kg N/ha, 60
kg P/ha and 60 kg K/ha with a side dressing of 30 kg N/
ha at 4 weeks after planting; (ii) a basal application of 60
kg P/ha with a side dressing of 30 kg N/ha; (iii) a side
dressing of 30 kg N/ha only and (iv) no fertilizer. The
cover crop was killed with 2.0 kg glyphosate/ha a.i. Side
dressing alone and no fertilizer were found to produce
significantly lower yields than a full application of basal
with a side dressing and a basal application of P with a
side dressing (Table 35). The preemergence herbicide
had no significant effect on yield. The results indicate
that some fertilizer is needed in mulch-conventional till-
age with in-situ mulch from a leguminous cover crop. A
preemergence herbicide is not necessary as weed
suppression by the mulch is an effective weed control
(Table 36).


Nutrient requirement of crops on Alfisols
N and K responses of cassava. The N and K response
Study of cassava conducted on an Alagba series (Oxic
Paleustalf) was initiated in 1978 at Ikenne. The 1979-1980
cropping season results are shown in Table 37. On this
plot, which is in the second cycle of continuous crop-
ping, the fresh tuber yields of both varieties, TMS 30555
and TMS 30572, showed a significant response to K ap-


plication at the rate of 60 kg K/ha. N application only
slightly increased tuber yield. TMS 30572 also gave
higher tuber yield than TMS 30555 at this particular lo-
cation. There is no difference in the percentage dry mat-
ter yield between the 2 varieties.
Differential P response of cowpea and soybean vari-
eties. Investigations were carried out at Ikenne -in the
humid region of Nigeria to determine differences in the
internal and external P requirements of 4 cowpea van-


Table 35. Effect of fertilizer and preemergence herbi-
cide on maize grain yield (IITA, 1980).
kg/ha
Full basal & side dressing with Primextra 3333 a*.
Basal P only and side dressing with Primextra 2970 a b
No fertilizer and No Primextra 2727 b c
Side dressing alone-No Primextra 2545 b c
Full basal & side dressing without Primextra 2303 c
Basal P only & side dressing without
Primextra 2182 cd
No Fertilizer and with Primextra 1727 d
Side Dressing alone with Primextra 1091 e
'Means having common letters are not significantly dif-
ferent at 5% level according to Duncan's Test.


Table 36. Effect of fertilizer and preemergence herbi-
cide on weed weight at maize harvest (IITA,
1980).


kg/ha
'AA


No fertilizer with Primextra 1803 a
Side dressing alone with Primextra 1741 a
Basal P only and side dressing with Primextra 1437 a
Full basal & side dressing-No Primextra 1144 a
Basal P only and side dressing alone-No
Primextra 1112 a
Side dressing alone-No Primextra 1061 a
No fertilizer and without Primextra 1032 a
Full basal & side dressing with Primextra 877 a
*Means having common letters are not significantly dif-
ferent at 5% level according to Duncan's Test.


Table 37. Effect of N and P application on tuber yield
of cassava cultivars TMS 30555 and TMS
30572 on an Alfisol (Oxic Paleustalf), Ikenne,
1980.
Fertilizer Treatment TMS 30555 TMS 30572
kg/ha Tuber yield t/ha
N K Fresh Dry Fresh Dry
0 0 19.52 8.42 19.50 8.02
0 120 21.48 9.42 23.85 9.51
60 120 23.29 9.39 21.14 9.07
120 120 21.35 9.60 25.42 9.95
120 0 18.29 8.47 21.83 9.79
120 60 21.56 9.78 26.92 11.68
Mean 20.92 9.18 23.11 9.67
LSD (5%) Variety means fresh tuber 3.08; dry tuber 1.85.
Between fertilizer treatments within variety:
fresh tuber 3.09; dry tuber 2.11.
Between fertilizer treatments among variety
fresh tuber 4.37; dry tuber 3.74


'








eties with different growing habits. The relationship be-
tween adjusted P concentrations in the soil at planting
time and cowpea yields is shown in Figure 26. The 4
varieties showed distinct differences in their external P
requirement. Without P, a local variety, Shaki, gave the
highest yield and has an external P requirement of about
0.06 ppm P while with P application, TVx 1193-7D, an
improved erect variety, gave the highest yield and has
the lowest external P requirement of about 0.016 ppm p.
Ife Brown and VITA-4 gave the lowest yields, and Ife
Brown has the highest external P requirement of about
0.10 ppm P while VITA-4 has an external P requirement
of about 0.06 ppm P. From these results, it thus appears
that though variety TVx 1193-7D is quite efficient in utiliz-
ing applied P in low P status soil, the local variety Shaki
does better.

The differential phosphate requirements of 2 soybean
varieties, TGM 51 x TGM 344 and TGM 479, were com-
pared in a field experiment conducted on an Alfisol at
Mokwa in the subhumid region of Nigeria. Results of the
trial as shown in Fig. 27 clearly indicate that variety TGM
479 has a significantly lower yield than variety TGM 51
x TGM 344. Despite their differences in yield, both vari-


S1200




8
<~C


Lso (5I)


I


S193 -7D


-' I


IFE
-I I I "ow
TRAL A tKlREN OWN

TRIAL Al IKENN6


I OXIC PALE
I MINOR SE
MAXIMUM
YIELD ^ 1N


EUSTALF
ASON 1980


Abs aSTED P CONCENTR N AT P p '
AOJtSTED P CONCENIRATION AT PLANTING. ppm


eties have similarly low external P requirements of about
.018 ppm P in soil solution. These low external P require-
ments may be attributed to other growth-limiting factors
as indicated by grain yields. In spite of the low yield, data
in Fig. 27 indicate the relatively higher efficiency of P
utilization by variety TGM 51 x TGM 344 over variety
TGM 479.

Management of siliceous Ultisols

Maize-cowpea rotation
A 5-year management trial at Onne shows that a produc-
tive maize-cowpea rotation system is possible on coarse-
textured deep and permeable Ultisols (Typic Paleudult)
on a predominantly flat to gently undulating coastal land
form. Maize was sown in early March and cowpea in late
September or early October. Maximum grain yield
throughout the 5 years ranges from 3.5 to 4.5 t/ha for
maize and from 1.3 to 1.5 t/ha for cowpea.
A well-balanced fertilization scheme is required for the
maize crop, N, P, K, S, Mg and Zn, and fertilization is
generally not needed for cowpea in the second season
as the residual fertility from the maize crop with residue
return as surface mulch is adequate to support the cow-
pea crop. Reduced tillage with residue mulch is recom-
mended because the coarse-textured, kaolin-dominated
soil may be easily compacted.
It is important to point out that the maize, TZPB, and
cowpea cultivars, VITA-1 and VITA-4, tested are fairly tol-
erant to soil acidity. The critical level of exchangeable Al
saturation, i.e., a level required to attain 90 percent of
maximum yield, for the maize cultivar ranges between
30-45 percent depending upon the rate of chemical fer-
tilizer used (Fig. 28). The critical level of Al saturation for


100

S 90
50
60-


Fig. 26. Relationships between adjusted P concentra-
tions and cowpea yield.




LSD (5%) TCM 51 (X)TGM 344

12000 &

oo0-


6 800-
>DO
Soo


S RIAL AT MOIWA


l 0 rcu tMLr
1980


95% OF MAXIMALU
/ YIELD


005 1o


o05 o


10 20 30 40 50 60 70


80 90


EXCH. AL SATURATION.%

Fig. 28. Relative yield of maize as affected by percent
exchangeable Al saturation in the soil.


\ \



50kg K
(1980)
150kg K
(1979)


Maize (IZPB)
Max Yield
398 tlha 1979 Ist season
A456 tlho 1980 ist season


ADJUSTED P CONCENTRATION AT PLANTTNO.P pp

Fig. 27. Relationships between adjusted P concentra-
tions and soybean yield.


'VV 7;-----~ ... r------i








both cowpea cultivars is as high as 60 percent when
chemical fertilizer is not applied in the second season
(Fig. 28). But, with moderate rate of fertilization, the crit-
ical level of Al saturation is reduced considerably, and
the 2 cowpea cultivars show differential response to soil
acidity, i.e., 30 percent for VITA-4 and 43 percent for
VITA-1 (Fig. 29).


100

90- *
SVita -I
80 o\
\o
70- Fertilized
1979, 2nd Season \
Vita-I 1.28 t/ha
60" Vita-4 1-50 tlha Vita-4

50



Vita-4

SVita I
60- No Fertilizer
1980 2nd Season
70- Vita-1 1-48 t/ha
Vita-4 1-36 1/ha
60 a ,


0 10 20 30 40 50 60 70


EXCH. AL SATURATION,%

Fig. 29. Relative yield of cowpea as affected by percent
exchangeable Al saturation in the soil.


Thus, liming is not necessary unless the exchangeable
Al saturation of the soil has reached a level beyond the
critical level of the crop to be grown. The critical level of
exchangeable Al saturation in such coarse-textured, ka-
olinitic Ultisols depends to some extent upon the rate of
fertilizer to be applied. The variability in the critical level
of exchangeable Al saturation is because of the large
increase in soluble Al in the soil solution after fertiliza-
tion. Such effects have not been taken into account be-
cause soil sampling is normally done before planting.
The effect of fertilizer salts on soil solution Al is shown
in Table 38.


Residual effect of lime
Because lime is scarce in many parts of the humid trop-
ics such as southeastern Nigeria, it is necessary to know
what minimum rates of lime are needed for optimum
crop production and what residual values may be ex-
pected. Results from an Onne trial are summarized as
follows:
Relatively low rates of lime would be adequate to sustain
crop yields under a maize/cowpea rotation system. It is
interesting to point out that with balanced fertilization,
respectable levels of maize and cowpea yields were
maintained for 5 years in the unlimed plots (pH 4.3)
where no severe Al toxicity effects were observed. Both
cowpea cultivars nodulated well with indigeneous acid-
tolerant rhizobia, and nodulation was only slightly re-
duced without liming.
Applied Ca in the form of lime leached readily from the
surface layer, which is accompanied by the subsequent
reappearance of exchangeable Al (Table 39). The in-
crease in CEC values due to liming is also short-lived.
The downward movement of Ca has little effect on the
subsoil pH and exchangeable Al, suggesting that Ca
leached in the form of neutral salts. The vertical distri-
bution of exchangeable Ca in the field profile measured
3 years after lime application follows the theory and for-
mulation of ion-exchange chromatography (Fig. 30). This
is in agreement with a previous laboratory leaching study
using undisturbed soil columns. Over 90 percent of the
applied Ca may be found between 0-90 cm depths 3
years after liming because of the strong subsoil acidity
(pH 4.3 and greater than 50 percent Al saturation). Re-
covery of the subsoil Ca, however, would require deep-
rooting species tolerant to high exchangeable Al levels.
Moreover, because a high lime rate in the surface soil
has little effect on the subsoil acidity, there would be no
advantage of applying a rate of lime more than required
to reach the exchangeable Al levels for the crop to be

Table 38. Concentration of Al in soil solution of a Ultisol
(Typic Paleudult) as affected by fertilization
(Onne, 1980).
Al in
Exch. At saturation
Soil pH saturation extract
(H20) % ug/ml
Unfertilized 4.3 60 2.7
Fertilized and incubated
6 weeks at field
capacity 3.9 46 17.1


Table 39. Changes in soil properties in the surface layer (0-15 cm) 5 years after lime application (IITA Onne substa-
tion, 1980).
Initial lime pH (H20) Exch. Ca, meq/100g Exch. Al, meq/100g ECEC, meq/100g
rate (1976)
t/ha. Initial # 5 Yrs. Initial 5 Yrs. Initial 5 Yrs. Initial 5 Yrs.
0 4.7 4.2 0.57 0.27 1.26 1.51 2.77 2.47
0.5 5.0 4.3 1.37 0.31 0.82 1.43 3.08 2.40
1 5.2 4.4 1.58 0.42 0.45 1.27 2.77 2.36
2 5.6 4.5 2.36 0.61 0.06 1.01 3.10 2.28
4 6.3 4.8 5.71 1.03 0.04 0.40 6.53 2.12
initiall soil samples taken one month after lime application.


--


90








EXCH. CA, meqll00g
0 05 1-0 1-5 2.0 2-5
0-15 r-i ---


Initial Lime Rate (1976)
*-* 0 t/ha
o-o 2 tlha
6a- 4 t/ha


EXCH. AL, meql 00g


Fig. 30. Vertical distributions of exchangeable Ca and Al
at 3 years after lime application.


grown. Thus, it is recommended that for Ultisols (Typi
Paleudult) or for Ultisols with similar mineralogy and tex
ture, annual rates of 200-400 kg/ha should suffice t(
maintain maize and cowpea yield. Under such circum
stances, lime could be regarded as a form of fertilizer
rather than a major soil amendment.

Leaching of nitrate under maize.
An experiment was established at Onne in 1980 to study
the pattern of nitrate leaching under field conditions.
Maize was planted in the first season and upland rice in
the second season. Three methods of N application were
used, 1 application at planting, 2 split applications: one-
half at planting and one-half at 4 weeks after planting
and 3 split applications: one-third at planting, one-third
at 4 weeks after planting and one-third at 8 weeks after
planting. A N rate of 150 kg/ha as calcium amonium ni-
trate was used. A bare fallow treatment was included.
The experiment was a split-plot design with 4 replica-
tions. Lime and unlimed treatments were the main plot.
Downward movement of inorganic N (NH,-N and NO,-N)
in the soil was monitored periodically up to a 120 cm
depth (Fig. 31). At the end of 4 weeks (129 mm rainfall),
the pattern of nitrate movement when all N was applied
at planting in the unlimed plots was similar to the bare
fallow and the crop plots. The peak concentration oc-
curred between 30-60 cm. At the end of 8 weeks (477 mm
rainfall), the nitrate peak in the cropped plots occurred
at a depth of 60-90 cm, but the nitrate peak in the bare
fallow plots was considerably deeper and broader, indi-
cating greater leaching. At the end of the first season
(940 mm rainfall), the nitrate peak moved to a depth of
105-120 cm. Liming increased the rate of nitrate leaching
in both bare fallow and cropped plots. When N was split
into 2 applications, nitrate peaks occurred in the upper
layer between 0-30 cm both at 4 and 8 weeks after plant-
ing, indicating less leaching.


Splitting N into 2 applications significantly increased
grain yield and N-uptake by the plant (Table 40), but fur-


NOz-N in Soil,jJg/g


90

105-. 1 O>c
120 Bre Follow, No
Bore Follow, No


0 5 10 15 20 25 O 5 10 15 20 25
C 0

> \ 0 0
I O> '.\ ". .o\


/
0 X

Bare Follow, N,


Maize, N


0 5 10 15 20 25

* 7 Tc


/ t>
0 A \

g/>
0 i
t>
Maize,%N


Fig. 31. Leaching of nitrate in unlimed plots under cropping and bare fallow. (No- no N applied, N,-150 kg N/ha applied
at planting, N,-150 kg N/ha split application, one-half at planting, one-half at 4 weeks after planting.)





j





t











j







I1



ft








I


Estimated fertilizer
N in soil (0-120 cm)
at harvest+ +
kg/ha


70.6
58.9
43.0
55.3
32.9
32.6
59.1


Estimated recovery of
applied N*


47.1
75.5
78.5
92.0
62.5
76.3
100.8


#Lo = unlimed; L = limed, 2t/ha; N rate = 150 kg/ha; N, = one application at planting; N, = 2 splits; N3 3 splits.
+ + Corrected for mineral N (NH,-N and NO,-N) in soil (0-120 cm) from unfertilized bare fallow plot (190.2 kg/ha).
**Crop removal plus estimated fertilizer N in soil (0-120 cm) at harvest.


their splitting into 3 applications had no significant effect
on yield though it reduced leaching loss.
Estimated percentage recovery of applied N is also given
in Table 40. Loss of applied N in the form of calcium
ammonium nitrate under cropping was not as high as
expected although more reliable measurements on N re-
covery can only be obtained with N-15 tagged fertilizers.
When N was applied in 3 split applications, nearly all the
applied N could be accounted for by plant uptake and
the amount present in the soil (0-120 cm) at the end of
I season. At 2 split applications, about 80 percent of the
applied N was recovered in plant and soil.
It is important to point out that the unfertilized bare fal-
low plot contained 60-80 kg/ha of mineralized N (NH.-N
plus N03-N) in the surface 30 cm layer for both the un-
limed and limed treatments, suggesting relatively high
rates of mineralization during the early part of the crop-
ping season. It appears that application of N fertilizer
may not be necessary at the time of planting during the
first season if sufficient mineralized N is already present
in the surface layer.


Lysimeter studies
The installation at IITA of 6 monolith lysimeters (80 cm in
diameter and 130 cm deep) with undisturbed profiles of


Monolith lysimeter cutting and installation at IITA Onne
substation.


the Ultisol (Typic Paleudult) from Onne was completed
in early 1980. The primary objectives are to study leach-
ing of nutrients under high-rainfall conditions and deter-
mine crop water use. The high-rainfall condition, which
prevails at Onne, was simulated during the experimental
period by supplementing natural rainfall with irrigation
using the 1979 rainfall regime at Onne as a basis. Nu-
trient losses over the 2 cropping seasons were deter-
mined by measurements of fertilizer ions in the leachate
collected as samples of the drainage through the profile,
and evaporation/evapotranspiration was assessed by the
water balance method.
Maize was planted as a test crop on 3 of the lysimeters
and in the surrounding area to maintain adequate fetch
while the remaining 3 were left bare. All except 1 of the
lysimeters was tension drained by applying a suction of
0.2 atmosphere at the base of the column. Fertilizers
were applied in each of the 2 seasons to all 6 lysimeters
as follows:
N (Calcium nitrate): 150 kg/ha, 3 split applications
P (Monocalcium phosphate): 60 kg/ha, basal
K (Potassium chloride): 150 kg/ha, basal
MG (Magnesium sulfate): 30 kg/ha, basal
No lime was applied during this preliminary run. As a
result, there was poor growth of maize inside the lysi-
meters due to strong soil acidity. On the basis of the
preliminary results, total drainage through the seasons
averaged 1,153 mm or 58 percent of the total equivalent
rainfall (2,012 mm) received by the bare (uncropped) lys-
imeters and 977 mm or 49 percent of the total equivalent
rainfall received by the cropped lysimeters. The corre-
sponding values of evaporation and evapotranspiration
were 832 mm and 1,035 mm, respectively, averaging 3.70
mm/day and 4.60 mm/day, respectively, over the period.
Preliminary leaching data of nutrient cations and anions
calculated as percentage of total amount applied are
given in Table 41.
These data indicated that nitrate and magnesium ions
leached readily; whereas, potassium ions, were prefer-
entially retained. Further studies are being conducted
under maize and upland rice cropping where adequate
amounts of lime have been applied to ensure normal
crop growth.

K and Mg response of cassava
Investigations on the K and Mg response of cassava va-
rieties TMS 30395 and 30211 were initiated on an Ultisol


Treatment#
LoN, (Bare)
LoN,
LoN,
LoN,
L N,
L N2
L N,


Grain yield
kg/ha


2,492 c
3,208 ab
3,376 ab
2,853 bc
3,499 a
3,717 a


Table 40. Maize grain yield and N recovery as affected by methods of application (IITA Onne substation, 1980).


N removed by crop
(grain + stover)
kg/ha


54.5 d
73.7 bc
82.7 ab
61.4 cd
81.6 ab
92.4 a








Table 41. Percentage of applied cations and anions In
the leachate after 2,012 mm of water under
bare fallow (uncropped, weed free) IITA,
1980).
Tension drained
Free drained (0.2 Atm)
Ions Lysimeter 1 lysimeter 6
%
NO, 78 70
Ca* 35 30
Mg 64 60
K* 9 9


at Onne in 1978. Results of the second year cropping
during the 1979-1980 season are shown in Table 42. In
the second year of cropping, the soil K-status even with
K application was very low. There was a distinct effect of
Mg application in increasing the soil Mg status. The
tuber yields of both varieties showed a more pronounced
and significant response to K application. Despite the
presence of Mg deficiency symptoms without Mg appli-
cations, similar to the first year results, there was no
definite response of tuber yield to Mg application.


Cropping systems

In 1980, research in cropping systems or crop manage-
ment focused on the following areas: mixed cropping,
alley cropping, live mulch system and the role of agro-
forestry in food crop systems. The ultimate goals are to
achieve high and stable crop yields while maintaining
long-range soil productivity. Several projects were initi-
ated to investigate the inclusion of leguminous cover
crops and managed tree and shrubs into food crop pro-
duction systems in an attempt to find more efficient, low-
energy input and stable alternative systems to traditional
bush fallow cultivation. Special emphasis was given to
the production system of plantain in the humid and per-
humid regions.

Intercropping agronomy and
meso/micro-climatic studies
Light regime and productivity in mixed crops. Competi-
tion for light and moisture are clearly 2 key factors in


mixed cropping systems. As a follow up on previous
studies showing or establishing a range of modifications
that may be brought about in the light regime in maize
canopies through modifications of planting geometry
and density (IITA Annual Reports 1978 and 1979),.studies
were carried out in 1980 with the aim of quantifying and
standardizing some of these relationships partly to pro-
vide a basis for optimal design in mixed cropping sys-
tems. Attempts were also made to relate the effects
of the modified light climates within the established
crop (maize) on the lower or slower growing intercrop
(cassava).
Results show that at full development of the maize can-
opy in a maize/cassava mixture, the percentage of inci-
dent radiation depleted at cob height is a power function
of the combined plant population. The relevant equation
is as follows:


Y., = 1.735X0O5'


r = .917"


where Y., is the amount of light intercepted (to cob level),
and X is the combined plant population (Fig. 32A). A
similar relationship was obtained at ground level (Fig.
32B).
As previously reported (IITA Annual Report 1979), plant
populations in this experiment were varied from 10,000
plants/ha in the pure cassava to 80,000 plants/ha in the
maize/cassava mixtures. The maize (TZPB) population
varied from 10,000 to 70,000 plants/ha by increasing the
number of maize plants per stand from 1 to 7. Spacing
was maintained at 1 m x 1 m with the plants along the
same row.
For the lower or slower growing cassava, which was
shaded through much of the growth of the maize, the
crop yields were very significantly affected by the
amount of light reaching it through the maize canopy
(Fig. 33). Again, a similarly linear relationship was ob-
tained between the cassava yield and the total light
transmitted through the combined maize/cassava can-
opy at full maize development (Fig. 34). These amounts
of transmitted light can also be systematically related to
the combined plant population as shown in Fig. 35. The
relationship between the 2 factors is expressed:


Y = 82.198e 10,65x


r = -0.903"


where Y, is the amount of light transmitted through the
canopy, and X is the combined plant population.


Table 42. Effect of K and Mg application on tuber yield of cassava cultivars TMS 30395 and TMS 30211 and K and
Mg status of an Ultisol (Typic Paleudult), Onne, 1980.


Fertilizer Treatment Soil K and Mg
kg/ha status TMS 30395 TMS30211
Me/1l0g Tuber yield t/ha
K Mg K Mg Fresh Dry Fresh Dry
0 40 0.09 0.33 15.84 6.47 14.99 5.66
30 40 0.09 0.27 19.41 8.08 18.67 6.11
60 40 0.11 0.33 19.97 8.84 18.20 6.36
120 40 0.10 0.30 20.13 8.52 19.08 6.73
120 0 0.11 0.22 21.47 9.39 17.33 6.69
120 20 0.11 0.22 19.47 8.06 17.50 5.97
Mean 19.38 8.23 17.63 6.25


LSD (5%) Variety means fresh tuber 0.63; Dry tuber 0.78.
Between fertilizer treatments within variety: fresh tuber 3.48; dry tuber 1.83.
Between fertilizer treatments among variety: fresh tuber 5.29; dry tuber 2.88.

32








Table 41. Percentage of applied cations and anions In
the leachate after 2,012 mm of water under
bare fallow (uncropped, weed free) IITA,
1980).
Tension drained
Free drained (0.2 Atm)
Ions Lysimeter 1 lysimeter 6
%
NO, 78 70
Ca* 35 30
Mg 64 60
K* 9 9


at Onne in 1978. Results of the second year cropping
during the 1979-1980 season are shown in Table 42. In
the second year of cropping, the soil K-status even with
K application was very low. There was a distinct effect of
Mg application in increasing the soil Mg status. The
tuber yields of both varieties showed a more pronounced
and significant response to K application. Despite the
presence of Mg deficiency symptoms without Mg appli-
cations, similar to the first year results, there was no
definite response of tuber yield to Mg application.


Cropping systems

In 1980, research in cropping systems or crop manage-
ment focused on the following areas: mixed cropping,
alley cropping, live mulch system and the role of agro-
forestry in food crop systems. The ultimate goals are to
achieve high and stable crop yields while maintaining
long-range soil productivity. Several projects were initi-
ated to investigate the inclusion of leguminous cover
crops and managed tree and shrubs into food crop pro-
duction systems in an attempt to find more efficient, low-
energy input and stable alternative systems to traditional
bush fallow cultivation. Special emphasis was given to
the production system of plantain in the humid and per-
humid regions.

Intercropping agronomy and
meso/micro-climatic studies
Light regime and productivity in mixed crops. Competi-
tion for light and moisture are clearly 2 key factors in


mixed cropping systems. As a follow up on previous
studies showing or establishing a range of modifications
that may be brought about in the light regime in maize
canopies through modifications of planting geometry
and density (IITA Annual Reports 1978 and 1979),.studies
were carried out in 1980 with the aim of quantifying and
standardizing some of these relationships partly to pro-
vide a basis for optimal design in mixed cropping sys-
tems. Attempts were also made to relate the effects
of the modified light climates within the established
crop (maize) on the lower or slower growing intercrop
(cassava).
Results show that at full development of the maize can-
opy in a maize/cassava mixture, the percentage of inci-
dent radiation depleted at cob height is a power function
of the combined plant population. The relevant equation
is as follows:


Y., = 1.735X0O5'


r = .917"


where Y., is the amount of light intercepted (to cob level),
and X is the combined plant population (Fig. 32A). A
similar relationship was obtained at ground level (Fig.
32B).
As previously reported (IITA Annual Report 1979), plant
populations in this experiment were varied from 10,000
plants/ha in the pure cassava to 80,000 plants/ha in the
maize/cassava mixtures. The maize (TZPB) population
varied from 10,000 to 70,000 plants/ha by increasing the
number of maize plants per stand from 1 to 7. Spacing
was maintained at 1 m x 1 m with the plants along the
same row.
For the lower or slower growing cassava, which was
shaded through much of the growth of the maize, the
crop yields were very significantly affected by the
amount of light reaching it through the maize canopy
(Fig. 33). Again, a similarly linear relationship was ob-
tained between the cassava yield and the total light
transmitted through the combined maize/cassava can-
opy at full maize development (Fig. 34). These amounts
of transmitted light can also be systematically related to
the combined plant population as shown in Fig. 35. The
relationship between the 2 factors is expressed:


Y = 82.198e 10,65x


r = -0.903"


where Y, is the amount of light transmitted through the
canopy, and X is the combined plant population.


Table 42. Effect of K and Mg application on tuber yield of cassava cultivars TMS 30395 and TMS 30211 and K and
Mg status of an Ultisol (Typic Paleudult), Onne, 1980.


Fertilizer Treatment Soil K and Mg
kg/ha status TMS 30395 TMS30211
Me/1l0g Tuber yield t/ha
K Mg K Mg Fresh Dry Fresh Dry
0 40 0.09 0.33 15.84 6.47 14.99 5.66
30 40 0.09 0.27 19.41 8.08 18.67 6.11
60 40 0.11 0.33 19.97 8.84 18.20 6.36
120 40 0.10 0.30 20.13 8.52 19.08 6.73
120 0 0.11 0.22 21.47 9.39 17.33 6.69
120 20 0.11 0.22 19.47 8.06 17.50 5.97
Mean 19.38 8.23 17.63 6.25


LSD (5%) Variety means fresh tuber 0.63; Dry tuber 0.78.
Between fertilizer treatments within variety: fresh tuber 3.48; dry tuber 1.83.
Between fertilizer treatments among variety: fresh tuber 5.29; dry tuber 2.88.

32










































Ch


Y1I735X0851


10 20 30 40 50 60
PLANT POPULATION (in 1000's)


70 80 90


Fig. 32A. Light intercepted by mixed maize/cassava crop
canopy (to cob level) at full maize development (10 wap)
as a function of plant population.









100

Yg 5 5010 622
90


s0


70-


60.


I-50


40


30


20


10-


S 10 20 30 40 50 60
PLANT POPULATION (n 1000's)


Y = 8"846 +t0397X
(r=-889*)


34



30



26

-J
w'
> 22-

U) X

18.



14.



10

10 20 30 40 50 60 80

PERCENT LIGHT TRANSMITTED (%)


Fig. 33. Cassava yield in a maize/cassava mixed crop as
affected by light transmission through the mixed crop
canopy at maximum maize height.


Y 5 694+03617X
(r -0888')


I0 20 30 40 0 60 70
PERCENT LIGHT TRANSMITTED(%)


80 90


Fig. 34. Cassava yield in a maize/cassava mixed crop as
- abo 9b affected by light transmission through the upper maize
canopy at maximum maize height.


Fig. 32B. Light intercepted by mixed maize/cassava crop
canopy (to ground level) a full maize development (10
wap) as a function of plant population.


'~















Y 8219;0 065"X


0 0 ZO 350 40 DO bU TU B IUUo
PLANT POPULATION 0inl000s)

Fig. 35. Light transmission through mixed cassava/
maize crop canopy at full maize development as a func-
tion of plant populations.


Induced micro-climate and crop response. In a related
experiment in 1980, using cassava of relatively prolific
growth, plant populations were maintained constant in
3 treatments at 12.500 plants/ha (cassava: 3001) and
Q 25,000 plants/ha (maize: TZPB). In a fourth treatment, the
maize population was increased to 40,000 plants/ha, and
the cassava population was reduced to 10,000 plants/ha.

Pure cassava with 12,500 plants/ha constituted a sixth
treatment, and pure maize at 25,000 and 50,000 plants/
ha were treatments 5 and 7, respectively.
Analyses of the partial results show that the amount of
light intercepted by the upper canopy of the maize (to
cob level) is significantly related to yield.
Observations on soil moisture and temperature in the
experiment also show marked differences in both vari-
ables under the different crops and crop combinations.
Fig. 36 compares the 6 weekly average mean relative soil
moisture contents under the pure maize, pure cassava
and maize/cassava combinations, respectively. Evi-
dently, the presence of cassava in the mixture has a ben-
eficial effect on the moisture available to the maize while
maize helps reduce the soil temperature as a result of
rapid canopy development (Fig. 37).

Within the mixed crops, appreciable differences were
observed with changes in planting geometry (Table 43).
Similarly, air temperature and humidity as reflected by
the wet bulb thermometer were also affected by the
planting pattern (IITA Annual Report, 1979).



Table 43. Comparative mean relative mixture content*.
Treatment 1 2 4
Period" 1 2 3 1 2 3 1 -2 3
Moisture content 72 67102 94 85123 83 70112
'The moisture content is in % of value at FMC.
"Period 1 = 2-6 WAP; Period 2 = 7-12 WAP; Period 3
= 13-18 WAP.


6100.

z
h
I-.
8 90o.
u

o 80-
IX
.J,
os
W 70.

,-J
ti

Z 60


50


S MAlZE CASSAVA


i \ CASSAVA

S j*MAIZE



\ 0


6 12 18 24
10/0 12/7 2/9 14/10
WEEKS AFTER PLANTING


30 32
25/11 0/1


Fig. 36. Relative soil moisture content in different crop!
crop mixtures as a function of time during the period of
growth.


o MAIZE/CASSAVA
- 4 SOLE MAIZE
SSOLE CASSAVA


0 4 8 12 16 20 28
WEEKS AFTER PLANTING


/ 4 -. x


32 36


Fig. 37. Soil temperature in different crop/crop mixtures
as a crop function of time during the period of growth.


Partial mechanization of maize/cassava intercropping.
Yields of maize planted mechanically on ridges were not
affected by cassava planted on the same ridges at 0, 7,
14 and 21 days after maize (IITA Annual Report, 1979).
Herbicide, however, depressed maize yield significantly
at the 5 percent probability level. The effects on cassava
show that delay of up to 21 days in planting cassava was
not critical to cassava yield (Table 44). However, signifi-


1v1 .. .


"~


lp








Table 44. Effect of relay times and herbicides on cas-
sava yield in maize/cassava intercropping.
Cassava relay Herbicide No Herbicide Mean
in days M/C' C2 M/C C M/C C
0 16.8 7.6 22.6 25.7 19.7 16.6
7 22.4 12.2 22.9 27.0 22.7 19.6
14 16.7 13.9 23.5 22.3 20.1 18.1
21 13.0 9.1 23.1 20.6 18.0 14.8
Mean 13.9 23.5
LSD between herbicide 2.7
Relay time 5.2
Relay time same herbicide 7.3
Relay time different herbicide 7.3
' Maize/cassava
2 Sole cassava


cant cassava yield reduction was observed where herbi-
cide was used. This yield reduction was ascribed not
only to the sensitivity to the herbicide but also to weed
competition resulting from failure of the herbicide. This
observation is substantiated by a tendency toward lower
yields by herbicide treated pure cassava. Shading by
maize appeared to have retarded weed growth, thus,
reducing the competitive effect on cassava. The results
confirm the compatibility of maize/cassava in inter-


cropping and highlight the potential hazard of herbicide
failure.

N response in maize/cassava intercropping. The N re-
sponse of intercropped maize/cassava on an Alagba soil
(Oxic paleustalf) at Ikenne that was initiated during the
1978/1979 season was repeated during the 1979/1980
season. During the second year, the maize crop was af-
fected by drought resulting in low yield (Table 45). De-
spite the low grain yields, the sole and intercropped
maize showed significant responses to N application. As
observed during the first year of cropping, intercropping
with cassava had no effect on maize grain yield. In cas-
sava, high tuber yields were observed with later harvest-
ing (13 months after planting), but no significant
response to N application was observed. This indicates
that the N requirement is lower for the cassava than the
associated maize. High N rates (120 kg N/ha) also tend to
decrease the tuber yield of cassava.

Effect of maize population on cassava yield. An experi-
ment was conducted to determine effects of maize
population on cassava development and yield in
intercropping where maize is planted in hills or clusters.
It simulated farm situations where many seeds are
placed in 1 position, and the number of surviving plants
depends on chance or are deliberately selected by the
farmers. The maize was spaced at 100m x 100 m with


Table 45. Effect of N application on yield of intercropped maize (variety TMS 30395) grown on Alagba soil (Oxic
paleustalf) (1979-80).
Cassava fresh
N-Rate tuber yield Maize grain
kg N/ha Cropping mixture t/ha yield LER*


Maize (1 x .33 m,
1 plant/hill)
Maize (1 x 1 m,
3 plants/hill)
Cassava(1 x 1 m)
Maize (1 x .33 m) + cassava
(1 x 1 m)
Maize (1 x 1 m) + cassava
(1 x 1 m)
Maize (1 x .33 m,
1 plant/hill)
Maize (1 x 1 m,
3 plants/hill)
Cassava(1 x 1 m)
Maize (1 x .33 m) + cassava
(1 x 1 m)
Maize (1 x 1 m) + cassava
(1 x 1 m)
Maize (1 x .33 m,
1 plant/hill)
Maize (1 x 1 m,
c plants/hill)
Cassava(1 x 1 m)
Maize (1 x .33 m) + cassava
(1 x 1 m)
Maize (1 x 1 m) + cassava
(1 x 1 m)


L-U (59%)
Maize crop slightly affected by drought.
Cassava harvested at 13 months.
Land equivalent ratio.


1.90

2.00


30.12

29.11

28.89




30.90

27.10

29.50




28.65

24.85

29.68
3.40


1.95

1.95


2.30

2.40


2.45

2.39

2.28

2.12


2.52

2.10
0.40


2.05

2.03


tPh




--P m


1-7 plants:hill to give 10,000-70.000 plants/ha. Cassava
was planted at 100 m x 100 m in the same rows as maize
but spaced 50 m from the maize along the same row to
give a population of 10,000 plants/ha. The land was
plowed and harrowed but not ridged. The fertilizer rec-
ommendation used was for maize and consisted of a
basal application of N.P.K. 15:15:15 at 400 kg/ha and a
side dressing of 30 kg N/ha as urea 4 weeks after planting
of maize.
The cassava growth was significantly affected by maize
population with tuber yields being significantly lower at
the higher maize populations. The marked differences
between maize populations suggested that maize popu-
lations should not exceed 30,000 plants/ha if good cas-
sava yields are expected. The maize yield indicates no
serious yield reduction of maize population if kept at
30,000 plants/ha. The results also support the practice of
thinning maize to 3 plants/hill in maize/cassava inter-
cropping in West Africa.
Weed control in maize/cowpea intercropping. The effect
of early weed interference in maize/cowpea intercrops is
modulated by the growing season. During the 1980 first
season, a maize/cowpea intercrop was more sensitive to
weed interference than each of the crops grown in pure
culture (Fig. 38.) However, during the 1980 second sea-
son, crop sensitivity to early weed interference peaked in
both the sole and intercrop at 2 weeks after planting.
This may be related to moisture conditions. Weed bio-
m s at the 2-week stage was higher in the second sea-
s ..Ichan the first season, thus, accounting for the more
severe weed interference during the second season.


Alley cropping

Alley cropping systems in forest zone
Effect of N application on maize/Leucaena alley crop-
ping. Results of a field experiment conducted at IITA on
the effect of N application in the maize/Leucaena leuco-
cephala alley cropping system are shown in Fig. 39. Sub-
stantial Leucaena dry matter and N yields are produced
with a total of 6 prunings. The total annual N yield of over
180 kg N/ha was quite remarkable.
During this cropping year, there was a significant effect
of the low N rates applied to the maize on the Leucaena
dry matter and N yields. There was, however, only a slight
effect from the high N rate applied.
The effect of N rates and removal of Leucaena prunings
on maize grain yield is shown in Figure 40. The results
clearly show that despite the high amount of N yield,
there was still a need for application of low N rates for
obtaining high yields. Removal of the Leucaena prunings
reduced the yield to about 54 percent. Without N appli-
cation but with Leucaena prunings only, the total maize


EARLY 1979


--K Sole Maize (40x IO' pit/ha)
--o Sole Cowpeo ( 50 x IO pit/ho)
*--- Maize/Cowpea Intercrop
(30/40xl03 pit/ho)


Pod of Leucaena leucocephala, a tree type legume
being used for soil fertility restoration.


0' _- I
0 2 4 6 8 16 0 2 4 6
WEED INTERFERENCE DURATION (WAP).


Fig. 38. The effect of weed interference on food energy
values of maize/cowpea intercrop.


Collecting leaves from Leucaena leucocephala. The
dried leaves will be used as a source of plant nutrient
and organic matter, the stems as stakes and firewood.


2
r P .,r
:'~n,~EU~ '
~I;
"- r.~ h _~~


-~b~




m


2










ii
ii
4





















I







I
(i
|
s











i










ii


grain yield was maintained at about 3.5 t/ha for the 2
seasons (total yield in 1979 was 3.6 t/ha.) The addition of
the Leucaena prunings has a distinct effect on soil or-
ganic matter and N levels (Table 46.)
Effect of legume species and alley width. Legumes es-
tablished between maize did not reach sizes at which the
quantity of leaves was regarded as sufficient to contrib-
ute significantly to soil nutrient levels. Alley width had no
significant effect on legume development during early
stages. The leaf yield and potential N contributions are
shown in Table 47. The leaf and N yield is related to alley
width.
Because of the low potential N contribution, the plot was
fertilized with 60 kg N/ha, 20 kg P/ha and 30 kg K/ha after
a soil test. The plot was Rome plowed and maize planted
with a single-row rolling injection planter in the 225 cm
alley and with a 4-row rolling injection planter in the
wider alleys. The spacing was 75 cm x 25 cm. The le-
gumes were 75 cm from the nearest maize. Maize yields
calculated with a correction for land devoted to legumes
are shown in Fig. 41. Neither alley width nor legume spe-
cies had a significant effect. It would appear that it is too
early to observe the effects of the different treatments.
Selection and evaluation of woody species for alley
cropping systems. The usefulness of fast growing
woody and herbaceous legumes in alley cropping sys-
tems is being evaluated on the Alfisols at IITA and on the


LSD (5%)

S MAIN SEASON
MINOR SEASON


ON 40+ 80+ ON 40+ 80+
30N 60N 30N 60N


DRY MATTER YIELD


NITROGEN YIELD


Fig. 39. Leucaena dry matter yield and N yield from maize/cassava alley cropping on Apomu soil series (Psammentic
Usthorthent). (Main season N rates: 0, 40 and 80 kg N/ha; minor season N rates: 0, 30 and 60 kg N/ha).


Fig. 40. Effect of N rates on maize grain yield from
maize/Leucaena alley cropping system on Apomu soil
series (Psammentic Usthorthent). (Main season N rates:
0, 40 and 80 kg N/ha; Minor season N rates: 0, 30 and 60
kg N/ha).


250




200



150 N
(.

_1
-j
100 >-

z


50



0


LSD(5%)
L II MAIN
- MINOR


--








Table 46. Some characteristics of Apomu surface (0-15 cm) soil before and after alley cropping.
Treatment* Org. C Total N Extr. P IN Am. Acetate Extr.
kg N/ha pH-H,O (%) (%) (ppm) K Ca. Mg. Na ECEC
me/100g
1976 (Before alley cropping)
6.2 0.98 0.12 24.7 0.25 2.63 1.02 0.06 4.40
End 1980 (with alley cropping)
ON* 5.7 0.96 0.11 19.4 0.16 5.07 0.35
ON 5.7 1.47 0.12 21.5 0.16 5.33 0.43
30N 5.5 1.24 0.13 18.7 0.14 5.72 0.34
60N 5.3 1.41 0.13 22.8 0.18 4.43 0.28
LSD (5%) 0.1 0.67 0.01 3.3 0.07 1.18 0.08
*Major season 1980 N rates 40 and 80 kg N/ha; Minor season 1980 N rates 30 and 60 kg N/ha.
**Leucaena prunings removed from this treatment.


Table 47. Legume leaf yield and potential N yield in
early stages of alley cropping.
Alley width Leaf yield N yield
Legume cm kg/ha dry wt. kg/ha
Pigeon pea 225 1321 47.6
375 793 28.6
675 440 15.9
Leucaena 225 1084 45.5
375 651 27.3
675 361 15.2
Tephrosia 225 600 22.8
375 360 13.0
675 200 7.6


I

-J
q 320


!N 20-
2


(2) Fast growing pulp, fuelwood and/or soil ameliorat-
ing species, such as Cordia alliodora, Albizia fal-
cataria, Cassia siamea, Sesbenia grandiflora,
Flemingia congesta, Samanea saman and Gmelina
arborea.
(3) Important multipurpose trees and shrubs, such as
Treculia africana, Irvingia gabonensis, Dacryodes
edulis, Pterocarpus spp., Chrysophyllum albidum,
Afzelia spp. Blighia sapida and Parkia clapperton-
iana.


Tephrosio Condida
Cojonus Cojan
Leucaeno Leucocephala
Glircidla Sepium

2 25 (m) alley width
375(m)
6-75(m)


T C L G

Fig. 41. Effect of shrub legume species and alley widths
on maize grain yield.

strongly acidic Ultisols at Onne. Emphasis is given to
those species that are established easily and can be
maintained through basal sprouts and coppices when
cut back periodically. The screening and evaluation in-
cludes more than 30 woody specimens as listed below:
(1) Planted and/or retained woody fallow species,
such as Acioa barteri, Anthonatha macrophylla, Al-
chornea cordifolia, Dalium guineense, Gliricidia
sepium, Leucaena leucocephala and Tephrosia Acioa baterii, one of the shrubs being tested for im-
candida. proved bush fallow.

38

I


I'~ly~d





I




I









ii

I


5-00

4-00


IBADAN IITA
ONNE


_ ISESBENIA GRANOIFLORA

t ALCHORNEA CORDIFOLIA
,'


_(LEUCAENA
-A'


bJ _j Z W
_1 0D LL < C)


I' /
/

SALBIZIA FALCATARIA
SrGMELANIA ARBOREA


0 1 2 3
DISTANCE FROM TREE ROWS (m)
Fig. 43. Light transmission through the canopies of es-
tablished fallow/alley cropping species in relation to
distance from tree rows (trees in 4 m-rows, E-W; OBS in
November).


Fig. 42b. Relative growth performance of selected tree-
shrub species at IITA and Onne after 18 months of es-
tablishment.

Figure 43 shows that Albizia falcataria and Gmelanai ar-
borea planted in 4 m rows are clearly incompatible with
alley cropping once they are fully established because of
their strong depletion of incident light. They could be
maintained possibly only as planted fallow.
Crops planted at less than 2 m from established Alchor-
nea cordifolia will also suffer severely from shading. Rea-
sonable performance can only be expected at distances
of at least 3 m from the tree rows. This is also true of
Leucaenea leucocephala. The distance from Sesbania
grandiflora can be reduced to 2 m and even 1 m for crops
with a fair degree of shade tolerance. In general, for all
the species, except the latter, cutting back after the first


Alchornea cordifola is an important native bush of West
Africa, associated in natural bush fallow for soil fertility
restoration.

The results of the first 2 years of screening and evalua-
tion indicate that, in general, the establishment and
growth performance of the shrub species were better at
IITA while the tree species were better at Onne (Figs. 42
a & b). Some of the shrub species that performed well
are being included in the alley cropping trials.
Light regimes in potential tree-shrub species for alley
cropping. Competition for light remains a key factor in
the suitability of different species in mixed stands. Tests
were made to determine the light characteristics within
alleys of different tree-shrub species established over the
past 2 years. The tree rows are oriented roughly east-
west.


__


5-00-
IBADAN IITA
O4-00- L ONNE
E
I- 300-


I


0*00

S2-00-
U- 0 > > <
1 n.- rr [ 0




Fig. 42a. Relative growth performance of selected tree
species at IITA and Onne after 18 months of establish-
ment.









year of growth may be the only practical way of using
them for alley cropping.
Establishing leguminous trees or shrubs for alley crop-
ping in the derived savanna.. Establishment and early
maintenance costs appear to be major deterrents in the
use of leguminous trees or shrubs for nutrient recycling
in alley cropping. To overcome these problems, the le-
gumes are being established by interplanting through
maize. A trial evaluating the potential of this method in
the derived savanna was initiated in 1980. In the inter-
planting, the legumes are spaced at 400 cm x 50 cm and
the maize at 100 cm x 100 cm with 3 plants/hill. Seeds
were used for Tephrosia candida, Cajanus cajan and
Leucaena leucocephala and cuttings for Gliricidia.
Because of adverse rainfall during the first season, maize
yields were lower than expected (Fig. 44). The legumes
had no significant effect on maize yield, and the maize
had no significant effect on legume yield; legumes
planted without maize were the same size as those
planted with maize.


2'0-

--

o

-a

a

0)
N
'0


Pure Moize
Maize- Pigeon peo
Moize Leucoeno
Moize Tephrosio
Maize Gliricidia


Fig. 44. Effect of shrub legumes on single maize crop.


Establishment of Tephrosia was very poor while that of
the other legumes was good. Growth of both Leucaena
and Gliricidia was poor even though adequate weed con-
trol was practised during the intercropping phase. By
November (6 months after sowing), these 2 legumes
were growing slowly with no marked effect on the adja-
cent vegetation. On the other hand, Cajanus cajan grew
vigorously and by November dominated the field. A well
developed canopy shaded out weeds preventing many
from flowering (Fig. 45). A closer between row spacing
(about 300 cm) could produce better weed control al-
though a closer spacing may hamper tractor drawn im-
plements.
The slow growth of Leucaena and Gliricidia suggests
that these legumes may require more than 1 growing
season to significantly affect field ecology. Vigorous
growing Cajanus cajan interplanted with maize in the


Twenty-month-old Albizia falcataria. Among the fastest
growing trees in the world, they are suitable agro-for-
estry species in the humid lowland tropics for control of


oo0 200
Ol,0onc. (Icm)i tfm pon o0* row


Fig. 45. Pigeon pea canopy structure and weed distri-


Imperata cylinderica grass as well as for site frtility bution in 4 m alley, 3 months after maize harvest,
improvement and in the derived savanna as a planted (malze/pigeon pea ,pure pigeon pea -,I
fallow species. _J -.


40








early rair could provide an effective green ground cover,
less prone to fire hazard, in the savanna regions. The
plants can be eradicated mechanically with the residue
providing mulch suitable for no-tillage cropping. The po-
tential contribution of N to the soil and protein for human
and animal consumption are other factors that warrant
further investigation of Cajanus cajan in savanna crop-
ping systems.

On-farm trials-Leucaena-maize
systems
The main objectives of the long-term, alley cropping
farm trials that began in 1980 are as follows: (1) to iden-
tify and enlist the cooperation of a set of participating
farmers, representing a range of farming systems and
farmer types involved in the production of yam and
maize in Nigeria: (2) to instruct the farmers on the agron-
omy of the prototypical Leucaena-maize-yam alley crop-
ping system; and (3) to see to the establishment of the
Leucaena hedgerows as an understory intercrop with
first season maize in preparation for use as live in situ
yam vine staking next year.
Trials were established on 9 plots at 6 different locations
across the yam belt of Nigeria (Fig. 46). Periodic visits
were made to each site to provide basic guidance and
monitor progress. In all cases, the farmers were encour-
aged to feel free to modify the system to fit their needs.
l Information on such modifications provides for a better
understanding of the working principles of appropriate
alley cropping systems for smallholder conditions.


Fig. 46. Map of Nigeria showing ecological zones and
sites of the Leucaena-maize-yam alley cropping system.
Farm trials in 1980. 1. Lagbe 2. Ijaye 3. Osara 4. Tawari
5. Yandev 6. Zaki Biam.

First year trials have yielded a number of preliminary
findings. Leucaena has been found to be a very hardy
plant that established well even under extremely adverse
conditions. A severe first season drought caused failure
of the maize intercrop in most sites, but Leucaena
growth continued at moderate levels. In order to cope
With the economic effects of the drought, farmers at-
tempted to substitute other intercrops such as cowpea


and sorghum. Heavy shading under cowpea retarded
Leucaena growth somewhat but from the standpoint of
risk-aversive small farmers, suboptimal establishment
growth of Leucaena appears to be a small price to pay
for steps taken to obtain an economic yield from their
fields in a bad year.
Where mechanized yam culture is likely to be an attrac-
tive way to reduce the labor costs of yam production, the
trials indicate that a 4 m between-row spacing for Leu-
caena may be more suitable than the experimental 2 m
spacing. Wider spacing may also be preferred where
farming traditions favor multiple vine support by fewer
stakes such as in the "tent staking" system of Tawari,
Nigeria. While allowing for such modifications, it seems
advisable to maintain a sufficient population of Leu-
caena to provide adequate mulch material, firewood and
other by-products to maximize overall returns. Where
firewood scarcity is a problem, the wood yield may be a
significant component of the net economic return from
the alley cropping system. The possibility of a double
Leucaena row in the 4 m spacings should be investi-
gated.
One potential variant, which aroused considerable inter-
est among farmers for whom the labor costs of weeding
are a major farm management constraint, is the use of
Leucaena shade to control Imperata cylindrica and other
heliophytic weeds. Although this use of alley cropping
has yet to receive systematic attention, a possibility
might be to rotate a 1 or 2 year closed-canopy fallow
through a large field set up for alley cropping. If, for
example, the field were divided into 4 sections, three-
fourths could be in alley crop production in any given
year with the remaining one-fourth in rotating fallow. Re-
search is needed to evaluate the actual weed control
potential of this alley cropping modification, but farmers
indicate any innovation that minimized the herbicide
need would be a major step toward making no tillage
and mulch farming techniques more widely acceptable.

Linear programming model of Leucaenal
rice alley cropping system
A linear programming model was developed to evaluate
the economic attractiveness of an experimental Leu-
caena/-rice alley cropping system under West African
smallholder conditions. Using production data represen-
tative of upland family rice farms in Sierra Leona and N
response data from the Rokupr Rice Research Station in
Sierra Leone, the model was used to explore the relative
profitability of various rice growing activities at 0, 20, 40,
60, 80 and 100 kg N/ha from 3 different sources: urea;
ammonium sulphate and in situ Leucaena hedgerows.
The main results indicate that under the conditions of
smallholder production in the model, it is consistently
more profitable to grow rice with N from Leucaena
hedgerows than from either of the 2 mineral N sources.
Furthermore, with labor as the limiting production factor,
the 2 components of the Leucaena/rice alley cropping
system always combine in the same economically opti-
mal proportions of 0.37 ha (3,700 linear meters) of Leu-
caena hedgerow to 1.28 ha for rice, grown in the alleys
between the hedgerows, for an optimum field size of 1.65
ha.
In order for rice production with urea or ammonium sul-
phate to become competitive with Leucaena-based rice


I- -








production, subsidy levels of 97 and 99 percent, respec-
tively, would be required.
The results of this modeling exercise must be regarded
as provisional until validated by field trials, but the ap-
parent economic attractiveness of the hypothetical Leu-
caena/rice alley cropping system would seem to justify
the research attention of agronomists.

Live mulch systems
Live mulch crop production involves planting a food
crop directly into a living cover of an established cover
crop without tillage or destruction of the fallow vegeta-
tion. This incorporates the soil conservation features of
organic mulch and no tillage and has the advantage of
smothering weeds and contributing N in the case of a
legum live mulch.
Weed competition, tillage and ground cover. Observa-
tions in 1980 showed marked differences in weed bio-
mass due to the weed control method and ground cover
type in maize. Although the field dry weight of maize
stover used as ground cover averaged 10 t/ha, this was
not enough to completely eliminate weed growth. Weed
biomass was identical in the unweeded check of the con-
ventional and no-tillage plots, and these were signifi-
cantly higher than in the unweeded check of the live
mulch plots (Table 48).


Table 48. Effect of weeding frequency and ground
cover on weed competition and maize (TZE
4) yield (IITA, 1980 First season).
Grain
Weed Weed D. wt. yield'
Ground cover control (t/ha) (t/ha)
Conventional Weed free 0 c 1.54 cde
tillage Weed x 2 0.8 b 1.65 cde
Unweeded
check 1.49 a 1.05 e
No tillage Weed free 0 c 2.57 a
Weed x 2 0.83 b 2.43 ab
Unweeded
check 1.4 a 1.84 bcd
Maize stover Weed free 0 c 2.27 ab
Weed x 2 0.91 b 2.39 ab
Unweeded
check 1.31 a 1.56 cde
Arachis repens Weed free 0 c 1.36 de
Weed x 2 0.27 c 1.52 cde
Unweeded
check 0.31 c 1.32 de
Psophocarpus Weed free 0 c 2.63 a
palustris Weed x 2 0.05 c 2.50 a
Unweeded
check 0.11 c 2.14 abc
Average stand concent of 50.27 x 10 pl/ha.
'Means followed by the same letter in the same column
are not significantly different at the 5% level of the New
Duncan's Multiple Range Test.

The unweeded check, live mulch plots had fewer weeds
at harvest than in each of the conventional and no-tillage
and maize stover plots that were weeded twice. Uncon-
trolled weed growth significantly reduced the maize
grain yield in the conventional and no-tillage and maize


stover plots but not in the live mulch plots. These results
confirm the finding of last year that live mulch crop pro-
duction has potential for minimizing the need to control
weeds in maize. The highest maize yield was observed in
a live mulch plot in which Psophocarpus palustris was
maintained.
High maize yields in this live mulch cover were not re-
lated to weeding treatment. On the other hand, compa-
rable yields were obtained in no-tillage and maize stover
plots that were weeded at least twice. Yield in the con-
ventional-tillage plots was significantly reduced even
when the plot was kept weed free.
Ground cover and N fertilization. The effect of ground
cover on the N fertilizer requirement of maize was inves-
tigated. All plots received a blanket application of 30 kg
PO, and K20/ha. Maize responded to varying levels of N
fertilizer applied in the conventional and no-tillage and
maize stover plots but not in the live mulch plot in which
Psophocarpus palustris was the ground cover (Table 49).

Table 49. Effect of N fertilizer level and ground cover
on maize (TZE 4) yield (IITA, 1980 First sea-
son).
N-fertilizer Grain yield
Ground cover (kg/ha) (t/ha)
Conventional 0 1.24 d'
60 1.49 cd
120 1.51 cd
No-tillage 0 1.63 cd
60 2.70 a
120 2.51 ab
Maize stover 0 1.74 cd
60 1.98 bc
120 2.49 ab
Arachis repens 0 1.09 d
60 1.72 cd
120 1.45 cd
Psophocarpus 0 2.47 ab
palustris 60 2.39 ab
120 2.41 ab
Average stand count of 50.6 x 103/p/ha
'Means followed by the same letter in the same column
are not significantly different at the 5% level of the New
Duncan's Multiple Range Test.


Typical live mulch stand in one of the field experiments
in 1980.


-IJ1








Without N fertilizer, the maize yield was twice as high in
the live mulch plot in which Psophocarpus palustris was
the ground cover as in the conventional-tillage plot.
Maize yield in the no-tillage and maize stover plots with-
out N fertilizer was as low as in the conventional-tillage
plot. The advantage of no-tillage over conventional till-
age under continuous cultivation is demonstrated only
when N fertilizer was applied. Without N fertilizer, the
maize yield was as poor in the no-tillage plot as in either
the conventional-tillage or maize stover plots. Results of
this study show that the best live mulch treatment elimi-
nated the need for a fertilizer application, and the N con-
tributed by the legume cover in the live mulch maize was
comparable to the 60 kg N/ha in the no-tillage maize.
The study of the live mulch production of maize shows
that (a) continuous maize production is possible under
the live mulch system without a bush fallow, (b) weed
pressure can be minimized, and (c) the requirement for
N fertilizer can be minimized or eliminated. These find-
ings have far reaching implications among small-holder
farmers who can neither afford the labor for weeding nor
the chemicals for fertilizing. Live mulch is an attractive
crop production practice that provides complete, year-
round ground cover, thus minimizing soil erosion and
soil structure loss.

Weed biology and herbicide
research

Biology of tropical weeds
Little is known about the biology of weeds in relation to
their control in tropical agriculture. Some aspects of
weed research focus on reasons for crop yield reduc-
tions caused by weeds. Allelopathy and other factors of
weed interference have been investigated in selected
tropical crops to develop effective weed control strate-
gies.
Allelopathy weeds vs. yams. Since previous observa-
tions have shown that yam (D. rotundata) is sensitive to
weed interference, studies were carried out from 1978 to
1980 to assess the nature and extent of this sensitivity. A
new method was designed and tested for assessing alle-
lopathy in root and tuber crops closely simulating field
conditions. Results of these studies show that full weed
interference caused a 75 percent reduction in yam tuber


yield (Table 50). When weed interference was limited to
the above ground vegetative parts of both weeds and
crops, only a slight yield reduction was observed; but
when the leachete from the roots of weeds was allowed
to come in contact with the soil in which the yam grew,
yam tuber yield was significantly reduced. This yield re-
duction caused by allelopathy was consistent for the 3
years in which this study was carried out.
When moisture was not limiting and plants received a
basal fertilizer treatment (30 kg N, P2Os and KO/ha), the
major reasons for the yield reduction caused by weeds
were allelopathy and other soil related factors. Each of
these 2 weed interference factors accounted for over 30
percent of the total loss caused by weeds (Fig. 47). Keep-
ing crops weed-free appears to be the only way to mini-
mize the yield reduction caused by weeds.
Weed interference studies. A study showed that a sig-
nificant decline in leaf area index (LAI) and tuber yield of
white yam occurred due to weed inference from 8 to
about 16 or more weeks after planting in tubers planted
at the onset of rains (Table 51).


E
I 60.



S40.



20-


A = ABOVE GROUND INTERFERENCE
B = ALLELOPATHY
C = NUTRIENT/ MOISTURE () INTERFERENCE


A B C
A B C


Fig. 47. Weed interference in yam.


Table 50. Mean fresh tuber yield and yield losses of white yam grown in wooden boxes as affected by mode of
weed interference (1978-80)


Mode of weed
interference


Fresh tuber yield


1978


1979


1980


kg/std %
Interference by aerial
factors 1.83 ab' 0.72 ab 2.48 a 16.44 20.88 11.70
Interference by allelo-
Pathy + aerial factors 1.26 bc 0.58 b 1.38 b 42.47 36.26 37.80
Full interference 0.53 c 0.22 c 0.47 c 75.80 75.82 78.80
Weed-free check +
polythene 2.19 ab 0.91 a 2.22 a 0.00 0.00 0.00
Weed-free check -
yenesheet 2.52 a 15.07
Means followed by the same letter in the same column are not significantly different at the 5% level of the Duncan's
New Multiple Range Test.


1978


Yield loss


1979


1980







Table 51. Mean values of yield and yield components of white yam as affected by duration of weed interference in
the field (1978-79).

Time (weeks)
LAI to 100% tuber Fresh tuber
Duration of (at 12 WA P) initiation yield (t/ha)
weed interference 1978 1979 1978 1979 1978 1979
W. F. M. 0.55 ab' 0.58 a 12 a 10 a 20.08 a 17.57 a
W. 1. 4 0.87 a 0.21 cd 14 d 10 a 18.75 ab 17.40 a
W. 1. 8 0.29 b 0.18 d 14 a 10a 13.96 bc 13.91 a
W. I. 12 0.22 b 0.16 d 14 a 10a 12.47 bc 7.40 bc
W. 1. 16 0.29 b 0.04 d 14 a 10a 6.47 d 6.06 bc
W. I. 20 0.21 b 0.06 d 14 a 10a 6.58 d 3.24 c
W. I. 24 0.30 b 0.02 d 14 a 10a 4.88 d 1.89 c
W. M. 0.24 b 0.06 d 14 a 10a 6.03 d 2.12 c
Weeded 3 + 8 + 12 0.94 a 0.74 a 14 a 10 a 19.71 a 12.25 bc
Weeded 3 + 8 + 12 + 16 0.82 a 0.55 bcd 14 a 10 a 20.88 a 17.28 a
'Means followed by the same letter in the same column are not significantly different at the 5% level of the Duncan's
New Multiple Range Test.


In the absence of weed interference, dry matter produc-
tion in yam vines and leaves peaks in phase II (vegetative
growth stage) and phase III (tuber bulking growth stage).
Weed interference during these periods severely reduces
growth in those organs, and this reduction during
phases II and III (12-16 weeks after planting) interferes
with assimilate production necessary for optimum tuber
bulking in the later part of phase IIl.
Ca matter production in weeds peaked at 8-12 weeks
and declined thereafter, indicating that the maximum
competition occurred during this period. Decline in tuber
yield was also most pronounced at this period (Fig. 48).


0-0 Weed fe up to flatudy
- Wed fetedd up to -,t.ty
I it III IV


4 8 12 16 20 2 28 32
WEED INTERrEPENCE (WAP)


Fig. 48. Effect of weed interference on yield and yield
components in yam.


Herbicide persistence in tropical soils
Field experiments were carried out at IITA and Onne to
determine the persistence of some selected commonly
used preemergence herbicides in the 2 ecologies. Atra-
zine, metolachlor and fluometuron were each applied at


3.0 and 6.0 kg/ha while pendimethalin was sprayed at 2.5
and 5.0 kg/ha on a conventional-tillage plot using a knap-
sack sprayer calibrated to deliver 200 1/ha spray volume.
Herbicide persistence was monitored by a bioassay
method involving tomato seedlings for atrazine and flu-
ometuron and rice seedlings for metolachlor and pendi-
methalin.
Atrazine and metolachlor each at 3.0 kg/ha were less
persistent than fluometuron and pendimethalin (Fig. 49).
Generally, all herbicides were more persistent at IITA
(rainfall 1,400 mm) than Onne (rainfall 2,400 mm). Atra-
zine at 3.0 and 6.0 kg/ha was present in soils at IITA at
nonphytoxic levels at 8 and 12 weeks after treatment,
respectively (Fig. 50). The persistence of metolachlor
closely followed that of atrazine while fluometuron and
pendimethalin showed pronounced persistence at IITA
at both low and high rates. Fluometuron, especially at a
high rate, persisted beyond the test period in the IITA
soil. Pendimethalin at 2.5 kg/ha persisted at high levels
for more than 8 weeks after treatment, but existed at very
low levels at 12 weeks after treatment.
Persistence of atrazine in soils at Onne was very short
and had declined to non-phytoxic levels by 8 weeks after
treatment (Fig. 49). Doubling the rate of atrazine did not
increase its persistence. Metolachlor applied at a high
rate persisted in Onne for more than 8 weeks after treat-
ment. Fluometuron could not be detected in the top soil
at Onne by 12 weeks after treatment. Persistence of pen-
dimethalin was identical at both IITA and Onne, irrespec-
tive of rates used.
While an atrazine sensitive crop could be planted at IITA
and Onne locations at 12 weeks after treatment, a flu-
ometuron sensitive crop could not be safely grown under
soil and rainfall conditions at IITA within 12 weeks after
treatment. All herbicides tested in soils at Onne were
either nontoxic or had very low herbicidal activity at 12
weeks after treatment.


Plantain improvement
Previous greenhouse trials indicated that growth regu-
lators applied close to the meristem of young plantain
(Musa sp.) suckers changed growth hormone balance
and sucker development. This suggested the potential















otrazine
(a)


0 I 2 4


flu
Cr



0

in

I


Sw




8 12 0
WEEKS AFTER TREATMENT


E ONNE
m IITA

ometuron 3.0kg/ho
(c)


metolachlor 3-0 kg/ha


0 1 2 4 8 12


pendamethalin 2.5 kg/ha
(d)


0 I 2 4 8 12


WEEKS AFTER TREATMENT

Fig. 49. Persistence of herbicides in surface soils.










200-


fluometuron

(c)


3I 3-0 kg/ha
6-0 kg/ho


WEEKS AFTER TREATMENT


metolachlor


ED 3-0 kg/ha
E 6-0 kg/ha


4 8 12
WEEKS


pendimethalin


(d)


*2-5 kg/ha
S5-0 kg/ha


AFTER TREATMENT


Fig. 50. Effect or rate (kg/ha) on herbicide persistence in soil.


otrazine ImO 30 kg/ha
6-0 kg/ha

(a)











S 2 3 4 8 12



0 I 2 3 4 8 12


180-
_J
o 160-
I-
S140-
0
LL
S120-

100-

80-

60-

c 40-
LL on


200








use of growth regulators in shortening the harvest cycle
interval between first and second ratoon crops. It also
suggested the possibility for rapid multiplication without
loss of yield from the mother plant. Studies in 2 field
trials were conducted.

Physiological study of the suckering
behavior
In the first trial, the pseudostem of a 7-month-old mother
plant was cut off and the apical meristem removed. The
growth regulators; GA (Gibberillic acid, GA + NAA (Nap-
thylene acetic acid), GA + cytokinin and ABA (abscisic
acid); were applied on alternative days in iml doses in
concentrations of 10-2 and 10-4 M. Five peepers per
mother plant were treated at 2-4 weeks after detopping
of the mother plant.
Treatments with GA/NAA were not considered because
the structure of the peepers seems to be changed. There
were no significant differences in height and girth after
4 weeks among the peepers of the 16 treatments (2 du-
rations x 2 concentrations x 4 hormones), except for
the height of the GA 10-2 M treated peepers. Peepers
injected with ABA were not significantly different in their
growth from the control.
In the second trial, the mother plant was retained. Treat-
ment began at 6 months after planting. Only 1 peeper per
plant was treated. Treatments with GA/NAA and GA/NAA
CYT were not considered because of abnormal changes
in the peepers. Suckers injected with GA, GA + flurenol
and GA + CYT showed, compared with the control, sig-
nificant differences in height and girth after 6 weeks.
Suckers injected with GA + CYT became significantly
thicker.
Also, there were no significant differences between du-
rations, but there were between the 2 concentrations. As
in trial 1, peepers injected with ABA did not differ signif-
icantly from the control.

The effects of GA on suckers in Trial 2 proved that the
significant growth of injected suckers is not linked to the
duration of the injection but to the hormone concentra-
tion. In the next experiment, 1 ml of Ga 10-2 M was in-
jected into the second peeper (P,) at 10 days after
emergence on 10 different plants. The injection was re-
peated once on the same peeper at 5 days after the first.
The controls were no treatment (neutral control), and


injection of 1 ml of H20 also repeated once after 5 days.
Observations were on the mother plant, P,, P2 and P, at
the time of first injection and 6 weeks after the second
injection (Table 52).
The GA treated peepers developed faster than the first
peepers on the same stool and the GA injection did not
significantly stimulate the growth of the first and third
peepers. No effects could be observed on the main pseu-
dostem. This points to a very localized action of GA on
the treated suckers only, and an immediate change in
the balance is enough to stimulate the growth. The H20-
treated peepers did not show any difference in growth
compared with the peepers of the neutral control, prov-
ing that tissue changes by the injection was not interfer-
ring with the development of a sucker.

Effect of Flurenol on apical dominance
Flurenol is known to counteract the apical dominance.
This effect on plantain was compared with the neutral
control (no treatment) and decapitation (Table 53). Flu-
renol was injected into the 4.5 month-old main pseudo-


Table 53. Mean height (Ho, H,) and girth (Go, G,) of the
second peeper and the main pseudostem at
0 and 6 weeks (in cm). Number of peepers at
0 and 6 weeks (N., N,).
Control Flurenol Decapitation
P, Ho 3.7 1.64 1.4
He 22.7 16.82 57.7 (1)
Go* 3.8 1.73 1.8
Go 13.2 9.27 16.8 (5)
*Girth at soil level
Mother- Ho 182.6 146.3 (5) 157.9
plant H8 264.5 2f T
Go *5 44.2 36.78 (5) 39.8
Go 37.9 3f4 (5) 32.9
G5 64.5 52 (1)
G, 1* 52 42.4 (1)
N** 2.3 0.9 (5) 1.4
N, 8.4 6.2 4.6 (1)
*Girth at 50 cm and 100 cm height
**Number of peepers
Means in the same row followed by (1) or (5) respectively,
are significantly different for 1% and 5%.


Table 52. Height and girth of second peeper, mother plant pseudostem and number of peeper at 0 and 6 weeks
after treatment.


Parameter
Height (cm)
Girth (cm)
Height
Girth
Height
Girth
Height
Girth (50 cm)
Girth (100 cm)
No. of peepers


Control Water GA
Start 6 weeks Start 6 weeks Start 6 weeks


8.1
6.7
24.8
13.1
5.2
5.5
200.1
48.8
41.1
4


24.6
13.4
65.7
24.9
15.5
12.9
285.9
68.9
54.7
10


'Significant differences between treatments at 5% probability.


8.2 28.6
8.3 16.4


200.0
47.9
40.1
3.8


277.5
65.1
53.2
9.6


7.6
6.6
16.7
10.2
4.6
4.0
196.6
49.3
41.9
3.8


S87.6*
20.1*
47.7
19.5
20.8
13.5
285.8
66.3
54.1
8.6


Type of Plant
Peeper,

Peeper,

Peeper3

Mother plant







stems of 10 different plants and repeated a second time.
Each time 2 ml was injected. Observations were made on
the mother plant and the second peeper at the time of
the first injection and 6 weeks after the second injection.
Flurenol treated plants did not show faster sucker devel-
opment nor higher peeper production. Differences in the
main pseudostem after 6 weeks are probably due to the
selected plants in the beginning of the experiment. Thus,
to counteract the apical dominance, repeated injections
seem to be necessary to maintain the change in hormone
balance. Decapitated plants gave bigger suckers
(maiden suckers) as the control of Flurenol treated
plants (peepers). Release from apical dominance was
not stimulating higher peeper-number which suggests
that the maiden suckers are dominating.

Effect of fertilizer and mulch
Plantain in backyards are growing under optimal condi-
tions because of high level of nutrients, as well as or-
ganic matter (Table 54.) In this experiment, the
nutritional requirements of 2 varieties of plantain (me-
dium and giant False Horn) were compared with that of
a banana (Kparanta). It is clear that in all cases fertilizer
had strong positive effects on growth, whereas the ef-
fects of mulch appeared less pronounced. The com-
bination of mulch and fertilizer showed positive
interaction.


Taole


54. Height and girth of a medium and a giant
False Horn plantain and a banana after 5.5
months.


Girth (cm)
Height at 50 cm
Treatments (cm) height
False Horn giant plantain
No mulch, no fertilizer 85.61 ab* 21.31 abc
No mulch, fertilizer 133.45 ab 31.14 abcd
Mulch, no fertilizer 119.14 ab 27.69 abc
Mulch and fertilizer 181.18 bc 42.92 cd
False Horn medium plantain
No mulch, no fertilizer 56.92 a 15.91 a
No mulch, fertilizer 116.04 ab 27.30 abc
Mulch, no fertilizer 123.09 ab 29.39 abcd
Mulch and fertilizer 181.15 bc 40.96 bcd
Banana
No mulch, no fertilizer 94.20 ab 22.94 abc
No mulch, but fertilizer 188.11 bc 38.78 abcd
Mulch, no fertilizer 153.17 abc 31.64 abcd
Mulch and fertilizer 266.95 c 53.14 d
*Means in the same column opposite the same letters)
are not significantly different from each other at 5% lev-
els. Mulch consisted mainly of Eupatorium.


Eastern Cameroon Farming
Systems Project
As part of the effect to develop the Eastern province of
Cameroon in cooperation with Zapi-Est (Zone d'Actions
Prioritaires Integrees de I'Est), the World Bank asked
IITA to assist the then Cameroon National Office of Sci-
entific and Technical Research in establishing a food
crop research station in that province. One of the re-


sponsibilities of IITA is to conduct an agronomic survey
of existing farming systems to determine research prior-
ities for the regional food crop research.
Agroeconomic surveys. The agroeconomic survey was
conducted with the following objectives: (1) to investi-
gate and analyze existing farming systems, (2) to gather
information on existing patterns of agricultural produc-
tion and resource use, (3) to identify major constraints,
and (4) to collect relevant information on marketing and
output supplies. A report titled, "Survey of food crop
farming systems in the Zapi-Est, East Cameroon," was
published.
Field trials. The field trials on varietal improvement, cul-
tural practices and fertilization were initiated in 1980 at
Bertoua in the savanna zone and at Doume in the forest
zone. The varietal improvement was carried out with
maize, groundnut, soybean, cowpea and upland and low-
land rice. Grain yield of selected maize varieties was 3 to
4 times that of the local variety; TZB was the top yielder
with 6.1 t/ha. Streak is a major problem for maize produc-
tion in the area.
Among the groundnut varieties tested, Bertoua Blanche
gave the highest yield of 2.1 t/ha. Soybeans performed
well in the area and yields ranged from 0.6 to 1.9 t/ha.
The top yielder was variety 20-67 TB. Though cowpeas
showed good growth, leaf diseases and insect damage
were commonly observed after flowering. Grain yields
varied from 0.2 to 1.4 t/ha with TVx 1948-OlE giving the
highest yield. High yields of lowland rice were obtained
with variety IM 16 giving the highest yield of 7.0 t/ha.
On newly cleared land at Bertoua, grain yield of maize
variety Ekona Mixed Color responded significantly to N
and P applications at rates of 60 kg N/ha and 40 kg P20O/
ha. Positive N x P interactions were also observed. Re-
gardless of level of fertilizer application, maize yield in-
creased significantly as the plant density increased from
33,000 to 66,000 plants/ha.
Field trials with groundnuts showed significant re-
sponses to application of lime, N and P (Fig. 51). N appli-

Relative yield
(%)


f0 No lime
Lime I = I ton of coo/ha
2 =2 tonsofCoO/ho


P I


= No P2 05
* 60 kg P205/ho
= 120 "


No N
\N 1 4 0 kg N/ho
2 80 kg W/ho


Fruit yield of control treatment 725 kg/ho.


Fig. 51. Response of groundnut (CV Bertoua Blanche) to
N, P and lime applications.








cation on long growth-duration rice variety IM 16 showed
that time of N application greatly influenced yield (Table
55). While basal application of 50 kg N/ha at 1 day before
transplanting did not increase yield, application of 50 kg
N!ha at panicle initiation did. It appears that the best
recommendation may be 50 kg N/ha basal applied and
sidedressed with 50 kg N/ha at panicle initiation.


Table 55. Grain yield of irrigated rice variety IM 16
under different treatments of rate and time
of N fertilizer application (Doume, 1980).
Fertilizer rate Grain yield
(kg N/ha) Time of application" (t/ha)
0 4.6
50 50 (B) 4.6
100 100 (B) 5.3
50 50 (PI) 5.9
100 50 (B) + 50 (PI) 6.6
100 40 (B) + 30 (30 DT) 5.5
+ 30 (PI)
'B = Basal, 1 day before transplanting.
PI = Panicle initiation.
DT = Days after transplanting.


Maize/groundnut intercropping has been extensively uti-
lized by local farmers. A field trial was conducted during
the second season to evaluate the potential of this sys-
tem and investigate the factors affecting yields of crops
when they are planted in association. Among the inter-
cropping treatments, the treatment of maize at 40,000
hills!ha seeded at 20 days after the seeding of groundnut
at 133,000 hills/ha gave the highest monetary return
(Table 56).
In general, however, the yield of both crops is reduced
when the crops are planted in association. The amount
of yield reduction varies with the seeding time of the
affected crop in relation to the seeding time of the asso-
ciated crop. The yield of maize planted in association
with groundnut, for example, was reduced in the follow-
ing order: maize seeded at 20 days before the seeding of
groundnut > maize seeded at the seeding of groundnut


> maize seeded at 20 days after the seeding of ground-
nut. A similar trend was also observed with groundnut
yield, and obviously both crops reacted negatively to late
planting and intercrop competition.



Small farms systems research
(Atebubu District, Ghana)
The small farms systems research is a component of the
USAID sponsored project of Managed Inputs and Deliv-
ery of Agricultural Services (MIDAS). The MIDAS project
is designed to organize and distribute all the inputs nec-
essary for food crop production by small farmers of
Ghana.
The small farms system research is designed to assist
the government in establishing an applied multidisciplin-
ary small farms research capacity with the following ob-
jectives in mind:
(1) To obtain a sound knowledge of the existing farm-
ing systems, the socioeconomic environment and
the positive and negative factors in services.
(2) To conduct applied research that is relevant to
these circumstances and responds to the needs of
the small farmers.
(3) To identify soil and farm management and produc-
tion practices that eliminate constraints.
(4) To increase small farmer production and income.
The project was initiated in 1980 with an appraisal of the
present food crop farming system practices in the re-
gion. For the survey, a group discussion approach was
used that was supplemented by the visit to individual
farmers and spot harvest checks. The survey covers 7
subdistricts-Atebubu, Amantiri, Abease, Prang, Kwame
Danso, Kajaji and Yeyi.
The survey was completed in 1980 and a report titled,
"An appraisal of the present farming systems of the Ate-
bubu District of Ghana," was published. During 1980,
preparations were also made in selection of a site for
establishing the experiment station. Actual field experi-
mentation, however, will be initiated in 1981.


Table 56. Yield of sole and intercropped maize and groundnut and their monetary values. (Bertoua, 1980 second
season).


Crop and date of
seeding
Treat- (M = Mai7- ,


ment


alP nt density Treat-


Crop Yield Kg/ha


Monetary value (CFAF)'


G = Groundnut) (x 103 hills/ha) ment Maize Groundnut Maize Groundnut TOTAL


C, M on 1 August 50 C, 3066 183,960 1
C, G on 1 August 200 C, 2277 284,625 2
M on 1 August, and 40
C G on 1 August 133 C, 2263 1206 135,780 150,750 2
M on 1 August, and 40
C, G on 20 August 133 C. 2959 539 177,540 67,375 2
M on 20 August, and 40
C. G on 1 August 133 C. 831 2122 49,860 265,250
M on 10 Sept., and 40
C, G on 1 August 133 C, 2245 280,625
At 60 CFAF/Kg of maize grain and 125 CFAF/Kg of unshelled groundnut (Retain price of PROVIV-ZAPI, 1980).
'Maize seeded on this date did not germinate.
Fertilizer rates maize 8N 8 P205; groundnut 20N 6 P20, in Kg/ha.


83,960
284,625

286,530

244,915

114,790

280,625


1




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