THE EFFECT OF NITROGEN FERTILIZER ON THE GROWTH AND YIELD OF AMARANTH (A CASE STUDY OF AMARANTH FARMERS IN NSUKKA LOCAL GOVERNMENT AREA, ENUGU STATE)

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Amaranth is one of the most important annual leaf vegetables in the tropics. It has a growing period of five to six weeks, which allows rural and urban farmers to take two or more crops from the same piece of land in a year, and it is a nutritious vegetable that contains relatively high amounts of minerals and vitamins (Akinmutimi & Okoroji, 2024). For the vegetable grower with a small plot and a need for quick returns, these features make amaranth one of the most dependable crops available. The same short cycle, however, means that the crop must be fed well and fed quickly: there is little time in a five-week season to correct a nutrient shortage once it appears.

Because the harvested product is the leaf and the tender stem, the part of the plant that the farmer sells is the part that nitrogen builds. Auwalu (1988) tested four nitrogen levels (0, 45, 90 and 180 kg N/ha) on vegetable amaranth at Samaru, Zaria, and found that nitrogen significantly increased plant height, leaf area, shoot dry weight and the length of harvested branches over the control. Applying 180 kg N/ha raised marketable yield by 19.5 per cent and raised the protein content of the edible yield. More recent work shows that the best rate is not fixed but depends on how the crop is managed. In Ethiopia, Birhanu et al. (2024) combined nitrogen levels with harvesting frequency and obtained the highest leaf yield (30.33 t/ha) at 103.5 kg N/ha with a two-week harvest interval. A farmer who harvests more often, as most vegetable growers do, may therefore need a different nitrogen strategy from one who harvests once.

Nigerian studies have also looked at nitrogen supplied through organic materials and through combinations of organic and mineral sources. Adekiya et al. (2019) applied poultry manure at rates from zero to 40 t/ha to green amaranth in 2016 and 2017 and found that it increased soil chemical properties, leaf mineral content, growth and marketable yield compared with the control; the best quality was obtained at 20 t/ha, which they judged to give a good balance between yield and economic outlay. At Umuahia in south-eastern Nigeria, Akinmutimi and Okoroji (2024) worked on a strongly acidic, continuously cropped Ultisol that was low in nitrogen (0.10 per cent total nitrogen). NPK fertiliser alone, at 200 kg/ha, gave only a small increase in fresh weight over the control, whereas poultry manure at 5 t/ha gave a much larger one, and the best yield came from poultry manure at 5 t/ha combined with 100 kg/ha of NPK. The same authors observe that information on the fertility requirements of amaranth is scanty in resource-poor settings, and that studies on integrated use of organic and inorganic fertilisers on the crop are scarce.

The economics of nitrogen have also changed. Farmers interviewed by the News Agency of Nigeria in 2025 reported that a bag of urea, which cost between N35,000 and N37,000 earlier, was then selling for between N47,000 and N50,000, and said that the high cost of fertiliser was pushing them away from some crops (AllAfrica, 2025). For an amaranth grower, whose income per bed or per plot is small and whose crop is sold quickly, the question has become not whether to use nitrogen but how little can be used without losing leaf yield, and whether a cheaper organic source can supply part of it.

Nsukka Local Government Area lies in the derived savanna of south-eastern Nigeria, a zone in which poor soil fertility is a major cause of low crop yields (Onwubiko, 2026). The University of Nigeria, Nsukka, has long been a centre of research on crops and soils. But research findings reported in the literature tell us what happens at the rates tested on research plots. They do not tell us which nitrogen sources the amaranth farmers of Nsukka actually use, at what rates, in how many applications, or how they decide. Nor do they tell us what growth and yield the farmers themselves report, or what stops them from using nitrogen in the way they would like. These are matters of farmers' practice and perception, and the appropriate way to study them is a survey of the farmers themselves.

This study therefore uses a structured questionnaire to describe nitrogen use among amaranth farmers in Nsukka Local Government Area and to relate it to the growth and yield that the farmers report. The aim is not to find a single best rate, which only controlled trials can do, but to establish what is done, what it appears to deliver, and where the constraints lie.

1.2 Statement of the Problem

Amaranth farmers in Nsukka depend on nitrogen fertiliser, chiefly urea, to keep their plots productive, and the evidence is clear that nitrogen raises leaf growth and marketable yield (Auwalu, 1988; Birhanu et al., 2024). But the price of urea has risen sharply (AllAfrica, 2025), and the published trials that could guide farmers give rates that come from other places, other varieties and other harvesting systems. The Ethiopian optimum of about 103.5 kg N/ha (Birhanu et al., 2024) and the 180 kg N/ha tested at Samaru (Auwalu, 1988), for example, are not directly transferable to the soils and practices of Nsukka.

The literature reviewed for this chapter also says very little about what vegetable farmers in south-eastern Nigeria do in practice. Information on the fertility requirements of amaranth is described as scanty (Akinmutimi & Okoroji, 2024), and nothing was found on the nitrogen sources, rates and timing that farmers in Nsukka use, on the growth and yield they report from them, or on the reasons for their choices. Farmers may be applying too little and sacrificing leaf yield, or too much and wasting scarce money, and may be mixing urea, compound fertiliser and manure in ways that have never been examined.

The consequences fall on several groups. Farmers cannot compare their practice with that of their neighbours. Extension officers cannot tell where advice on fertiliser economy is most needed. Researchers who plan nitrogen trials for the area have no farmer-level information on the rates and sources that would make their treatments relevant. In a season of high fertiliser prices, each of these gaps has a direct cost.

The problem addressed by this study is thus the lack of survey evidence on the nitrogen sources and rates used by amaranth farmers in Nsukka Local Government Area, on the growth and yield that the farmers report at different rates, and on the constraints that limit their use of nitrogen.

1.3 Objectives of the Study

The general objective is to determine the effect of nitrogen fertiliser on the growth and yield of amaranth as reported by farmers in Nsukka Local Government Area. The specific objectives are to:

a) describe the socio-economic and farm characteristics of amaranth farmers in the area;

b) identify the nitrogen sources (urea, compound fertiliser, manure and others) and the rates and timing of application used by the farmers;

c) determine the growth and yield that the farmers report at different nitrogen rates; and

d) identify the constraints that limit the farmers' use of nitrogen fertiliser.

1.4 Research Questions

The study will answer four questions. Who are the amaranth farmers of Nsukka, and how large and how intensively managed are their plots? Which nitrogen sources do they use, and at what rates and times? What growth and yield do they report at different rates? And what prevents them from using nitrogen in the way they would wish?

1.5 Research Hypotheses

Hypothesis 1. There is no significant relationship between the rate of nitrogen applied and the yield reported by amaranth farmers.

Hypothesis 2. There is no significant difference in the yield reported by farmers who apply nitrogen and those who do not.

Hypothesis 3. The socio-economic characteristics of the farmers (age, sex, education, plot size and farming experience) have no significant relationship with the rate of nitrogen they apply.

Each hypothesis will be tested at the 5% level of significance.

1.6 Significance of the Study

• Amaranth farmers: a clearer picture of how nitrogen use relates to the yields their neighbours report, and of the constraints they share, at a time when urea has become expensive.

• Extension workers in Enugu State: evidence on the rates and sources in use, showing where advice on fertiliser economy and on the use of cheaper organic sources is needed most.

• Researchers and students: farmer-level data from Nsukka to read alongside trial results from research stations, and a basis for choosing relevant treatments in later nitrogen trials.

• Policy makers: information on the barriers that vegetable growers face in obtaining and using nitrogen fertiliser, which can inform input-support programmes for horticultural crops.

1.7 Scope and Delimitation of the Study

The study covers amaranth farmers in Nsukka Local Government Area of Enugu State who grew the crop in the most recent season. It is a cross-sectional survey using a structured questionnaire and concentrates on nitrogen fertiliser, whether applied as urea, in compound fertiliser or through manure, and on growth and yield as reported by farmers. It does not cover phosphorus or potassium, varietal comparison, pest management, or the processing and marketing of amaranth.

1.8 Limitations of the Study

Vegetable growers rarely weigh their harvest, so yields will be reported in local units such as bundles or baskets and converted with the help of sample measurements, which introduces some error. Farmers may apply nitrogen in several split doses, in compound fertiliser or through manure, and the quantity of nitrogen they apply may be imperfectly estimated from the number of bags, cups or basins used. Because amaranth is harvested repeatedly over a short season, farmers may find it hard to state a single yield. As in any survey, the relationships found are associations and do not prove cause; farmers who apply more nitrogen may also differ in soil, variety, watering and management. Finally, time and funds limit the number of respondents.

1.9 Definition of Terms

Nitrogen fertiliser: any fertiliser applied mainly to supply nitrogen, such as urea, and rate of application means the quantity of fertiliser, or of nitrogen in it, applied per unit of land.

Growth: is the development of the plant as reported by farmers (height, leaf size and number of leaves), and yield is the quantity of marketable leaves and stems harvested from a given area.

Amaranth: refers to the leafy vegetable species of the genus Amaranthus grown by farmers in the area. A split application is the division of the total fertiliser into two or more doses applied at different times.

References

Adekiya, A. O., Aboyeji, C. M., Dunsin, O., Asamu, F., Owolabi, A. O., Aremu, C. O., Oyetunji, D. A., Oloye, A. D., & Owolabi, I. O. (2019). Poultry manure addition affects production, plant nutritional status and heavy metals accumulation in green amaranth (Amaranthus hybridus). International Journal of Agriculture and Biology, 993–1000.

Akinmutimi, A. L., & Okoroji, M. C. (2024). Effects of organic and inorganic fertilizers on soil chemical properties and the yield of Amaranthus species in a continuously cropped Ultisol. International Journal of Agriculture and Environmental Research, 10(1), 64–74. https://doi.org/10.51193/IJAER.2024.10105

AllAfrica. (2025, July 22). Nigeria: High fertiliser cost – Farmers dump rice, maize cultivation. https://allafrica.com/stories/202507220646.html

Auwalu, B. M. (1988). The effects of nitrogen and plant population on the growth and yield of vegetable amaranth (Amaranthus cruentus L.) [Master's thesis, Ahmadu Bello University, Zaria]. Kubanni Repository. https://kubanni.abu.edu.ng/handle/123456789/4908

Birhanu, T., et al. (2024). Leaf and seed yield response of vegetable amaranths to nitrogen fertilizers applications and harvesting frequency at Jimma, South West, Ethiopia. Discover Food.

Onwubiko, G. N. (2026). Comparative assessment of the morphological traits of local maize (Zea mays L.) varieties upon exposure to varying rates of poultry manure. Current Research in Agricultural Sciences, 13(1), 104–113. https://doi.org/10.18488/cras.v13i1.4944