THE EFFECT OF NPK FERTILIZER APPLICATION RATES ON THE GROWTH AND YIELD OF MAIZE (A CASE STUDY OF MAIZE FARMERS IN GWAGWALADA AREA COUNCIL, FCT)

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Maize (Zea mays L.) is one of the most important cereal crops in Nigeria, used as human food, as livestock and poultry feed and as an industrial raw material. According to United States Department of Agriculture figures quoted by Ngonadi et al. (2023), Nigerian maize production rose to about 11.6 million tonnes in 2021/2022, which reflects the size of the crop's role in food supply and farm incomes.

Maize responds strongly to fertilizer because it grows fast, produces a large amount of biomass and takes up large quantities of nitrogen, phosphorus and potassium. Many savanna soils are low in organic matter and in these nutrients. Muhammad et al. (2024) list low soil fertility, poorly distributed rainfall, non-use of optimum plant density, poor implementation of improved agronomic practices and use of indigenous unimproved varieties among the factors that limit large-scale maize production in their study area. Ederigbe et al. (2024), working on four farmers' fields at Minna, found that the soils were moderately to slightly acidic and low in soil organic carbon, nitrogen and phosphorus.

NPK fertilizer is the most commonly used source of these nutrients. The widely sold NPK 15:15:15 contains equal proportions of nitrogen, phosphorus and potassium, so that, for example, 150 kg/ha supplies 22.5 kg each of N, P2O5 and K2O (Ederigbe et al., 2024), which is a small amount compared with the needs of a productive maize crop. The application rate therefore matters: too little leaves the crop short of nutrients and lowers yield, while too much raises cost, may be wasted and can harm soil and water.

Nigerian trials show how maize responds to NPK rate. At Samaru in the northern Guinea savanna, Muhammad et al. (2024) tested NPK rates of 200, 300 and 400 kg/ha with four intra-row spacings and three varieties. They found that each increase in NPK from 200 to 400 kg/ha significantly produced taller plants, longer ear height, heavier 100-grain weight and higher grain yield and shortened the number of days to 50% tasseling, and they recommended 400 kg/ha of NPK with the variety SAMMAZ 40 at 20 or 25 cm intra-row spacing. In the southern Guinea savanna at Minna, Ederigbe et al. (2024) compared the farmers' usual practice of 150 kg/ha of NPK 15:15:15 with a special-blend NPK at 600 kg/ha, cow dung and combinations of these. All fertilized treatments significantly outperformed the unfertilized control in plant height and leaf area index, there were no significant differences among the NPK treatments and their combinations with cow dung, and the special-blend NPK produced the tallest plants and the highest yield (1.92 t/ha).

These studies show that NPK application raises maize growth and yield and that rates recommended on research stations are well above those farmers commonly apply. They also show that the response depends on the soil, the variety and the particular fertilizer product used. What farmers actually apply, how they choose the rate, and what they observe on their own fields are matters that experimental trials do not record.

Gwagwalada Area Council is in the Federal Capital Territory, in the Guinea savanna, where maize is grown by smallholders during the rainy season. This study therefore used a structured questionnaire to examine the NPK application rates used by maize farmers in Gwagwalada and their perceived effects on the growth and yield of maize.

1.2 Statement of the Problem

Maize farmers in Gwagwalada Area Council use NPK fertilizer, but the rates they apply differ and are usually decided by price, availability and personal experience rather than by soil test or recommendation. Experimental evidence shows that yield rises with NPK rate on savanna soils (Muhammad et al., 2024) and that the farmers' usual rate of 150 kg/ha may be well below what is needed for high yields (Ederigbe et al., 2024), but it is not known what rates farmers in Gwagwalada use or how they perceive the results.

The studies reviewed here were conducted at Samaru and Minna, partly on research stations and partly on farmers' fields in other agro-ecological conditions (Ederigbe et al., 2024; Muhammad et al., 2024), and the literature consulted for this study did not reveal a survey of NPK application rates and perceived effects among maize farmers in Gwagwalada. Because soil fertility and rainfall differ between locations, results from other sites cannot be assumed to hold in Gwagwalada.

As a result, farmers may apply too little fertilizer, so that yields stay low, or may spend on more than the crop can use. Extension agents also lack local information on which to base advice. This study was undertaken to provide it.

1.3 Objectives of the Study

The main objective of the study was to assess the effect of different NPK fertilizer application rates on the growth and yield of maize among farmers in Gwagwalada Area Council, FCT, using a structured questionnaire. The specific objectives, each of which corresponds to a section of the questionnaire, were to:

(i) describe the socio-economic characteristics of the respondents, namely age, sex, educational level, farming experience, farm size and source of labour.

(ii) identify the NPK fertilizer rates and methods of application currently used by the respondents in the production of maize

(iii) ascertain the respondents' perception of the effect of different NPK fertilizer application rates on the growth of maize ;

(iv) ascertain the respondents' perception of the effect of different NPK fertilizer application rates on the yield of maize ; and

(v) identify the constraints faced by the respondents in the use of different NPK fertilizer application rates and the measures they suggest for improvement .

1.4 Research Questions

The following research questions, which correspond to the sections of the questionnaire, guided the study:

(i) What are the socio-economic characteristics of the respondents?

(ii) What NPK fertilizer rates and methods of application do the respondents use in the production of maize?

(iii) How do the respondents perceive the effect of different NPK fertilizer application rates on the growth of maize?

(iv) How do the respondents perceive the effect of different NPK fertilizer application rates on the yield of maize?

(v) What constraints do the respondents face in the use of different NPK fertilizer application rates, and what improvements do they suggest?

1.5 Research Hypotheses

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

H01: There is no significant relationship between the socio-economic characteristics of the respondents and their NPK application rate.

H02: There is no significant difference in the perceived growth of maize among respondents who differ in their NPK application rate.

H03: There is no significant difference in the perceived yield of maize among respondents who differ in their NPK application rate.

1.6 Significance of the Study

The findings will give maize farmers in Gwagwalada information on the NPK rates used by their peers and those they perceive to give better growth and yield, which may help them use fertilizer more efficiently. Extension agents will obtain local information for fertilizer recommendations, and input suppliers will understand farmers' needs better.

The study will also add to the literature on maize production in the Guinea savanna of Nigeria.

1.7 Scope and Limitations of the Study

The study covers maize farmers in Gwagwalada Area Council, FCT. It is limited to NPK fertilizer application rates and covers the respondents' socio-economic characteristics, fertilizer practices, perceived effects on growth and yield, and constraints. It does not include soil analysis or controlled field measurement of yield.

Limitations include reliance on respondents' recall and perception, the difficulty some farmers have in converting local measures of fertilizer (such as cups or bags) to standard rates, and the limited number of respondents who could be reached. The findings should be applied with care outside the study area.

1.8 Definition of Terms

NPK fertilizer: a compound fertilizer containing nitrogen (N), phosphorus (P) and potassium (K), such as NPK 15:15:15.

Application rate: the quantity of fertilizer applied per unit area or per plant.

Growth: the visible development of the maize plant, such as height, leaf number and vigour, as perceived by farmers.

Yield: the quantity of maize grain harvested per unit area.

Area Council: the local government unit of the Federal Capital Territory.

Questionnaire: a structured set of written questions used to collect information from respondents.

REFERENCES

Ederigbe, R., Eleojo, S. F., Ezekiel-Adewoyin, D., & Osunde, A. O. (2024). The effect of organic and inorganic fertilizers on the production of maize in Minna, southern guinea savanna zone of Nigeria. SVU-International Journal of Agricultural Sciences, 6(3), 121–128. https://doi.org/10.21608/svuijas.2024.287749.1367

Muhammad, A., Mani, H., Ibrahim, R., Bugaje, S., Dauda, H., Saleh, M. H., Mahmoud, B. A., & Dalhat, F. D. (2024). Performance of three maize varieties as influenced by NPK fertilizer rates and intra-row spacings at Samaru, northern Guinea savanna, Nigeria. FUDMA Journal of Sciences, 8(6), 87–90. https://doi.org/10.33003/fjs-2024-0806-2743

Ngonadi, E. N., Uko, I., & Okonkwo, N. J. (2023). Profitability of selected weed control methods in maize (Zea mays L. Moench) production at Igbariam in three successive months. International Journal of Agriculture, Food and Biodiversity, 2(1), 37–42. https://journals.unizik.edu.ng/ijafab/article/download/2799/2262/6729