THE EFFECT OF DIFFERENT MULCHING MATERIALS ON THE GROWTH AND YIELD OF COWPEA (A CASE STUDY OF COWPEA FARMERS IN MAIDUGURI METROPOLITAN AREA, BORNO STATE)

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

In the semi-arid north-east, the cheapest resource a cowpea farmer can add to a field is something that is already lying on it: millet and sorghum stalks, dry grass, husks and leaf litter. Spread on the soil surface, such material is called mulch, and its main promise in a dry environment is that it saves water. Cowpea is grown by the majority of farmers in the semi-arid north-east, yet Ekle et al. (2023) note that the productivity of the crop in the region has declined over the last decades, which is a serious matter for a crop on which so many households depend for food and cash.

Research at Maiduguri itself shows that mulch can make a difference. Ekle et al. (2023) tested tillage and millet residue mulch rates on cowpea at the Teaching and Research Farm of the University of Maiduguri and found that all the yield parameters were significantly affected by the treatments; grain yield and its components were higher under no-till as the amount of residue increased, and water use efficiency differed among treatments. For other cereals grown in the same city, Eze et al. (2014) applied rice husk mulch to sorghum and millet on a sandy loam soil. At one site, applications of 10 and 15 t/ha produced significantly higher grain yield than no mulch, by 14.3 and 15.3 per cent respectively, and stover yield rose with the rate of mulch at both sites; however, at that site the harvest index at 15 t/ha was lower than at 0 and 10 t/ha, which shows that more mulch does not improve every aspect of the crop.

Evidence from the wider Sahel indicates that the material matters as much as the amount. Ibrahim et al. (2015) compared Acacia tumida pruning, millet residue and manure as mulch on millet in Niger and found that grain yield increases relative to the unmulched control were 51 per cent for manure, 46 per cent for Acacia mulch and 36 per cent for millet mulch. They also point out that the limited availability of soil organic amendments is a problem in the Sahel, which means that the supply of mulch material is itself a constraint in biomass-scarce environments. A farmer in Maiduguri must therefore decide not only whether to mulch but with what, and the choice depends on what the farm and the neighbourhood can supply.

The amount of mulch applied also matters. Adebimpe et al. (2017) tested mulching with elephant grass on cowpea in southern Nigeria and found that mulching significantly increased soil moisture content. Their results also carry a warning: growth and yield parameters improved at 30 per cent mulch cover and then declined at 60 and 90 per cent cover. More mulch is therefore not necessarily better, and a farmer who piles on residue in the hope of saving water may be reducing the yield.

What farmers do about mulching is only partly documented. In Oyo State, Akinnagbe and John (2023) surveyed 200 arable crop farmers and found that every one of them reported adopting mulching and 91 per cent used it frequently, making it one of the most frequently used conservation practices, but the factors that most affected how effectively farmers used such practices were population pressure on land and the availability of funds. In Katsina State, Danmusa and Umar (2024) found that labour was a significant determinant of cowpea output, and the work of collecting, carrying and spreading mulch adds to the labour bill of a crop whose production is already demanding. Whether farmers in the semi-arid north-east face the same constraints, and whether they find the practice worthwhile, is not known from the literature reviewed for this chapter.

The evidence from Maiduguri itself comes from experimental plots on a university farm, where the materials, rates and timing of mulching are chosen by the researcher. Farmers in Maiduguri make these choices in different circumstances. They have to find the material, often in competition with other uses of crop residues, to decide how thickly to spread it and when, and to judge from what they see in their own fields whether it was worth the effort. Their reports of how the cowpea grew and what it yielded under different mulches, or none, are information that trials cannot provide and that no study reviewed here has gathered for Maiduguri. This study sets out to collect it with a questionnaire.

1.2 Statement of the Problem

Cowpea productivity in the semi-arid north-east has declined (Ekle et al., 2023), and soil moisture is the chief limit on growth in the environment in which Maiduguri farmers work. Mulch is an obvious remedy, and trials at the University of Maiduguri show that residue mulch can raise cowpea yield (Ekle et al., 2023). But the same body of evidence shows that the effect varies with the material (Ibrahim et al., 2015), with the amount (Adebimpe et al., 2017; Eze et al., 2014) and with tillage (Ekle et al., 2023), so the benefit cannot be assumed to follow from the mere use of mulch.

It is not known which mulching materials cowpea farmers in Maiduguri actually use, in what quantities, at what stage of the crop and for what reasons; how they rate the growth and yield they obtain under each material, and under no mulch; or what prevents them from using mulch more widely. The shortage of organic materials in the Sahelian environment (Ibrahim et al., 2015) and the labour that mulching requires (Danmusa & Umar, 2024) suggest that the practice may be more demanding for farmers than the trials imply, but there is no local evidence to confirm or refute this.

Without that knowledge, extension advice on mulching in Borno State is based on research-farm results and general principles, and may not suit the materials, budgets and labour available to farmers. Farmers who might benefit from a particular material do not learn from the experience of others. Researchers designing the next round of trials have no farmer-level information about which materials and rates are practicable.

The problem this study addresses is the absence of farmer-level evidence, for Maiduguri Metropolitan Area, on the mulching materials used by cowpea farmers, on the growth and yield they report with each, and on the constraints that limit the practice.

1.3 Objectives of the Study

The study aims to assess the effect of different mulching materials on the growth and yield of cowpea as reported by farmers in Maiduguri Metropolitan Area.

1. describe the socio-economic and farm characteristics of the farmers

2. identify the mulching materials farmers use, the quantities they apply and the stage of the crop at which they apply them.

3. determine the growth and yield they report with each material and with no mulch.

4. establish whether reported yield differs between materials; and identify the constraints that limit the use of mulch.

1.4 Research Questions

1. Which mulching materials do cowpea farmers in Maiduguri use, in what quantities and at what stage of the crop?

2. What growth and yield do the farmers report with each material, compared with no mulch?

3. Does the reported yield differ significantly between materials?

4. What constraints limit the use of mulch?

1.5 Research Hypotheses

Hypothesis 1. There is no significant difference between the cowpea yield reported by farmers who use mulch and that reported by farmers who do not.

Hypothesis 2. There is no significant difference in the cowpea yield reported by farmers using different mulching materials.

Hypothesis 3. The socio-economic characteristics of the farmers (age, sex, education, farm size and farming experience) have no significant relationship with their use of mulch.

The three hypotheses will be tested at the 5% level of significance.

1.6 Significance of the Study

The findings will help cowpea farmers in Maiduguri by showing which materials their fellow farmers find most useful and what the practice demands in labour and cost. Farmers who do not yet mulch will see what others report, and those who do will see how their choices compare.

Extension workers in the Borno State Agricultural Development Programme and in the research institutions of the area can use the results to advise on materials and amounts, and to decide whether the practice should be promoted, modified or supported with measures that ease the supply of mulch. The study will also give researchers at the University of Maiduguri and elsewhere farmer-level information with which to design trials that reflect conditions on real farms.

More broadly, the study adds to the small stock of farmer-level information on mulching in the north-east, a region where soil moisture is the main limit on production and where cowpea productivity has been declining (Ekle et al., 2023).

1.7 Scope and Delimitation of the Study

• Place and people: cowpea farmers in Maiduguri Metropolitan Area, Borno State, who grew cowpea in the most recent cropping season.

• Method: a cross-sectional survey using a structured questionnaire, supported by observation of a sample of fields where this is possible.

• Content: the mulching materials in use, the quantities and timing of application, the growth and yield reported with each material and with no mulch, and the constraints on the practice.

• Excluded: plastic film mulch, tillage comparisons, soil analysis, varietal comparison and crops other than cowpea.

1.8 Limitations of the Study

• Self-reported outcomes: growth and yield are as farmers report them and may be imprecise.

• Association, not cause: farmers who mulch may also manage their fields better in other ways, so differences in yield cannot be attributed to mulch alone.

• Amount of mulch: farmers rarely measure how much mulch they apply, so comparisons across amounts will be rough, and the materials may differ in quality.

• Access and resources: security conditions and limited time and funds may restrict the communities and respondents that can be reached.

1.9 Definition of Terms

Mulch: Material spread on the soil surface around crop plants to conserve moisture, moderate temperature or suppress weeds.

Mulching materials: The materials used as mulch, such as crop stalks, grass, husks and leaf litter, as reported by the farmers.

Growth: The development of the cowpea plant, described by farmers' reports of vigour, height and ground cover.

Yield: The quantity of cowpea grain harvested per unit area, as reported by the farmer.

Semi-arid: A climate in which rainfall is low and unreliable, so that soil moisture limits crop growth for much of the year.

References

Adebimpe, O., et al. (2017). Cowpea response to compaction and mulching on a sloping loamy sand soil in Southern Nigeria. Agricultural Engineering International: CIGR Journal, 19(1).

Akinnagbe, O. M., & John, A. M. (2023). Use of conservation practices among arable crop farmers in Oyo State, Nigeria. Journal of Agricultural Extension, 27(2). https://doi.org/10.4314/jae.v27i2.11

Danmusa, A. H., & Umar, A. S. S. (2024). Determinants and profitability of cowpea production in Safana Local Government Area, Katsina State, Nigeria. Sahel Journal of Life Sciences FUDMA, 2(1). https://doi.org/10.33003/sajols-2024-0201-029

Ekle, A. E., Ali, E., Iorlaha, V. A., Yisa, K. M., Kundet, A., Silas, Y. G., Kolo, P. N., & Ngala, A. L. (2023). Effect of tillage and millet residue mulch rates on water use efficiency of cowpea [Vigna unguiculata (L.) Walp] in Maiduguri, Nigeria. Adamawa State University Journal of Scientific Research, 11(1).

Eze, P. C., Alhassan, A. B., Kwari, S. J., Dada, Y. M., Tsado, P. A., & Lawan, A. N. (2014). Yield of sorghum and millet as affected by rice husk mulch on a sandy loam soil in Maiduguri, semi-arid north-east Nigeria. Nigerian Journal of Soil Science.

Ibrahim, A., Abaidoo, R. C., Fatondji, D., & Opoku, A. (2015). Integrated use of fertilizer micro-dosing and Acacia tumida mulching increases millet yield and water use efficiency in Sahelian semi-arid environment. Nutrient Cycling in Agroecosystems, 103(3).