STUDIES ON OIL PALM BASED CROPPING 
SYSTEMS IN GHANA

By

BERNARD NARH NUERTEY



STUDIES ON OIL PALM BASED CROPPING SYSTEMS 
'IN GHANA

By

BERNARD NARH NUERTEY

Thesis submitted to the Board of Graduate Studies, in 
partial fulfilment of the requirements for the award 
of the degree of Doctor of Philosophy in crop 
science.

OCTOBER, 1999



Q 364054



DECLARATION

I certify that the field work related to this thesis 
"Studies on oil palm based cropping systems in Ghana" 
was carried out by me, Bernard Narh Nuertey, of the 
Department of Crop Science, U.G at the Oil Palm 
Research Institute, Kusi in Ghana. This thesis has 
never been presented on any occasion at any
University for the award o

(Supervisor)
Crop Science Department 
Faculty of Agriculture 
University of Ghana 
Accra-Ghana

a degree.

(Supervisor)
Crop Science Department 
Faculty of Agriculture 
University of Ghana 
Accra-Ghana.

(Supervisor)
Oil palm research Institute 
C.S.I.R 
P. 0. Box 7 4 
Kade - Ghana



DEDICATIO

Dedicated to my wife Betty, and children - Ama,

Nelia, Nana, Galina and Luda.

On many occasions, you were left alone at home 

without my protection, as I had to be elsewhere for 

this work. Thank you for the sacrifices made. And may 

the almighty God bless you.



iii

ACKNOWLEDGEMENTS

I wish to thank the following people and organisations for 
their roles played in the preparation of this thesis:

My supervisors at the Department of Crop Science, 
Legon, Dr K. Ofori and Prof. E. V. Doku for their 
suggestions, constructive criticisms and 
encouragement in my course of studies;
My institutional supervisor Dr J. B. Wonkyi-Appiah. 
The Heads and staff of the Crop Science Department 
Legon, and the Agronomy Division of the Oil Palm 
Research Institute, C.S.I.R Kade;
Mr. W.A. Asante of Crop Science Department and 
Mr. Wilson Dogbe of Savana Agricultural Research 
Institute for assisting in the statistical analysis 
of data. Mr. F.M. Tetteh, of Soil Research Institute 
for carrying out the chemical chemical analysi 
the soil/leaf samples.
Mr./Mrs Okyere Mensuo for providing me with 
accommodation during my stay in Accra for these 
study;
Mr. A.K. Nantwi, for allowing me the use of his 
personal library;
The Oil Palm Research Institute, Kade of the CSIR for 
granting me the study leave to undertake these 
studies.

Finally, I am thankful to all those who typed the various 
manuscripts which gave form to this thesis.
May almighty God bless you all. Amen.



TABLE OF CONTENTS

Declaration... i

Dedication... ii

Acknowledgements.................................................................................. iii

Table of Contents.......................................................................................iv

List of Tables..............................................................  xi

List of Figures.............................. f  (   I ■............................^

List of Plates..................................................  xvii

Abstract............................................................... xviii

CHAPTER ONE:........................................................................................1

1.0 INTRODUCTION......................................................................................1

CHAPTER TWO:...................................................................................... 4

2.0. LITERATURE REVIEW:........................................................................... 4

2.1 The Physiology of growth and development of the oil palm...................4

2.1.1 The role of leaves in dry matter accumulation of p lan ts ........................4

2.1.2 Oil palm dry matter accumulation and distribution................................. 7

2.2 Factors influencing growth and development of the oil palm............... 8

2.2.1 Climatic Factors............................................................................................8

2.2.1.1 Rainfall and water balance......................................................................... 9

2.2.1.2 Temperature  11

..2.2.1.3 Light use for oil palm growth and Development.................................. 12



V

TABLE OF CONTENTS (CONTINUED)

2.2.2 Soil factors affecting the growth, development and yield

of the oil palm................................................................................................ 15

2.2.2.1 Soil physical factors........................................................................................ 15

2222 Mineral nutrient requirement.........................................................................16

2.3 Oil Palm Cropping System s..........................................................................19

2.3 .1 Monocrop oil palm with leguminous cover crop........................................19

2.3.2 Intercropping oil palm with food crops.......................................................23

2.3.3 Influence of climate on choice of intercrop................................................24

2.3.4 Soil conditions and choice of intercrops.....................................................25

2.3.5 Socio-Economic factors and choice of interrcrops.................................... 25

2.4 Growth and Yield of intercropped oil palm :.................................................26

2.5 Growth and yield of food crops intercropped in oil palm:........................... 29



vi

CHAPTER T H R E E ........................................................................................... 30

3.0 MATERIALS AND M ETHODS......................................................................30

3.1 A survey o f oil palm based cropping systems in Ghana...................................30

3.2 Physiological and agronomic studies on oil palm

based cropping systems...................................................................... 33

3.2.1 Experimental Site.................................................. | ~ 7 ............... V§§............... 33

\V V  JB3.2.2 Experimental, design and crop management ................34

3.2.3 Data collection.......................................................................................................40

3.2.3.1 Rainfall data................   40

3.2.3.2 Growth, development and yield of oil p a lm ....................................................40

3.2.3.3 Nutrient dynamics, soil moisture retention and solar

inlerception by oil palm.....................................................................................43

3.2.3.4 The performance of food crops intercropped with oil palm......................... 47

3.2.3.4.1 M aize....................................................................................................................47

3.2.3.4.2 Tuber yield of intercropped cassava.................................................................49

3.2.3.4.3 Growth, development and yield of plantain..................................................49

3.2.3.5 Weed growth and succession.............................................................................. 51

3.2..3.6 Agro-economic analysis of intercropping

food crops food crops in oil palm..................................................................52

TABLE OF CONTENTS (CONTINUED)



4.0

4.1

4 . 1.1

4 . 1.2

4 . 1.3

4 . 1.4

4 . 1.5

4 . 1.6

4 . 1.7

4.2

4 .2.1

4 . 2.2

4 . 2 .2.1

4 .2 .2.2

4 .2 .2.3

4 . 2 .2.4

4 .2 . 2.5

4.2.2.6

vii

TABLE OF CONTENTS (CONTINUED)

CHAPTER FO U R.......................................................................................55

R E SU L T S..................................................................................................... 55

Features of oil palm based cropping systems in Ghana............................55

Age distribution of oil palm farm ers............................................................55

Level of education of farmers........................................................................55

Composition of dependants...........................................................................55

Income from oil palm produce.......................................................................58

Income ftom intercrops.............................................................  ^9

Agronomic practices of farmers............................ \-Q & ................. 61
\vls \ / J j '

Duration of intercropping.............................V tw v  ... .J .jb /t................. 63

Physiologyical and agronomic studies on oil palm

cropping systems............................................................................................ 65

The weather during the period of experimentation at Kusi...................... 65

The effect of intercropping food crops in oil palm

on growth, development and yield of the oil palm................................... 70

Leaf Area (LA).............................................................................................. 70

Leaf Area Index (LAI).................................................................................. 71

Rate of Leaf Production................................................................................ 72

Frond dry weight............................................................................................ 74

Inflorescence production of oil palm.......................................................... 72

Yield of oil palm........................................................................................... 74



viii

4.2.3

4.2.3.1 

4.2 3.2

4.2.3.3

4.2.3.4 

4.2..3.5

4.2.3.6

4.2.3.7

4.2.3.8

4.2.4

4.2.4.1

4.2.4.2

4.2.4.3

4.2.4.4

4.2.4.5

4.2.4.6

TABLE OF CONTENTS (CONTINUED)

Effects of intercropping on nutrient dynamics, soil moisture

retention and solar interception by oil p a lm ............................................. 78

Soil acidity (pH)........................................................................................  78

Soil organic matter (% ).............................................................................  81

Total nitrogen (%)....................................................................   82

Available phosphorus (mg/kg so il) .............................................  84

Available potassium (mg/kg soil)............. ..................... .......................... 86

Dynamics of oil palm nutrient up-take..............................  87

Soil moisture status....................................................................................  89

Light interception by oil palm :................................................................... 91

The performance of the food crops intercropped with oil Palm  93

Growth of maize in oil palm-maize intercrop system.............................. 93

Grain yield and components of grain yield of maize in

intercropping systems................................................................................. 94

Tuber yield of cassava in oil palm intercropping sysyems..................... 97

Growth of plantain intercropped with maize and oil p a lm .....................98

Lodging damage in sole and intercropped plantain................................ 99

Effect of intercropping on bunch yield of plantain:.............................. 100



ix

j :1
TABLE OF CONTENTS (CONTINUED)

4.2.4 7 Performance of maize and Cassava as influenced by

Spatial arrangement in oil palm.................................................... 102

4.2.5 The effect of intercropped food crops on weed succession

and Growth in oil palm............................................................ 104

4.2.5.1 Influence of cropping systems on weed species

Present..............................................................................................104

4.2.5.2 Weed supression ability by the various cropping systems 107

4.2.5.3 Effect of intercropping food crops in oil palm on

Weed growth....................................................................................108

4.2.5.4 Relative contribution of weed species to the total biomas

of weeds............................................................................................109

4.2.6 Agro-economic analysis o f intercropping food crops

in oil palm....................................................................................... I l l

4.2.6.1 Establishment Costs.........................................................................I l l

4.2.6.2 Maintenance and harvesting costs.................................................112

4.2.6.3 Annual revenue from oil palm and food intercrops.................  113

4.2.6.4 Economic evaluation of oil palm based cropping

System s........................................................................................... 115



X

TABLE OF CONTENTS (CONTINUED)

CHATTER FIVE..................................................................................................... 117

5.0 DISCUSSION............................................................................................................. 117

5.1 Oven iew of oil palm based cropping system in Ghana........................................117

5 .2 Growth and yield of oil palm intercropped with food crops............................. 121

5 .3 The effect of intercropped food crops on nutrient dynamics,

soil moisture Retention and solar interception by the oil p a lm ........................123

5.4 Performance of food crops intercropped in oil p a lm ........................................  128

5.5 The effects of intercropped food crops on weed succession

and growth in oil p a lm ............................................................................................129

5.6 Economics of intercropping food crops in oil palm for the

small scale farm er..................................................................................................  131

CHAPTER SIX:.................................................................................................  134

6.0 CONCLUSIONS..................................................................................................  134

7.0 REFERENCES.......................................................................................................  136



LIST OF TABLES

TABLC PAGE

2.1 Soil Nutrient Availability indices 18

2.2 Critical level o f oil palm leaf Nutrient Status 19

4.1 Age of farmers (%) 56

4.2 Level o f formal education 57

4.3 Composition of dependents on farm revenue 57

4.4 Relative (%) incomes from various oil palm produce (%) 59

4.5 Relative (%) incomes from food intercrops 60

4.6 Frequencies(%) of planting materials and planting density

used by farmers. 62

4.7 Frequencies (%) of weed control methods adopted

by farmers 63

4.8 Distribution of farmers in terms of duration of

intercropping food crops in oil palm ' 64
. ; .•*" N O *

4.9 Mean monthly temperature (°C) ’ .-/> 67V J oj
4.10 Monthly amount of rainfall (mm) 68

4.11 Monthly water deficit (mm) 69

4.12 Oil palm leaf area (m2) as affected by

cropping systems 71

4.13 Leaf area index (LAI) in relation to cropping systems. 72



Xii

Table

4.15

4.16

4.17

4.18

4.19

LIST OF TABLES (CONTINUED)

Page

Leaf production per month under various

cropping systems 73

Frond dry weight(Kg) accumulation in relation
to cropping systems 74

Number of inflorescence per plot and sex ratio 
under various intercropping systems 76

Effect of intercropping oill palm with food crops
on yield of the oil palm . 76

Effect of intercropping food crops in oil palm on 

Dynamics of soil pH from 1994 to 1997 

78

Effect of intercropping food crops in oil palm on 

dynamics of organic matter (%) at 0 -  15 cm 

and 15 -  30 cm depth from 1994 to 1997

4.20 Effect of intercropping food crops in oil Palm on 

dynamics of total N (%) from 1994 to 1997 84



xiii

Table

4.21

4.22

4.23

4.24 

4.25.

4.26

4.27

4.28

LIST OF TABLES (CONTINUED)

Page

Effect of intercropping food crops in oil palm on

Dynamics of available phosphorus (mg P kg -1 soil)

from 1994 to 1997 86

Effect of intercropping food crops in oil palm

on dynamics of available K (mg K kg-1 soil) 87

Effect of intercropping food crops in oil palm

on dynamics of available leaf N, P, and K 89

Percentage soil moisturee of various intercropped 

combination during a dry season 91

Effect of intercropping food crops on

% light interception by the oil palm. 92

Growth of maize in oil palm based cropping system

From 1994 to 1996 94

Major season maize yield as influenced by

System 96

Minor season maize yield as influenced by

cropping systems 96

\ i



xiv

4.29.

4.30

4.31.

4.32.

4.33.

4.34

4.35.

4.36.

4.37. 

4.38

Tuber yield of sole and intercropped cassava 98

The growth of sole and intercropped plantain at

Flowering 99

Lodging damage oF plantain by wind 100

Yield of sole and intercropped plantain in oil palm 101
0

Effect of spatial arrangement on intercropped

cassava yield 103

Effect of spatial arrangement on grain yield of

Intercropped maize. 103

Weed species present under various cropping

systems 106

Effect of intercropping food crops and cover

crops in oil palm on weed growth during(dry weight)

during the growing season of 1995 and 1996 (g/m2) 108

Percentage contribution of weed species to the

total biomass of weeds per plot for 1995 and 1996. 110

Establishment costs for various

Cropping systems. (0 ’ 000/ha) 112

LIST OF TABLES (CONTINUED)



X V

4.39.

4.40.

4.41

4.42

LIST OF TABLES (CONTINUED)

Maintenance and harvesting costs Ha “'for 

oil palm - food crop intercrops (0’OOO) 

Selling prices of oil palm and food crops 

Revenue from oil palm based cropping 

cropping system.

Economic evaluation of the oil palm based 

cropping system



xvi

LIST OF FIGURES

Fig.

3.1 Areas climatically suitable for oil palm 

Production in the forest zone of Ghana

Page

32

. 1 . Relative weediness of the various cropping 

systems 107



xvii

LIST OF PLATES 

Plate Page

3.1 Oil palm with Pueraria cover crop 38

3.2 Oil palm intercropped with cassava 38

3.3 Oil palm intercropped with plantain 39

3.4 Oil palm intercropped with maize 39

3.5 Tube Solarimeter installed above the canopy

of the oil palm. 46

3.6 Tube solarimeter installed beneath the canopy

of the oil palm. 46

/ V :.V;V>



ABSTRACT
A survey was conducted in 1994 to gather information 

on the practice of intercropping food crops in oil 

palm on small-scale farms in the oil palm zones of 

southern Ghana. The objective was to identify and 

study intercropping systems used in oil palm 

production. Data was collected by interviewing a 

total of 72 oil palm farmers from the oil palm 

growingregions,(Eastern,

Central,Western,Ashanti,Brong-Ahafo,and Volta) at 

their farm locations. The responses indicated that 

the small-scale oil palm farmers in Ghana commonly 

intercrop oil palm with maize, cassava and plantain 

especially during the first three years of the crop. 

The three staple crops, maize, cassava and plantain 

were intercropped in oil palm between 1994 and 1997 

at the Oil Palm Research Institute, Kusi, Ghana to 

assess their effects on the growth, development and 

yields of oil palm. Intercropping was compared to 

the standard system of cover cropping oil palm with 

pueraria.

XV111

v.fIS/



xix

Nutrient dynamics, soil moisture retention, and solar 

interception by the oil palm were also examined.

The performances of the food crops were also assessed 

as well as the ability of the cropping systems to 

control weeds was assessed. An economic analysis was 

also carried out.

There were seven treatments, consisting of:

(i) sole oil palm with pueraria cover crop;

(v-vii) sole crops of maize, cassava and plantain 

respectively.

These were arranged in a randomnized complete block 

design and replicated four times.

Intercropping oil palm with maize, cassava and 

plantain had no adverse effect on the growth, 

development and yield of the oil palm. The Oil palm 

+ maize + maize intercrop and oil palm cover- cropped 

with pueraria positively influenced soil moisture 

retention, nutrient uptake and accumulation and light 

interception by the oil palm more than what pertained 

with oil palm + maize + cassava and oil palm + maize 

+ plantain.

(iii) oil palm + maize + plantain

(ii) oil palm + maize + cassava;

(iv) oil palm + maize + maize;



X X

Yields of the intercropped food crops compared 

favourably with yields of these crops when solely 

cropped.

The sole oil palm with pueraria cover crop and oil 

palm + maize + maize association controlled weeds 

better than the oil palm + maize + cassava and oil 

palm + maize + plantain associations. Intercropping 

oil palm with maize, cassava and plantain was found 

to be economically beneficial to the small-scale oil 

palm farmer.



1

CHAPTER ONE

1.0 : INTRODUCTION

The oil palm industry has developed over the last 

two decades into a huge and important industry, which 

comes next only to Cocoa in the agricultural sector of 

Ghana's economy. Small-scale farmers who occupy about 70% 

of the estimated total area of 145,500 hectares under oil 

palm (Anonymous, 1989; Anonymous, 1990) dominate Oil Palm 

cultivation in Ghana. The development estates account for 

the remaining 30% of the oil palm production area. In 

Ghana, oil palm is cultivated as a monocrop by the 

development estates and their affiliated small holders as 

well as out-growers.

The practice of the development estates has been to 

inter plant the oil palm rows with Pueraria sp, a 

leguminous cover crop. The leguminous cover crop is 

expected to conserve soil moisture, suppress weed growth 

and control soil erosion. It also improves soil fertility 

by fixing atmospheric nitrogen into a form for use by 

plants.



2

There is also evidence that the leguminous cover crop may 

compete with the oil palm and may do so more than even 

intercropped food crops (Hartley 1988) .

In spite of the many benefits of the leguminous 

cover crop, the small scale farmers do not plant them 

under the oil palm. This is partly due to lack of 

immediate economic returns accruing from them. They 

instead, intercrop the oil palm with food and other cash 

crops for three to four years. Integration of food and 

tree crop farming has become necessary also because most 

of the areas around the large estates (BOPP, TOPP, etc.) 

which were once exporting food crops have become net 

deficit areas. Some farmers are therefore forced to 

remove palm fronds to create space for intercrop food 

crops.

The standard 8.8-m triangular spacing used for oil 

palm provides wide spaces between the young palms. There 

is therefore considerable waste of solar radiation and 

weed problems from transplanting to canopy closure which 

takes between three and five years.(Chee et al., 1992).



3

Farmers may seem justified then by grng food and/or 

cash crops between oil palm trees until canopy closure. 

The question to which solution needed be found is whether 

intercropping of food crops in establishing oil palm is 

more beneficial than sole cropping in small holdings or 

otherwise. The type of crop used as intercrop changes 

from one locality to another depending on the food 

culture of the people.

There is no information on the compatibility of all these 

food crops grown in association with the oil palm with 

respect to the use of resources for growth and 

development.

The objectives of this study therefore were:

(i) to identify the food crops commonly intercropped

with oil palms in Ghana;

(ii) to assess the effects of these food crops when

intercropped with oil palm on the growth,

development and yield of the oil palm;

(iii) to assess the performance of food crops

intercropped in oil palm;



4

(iv) to assess the effects of the intercropped food

crops on the use of nutrients, water and light by 

the oil palm;

(v) to study the effects of the intercropped food

crops on weed suppression and control; and

(vi) to evaluate the economics of intercropping food

crops with oil palm.

CHAPTER TWO 

2.0: LITERATURE REVIEW

2.1: The physiology of growth and development of oil

Palm

Oil palm productivity is influenced by the total dry 

matter production of each palm. Dry matter production is 

highly dependent on the photosynthetic rate of the palm 

(Dolmat, 1996).

2.1.1 The role of leaves in dry matter accumulation
Of plants



5

Various concepts are used to characterise the role of

leaves in dry matter accumulation in relation to growth 

analysis of plants.

(i) Leaf area (LA): This is the area of the leaf surface

Usually used to quantify the photosynthetic component.

Leaf area expansion is initially more related to air 

temperature (Milthorpe, 1959), subsequently, LA expansion 

is more responsive to solar radiation (Blackman and 

Black, 1959). Nutrient deficiency reduces growth in 

general and leaf area in particular. Corley and Mok 

(1972) showed that N & K increases LA. Restriction in 

water supply was demonstrated to affect leaf expansion

(Boyers 1970; Acevedo et al. 1971) . A range of 

techniques for measuring the area of leaves is available 

and has been described by Bleasdale (1973). Leaf 

development can be plotted with time and related to dry 

matter production.

(ii) Net Assimilation Rate (NAR) : It is defined as the 

rate of increase in plant dry weight per unit leaf area 

over a given period (Gregory, 1926). NAR expresses 

growth in terms of foliar surface and therefore allows us



6

to see if any treatments make the leaves more efficient 

or if the efficiency merely changes with time. NAR 

declines with leaf age (Watson, 1947; Hermandez-Gil and 

Schaedle, 1973) limited by solar radiation (Blackman and 

Black, 1959) and governed by temperature (Gregory, 1926 

and Milthrope, 1959).

(iii) Leaf Area Index (LAI): Defined as the ratio of leaf

area to ground area covered (Watson, 1947 and Harper,

1983) . LAI varies according to leaf orientation (Pearce 

et al., 1967). Kriedemann and Smart, (1971) demonstrated

that vertically oriented foliage makes good use of both

diffuse and direct sunlight and can therefore achieve 

greater LAI. Corley and Mok, (1972) showed that high N 

levels give rise to faster LAI development. Similar 

effects have been observed with irrigation. (Ochs and 

Vanderwegen, 1969) . High values of LAI may not 

necessarily be desirable because the lower leaves in the 

canopy are shaded and their efficiency is reduced. LAI 

values usually fall between 1 and 8. There is normally 

restriction in growth of some crops when LAI declines 

rapidly.



7

(iv) Leaf area duration (LAD): This is a measure of 

persistence of the leaf canopy. If leaf area index is

plotted against time, the area under the curve is a 

measure of the duration of the leaves. Corley (1973) has 

suggested that provided leaves are not removed by 

pruning, their life depend in part on the intensity of 

light reaching them through the canopy.

(v) Crop growth rate (CGR) : The rate of increase of dry

matter production per unit of time. Growth rates can be 

compared at different times in the season for different 

treatments. CGR is affected by a range of factors including 

temperature (Milthrope, 1959), radiation levels, (Blackman and 

Black, 1959), water (Acevedo et al. 1971) and nutrient supply 

(Corley and Mok, 1972) the type and age of the plant (Watson, 

1947) These factors affect the size and efficiency of the leaf 

canopy and hence the ability of the crop to convert solar 

energy into useful growth.



2.1.2 DRY MATTER ACCUMULATION AND DISTRIBUTION IN oil PALM
The dry matter produced is used for both vegetative and 
reproductive growth. In the oil palm, vegetative growth 
assumes priority over the reproductive growth (Hartley, 1988). 
Thus the requirements of vegetative growth must necessarily be 
satisfied before dry matter is diverted into fruit production.

For economic production of the oil palm therefore it is 
imperative that management practices which would enhance the 
availability of such factors influencing vegetative growth and 
development of the oil palm are adopted.

2.2: Factors influencing growth and development of 

Oil palm

Many factors affect the rate of photosynthesis of the 

palm. These are predominantly climatic, edaphic and 

agronomic practices.

2.2.1: Climatic factors

Oil palm is now grown in most tropical countries where 

the climate is favourable. Differences in climatic 

factors affect productivity. Rainfall, temperature and 

light intensity are the main climatic factors, which 

affect the growth and development of the oil palm.



9

2.2.1.1: Rainfall and water balance

The annual rainfall distribution relative to potential 

evapotranspiration with the buffering effect of soil 

water reserves defines the water available for plants 

(Surre, 1968) . In the Sub-region of West Africa, the 

seasonality of rainfall and the long drought which lasts 

2 to 4 months in a year result in huge water deficits. 

The amount and distribution of rainfall and therefore 

soil moisture availability influence leaf production.

There is evidence that within West Africa, annual leaf 

production is low in areas with rainfall of 1250 mm and 

below.

Broekmans (1957) showed that in Nigeria palms of the 

same genetic origin gave varied averages of leaf 

Production when planted in areas with varied annual 

rainfall. At Umuahia, with an annual rainfall of 2108 mm, 

the average annual leaf production was 23.1. While at 

Ibadan, with an annual rainfall of 1219 mm, the yearly 

mean leaf production was 20.5 in the adult palm.

De Berchoux and Quency (1980) noted that stem growth 

was fastest in plantations sited where water supply was



satisfactory against slowest stem growth on plantations 

sited where there was limited water supply.

Quency and de Taffin (1981) observed that the 

insufficient water supply in West Africa mainly affects 

the sex ratio of the palms and thus determines the number 

of bunches produced.

Olivin (1968) found good correlation between the 

mean annual water deficit and the average production 

level. Surre(1968) and IRHO, (1969) also reported direct 

relationships between the magnitude of water deficit 

estimates and bunch yield. Desmarest (1967) and IRHO 

(1967) demonstrated that, in the Cote d'Ivoire yields of 

fresh fruit bunches could be raised by irrigation from

7.5 T Ha-1 to 26t/ha.

This was collaborated by the work of Ochs and vander 

Wegen (1969) who also reported yield increases of 13 T 

ha-1 by applying irrigation in the Cote d'Ivoire.

Rees (1989) thought irrigation may not be 

economically feasible considering the large areas 

involved in oil palm cultivation and the cost of the 

necessary equipment coupled with their maintenance costs.



11

Therefore husbandry practices that conserve soil moisture 

might be the best option.

2 .2.1.2: Temperature

There are indications that temperatures below 20°c for any 

extended period are generally deleterious to oil 

palms(Hartley, 1988) . Henry (1957) showed that growth

of young seedlings at 25°C is seven times and at 20°C 

three times as rapid as at 17.5°C. There is little 

definitive information on temperature effects on growth 

and development of oil palm.

Rees (1989) attributed this lack of information to the 

fact that field temperatures are not controllable and 

therefore renders work on temperature effects only 

academic. He however agreed that the knowledge on 

temperature fluctuations could be an important 

consideration when siting new plantations.

Hartley (1988) found temperature differences to be 

the most distinguishing climatic factor between Yangambi, 

Zaire and the Far East. Yanganbi had a minimum of between 

19.3°C and 20.3°C while the Far East had a minimum of 

2J C. The former had a lower yield than the latter.



12

2.2.1.3: Light use for oil palm growth and

Development

Another environmental factor which has a large influence 

on the photosynthetic output of the oil palm tree is 

light.

Solar radiation is often measured as sunshine hours only. 

From several observations, Hartley (1988) inferred the 

importance of solar radiation for growth and bunch 

production of the oil palm.

Corley (1973) showed that the number of leaves 

produced depends on the light intensity reaching the 

oldest leaves of the canopy.

Thus, under heavy shade, the growth of the leaves is very 

much depressed. Milthorpe (1956) showed that yield of 

crops depends largely on the rate of development and 

maintenance of leaf surface.

In the oil palm where each frond axil subtends only 

one inflorescence, the rate of frond production sets an 

upper limit to the rate of inflorescence production. 

Bunch production therefore depends on the number and size



13

of fronds and the proportion of them providing 

in florescence.

Shading adult palm reduces the production of female 

inflorescence. Sparnaaij, (1960) demonstrated this by 

pruning the leaves of adjacent palms to increase the 

production of female inflorescence. A positive though 

not strong correlation has been found between sunshine 

data in the preceding 12 months and yield some 28 months 

later (Hartley, 1988).

In countries such as Nigeria and Ghana and other 

West African countries with marked seasonal differences 

in hours of sunshine, the differentiation of female 

inflorescence as shown by the sex ratio at flowering two 

years later, is much higher during the months with many 

hours of sunshine than during the months with few 

(Broekmans, 1957).

The exact requirements, either in terms of radiation 

or sunshine hours for optimum yield are unknown. Records 

however kept for some high oil palm production areas in 

terms of annual averages of daily sun-hours range from



14

over 6 hours in parts of Malaysia, Zaire and Brazil, to

4.6 hours in Nigeria and even lower in Cameroun (Hartley 

1988) .

Rees (1988) reported on the seasonal radiation 

distribution at the Nigerian Institute for Oil Palm 

Research (NIFOR) which has three wet-season months of 

only 2.3 and 2.4 hours compared with the lowest monthly 

value in Kuala Lumpur of 4.9 hours.

At NIFOR, the total incident light (PAR) was 

2.43 x 10® Jui-2 annum"1 unevenly distributed so that the 

highest monthly value was about 1.4 times higher than 

that of the lowest mouth. The annual totals for some 

sites in Malaysia are higher than this.

Corley et al (1971) and Corley (1973) observed 

incident light (PAR) for Layang-layang and coastal West 

Malaysia as value of 2.55 x 109 Jui”2 annum -1 and 3.2 x 109 

Jui"2 for Layang - layang and Coastal West Malaysia annum-1 

respectively.

Rees (1962), Rees and Tinker (1963) measured intercepted 

light by adult palms in Nigeria and indicated that the 

proportion intercepted was 87% at a leaf area index of



15

4.9, some 13% was not trapped and therefore lost. This 

may be due to the wide spacing of the oil palm.

2.2.2: Soil factors affecting the growth, development

And yield of the oil palm

Besides the inherent fertility of the soil, mineral 

nutrient absorption by the oil palm is highly dependent 

on such soil physical properties as aeration, moisture 

status and soil pH(Jacquemard, 1998).

2.2.2.1: Soil physical factors

According to Hartley (1988) for optimum oil palm 

production, the soil must be deep and loamy with a well- 

developed structure. Soil should have a loose friable 

consistency and must be without impervious layers in the 

top 1.5 meters. Drainage must be good to ensure aeration. 

The soil must however be capable of holding ample 

moisture for the oil palm (Olivin, 1968; Ochs and Olivin, 

(1969) .

Growth and development of the oil palm is impaired on 

soils with high water table especially the young plants 

which cannot tolerate stagnant water. Heavy, badly



16

drained soils and coarse sandy soils, which are easily 

depleted of moisture, are not suitable. Dolmat et ad. 

(1982) and Rasmussen et al, (1981) showed that peat soils 

could be suitable provided they are well drained and deep 

enough to provide sufficient anchorage for the root 

system of the oil palm. In areas with marked dry seasons 

like some parts of West Africa, Olivin and Ochs (1978) 

postulated that a soil of good water holding capacity and 

of good moisture retention is valuable.

vander Vossen (1969) observed that the oil palm best 

flourishes in areas of acid soils with pH between 

4 and 6.

2.2.2.2: Mineral nutrient requirement

The oil palm needs large quantities of nitrogen (N), 

phosphorus (P) , potassium (K) and magnesium (Mg) which 

are important for both vegetative and fruit production 

(Dolmat, 1996) .

These nutrient requirements of the oil palm vary with age 

(Foster and Chang, 1977), variety (Poon ET al., 1970), 

level of production and management practices which among



17

others include planting density and cover management 

(Hartley 1988).

Yield potential of the environment also dictates 

nutrient requirement. Therefore when yield is restricted 

by such factors as inadequate rainfall, shallow soil 

depth and poor drainage, nutrient requirement is also 

depressed (Foster et al., 1985). The natural nutrient 

supply of any soil is only of limited capacity. Extra 

supplies in the form of fertilisers are practically 

always needed. These are applied from the very first year 

of planting in the field.

Soil analysis indicates the quantity of elements at 

the disposal of the palm. Soil nutrient supply 

capacity indices are shown in Table 2.1. Fertiliser 

is applied to bring the soil nutrient supply 

capacity from low to the high profile as and when 

necessary.



18

Table 2.1: Soil Nutrient Availability Indices

Nutrient High Medium Low

N (Total)% > 0.2 0.1 - 0.2 0 - 0.1

P (available) 

(mg/kg Soil) > 20 10 - 20 0 - 1 0

K (available) 

(mg/kg Soil) >100 50 - 100 0 - 5 0

Organic Matter 

Content (%) > 3 1.5 - 3 < 1.5

Fcliar analysis identifies and quantifies the deficiency 

of individual nutrients so that fertiliser adjustments 

can be calculated.

The leaf nutrient concentrations are indicative of 

the nutrient status of the palm trees. Critical leaf 

nutrient levels are presented in Table 2.2. Below or 

above these sufficiency levels, fertiliser use needs to 

be increased or withheld.



19

Table 2.2: Critical Levels of Oil Palm Leaf Nutrient 
Status

AREAS N P K Ca Mg Sources

Ivory Coast 
& Benin 2.50 0.15 1. 00 0. 60 0.24 IRHO (1960)

N igeria 2.50 0.16 1.00 _ 0.28 WIFOR (1956)

Malaysia 2.40 0.15 1.00 0.60 0.24 Ollagnier(1963)

2.3: Oil palm cropping systems

Two broad types of cropping systems are identified with 

the production of oil palm in Ghana. The oil palm is 

either cultivated as a monocrop with various cover crops 

and/or in association with food crops (Sparnaaij, 1991).

2.3.1: Monocrop oil palm with leguminous cover crops

Oil palm is cultivated as a monocrop by the development 

estates and their affiliated small holders as well as 

out-growers. The practice of these development estates 

has been to inter plant the oil palm in inter rows with 

leguminous cover crops. These cover crops include 

Pueraria phaseoloides, Pueraria javanica, Calapogonium 

mvcunoides, Calapogonium caesuleum, Centrosema pubescens 

and Mucuna cochichinensj-s (Hartley, 1988) . The natural



20

plant cover consisting of broad leaves and grasses 

persists as weeds where no effort is made to incorporate 

the leguminous cover crops. Gray and Hew (1968)and Tan 

and Ng (1973) have established that leguminous covers are 

beneficial to the oil palm as compared to the other inter 

row covers such as grasses.

Legume covers are established during the planting of 

the oil palm and their benefits are numerous. They enrich 

the soil with organic matter and improve the nutrient 

status especially Nitrogen. Foster (1976) observed that 

legume cover is beneficial to a tree crop in the initial 

years because it does not compete with it for the soil 

nitrogen while in the fourth to sixth year, the legume 

cover releases considerable amount of nitrogen and 

organic matter to the soil as it dies out. The total N 

supplied by a legume crop to an oil palm plantation is 

equivalent to 3 to 4 kg of ammonium sulphate applied per 

palm per year for three years (Hartley, 1988) . Broughton 

(1976) found that leguminous covers increased oil palm 

leaf contents of N, P and Mn over those obtained with 

other types of covers.



21

Tan and Ng (1981) and Hew and Tam (1972) made similar

observations.

There is also the added control of soil erosion and 

water run-off especially in hilly terrain as well as the 

improvement of soil physical properties. Leguminous cover 

crops are sown before planting of the oil palm and 

therefore provide some protection to the bare soil

against erosion by reducing the impact of the heavy 

rains, which erode the topsoil.

Zaharah et al (1986)and Agamuthu and Broughton 

(1985) showed evidence that Pueraria phaseoloides 

contributed about 150 kg N per hectare per year to oil 

palm plantations. Chemara (1968) discovered that the

presence of a leguminous cover more effectively raised 

the leaf N concentration in young oil palms than the 

application of 2 kg of ammonium sulphate per palm per 

year.

Song and Yap (197 6) postulated that the reduction in 

soil erosion are due in part to improved aggregation of 

the soil particles and increased water infiltration 

rates. This they claimed resulted from the increased

readily decomposable organic matter added to the soil by



22

the legume cover. In addition, the extensive root system 

of legumes acts as a permeable barrier thus reducing the 

rate of run-off. Agamuthu and Broughton (1985) estimated 

the leaching losses under legume covers to be 63 kg N per 

hectare per year less than the losses under other plant 

covers.

Soil moisture is conserved from reduced by evaporation as 

the legume cover protects the soil surface from the 

direct effect of sunlight.

One good method to suppress noxious weeds such as 

Chromolaena odorata especially during the immature phase 

is to grow the legume cover crop in the inter rows. 

Vigorous and luxuriant weed growth poses a serious 

competition to the main crop. Rajaratnam et al., (1977) 

reported of competition for nutrients between the oil 

palm and weeds. Gray and Hews (1968) reported yield 

reductions due to weeds of 6% to 20% in a mature oil 

palm. Teo et al (1991) observed an increase in yield of 

about 11.8% when a noxious weed, Ischaemun muticum was 

totally removed.

There are however some negative effects of cover 

crops on the oil palm. Ochs and Daniel (197 6) observed



23

that in drier climates legume covers can cause a decrease 

in yields of oil palm due probably to competition with 

the crop for water during the dry season.

Aya and Lucas (1977) considered the initial poor

establishment of legumes a hindrance to the control of 

erosion and viewed the subsequent vigorous growth as 

providing strong competition for water and nutrients.

2.3.2: Intercropping oil palm with food crops

Andrews and Kassam (197 6) defined intercropping as

growing two or more crops simultaneously on the same

field. Crop intensification is said to be both in time

and space dimensions. The practice of intercropping is 

ccmmon among small-scale farmers in tropical Africa 

especially West Africa (Onochie, 1977).

The oil palm is grown as cash crop by these category 

of farmers who also intercrop it with food crops 

(Hartley, 1988). Crop combinations are many and varied. 

These combinations depend on the food culture of the 

area. Other factors such as climate, soil, age of palm 

and socio-economic determine the choice of crops grown.



24

2.3.3: Influence of climate on choice of intercrop

Oil palm is generally grown in the forest belt in West 

Africa. The area is characterised by bimodal rainfall

amounting to or more than 2000 mm. The growing period is

more than 200 days extending from March/April to 

October/November. Food production in this area is based 

on associations of maize, cassava, plantains, cocoyams 

and vegetables that are the dominant staples 

(Ckigbo and Greenland, 1976, Steiner, 1982). These are 

also the crops mainly intercropped with oil palm in 

combinations determined only by the farmer.

Onwubuya et al., (1988) noted that Nigerian peasant 

farmers pruned oil palm groves to the spear leaf in order 

to allow sufficient light for food crops. The same is 

practised in Ghana.

On the plantations, the small-scale farmers

intercrop oil palm with food crops but this is limited to 

the early stages when the oil palms have not yet

developed a closed canopy. This is because the majority 

of the food crops grown as intercrops with oil palm such



25

as maize, plantain and cassava are not suited to growing 

under shade except cocoyam (Hartley, 1988) .

2.3.4: Soil conditions and choice of intercrop

Wilson and Ademiran (1976) observed that cassava is an 

important staple of the tropical rain forest zone because 

it is very tolerant to low soil pH, low soil fertility 

and low moisture regimes, which characterise the tropical 

rain forest zone. Maize and plantain are also dominant 

components adapted to the small-scale farmers' situation 

in these zones as they grow well on freely drained soils 

(IITA, 1977) .

2.3.5: Socio-economic factors and choice
Of intercrops

Socio-economic factors have also been shown to influence 

the decision of small-scale farmer to practice 

intercropping. Norman (1974) established that personal 

tastes, tradition and religious convictions condition 

social factors. Getalum (1977) emphasised the fact that 

in Ethiopia crop production is for home use and food that 

habits are based on ethnic differences, cultural biases



26

and education as well as religious convictions. Economic 

factors however are based on magnitude of inputs and 

outputs, dependability of returns, prices and ease of 

transport.

Bradfield (1986) stressed those transportation 

facilities and costs are other major factors affecting 

the feasibility of crop production in a given area. Quite 

typically if roads are either unavailable or passable 

only at certain seasons of the year, farmers may adopt 

the cropping systems of crops that mature during the dry 

seasons of the year when the roads are passable.

If there are no roads at all, the farmers usually opt for 

A combination of subsistence crops.

His taste and what crop brings in maximum revenue to 

sustain his family until his palms mature (Norman 1974) 

guide the small-scale farmer's decision among others.

2.4: Growth and yield of intercropped oil palm

In the West African sub-region especially in Ghana, most 

small-scale farmers intercrop their oil palm with food 

crops during the early years of establishment.



27

Various studies have shown that tree crops can be 

successfully grown in association with food crops before 

their canopies are fully developed.

Sparnaaij (1957) in Nigeria reported that 

intercropping of oil palm with maize, cassava and 

plantain during the early years of tree establishment 

generally had no adverse effect on the growth and yield 

of the palm.

It has also been reported in Indonesia that growing 

food crops in association with rubber and oil palm do not 

have adverse effect on the young rubber or oil palm (Tan, 

I960; Srepadyo and Tan, 1968) . The findings of Onwubuya 

and Eneh (1987) and Nigeria Institute for Oil Palm 

Research (NIFOR, 1988) also agree with Sparnaaij (1957) 

that intercropping oil palm with food crops generally has 

no adverse effect on the growth and development of the 

oil palm. They observed that more leaves were produced 

per palm in the intercropped treatments than in the 

treatment with cassava.

Mean height, girth and sex ratio of oil palm 

were also highest in the combination with maize.



28

Results from the work of Ofo et al., (1988) also

confirmed some of the earlier findings. Cropping system 

involving cassava had significantly lower number of 

leaves, smaller girths and shorter palms than the rest 

involving maize, melon and maize + melon combinations. 

The palms grown with a mixture of legumes also had low 

numbers of leaves, shorter trees and small girths. Oil 

palm intercropped with maize, melon and maize + melon 

also produced a significantly higher sex ratio (ratio of 

female to total inflorescence) than any of the crop 

combinations in which cassava and sole cropped oil palm 

with legume was involved.

Christian (1959) in Ghana showed that leguminous covers 

might be more competitive with palms than intercropped 

food crops.

Work at NIFOR (1988) showed results of soil studies, 

which indicated decreases with time in soil, pH and which 

significantly, increased. Hartley (1988) also reported of 

increased adverse effects of palm shade on intercropped 

food crops with time as light interception by the oil 

palm increased.



29

2.5 Growth and yield food crops intercropped with oil 

palm

Hartley, (1988) observed that in oil palm shading and 

competition for light are the major factors for yield 

suppression of food crops by oil palm and other tree 

crops. The extent of shading and radiation distribution 

within canopies varies with tree species and is related 

to tree growth stage (Rosenberg, 1974, and Vandermeer, 

1989),

Work on intercropping has shown that yield advantages can 

be achieved as reported by Wilson and Agboola (1979) for 

cassava + maize and Onwubuya and Eneh (1987) for oil palm 

and some annual crops.

Ofoh et al., (1988) by intercropping some food crops with

oil palm found that irrespective of the cropping system 

there were no significant differences in the yields of 

the food crops. However yields from the sole cropped 

maize, cassava and melon were highest.



30

CHAPTER THREE

3.0: MATERIALS AND METHODS

3.1: A survey of oil palm based cropping
Systems in Ghana

A survey of oil palm-based cropping system was

carried out to identify and study intercropping systems

used in oil palm production. It was also necessary to 

understand the socio-economic background of farmers and

to relate such information to their practices.

The objective was to identify food crops suitable 

for intercropping with oil palm. It was also to provide 

to relevant information for designing agronomic trials 

aimed at improving and sustaining oil palm production 

within the socio-economic context of the small-scale 

farmer.

Climatic conditions confine economic oil palm cultivation 

tc the lowland tropical rain forest and moist semi- 

deciduous forest zone in the southern part of Ghana, 

van der Vossen (1969) using values of mean annual water 

deficit delineated this area into three climatic zones 

for economic oil palm cultivation (figure 3.1).



31

These areas described by van der Vossen (1969) cover six 

regions, namely Eastern, Ashanti, Western, Central,

Brong Ahafo and Volta (Figure 3.1). Farm visits were 

carried out in these six-oil palm-producing regions. In 

each region, two districts were selected. Each district 

was divided into two sub-districts and three farms were 

visited in each sub-district.

Farmers were interviewed using a detailed 

questionnaire. Questions were on agronomic practices, age 

of farmers, and their level of education, type of 

dependants and income from oil palm and food intercrops. 

Agronomic questions centred on land preparation, time of 

intercropping, duration of intercropping, plant 

population, choice of food intercrop, intercropping 

pattern, time of canopy closure, yield of food intercrop 

and oil palm yield. Other questions were on the age of 

farm, size of farm and variety of oil palm grown.



32

F i g . 3 . 1 :  A r e a s  c l i m a t i c a l l y  s u i t a b l e  f o r  o i l  p a lm

p r o d u c t i o n  i n  t h e  f o r e s t  z o n e  o f  G h a n a .

AKAAAKUMADAN''SUNYAN

BECHEM

KWADASO
KUMASI PANKESE

BUAKU

KWAMOSO

TWIFO _  
PRASO ££ 

f>.PRE5TEA ' A 
BANDAE ^

i5t> / *ObeM ,'

"ASHCUHA/
fcCCRA

AIYINAS1
'HALF ASSINl

Xg|TAK0RAD1 

SESE

KEY

- . —  . LIMIT OF THE FOREST ZONE
150 150 MEAN ANNUAL WATER DEFICIT (mm) OPTIMUM RAINFALL FOR OIL

PALM PRODUCTION
J£- 250 250 MEAN ANNUAL WATER DEFICIT (mm) FAVOURABLE RAINFALL AREA FOR

OIL PALM PRODUCTION
400<—-- 4 00 MEAN ANNUAL WATER DEFICIT (mm) SUITABLE RAINFALL AREA FOR

OIL PALM PRODUCTION
BE REGIONAL CAPITAL

Source: van der Vossen (1969)



33

3.2: Physiological and agronomic studies on

Oil palm based cropping systems

3.2.1: Experimental Site

The experiment was conducted from 1994 to 1997 at the Oil 

Palm Research Institute (OPRI), Kusi

(06.00N, 001.45w), which is about 450 meters above sea

level.

The experimental area was fairly flat but gently slopping 

in the North-South and East-West directions. The natural 

vegetation of the area is semi-deciduous forest type.

The original vegetation was cleared in 1967 and planted 

to oil palm, which was felled in 1991. A regrowth of 

bush dominated by Chromolaena odorata and relics of 

Pvararia phaseoloides and Carica papaya was the 

vegetation cleared for this experiment. Soils in the 

experimental area are sedentary. The soils of the Nzema 

series (Acrtdol, FAO) occur in upper to middle slopes and 

cclluvial soils of the Kokofu series on the lower parts 

(Asiamah and Senayah, 1991) .

The area is in a zone characterised by relatively high



34

Rainfall which falls in two seasons. The major rainy 

Season occurs from April to July. The minor rainy season 

Begins in September to the end of October or 

Mid-November. Average annual rainfall is about 1425 mm.

3.2.2: Experimental treatments, design and crop
Management

The experiment was consisted of 7 treatments arranged in 

a randomised complete block design with 4 replications.

The planting material was tenera (D x P ex OPRI) . 12

months old seedlings were transplanted in the field in

April 1994. Each plot measured 35.2 x 22 .7 m and had 12 

seedlings. Planting was done at a spacing of 8.8 m 

triangular or the equivalent of 148 palms per hectare.

The treatments were as follows:

(i). oil palm + pueraria: oil palm interrows were seeded 

with a leguminous cover crop, Pueraria phaseoloides 

The cover crop was seeded at 0.5 kg per plot in April

1994 after transplanting of the seedlings. This is 

standard estate practice, which served as the main

control in this experiment (plate 3.1)



35

(ii) . Oil palm + maize + cassava: oil palm interrows 

were cropped with maize and cassava during the major 

seasons.

Maize (var. Okomasa ex CRI) was planted on 20th April 

1994, at 0.7m x 0.5m with three seeds per stand but 

thinned to two at one week after emergence resulting in a 

plant population of 3780 per plot.

There were 27 rows per plot. The cassava, a mixture 

of Nzema, and Ankra was planted on 6th May 1994, about two 

weeks after emergence of maize and spaced at 1m within 

rows thus giving a plant population of 945 plants/ha. 

Maize and cassava rows were spatially arranged on the 

same row as oil palm and in rows 0.7m, 1.4m, 2.1m and 2.8

metres equidistant away from the palm row. The maize was 

harvested on 24th August. Cassava was harvested in March 

the following year. The cycle was repeated every year for 

the three years of experimentation (plate 3.2.)

(iii). oil palm + maize + plantain: the oil palm 

interrows were cropped with maize and plantain in the 

major season in 1994. The maize was planted and



36

harvested in the same manner and time as in the previous 

treatment and at the same plant population.

The plantain, false horn variety 'Apantu pa' , was 

planted at 3 m triangular in the interrows of the oil 

palm thus giving 88 plants per plot or ha-1.

The nearest plantain rows with reference to the oil palm 

rows were 1.2 m equidistant away from the oil palm rows.

After the first cycle maize, the plantain was maintained

up to the first Raton crop ending January 1997 

(Plate 3.3)

(iv). Oil Palm + Maize + Maize: oil palm interrows were

cropped with maize in the major season and followed by 

maize in the minor season. Major season maize was 

planted on 20th April and harvested on 24th August as for

treatment (ii). The minor season maize was planted on 6th

September 1994 and harvested on 3rd January 1995.

Spacing and plant population for both major and minor 

season maize was the same as in treatment (ii).

The cycle was also repeated every year for the three 

years of experimentation 1994, 1995 and 1996 (plate 3.4)



37

(v). Sole crop of maize, cassava and plantain were

also grown as controls on similar plot sizes and were 

planted and harvested in the same way as those in the 

Associations.

Fertilizer was applied to oil palm seedlings six 

months after transplanting, and thereafter, in September 

every year. Nitrogen was applied at 42g, P at 48g and K 

at 250g per tree (Anon, 1988). No fertilizer was applied 

to the food crops (maize, cassava and plantain.)

The food crop plots were weeded two times in a 

season. The leguminous plots in treatment 1 were slashed 

and a circle of lm around the palm was clean-weeded every 

three months. Plantain was mulched with chopped dried 

weeds at the pre-harvesting period. The pseudostem and 

leaves were used for mulching after harvesting.



38

Plate 3.2: Oil Palm Intercropped with cassava (T2)



39

Plate 3.3: Oil Palm intercropped with plantain (T3)

P l a t e  3 . 4 :  O i l  P a lm  i n t e r c r o p p e d  w i t h  m a iz e  (T 4)



40

3.2.3: Data Collection

3.2.3.1: Rainfall Data
Temperature and rainfall data were collected for the 

site. Monthly and annual water deficits were calculated 

from the rainfall data using the formula:

D = R + P - Pe

Where D = water deficit; R = theoretical soil moisture 

reserve at the end of the previous month;

P = precipitation or rainfall for the month;

Pe = potential evapotranspiration for the month 

(Surre, 1968).

3.2.3.2: Growth, development and yield of oil palm

(i) Leaf area per palm (LA)

LA = b (n X LW). Where n = number of leaflets;

Lw = mean of length x mid - width for a sample of the 

largest leaflets, and b, the correction factor = 0,55

(Hardon et al; 1969).



41

(ii) Leaf area index (LAI)
Having estimated the leaf area (LA) of a palm, it was 

related to the ground area. LAI was thus estimated:

Leaf area 
LAI = ___________

Ground area

(iii) Frond dry weight (FDW)

A non-destructive method as described by Corley (1971) 

was used to estimate this parameter which also allows for 

estimation of Dry matter production rates. A pair of 

callipers was used to measure the width and depth of 

petiole, that is the point of insertion of the lowest 

leaflet. The values obtained were put into a formula to 

estimate the FDW (Corley 1971)thus:

FDW = 0.1026 width x depth + 0.2362 (Kg)

(iv) Rate of leaf production (RLP)

Six months after transplanting the oil palm seedlings to 

the field, leaf number one, which is the youngest fully 

expanded leaf was identified and tagged. All functional



42

leaves were then counted up to the tagged leaf.

Subsequent counts were made at six - monthly intervals.

After the identification and tagging of leaf No.l, the

leaves between the current and the previous reference

leaves were counted. The total number of leaves counted

was related to time for the growth rate of leaf

production. The calculation was thus:

N 2 -  N i  

RLP = __________

T2 -  T i

Where N2, Ni were total leaf counted at the periods T2, Ti 

Respectively.

(v) Sex ratio

Male and female inflorescences produced on the palms were 

counted at bi-weekly intervals. Counted inflorescence was 

marked to avoid re-counting.

Sex ratio was then calculated from the floral production

data obtained using the formula of Corley et al. (1971):

No of female inflorescence 
Sex ratio =-----------------------------------

Total inflorescence (Male + Female).

Flowering started in August 1995 and it was monitored up

to December 1997.



43

(vi) Yield of oil palm.
Weekly individual yield recording was carried out as soon 

as palms came into bearing. The weights and numbers of 

the fresh fruit bunches (FFB) harvested were recorded 

for individual palms at each harvesting round. The data 

obtained was used to estimate yield per hectare.

3.2.3.3: Nutrient dynamics, soil moisture retention and
solar interception by the oil palm. 

(I) Soil fertility status

To assess the dynamics of soil nutrient accumulation, 

soil sampling was undertaken before land clearing and 

after every cropping cycle at 0 - 15 cm and 15 - 30 cm 

depths. 4 soil samples each from plots having a common 

treatment were bulked and mixed to form a composite. Sub­

samples of the composite were air dried, ground and 

passed through a 2-mm mesh sieve for analysis.

Soil pH was determined in a 1:1 soil and water 

suspension using a pH meter with glass electrode. 

Organic-Carbon was determined by the Walkey-Black 

dichromate method. Total nitrogen was determined by the



44

Kjedjahl method. Available phosphorus was determined by 

the Bray's No.l method and potassium by flame photometry.

(ii) Leaf nutrient dynamics

To determine the dynamics of oil palm nutrient uptake, 

leaf samples of the oil palm lamina from the central 

leaflets of leaf No.17 were taken at six-monthly 

interval.

The leaf samples were cleaned with cotton wool and 

distilled water, oven-dried at 60° C for 72 hours, ground 

and analysed for N, P and K. Nitrogen was determined by 

the kjeldahl's method, Phosphorus by the vanado-molybdate 

method and potassium by flame photometry.

(iii) Soil moisture status during the dry season

To assess which cropping system had best conserved soil 

moisture, especially during the dry season, soil moisture 

status was determined monthly over the dry season, 

November - March. Soil samples were taken at the depths 

of 0 - 15cm and 15 - 30cm. Sampling dates were delayed 

for at least six rainless days whenever the rains fell on



45

sampling dates. Soil samples were collected in aluminium 

cans, which were covered immediately. The samples were 

then weighed before and after oven drying at 80°C for 48 

hours. Gravimetric soil water content (%) as mass of 

water (g) related to mass of oven dry soil (g) and 

multiplied by 100.

(iv) Light interception by the oil palm

To study the influence of the various cropping systems on 

light interception by the oil palm canopies, two tube 

sclarimeters were used. Each solarimeter was connected 

to a Microvolt integrator (NV2) . One tube solarimeter was 

installed above the canopy of the palm about one meter 

above leaf No.l (plate 3.5) and the other were placed 

directly beneath the canopy (plate 3.6). The tubes were 

installed and set or reset on the plots at 0930 hours. 

Daily readings were taken hourly from 1030 hrs to 

1530 hrs. Measurements from the two solarimeters were 

used to estimate percentage interception of solar 

irradiance by the oil palm. Solar irradiance above canopy 

was used as basis for comparism.



46

Plate 3.5 Tube Solarimeter installed above the 

Canopy of oil palm (arrowed)

Plate 3.6 Tube Solarimeter installed beneath the 

canopy of the oil palm (arrowed)

$$• (  
(i '



47

3.2.3.4: The performance of food crops intercropped with
oil palm.

3 . 2.3.4.1 Maize

Data on growth, development and yield of maize were taken 

monthly until the maize was harvested.

A maize row were arranged on the same row as oil palm and 

coded 0, and on rows 0.7 m, 1.4 m, 2.1 m and 2.8 metres 

equidistant away from the palm row.

(i). Leaf Area (LA) Per Plant

Thirty plants were randomly selected and tagged in each 

plot. The length and the greatest width of leaves on 

these plants were measured at each sampling time. Maize 

leaf area was then estimated from the quotient of the 

leaf length and the greatest width multiplied by the 

constant 0.75 (Moll and Krampath, 1977). The formula 

was thus:

LA = Length x width x 0.75.



48

(ii). Rate Of Leaf Production (RLP)

At each sampling time all functional leaves on each 

tagged plant were counted. The total number of leaves 

counted at the different time periods was used to 

estimate RLP.

N2 -  N i
RLP = ------

T2 -  Ti

Where N2, Ni were total leaves counted at the periods T2,

Ti respectively.

(iii). Plant Height
The heights of the thirty-tagged plants in each plot were 

taken monthly. Height was taken from the ground level to 

the tallest leaf tip and mean height per plant 

calculated.
(p / \ %

(iv). Grain Yield

Rows in each plot were harvested separately. Yield 

parameters recorded were 1000 seed weight and grain yield 

per unit area.



49

3. 2.3.4.2 Tuber yield of intercropped cassava

Like the maize, the various rows of cassava were 

harvested separately. The fresh tuber weights were 

recorded for each plot. Growth and development 

measurements of cassava could not be taken due to the 

mixed population of cassava varieties planted. While some 

plants were short and branched profusely so close to the 

soil level (i.e. Nzema var.) others were tall and almost 

did not branch (i.e. Ankra var.).

The two varieties grown and identified were however 

supposed to have same yield potential of 25t ha'1.

3.2.3.4.3 Growth, development and yield of plantain

Growth and development measurements started at three 

Months after planting of plantain and thereafter 

continued monthly until flowering. Ten plants per plot 

were randomly selected for measurements. The Data 

collected were:

(i). Plant height at flowering

Height of the plants was taken from soil level to the 

point where the peduncle emerged from the pseudostem.



50

( i i ) . Girth of the pseudostem

The girth of the pseudostem was measured at a height of 

1 m from ground level using a measuring tape.

( i i i ) . Rate of leaf production (RLP)

This was determined as described for maize using leaf 

production over time.

N2-Ni
RPL = ----------

T 2- T i

Where N2,Ni were total leaves counted at the periods T2, Ti 

respectively.

( i v ) . Leaf area (LA) per plant
Plantain leaf area was determined as the product of the 

leaf length and the greatest width multiplied by the 

constant 0.81.

(v). Type and rate of wind damage

The type and incidence of lodging were assessed from 

weekly counts of lodged plantain suckers and especially 

after rains.



51

Counted lodged plantain suckers were immediately cut into 

pieces and disposed of as mulching material which ensured 

avoidance of duplication of counts. Cumulated count of 

lodging was recorded for each plot.

(vi). Yield and components of yield

At harvesting, bunches were weighed and the number of 

hands per bunch as well as the number of fingers per hand 

and peduncle weight were recorded. Finger weight was also 

recorded. The total fruit weight was obtained as the 

bunch weight minus the peduncle weight. Yield of plantain 

between February 1995 and January 1996 was recorded for 

1995. Bunches harvested between February 1996 and 

February 1997 was entered for 1996

3. 2.3.5: Weed growth and succession

Weed samples were taken on the eve of each weeding 

exercise. Weed species and their intensities were 

recorded with a quadrat of 100 cm x 50 cm. The average 

over two locations randomly selected in each plot was



52

determined. The quadrat was placed and weeds within it 

were cut, identified and sorted into species.

They were then oven-dried for 48 hours at 80°c for 

dry weight determination. The data was used to study the 

weed control efficiency by the various systems between 

1995 and 1996. Relative weediness(DW) of species was 

calculated as follows:

Treatment's species Weed Dry Weight x 100
DW =----------------------------------------------

Total Treatment Weeds Dry Weight

3.2.3.6: Agroeconomic analysis of intercropping

Food crops with oil palm.

The cost benefit analysis of intercropping food crops 

with oil palm was by comparing production cost and 

revenue for sole oil palm with that of intercropped oil 

palm. Records were kept of cost of inputs, equipments and 

labour used for the experiment. Labour cost at the period 

of study was used as well as the current market prices of 

produce.



53

(i) Production Costs of the cropping systems

Total cost was calculated as X= a+ b+ c+ d+ e.

Where variables a,b,c,d and e were:

a - cost of planting materials/seeds 

b - labour cost throughout the cropping cycle 

c - harvesting costs

d - storage costs, if there were any and 

e - marketing costs

(ii) Value of produce (V)

The economic yields of the oil palm and food crops were 

multiplied by the mean market prices for the three years 

to give value in monetary terms. The computation was:

V = paYa + pb Yb 

Where pa, pb are constants measuring the value in 

monetary terms of unit amounts of A and B, assuming that 

quality of produce remains same and that there was no 

change in cost price.



54

(iii) Net returns (Benefits)

All costs were deducted from the revenue and the 

resulting Net Returns for oil palm 'with' and 'without' 

intercropping compared.

BENEFITS = REVENUE - COSTS 

(iv). Economic assessments

The cost benefit ratio, which is the return per cash 

invested, was calculated by relating Gross Income to 

Total cost of production or cash invested. This was 

obtained from the formula:

Gross Return
Cost benefit ratio = --------------------------

Total cost of cultivation

The income equivalent Ratio (IER) which is the relative 

land area under sole crops, that is required to produce 

the incomes achieved in intercropping was extrapolated 

using the sole oil palm with pueraria cover crop as the 

basis of comparison.



55

CHAPTER FOUR

4.0: RESULTS
4.1: Features of oil palm based cropping systems in

Ghana

4.1.1: Age distribution of oil palm farmers

Over 70% of oil palm farmers studied were aged between 30 

and 60 years old (Table 4.1) . In the Western and Central 

regions, about 90% of the oil palm farmers were in this 

category. About 22% of the farmers were over 60 years 

Old. Farmers under 30 years rarely planted oil palm.

4.1.2. Level of education of farmer

Eighty-one percent of the respondents had some formal 

education (Table 4.2). Fifty percent of those interviewed 

had only primary school education, and only 3.5% went 

beyond Secondary School.

4.1.3. Composition of dependants

On the national scene, the mean age of dependants, above 

18 years was highest and the least was recorded for those



56

below 10 years (Table 4.1). Over 40% of the dependants 

were above 18 years, except for Central region.

Table 4.1: Age of Farmers (%)

Region
Age of farmers (yr.)

< 30 30 - 60 > 60

Eastern 75 25
Aconite - 80 20
Western 10 90 -
Central - 88.9 11.1
B/Ahafo - 62.5 37.5
Volta - 60 40
Average 1.7 76.0 22.3



57

Table 4.2: Level of Formal Education (%)

Region
Level of education

No School
Primary
school

Secondary
school

Tertiary
Level

Eastern 25 75 _ -

Ashanti 10 70 10 10
Western 20 40 40 -
Central 11.1 44.1 33.4 11.1
B/Ahafo 25 37.5 37 . 5 -
Volta 20 30 50 -
Average 18.8 49.5 28.5 3.5

Table 4.3: Composition of Dependants on Farm Revenue (%)

Region
Age of Dependants

< 10 yrs 10 - 18yrs > 1 8  yrs

Eastern 25.8 25. 8 48.4
Ashanti 22.9 35.5 41. 6
Western 26.5 30. 6 42.9
Central 37.3 33. 6 29.1
Brong Ahafo 27.7 26.5 45. 6
Volta 16.7 38.9 44 . 4
National Average 26.2 31. 8 42 . 0



58

4.1.4: Income from oil palm produce

Table 4.4 shows the proportion of farm income from 

various oil palm produce. On the average, farmers 

generated about 38% of their income from sale of bunches. 

In the Volta region, however, palm oil generated the 

highest revenue of 32% followed by sale of 7 bunches 

(30.7%), kernel (16%), kernel oil (9.3%), palm wine (8%) 

and loose fruit (4%) .

In the Western region about 55% of income from oil 

palm came from bunches and only 7% from palm oil.

Between 22.7% and 54.9% of revenue was record from sale 

of bunches in the Eastern, Central, Western and Ashanti 

regions.



59

Table 4.4: Relative incomes from various oil palms 
Produce (%)

Region Bunches Fruits Palm
Oil

Kernel Kernel
Oil

Palm
Wine

Eastern 22.7 25.0 22 .7 9.0 9.0 4.5
Ashanti 34.4 31.2 23. 6 - - -
Western 54.9 32.9 7.3 - - -
Central 41.3 21.2 21.7 - 9.3 -
Brong Ahafo 47.3 27.0 14 . 9 - - -
Volta 30.7 4.0 32.0 8.0 9.3 8.0
Mean 38.0 24.1 20.4 2.1 4.6 2.1

4.1.5: Income from food intercrops

Farm income from food intercrops is presented in Table 

4.5. Maize, cassava and plantain in a declining order of 

importance are the major food crops used as intercrops in 

oil palms. They provide 32.0%, 30.5% and 16.1% of

revenue to the farmer beside the oil palm produce.

The same trend is exhibited in the regions except in the 

Volta region where maize provided 5.8% more income than 

cassava.



60

Cocoyams, fruits, vegetables, yams and rice follow in 

declining order of importance as intercrops providing 

extra revenue to the farmers. Farmers indicated that 

consumption of these intercrops takes precedence over 

their sale for extra income.

Table 4.5: Relative Incomes from Food Intercrops (%)

Region Maize

Cassava

Plantain
____

 
_

Cocoyam

Fruits

Vegetables

Yams

Rice

Eastern 32 . 6 32 . 6 11. 6 7 . 0 9.2 7.0 - -

Ashanti 29.3 26.0 23.6 7.3 3.3 8 . 9 1. 6 -

Western 36.4 29.9 20.6 6.6 2.8 3.7 - 4 . 0

Central 32.0 27 .1 17.3 3.3 10.2 1. 0 5 . 1 3.7

B/Ahafo 28 . 0 27.1 15 . 9 9.3 - 5 . 6 10.3 -

Volta 33. 9 39.7 7.53 4 . 9 6.1 4 .1 3.8 -

Mean 32.0 30.4 16.7 6.4 5.3 5.1 3.5 1.3



61

4.1.6: Agronomic practices of farmers

Categorisation of farmers according to some agronomic 

practices is shown in Tables 4.6. and 4.7. The practices 

of farmers seemed to change little from region to region. 

Nc respondent planted his palms at a wider spacing than 

the recommended 8.8-m triangular (148 plants hectare”1). 

Over 70% of the farmers in the Volta region planted 

denser than the 148 palms hectare’1. (Table 4.6)

In the Brong Ahafo region, 33.3% planted denser than 

148 plants hectare"1. Between 77.8% and 90% of farmers in 

the Eastern, Ashanti, Western and Central regions planted 

at 148 palms hectare-1.

All farmers interviewed except some in the Brong 

Ahafo and Volta regions planted the improved material, 

'Tenera'. About 58% of respondents in the Volta Region 

planted unimproved 'Dura' materials collected as 

volunteer plants from other plantations and or tendered 

the natural oil palm grove.

All farmers visited during the survey had weed 

problems. Most of their farms especially, the younger 

ones were infested With Chromolaena odorata.



62

The most common among the weed control measures adopted 

was hand weeding followed by slashing (Table 4.7).

Less than 10% of the farmers interviewed used herbicides 

and this was mostly used to control weeds in maize 

intercrops.

Table 4.6: Frequency of planting materials and
planting density used by farmers. (%)

Region

Planting density 
(plants/hectare)

Planting material

148 >148 Tenera Dura

Eastern 80 20 100 -
Ashanti 90 10 100 —
Western 90 10 100 —
Central 77 . 8 22.2 100 -
Brong Ahafo 66.7 33.3 80 20
Volta 27.3 72.7 41.7 58.3
Mean 72.0 28 . 0 87 . 0 13.0



63

Table 4.7: Frequency (%) of weed control methods 
Adopted by farmers.

Region
Weed Control Method

Weeding Slashing Herbicides

Eastern 50 25 25
Ashanti 76.9 7 . 7 15.4
Western 100 - -
Central 66.7 22 .2 11.1
Brong Ahafo 67 . 6 22.5 9.9
Volta 83.4 8 . 3 8.3
Mean 74 .1 14.3 11. 6

4.1.7: Duration of intercropping

The duration of intercropping food crops in oil palm is 

presented in (Table 4.8). In the Eastern, Ashanti, 

Western and Central regions, young palms were 

intercropped up to three years. Some farmers in the 

Central, Brong Ahafo and the Volta regions planted 

intercrops for six years.



64

Table 4.8: Distribution of farmers in terms of duration 

of intercropping Food crops. (%)

Region
Intercropping Duration

1 - 3  yrs. 4 - 6  yrs.

Eastern 100 _
Ashanti 100 -
Western 100 -
Central 90 10
Brong Ahafo 16.7 83.3
Volta 66.7 33.3
National Mean 78.9 21.1



65

4.2: Physiological and agronomic studies on oil

palm based cropping systems.

4.2.1: Weather during the Period of experimentation at
Kusi .

The temperature, rainfall, and water deficit in the years 

of experimentation followed the same trend as the long­

term area means. Mean monthly temperatures fluctuated 

between 22.6°C and 31.1°C, and the yearly mean was between 

2 6 . 3°c and 26.9°c (Table 4.9).

The mean annual rainfall of the area is 1512 mm and was 

distributed in a bimodal pattern. The major rains fell 

between March and June and followed by a short dry season 

in July to August. The minor rains were in September and 

October.

The major dry season started from November to March. 

Rainfall pattern from 1994 to 1997 seemed to follow same 

trend. The wettest year was 1995 with a total rainfall 

of 1768 mm while 1996 was the driest year with 1306 mm 

rainfall (Table 4.10).

Monthly water deficits were recorded for January and 

February for 1994 through to 1996 and from January to



66

March in 1997. January to March is usually the driest 

period for the area (Table 4.11).

Comparatively, moisture retention of the soil during the 

period of experimentation was better than the average for 

the area.



67

Table 4.9: Mean Monthly Temperatures (°c) 1994 - 1997

Month Area Mean
YEAR

1994 1995 1996 1997

January 28.2 25.5 26.1 26.3 26.9
February 26.9 27.8 27.8 27.8 27 . 9
March 27 . 8 27.2 26.7 27.7 28.0
April 27.5 27.7 27.7 27 . 6 24.7
May 27 .1 26.6 27.2 27.1 26.4
June 26.2 26 31.1 26.0 26.2
July 22. 6 24 . 9 25.3 25.5 25.1
August 24.9 25.0 25.4 26.1 25.2
September 25.8 25.4 26.1 27.5 26.6
October 26.3 26.5 26.5 26.5 27.4
November 26.8 26.9 26.9 27 .1 26.9
December 26.1 25. 9 25.9 26.5 26.7
Mean 26.4 26.3 26.9 26.7 26.5



Table 4.10: Monthly Amount of rainfall (mm) 1994 - 1997

Month Area Mean
YEAR

1994 1995 1996 1997

January 22.5 91. 6 24.4 8.4 8.6
February 40.5 8 . 9 9.9 36.1 30.5
March 135.9 128 .1 153. 6 224 .2 45.7
April 167 . 8 211.2 285.0 89.1 238 . 7
May 214 . 6 199.3 247.3 201. 3 150.3
June 211.3 164.9 252 .4 213.4 314 . 6
July 119.7 81.5 133. 9 148 . 4 91. 8
August 94 . 8 59.2 175.4 95.5 66.9
September 145.1 170.3 148.9 52 . 5 88.9
October 187.3 180.1 162 . 0 115.2 150.0
November 121.8 164 . 5 119.0 49.5 118.0
December 50.8 0.0 56.1 72.4 56.7
Total 1512.1 1459.6 1767.9 1306.0 1360.7



69

Table 4.11: Monthly water deficit (mm) 1994 - 1997

Month Area Mean
YEAR

1994 1995 1996 1997

January 102.4 0.0 75. 6 36.5 141.4
February 115.0 134.4 140.1 113.9 119.5
March 31.5 21. 9 0.0 0.0 30.5
April 6.1 0.0 0.0 0.0 0.0
May 3.5 0.0 0.0 0.0 0.0
June 0.0 0.0 0.0 0.0 0.0
July 0.7 0 . 0 0.0 0.0 0.0
August 25.2 0.0 0.0 0.0 0.0
September 8.9 0.0 0.0 0.0 0.0
October 7 . 6 0.0 0.0 0.0 0.0
November 9.2 0.0 0.0 0.0 0.0
December 20.4 0.0 0.0 0.0 0.0
Total 330.5 136.3 215.7 150.4 291.4



70

4.2.2: The effect of intercropped food crops 

on growth, development and yield of oil palm.

4.2.2.1: Leaf area (LA) development

Table 4.12 shows oil palm leaf area as affected by 

cropping systems. Significant differences in leaf area 

among the various intercropped systems occurred only at 

18 and 36 months after plantin. Mean leaf area per palm 

at six months after planting was 4.65 m2. This increased 

to 92.97 m2 at thirty-six months after planting. Leaf area 

development was 95.3%, 124%, 88.3%, 33.4% and 80.4% at

12, 18, 24, 30 and 36 months after planting respectively. 

Highest increase in leaf area at 18 months after 

planting.

Leaf area was highest in the system with oil palm 

intercropped with maize in both major and minor season. 

The lowest LA development was for the system oil palm + 

maize + cassava (Table 4.12).



71

Table 4.12: Oil Palm Leaf area (m2) as affected 
by cropping systems

a
CROP COMBINATION Months after planting

6 12 18 24 30 36

Op + Pue 4.75 9.40 20.11 39. 90 52.71 92 .14

OP + Ma + Ca 3.88 7.75 16. 05 33.10 45. 64 81.50

OP + Ma + PI 4.78 9. 64 19. 98 38. 92 52.21 94 .12

OF + Ma + Ma 5 .17 9.54 26.48 73.70 55.54 104.13

LSD (P=0. 05) NS NS 6. 15 NS NS 14 .18

CV (%) 15.66 17 . 45 18 . 60 12. 12 8.71 9.53

a: OP = Oil Palm; Ma = Maize; Ca = Cassava; PI = Plantain 
and Pue = Pueraria.

4.2.2.2: Leaf area index (LAI)

The LAI of the oil palm also varied with the cropping 

Systems (Table 4.13). The lowest LAI was recorded for 

Oil palm + maize + cassava treatment.

The trend of attainment of LAI was similar to that of LA 

Development.



72

Table 4.13: Leaf Area Index in relation to 
Cropping system.

A
CROP COMBINATION Months after planting (MAP)

6 12 18 24 30 36

Op + Pue 0.04 0.08 0.17 0. 32 0. 43 0.77

OP + Ma + Ca 0.03 0.06 0.13 0.27 0.38 0. 68

OP + Ma + PI 0. 04 0.08 0.16 0.32 0.42 0.77

OP + Ma + Ma 0. 05 0.08 0.21 0.36 0.46 0.85

LSD (P=0.05)b NS NS 0.05 NS NS 0.10

CV (%) 22 .36 14 .25 17 . 05 16.24 9.82 88.26

a: OP = Oil Palm; Pue = Pueraria; Ma = Maize;

Ca = Cassava and PI = Plantain 

NS = Not significant

4.2.2.3: Rate of Leaf production

Leaf production per month was significantly (P < 0.05) 

affected by the cropping systems but only during the 

first six months(Table 4.14).



73

Oil palm cover cropped with pueraria and oil palm in 

association with maize + maize had

higher rates of leaf production than oil palm with 

cassava or plantain (Table 4.14).

Table 4.14: Leaf Production per month under
various cropping systems

CROP
a

COMBINATION Months after planting (MAP)

6 12 18 24 30 36

Op + Pue 1.5 2.0 2.5 3.2 3.9 5.0

OP + Ma + Ca 1.3 1. 9 2 .1 2 . 9 3 . 6 4 . 9
OP + Ma + PI 1. 4 1.9 2 . 4 3.0 3.5 4 . 9
OP + Ma + Ma 1.5 2.2 2 . 9 3.5 3.8 5.1
LSD (P=0.05) 0.2 NS NS NS NS NS
CV (%) 18 . 0 25.1 20.1 15.7 13. 6 10.04

a : Op = Oil palm; Pue = Pueraria; Ma = Maize;

Ca = Cassava; PI = Plantain and NS = not significant



74

4. 2.2.4: Frond dry weight

Table 4.15 shows frond dry weight (FDW) as affected by 

various cropping systems. The FDW of the oil palm was 

significantly affected by intercrop (P<0.05). Rate of 

increase in FDW was highest in oil palm + maize + maize 

treatment and lowest in oil palm + maize + cassava. 

Differences in FDW of oil palm grown in association with 

the various intercrops were significant (P < 0.05)at all 

the sampling times.

Table 4.15: Frond Dry weight (kg) accumulation in
relation to cropping systems

a
CROP COMBINATION

Months after planting

6 12 18 24 30 36

Op + Pue 0.41 0. 47 0.71 0.84 0. 98 1.02

OP + Ma + Ca 0 .37 0.44 0. 66 0.76 0.89 0. 92

OP + Ma + Ca 0.39 0.45 0. 68 0.81 1. 03 1. 01

OP + Ma + Ma 0.38 0.48 0.72 0.84 1. 04 1.06

LSD P=0.05) 0.031 0.02 0.02 0.027 0.026 0.03

CV ( ) 12. 9 11. 0 7.30 6.22 5.09 5.04

i: Op = Oil palm; Pue = Pueraria; Ma = Maize; Ca = Cassava; 

PI = Plantain and NS = not significant.



75

4. 2.2. 5: Inflorescence production of oil palm

Table 4.16 shows inflorescence production by oil palm 

from 1995 to 1997. In 1995, only male inflorescences were 

produced. Sole cropped oil palm and oil palm intercropped 

with maize + maize produced higher number of male flowers 

than the combinations with plantain and cassava.

In 1996, female flower production was significantly 

( P < 0.05) affected by the various cropping systems.

Again, sole - cropped oil palm with pueraria cover crop 

and oil palm intercropped with maize + maize produced 

higher number of female flowers than the combinations 

with plantain and cassava.

The sex ratio ranged from 42% in oil palm with maize + 

cassava to 65% in oil palm intercropped with maize in 

both seasons in 1996. A similar trend in sex ratio was 

maintained in 1997 as in 1996.



76

Table 4.16: Number of inflorescence per plot and sex
ratio under various intercropping systems

Crop

Combination

Number of Male 

Inf1ores cence

Number of 

Female inflore. bSex Ratio (%)

1995 1996 1997 1996 1997 1996 1997

Op + Pue 34.5 100 30 146.1 53.2 59.4 63.9
OP + Ma + Ca 7 . 9 125 39.3 87 . 4 45 . 0 42 . 3 53.3
OP + Ma + PI 9.0 92 .5 38.2 100.7 55.0 52 .1 59.0
OP + Ma + Ma 31.8 100.5 25.0 183.0 56.9 64 . 6 69. 4

LSD (P=0.05) NS NS NS 44 . 2 NS NS NS
CV (%) 71.0 23 . 4 26.5 20.4 27.3 14 . 9 15. 12

a: Op = Oil Palm; Pue = Pueraria; Ma = Maize;

Ca = cassava; PI = Plantain and NS = Not significant

b. No. of female infloresence/No. of male + female 

Inflorescences

4. 2.2.6: Yield of the oil palm

In Table 4.17, the number of bunches per palm, single 

bunch weight and fresh fruit bunches per hectare are 

presented for the period August to December, 1996 and 

for the full year in 1997. Harvesting of fresh fruit



77

bunches (ffb) started in August 1996, some twenty-seven 

months after transplanting the oil palm seedlings to the 

field. Significant differences (P <0.05) among the 

cropping systems were found for some yield parameters. 

Number of bunches produced per palm varied significantly 

(P < 0.05) among the intercrops for the five months in 

1996 but differences were not significant for 1997.

The average of bunches produced per palm in 1996 was 2.4 

for the oil palm + maize + maize treatment. This was about 

70%, 74% and 20% higher than oil palm + maize + cassava, oil 

palm + maize + plantain and oil palm + pueraria respectively. 

A similar trend was obtained in 1997. There was very little 

variation in the average single bunch weight among the 

treatments. Thus the number of bunches produced per tree 

greatly influenced the yield of fresh fruit bunches.