THE EFFECT OF DIFFERENT PLANTING SPACINGS ON THE GROWTH AND YIELD OF CASSAVA (A CASE STUDY OF CASSAVA FARMERS IN NSIT IBOM LOCAL GOVERNMENT AREA, AKWA IBOM STATE)

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Every planting season, a cassava farmer in the

south-south of Nigeria faces a small decision with large consequences: how far apart should the cuttings go? Some farmers set them close together to make use of every metre of a small plot. Others space them widely so that each plant has room to spread. Most simply repeat what they saw their parents do. The decision is rarely written down or tested, yet it settles how many plants stand on each hectare and, with them, how much root can be harvested.

Cassava (Manihot esculenta Crantz), a woody shrub of the family Euphorbiaceae, is grown mainly for its starchy storage roots. In Nigeria the roots are turned into gari, fufu, lafun, starch and flour, the leaves are eaten as a vegetable in some communities, and the stems supply planting material. Cassava tolerates poor soils and uneven rainfall better than most staples, and this has made Nigeria widely regarded as one of the largest producers in the world.

Yet what farmers harvest is modest. Kreye et al. (2020) describe cassava as a staple food crop in Nigeria whose root yields hardly exceed 10 t/ha. Onasanya et al. (2021) attribute the low yields to poor soil fertility and to the fact that farmers do not use improved germplasm, clean planting material or improved crop management. Both papers argue that intensifying smallholder production is central to food security and incomes.

Spacing is among the cheapest management levers available. Because cassava is planted from stem cuttings, the farmer decides the distance between stands and between rows, and that decision fixes the plant population. A spacing of 1 m × 1 m gives 10,000 plants per hectare, while 1 m × 0.8 m gives 12,500. Closer spacing puts more plants on the land and shades out weeds sooner, but it also raises competition for light, water and nutrients, which can lower the size and number of roots on each plant. Wider spacing gives each plant more room but leaves soil uncovered for longer, so that weeds thrive and fewer plants stand per hectare.

What does the evidence from Nigeria say? In 230 farmers' fields in south-western Nigeria, Onasanya et al. (2021) tested plant densities of 10,000 and 12,500 plants/ha alongside tillage, fertilizer and weed control. Planting at 12,500 plants/ha raised fresh root yield by 1.5 t/ha, and fertilizer added a further 4.2 t/ha in one season. Kreye et al. (2020) compared cassava spacings of 0.5 m by 2 m and 1 m by 1 m in cassava–legume arrangements in demonstration and on-farm trials. Intercropping with cowpea reduced cassava root yield by 2.4 t/ha on average, and median yields were about 15 to 20 t/ha in demonstration plots but only about 10 t/ha in farmers' trials. The authors concluded that intensification measures must fit the site and the farmer.

Two points stand out. The first is the gap between managed plots and farmers' fields. The second is that farmers' reasons for choosing a spacing, which include tradition, land scarcity, the cost and supply of cuttings, whether cassava is intercropped, and ease of weeding and harvesting, are rarely recorded. A questionnaire survey can capture both the spacings in use and the effects that farmers themselves observe.

Nsit Ibom Local Government Area lies in Akwa Ibom State, in the humid south-south, where cassava is both a food and a cash crop for smallholders. This study surveyed cassava farmers in the area to document the spacings they use and what they perceive those spacings do to growth and yield.

1.2 Statement of the Problem

The difficulty is not that cassava farmers in Nsit Ibom lack a spacing, but that no one has asked them which spacing they use, why, and what happens as a result. Work in south-western Nigeria shows that plant population can change root yield (Onasanya et al., 2021) and that the value of any management option depends on the site and the farmer (Kreye et al., 2020). Those findings come from a different soil and rainfall setting, and the literature consulted for this study did not reveal a survey of spacing practices among cassava farmers in Nsit Ibom.

Without this information, some farmers may be planting too closely, using up cuttings and risking smaller roots, while others plant too widely and spend heavily on weeding. Extension workers who are asked about spacing have only results from elsewhere to quote. This study was therefore undertaken to supply local information drawn directly from the farmers.

1.3 Objectives of the Study

The general objective was to find out, through a questionnaire survey, how planting spacing affects the growth and yield of cassava as experienced by farmers in Nsit Ibom Local Government Area. The specific objectives were:

1. To describe the personal and farm characteristics of the cassava farmers surveyed.

2. To record the spacings farmers use and the reasons for their choice.

3. To find out how farmers rate cassava growth (vigour, height, branching and canopy cover) under close, medium and wide spacing.

4. To find out how farmers rate root yield and root size under the same spacings.

5. To list the problems farmers meet in choosing spacing and the improvements they propose.

1.4 Research Questions

1. Who are the cassava farmers in Nsit Ibom, and what are the sizes and types of their farms?

2. Which spacings do they use, and why?

3. Do farmers consider that cassava grows better under close, medium or wide spacing?

4. Do farmers consider that roots are more plentiful or larger under one spacing than another?

5. What difficulties do they face, and what changes do they want?

1.5 Research Hypotheses

Each hypothesis is stated in null (H0) and alternative (Ha) form and was tested at the 0.05 level of significance.

H01: Farmers’ socio-economic characteristics are not significantly related to the spacing they use.

Ha1: Farmers’ socio-economic characteristics are significantly related to the spacing they use.

H02: Farmers’ ratings of cassava growth do not differ significantly among close, medium and wide spacing.

Ha2: Farmers’ ratings of cassava growth differ significantly among close, medium and wide spacing.

H03: Farmers’ ratings of cassava root yield do not differ significantly among close, medium and wide spacing.

Ha3: Farmers’ ratings of cassava root yield differ significantly among close, medium and wide spacing.

1.6 Significance of the Study

Farmers will see how their own practice compares with that of their neighbours and with what other farmers report, which can help them choose spacings that suit their land and the cuttings they can afford. Extension agents will gain local information on spacing, which can replace advice borrowed from other regions. Organisations that distribute improved cuttings will understand how farmers plant and can plan their support accordingly. Finally, the study adds a south-south survey to a literature that is dominated by trials in the south-west.

1.7 Scope and Limitations of the Study

The study covers cassava farmers in Nsit Ibom Local Government Area, Akwa Ibom State, and deals only with planting spacing, its use, and its perceived effects on growth and yield. It does not measure growth or yield in the field.

Because the data rest on farmers' memory and judgement, answers may not match measured values. Cassava takes many months to mature, so recall of yield from earlier seasons may be imperfect, and only a limited number of respondents could be reached. The findings should be applied with care elsewhere.

1.8 Definition of Terms

Planting spacing – the distance between cassava stands within and between rows, which fixes plant population.

Plant population – the number of cassava plants per hectare.

Stem cutting – a piece of cassava stem used as planting material.

Growth – visible development of the plant (height, branching and canopy cover) as rated by farmers.

Yield – the quantity of fresh cassava roots harvested per unit area.

REFERENCES

Kreye, C., Hauser, S., Pypers, P., & Vanlauwe, B. (2020). Intensification options of small holders’ cassava production in south-west Nigeria. Agronomy Journal. https://doi.org/10.1002/agj2.20419

Onasanya, O., Hauser, S., Necpalova, M., Salako, F. K., Kreye, C., Tariku, M., Six, J., & Pypers, P. (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, Article 108038. https://doi.org/10.1016/j.fcr.2020.108038