THE EFFECT OF INTERCROPPING ON THE GROWTH AND YIELD OF MAIZE AND COWPEA (A CASE STUDY OF FARMERS IN MINNA AREA, NIGER STATE)

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Maize (Zea mays L.) is one of the most important cereal crops in Nigeria. It is eaten fresh, roasted, boiled or processed into pap, flour and other foods, and it is a major ingredient in livestock and poultry feed. Cowpea (Vigna unguiculata L. Walp.) is a leguminous crop widely grown in the Nigerian savanna as a source of low-cost plant protein; the grain is used in many local dishes, and the leaves and haulms are used as vegetable and fodder. Because cowpea fixes atmospheric nitrogen through bacteria in its root nodules, it also contributes to soil fertility.

Growing maize and cowpea together is a long-standing practice among smallholder farmers in the savanna zones of Nigeria. The two crops differ in their growth habits: maize is tall and requires a large amount of nitrogen, while cowpea is lower growing, supplies nitrogen through fixation and covers the soil between rows. In principle this allows the crops to use light, water and nutrients more fully than either would alone, and it spreads risk, since a poor result in one crop may be offset by the other. A common measure of the benefit of intercropping is the land equivalent ratio (LER), which shows how much land sole crops would need to produce the combined yield of the intercrop; a value above 1 means that the intercrop uses land more efficiently.

Recent evidence from Nigeria supports this. Habib et al. (2024) tested two cowpea varieties and four maize-to-cowpea row arrangements at Kano and Minjibir in the Sudan savanna and recorded LER values above 1.0 for all combinations, with the highest values (1.58 and 1.40 at the two sites) from cowpea variety SAMPEA 21 in alternate single rows. Maize yield was also highest under this arrangement. At the continental level, Daryanto et al. (2020) synthesised studies of grain legume and cereal intercropping in Africa and reported ecosystem benefits, including 23% lower weed biomass, 37% lower Striga emergence and 29% lower stemborer abundance, as well as a 15% increase in soil organic carbon.

Intercropping also has costs, and its benefits depend on how the crops are arranged. In the Guinea savanna of northern Ghana, Kermah et al. (2017) found that sole crops of maize and legumes produced more grain per unit area than the respective intercrops, although all intercrop patterns had an LER greater than one and converted intercepted radiation into grain more efficiently. Mucheru-Muna et al. (2010) studied a staggered maize–legume intercrop arrangement in the highlands of central Kenya and examined its effect on crop yields and economic returns, while Dahmardeh et al. (2010) examined the effect of maize–cowpea intercropping on yield and soil chemical properties. These studies show that factors such as row arrangement, planting time, variety and plant density determine whether the competition between the crops is outweighed by their complementarity.

The Minna area of Niger State lies in the Guinea savanna, where maize and cowpea are commonly grown and intercropping is routine. Rainfall, soils and varieties in the area differ from those of Kano, northern Ghana or Kenya, and these differences may change the outcome of intercropping. This study was therefore designed to determine the effect of intercropping on the growth and yield of maize and cowpea among farmers in the Minna area.

1.2 Statement of the Problem

Farmers in the Minna area grow maize and cowpea together largely by tradition, and few have information on how the intercrop performs compared with each crop grown alone. Studies from elsewhere show that intercropping can increase land-use efficiency (Daryanto et al., 2020; Habib et al., 2024), but they also show that each crop may yield less than it does when sown alone (Kermah et al., 2017), so that the balance of gain and loss depends on the arrangement and environment.

The trials reviewed here were conducted in other places, including Kano, northern Ghana and Kenya, and the literature consulted for this study did not reveal a measured comparison of sole and intercropped maize and cowpea carried out with farmers in the Minna area. Because rainfall, soil and varieties differ from place to place, results from these studies cannot be assumed to hold in Minna.

The effect is that farmers cannot tell whether intercropping gives them a better return from their limited land than sole cropping, and extension agents have no local figures on which to base advice. This study was undertaken to address that problem by determining the effect of intercropping on the growth and yield of maize and cowpea in the Minna area.

1.3 Objectives of the Study

The main objective of the study was to determine the effect of intercropping on the growth and yield of maize and cowpea among farmers in the Minna area, Niger State. The specific objectives were to:

(i) compare the growth of maize and cowpea under sole cropping and intercropping;

(ii) compare the grain yield of each crop under the two systems; and

(iii) calculate the land equivalent ratio to determine whether intercropping makes better use of land than sole cropping.

1.4 Research Questions

The following research questions guided the study:

(i) How does intercropping affect the growth of maize and cowpea?

(ii) How does intercropping affect the grain yield of maize and cowpea?

(iii) Does intercropping give a land equivalent ratio greater than one in the study area?

1.5 Research Hypotheses

The following null hypotheses were tested at the 0.05 level of significance:

H01: Intercropping has no significant effect on the growth of maize and cowpea.

H02: Intercropping has no significant effect on the grain yield of maize and cowpea.

1.6 Significance of the Study

The findings will help farmers in the Minna area decide whether to intercrop on their limited land. Extension agents will have local figures to compare with results from Kano, Ghana and elsewhere.

The study will also add to the evidence on legume-based cropping systems in the Guinea savanna.

1.7 Scope and Limitations of the Study

The study covers maize and cowpea farmers in the Minna area of Niger State and is limited to growth, grain yield and land use efficiency. Soil nitrogen balance, profitability and pest dynamics are outside its scope.

Limitations include the single season and the limited varieties and row arrangements studied, so results should be read as specific to the sites and season involved.

1.8 Definition of Terms

Intercropping: growing two or more crops together on the same land in the same season.

Sole cropping: growing a single crop alone on a piece of land.

Land equivalent ratio (LER): the relative land area required by sole crops to produce the yields obtained in an intercrop.

Growth: measurable plant development, such as height and leaf number.

Yield: grain harvested per plant or per unit area.

REFERENCES

Dahmardeh, M., Ghanbari, A., Syahsar, B. A., & Ramrodi, M. (2010). The role of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L.) on yield and soil chemical properties. African Journal of Agricultural Research, 5(8), 631–636.

Daryanto, S., Fu, B., Zhao, W., Wang, S., Jacinthe, P.-A., & Wang, L. (2020). Ecosystem service provision of grain legume and cereal intercropping in Africa. Agricultural Systems, 178, 102761. https://doi.org/10.1016/j.agsy.2019.102761

Habib, F. M., Bello, T. T., Miko, S., & Shittu, E. A. (2024). Yield and yield components of maize/cowpea intercrop as affected by row-arrangement and cowpea varieties in the Sudan savannah. FUDMA Journal of Agriculture and Agricultural Technology, 10(4), 47–55. https://doi.org/10.33003/jaat.2024.1004.06.377

Kermah, M., Franke, A. C., Adjei-Nsiah, S., Ahiabor, B. D. K., Abaidoo, R. C., & Giller, K. E. (2017). Maize-grain legume intercropping for enhanced resource use efficiency and crop productivity in the Guinea savanna of northern Ghana. Field Crops Research, 213, 38–50. https://doi.org/10.1016/j.fcr.2017.07.008

Mucheru-Muna, M., Pypers, P., Mugendi, D., Kung’u, J., Mugwe, J., Merckx, R., & Vanlauwe, B. (2010). A staggered maize–legume intercrop arrangement robustly increases crop yields and economic returns in the highlands of Central Kenya. Field Crops Research, 115, 132–139.