CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Cassava is among the most important food crops cultivated in Nigeria, which is also the world's largest producer of the crop. A report prepared for the Food and Agriculture Organization (FAO) and the International Fund for Agricultural Development (IFAD) estimated Nigeria's cassava production at approximately 34 million tonnes in 2002 (Phillips et al., 2004). More recently, a modelling study estimated that the country produces over 59 million tonnes of fresh cassava roots annually (Srivastava et al., 2023). A large proportion of this production comes from small-scale farmers, who depend on cassava both as a major food source and as a means of earning income (Umunakwe et al., 2015). Improving the quantity of cassava harvested per hectare is therefore important for household food security, rural livelihoods and industries that use cassava as raw material.

Despite the importance of the crop, the yields obtained by many farmers remain considerably lower than its potential yield. Srivastava et al. (2023) examined the cassava yield gap in Nigeria using a crop modelling approach. Their findings showed that inadequate nutrients and water availability contribute significantly to the difference between actual and attainable yields. The study further suggested that cassava yields could potentially increase up to five times under improved conditions. However, the potential yield estimates were based on favourable conditions, including suitable planting dates, appropriate plant populations and improved varieties. This indicates that planting density is one of the important management decisions that can influence cassava production and is largely determined by the farmer.

Research conducted on smallholder farms in East Africa also demonstrates that several factors influence cassava yield. Fermont et al. (2009) combined farm surveys with 99 on-farm trials and six on-station experiments in Uganda and western Kenya. They observed considerable differences in yield among farms, which were associated with labour availability, soil conditions and harvesting periods. Their findings also showed that poor soil fertility, early water stress and inadequate weed management reduced yields by 6.7, 5.4 and 5.0 tonnes per hectare, respectively, even where improved planting practices and varieties were used. Many farms also experienced more than one production constraint. These findings indicate that plant population density should not be considered in isolation because other farm and environmental conditions also influence cassava yield. Consequently, surveys of farmers' fields should collect information on these related factors when examining the relationship between planting density and yield.

Plant population density in cassava production is determined by several planting decisions. These include the distance between rows, the distance between plants within each row, the number of stem cuttings planted at each stand, and the method of land preparation, such as flat planting, mound planting or ridge planting. Each of these decisions has financial and labour implications. For example, closer spacing requires more stem cuttings per hectare, which farmers must produce, purchase or reserve from previous harvests. It may also increase the labour required for planting and weeding. On the other hand, wider spacing reduces the quantity of planting materials required but leaves more exposed soil between plants during the early stages of crop growth. These differences help explain why farmers within the same community may use different planting densities and why the most suitable density may vary according to their individual circumstances.

Experimental studies have provided evidence that planting density can influence cassava yield. Onasanya et al. (2021) investigated the effects of tillage, plant population density, weed management and fertiliser application in 230 farmers' fields in south-western Nigeria over two years. They reported that increasing the population from 10,000 to 12,500 plants per hectare improved root yield by 1.5 Mg/ha across the tillage treatments, while fertiliser application increased yield by 4.2 Mg/ha. Similarly, Uko et al. (2026) conducted a study at Umudike in south-eastern Nigeria, comparing planting distances of 1 m × 0.6 m, 1 m × 0.8 m and 1 m × 1 m using two cassava varieties with different branching characteristics. Their findings showed that the closer spacing treatments produced the highest fresh root yields. They also observed that the effect of spacing on leaf area differed between the two varieties. Although both studies suggest that closer planting can improve cassava yield under certain conditions, they were conducted using specific varieties and experimental locations. Their findings do not necessarily describe the planting densities used by farmers who make their own planting decisions under different field conditions.

Information on the actual planting practices of cassava farmers is less extensive. Anyanwu (2018) surveyed 120 cassava farmers in Imo State using a structured questionnaire and found that planting spacing was among the least adopted cassava production technologies. Its mean utilisation score was 2.4, compared with an overall mean of 2.6 for agronomic practices. The study identified high labour costs, limited access to credit, inadequate farmland, pests and diseases as major constraints affecting farmers. In Abia and Imo States, Nwaobiala (2018) reported relatively high adoption levels of cassava agronomic practices, with adoption indices of 86% and 80%, respectively. The study also found that radio programmes, extension agents and other farmers were important sources of agricultural information. In another study conducted in Imo State, Umunakwe et al. (2015) found that 92.7% of the farmers obtained information about improved cassava varieties through farmers' groups. The major challenges identified included inadequate credit facilities, limited access to information and the land tenure system. These findings suggest that farmers may be familiar with recommended cassava production practices but may not always apply the recommended planting density. Their decisions may be influenced by the cost of production, availability of land, labour requirements and access to agricultural information.

Cassava is also frequently cultivated alongside other crops, particularly in southern Nigeria. Anyanwu (2018) reported that farmers in Imo State practised cassava-based intercropping systems, including cassava/maize/egusi and cassava/maize/telferia combinations. Growing cassava with other crops can influence the level of competition for sunlight, water, nutrients and available space. Therefore, a planting density that is suitable for cassava grown alone may not produce the same results when it is cultivated with other crops. For this reason, the cropping system should be considered when examining the relationship between plant population density and cassava yield on farmers' fields. Ikwerre Local Government Area is located in Rivers State, within the Niger Delta region. The literature reviewed for this study does not identify a specific investigation of the plant population densities used by cassava farmers in the area.

This study will therefore examine the planting distances and plant population densities commonly used by cassava farmers in Ikwerre Local Government Area. It will also collect information on the yields reported by farmers and consider other conditions associated with their production activities, including cropping systems, cassava varieties, soil conditions and labour availability. In addition, the study will investigate the reasons behind farmers' planting decisions and the challenges they face when selecting planting densities. The information obtained will provide a local understanding of cassava planting practices and serve as a basis for developing more relevant agricultural recommendations for farmers in the area.

1.2 Statement of the Problem

A considerable difference exists between the cassava yields obtained by Nigerian farmers and the yields that the crop can potentially produce. Plant population density is one of the production factors that farmers can adjust through their planting decisions, although doing so requires sufficient planting materials and labour (Srivastava et al., 2023). Research findings have established that planting density can influence cassava root yield. For instance, Onasanya et al. (2021) reported increased root yield with moderately closer planting in farmers' fields in south-western Nigeria, while Uko et al. (2026) found that closer planting distances produced higher yields in their experiment at Umudike. However, these findings also indicate that the response to planting density may depend on the variety, location and prevailing field conditions. It is therefore not appropriate to assume that the same planting density will produce similar results among farmers in Ikwerre Local Government Area.

Existing surveys have also shown that planting spacing is one of the cassava production practices that farmers in parts of south-eastern Nigeria do not consistently adopt (Anyanwu, 2018). The challenges associated with the adoption of recommended practices include high labour costs, limited access to credit, inadequate farmland and insufficient agricultural information. However, there is limited information about the actual plant population densities used by cassava farmers in Ikwerre. In particular, there is a need to understand how planting densities vary according to farm size, cropping system, cassava variety and the cost or availability of stem cuttings. There is also a need to examine the root yields farmers report under different planting densities. Without this information, it is difficult to determine whether farmers are using densities that may be too low, thereby limiting their possible yields, or densities that are unnecessarily high and require additional planting materials without corresponding yield benefits.

The absence of local information creates practical difficulties for agricultural development and extension services in the area. Extension officers and other agricultural advisers have limited local evidence for assessing whether the planting densities used by farmers are appropriate for their production conditions. A general planting recommendation may not address the different circumstances of farmers, particularly those with differences in land availability, labour resources and cropping systems. Farmers also have limited information for comparing their planting practices and reported yields with those of other farmers within their communities. Furthermore, researchers planning future cassava production experiments in Ikwerre may lack the necessary information about the planting densities commonly used by local farmers when selecting appropriate experimental treatments. As a result, opportunities to improve cassava production through better-informed planting decisions may remain underutilised.

The major problem addressed by this study is the limited availability of survey information on the plant population densities used by cassava farmers in Ikwerre Local Government Area, the growth and root yields they report under different densities, and the factors influencing their planting decisions. The study will use a structured questionnaire to obtain information from cassava farmers across the area. This approach will help describe existing planting practices, farmers' experiences and the production challenges associated with their choice of plant population density.

1.3 Objectives of the Study

The main objective of this study is to assess the relationship between plant population density and the growth and yield of cassava as reported by farmers in Ikwerre Local Government Area, Rivers State.

The specific objectives are to:

(i) describe the socio-economic characteristics and farm-related conditions of cassava farmers in the study area;

(ii) identify the planting distances and corresponding plant population densities used by cassava farmers;

(iii) examine the growth characteristics, including plant vigour, height and branching, as well as the root yields reported by farmers under different plant population densities;

(iv) determine the relationship between plant population density and reported cassava root yield, while considering cropping system, variety and farm size; and

(v) identify the factors that influence or limit farmers' choice of cassava planting density.

1.4 Research Questions

The following research questions will guide the study:

1. What are the socio-economic characteristics and farm-related conditions of cassava farmers in Ikwerre Local Government Area?

2. What planting distances and plant population densities are commonly used by cassava farmers in the study area?

3. What growth characteristics and root yields do farmers report under the different plant population densities?

4. Is there a significant relationship between plant population density and the root yield reported by cassava farmers?

5. What factors influence or limit farmers' choice of plant population density?

1.5 Research Hypotheses

The following null hypotheses will be tested at the 5% level of significance:

H01: There is no significant relationship between plant population density and the root yield reported by cassava farmers.

H02: There is no significant difference in the reported root yield of farmers who use the highest plant population density and those who use the lowest plant population density.

H03: There is no significant relationship between farmers' socio-economic and farm characteristics, including age, sex, educational level, farm size, farming experience and cropping system, and the plant population density they use.

1.6 Significance of the Study

The findings of this study will be useful to cassava farmers in Ikwerre Local Government Area because they will provide information on the planting distances commonly used in the area and how these relate to the yields reported by other farmers. This will allow farmers to compare their own planting practices with those of other cassava producers within their communities. Where farmers observe that their planting densities differ considerably from those associated with better reported yields, they may be encouraged to reconsider their planting decisions in relation to their available resources and farm conditions.

The study will also benefit the Rivers State Agricultural Development Programme and other agricultural extension organisations. The findings will provide information on whether the planting densities used by farmers differ from recommended practices and the reasons for such differences. For example, the study may help identify whether farmers' choices are mainly influenced by the cost of stem cuttings, labour availability, limited farmland or inadequate agricultural information. Understanding these constraints will help extension providers determine whether farmers require improved technical guidance, better access to planting materials or other forms of production support.

Researchers and students interested in cassava production will also benefit from the study. It will provide survey information on farmers' planting practices in the Niger Delta, which can be considered alongside findings from experimental studies conducted in Umudike and south-western Nigeria. In addition, the findings may serve as a reference for future research and on-farm experiments in Ikwerre Local Government Area. Researchers may use the information on existing planting densities to select relevant treatments and develop experiments that reflect the production conditions of local farmers.

1.7 Scope and Delimitation of the Study

This study is restricted to cassava farmers in Ikwerre Local Government Area of Rivers State. It will adopt a cross-sectional survey design, using a structured questionnaire administered to farmers who cultivated cassava during the most recent production season.

The study will examine the planting distances between rows and between individual plants, as well as the number of stem cuttings planted at each stand. These measurements will be used to estimate the plant population density per hectare. Information will also be collected on cassava growth characteristics and root yields as reported by the farmers. Where possible, farmers' reports will be supplemented by measurements taken from selected sample plots.

The study will also consider cropping system, cassava variety and farm size when examining the relationship between plant population density and reported yield. However, it will not investigate fertiliser application, weed control, pest and disease management, or the processing and marketing of harvested cassava roots.

1.8 Limitations of the Study

The study may encounter the following limitations:

a) Dependence on farmers' reports: Information on cassava yield will partly depend on farmers' ability to remember and estimate their harvests. Since cassava is often harvested gradually over several months, some farmers may find it difficult to provide an accurate estimate of the total yield obtained from a particular field.

b) Inability to establish direct causation: The survey can identify relationships between plant population density and reported root yield, but it cannot conclusively establish that planting density alone caused differences in yield. Farmers using different planting densities may also have differences in soil conditions, cassava varieties and other management practices.

c) Differences in harvesting periods: Cassava fields may be harvested at different crop ages. Some farmers may harvest earlier than others, and premature harvesting may affect the quantity of roots obtained. Fermont et al. (2009) identified early harvesting as one of the factors associated with reduced cassava yield. Such differences may therefore influence comparisons among farmers.

d) Limited time and financial resources: The time and funds available for the research may restrict the number of communities and respondents that can be covered during data collection.

1.9 Definition of Terms

Plant Population Density: The number of cassava plants established on a hectare of farmland. In this study, it will be estimated using the planting distances and number of cuttings planted at each stand.

Planting Spacing: The distance maintained between cassava rows and between individual plants within each row.

Growth: The development and physical characteristics of cassava plants. In this study, it will be assessed through reported plant vigour, height and branching.

Root Yield: The quantity or weight of fresh cassava storage roots harvested from a given area of farmland, expressed on a per-hectare basis where sufficient information is available.

Stem Cutting: A section of a mature cassava stem used as planting material for establishing a new cassava crop.

Cropping System: The method of cultivating cassava, either as a sole crop or together with other crops on the same farmland, commonly referred to as intercropping.

REFERENCES

Anyanwu, C. G. (2018). Constraints to adoption and utilization of cassava production technologies among farmers in Imo State, Nigeria. Scientific Papers Series Management, Economic Engineering in Agriculture and Rural Development, 18(1).

Fermont, A. M., van Asten, P. J. A., Tittonell, P., van Wijk, M. T., & Giller, K. E. (2009). Closing the cassava yield gap: An analysis from smallholder farms in East Africa. Field Crops Research, 112(1), 24–36. https://doi.org/10.1016/j.fcr.2009.01.009

Nwaobiala, C. U. (2018). Farmers' adoption of cassava agronomic practices and intercrop technologies in Abia and Imo States, Nigeria. Journal of Agricultural Extension, 22(2).

Onasanya, O., et al. (2021). On-farm assessment of cassava root yield response to tillage, plant density, weed control and fertilizer application in southwestern Nigeria. Field Crops Research, 262, 108038. https://doi.org/10.1016/j.fcr.2020.108038

Phillips, T. P., Taylor, D. S., Sanni, L., & Akoroda, M. O. (2004). A cassava industrial revolution in Nigeria: The potential for a new industrial crop. International Fund for Agricultural Development & Food and Agriculture Organization of the United Nations.

Srivastava, A. K., Ewert, F., Akinwumiju, A. S., Zeng, W., Ceglar, A., Ezui, K. S., Adelodun, A., Adebayo, A., Sobamowo, J., Singh, M., Rahimi, J., & Gaiser, T. (2023). Cassava yield gap—A model-based assessment in Nigeria. Frontiers in Sustainable Food Systems, 6, Article 1058775. https://doi.org/10.3389/fsufs.2022.1058775

Uko, I., Ekeleme, F., Amadioha, A. C., Chukwu, L. I., & Uko, S. C. (2026). Effect of weed management methods and plant spacing on the growth and yield of cassava morphotypes. Agriculture, Food, and Natural Resources Journal, 5(1), 11–20. https://doi.org/10.5281/zenodo.20049591

Umunakwe, P. C., Nwakwasi, R. N., Ani, A. O., Ejiogu-Okereke, E. N., & Nnadi, F. N. (2015). Constraints to the adoption of improved cassava varieties among rural farmers in Imo State, Nigeria. Asian Journal of Agricultural Extension, Economics & Sociology, 6(1), 56–63.