PERFORMANCE OF EARLY AND LATE MAIZE (Zea mays L.) VARIETIES UNDER DIFFERENT FERTILIZER APPLICATION TIMINGS FOLLOWING BUSH FALLOW IN THE TROPICAL RAINFOREST ZONE OF NIGERIA

Abstract

Optimizing fertilizer application timing is essential for improving maize productivity and sustaining soil fertility in tropical agroecosystems. This study evaluated the growth and yield performance of early- and late-maturing maize (Zea mays L.) varieties under varying fertilizer application schedules following a bush fallow system in the rainforest zone of Nigeria. The experiment was conducted at the Research Farm of the University of Benin during the early cropping season. A Randomized Complete Block Design (RCBD) with a split-plot arrangement and four replications was employed. The treatments consisted of two maize maturity groups (early and late varieties) and seven fertilizer application timings: no fertilizer application, one week before planting, at planting, one week after planting, two weeks after planting, three weeks after planting, and four weeks after planting. Agronomic parameters assessed included plant height, ear height, days to tasselling and silking, physiological maturity, total dry matter accumulation, harvest index, 1000-grain weight, and grain yield per hectare. Results indicated that fertilizer application timing significantly influenced maize growth, dry matter accumulation, and grain yield. Early-maturing maize varieties produced significantly higher grain yields than late-maturing varieties under the prevailing environmental conditions. Fertilizer application at critical vegetative growth stages enhanced nutrient uptake efficiency and improved overall crop performance. The findings suggest that appropriate synchronization of fertilizer application with crop nutrient demand is essential for maximizing maize productivity in bush fallow systems. The study contributes to sustainable nutrient management strategies and climate-resilient maize production in tropical rainforest agroecologies.

CHAPTER ONE

INTRODUCTION

Background to the Study

Maize (Zea mays L.) is one of the world’s most important cereal crops due to its wide adaptability, high yield potential, and diverse industrial and nutritional uses. Globally, maize serves as a staple food for millions of people while also functioning as a major source of livestock feed and raw material for agro-based industries (Bello et al., 2010). It ranks after wheat and rice in terms of global importance and contributes significantly to food security, especially in developing nations where population growth continues to place pressure on agricultural production systems.

In Nigeria, maize has become a strategic food and commercial crop because of its versatility and increasing demand for human consumption, poultry feed formulation, brewery industries, and biofuel production. The crop is cultivated across various agroecological zones of the country, particularly within the humid rainforest and derived savannah regions where climatic conditions support multiple cropping seasons annually (IITA, 2006). The tropical rainforest ecology of southern Nigeria provides favourable environmental conditions for maize cultivation due to abundant rainfall, high solar radiation, and relatively long growing periods.

The bimodal rainfall distribution characteristic of the rainforest zone permits the cultivation of both early- and late-season maize crops. Early-maturing maize varieties are usually planted at the onset of the rainy season and harvested within a shorter growth cycle, thereby helping to bridge seasonal food shortages. In contrast, late-maturing varieties are cultivated during the second rainfall cycle and generally possess longer vegetative and reproductive phases that may influence yield performance under varying environmental conditions.

Despite the increasing importance of maize production in Nigeria, average grain yields remain considerably lower than global standards. One of the major constraints responsible for low productivity is declining soil fertility resulting from continuous cultivation, nutrient mining, shortened fallow periods, and inadequate fertilizer management practices (Buresh et al., 1997). Soil nutrient depletion, particularly nitrogen deficiency, has become a serious challenge in tropical agricultural systems where most soils are inherently low in organic matter and essential plant nutrients.

Nitrogen is regarded as one of the most critical nutrients required for maize growth and grain development because it directly influences photosynthesis, vegetative growth, dry matter accumulation, and kernel formation (Adediran and Banjoko, 1995). Deficiency of nitrogen often results in poor crop establishment, reduced leaf area development, premature senescence, and low grain yield. However, the efficiency of nitrogen utilization by maize depends not only on the quantity applied but also on the timing of fertilizer application.

Appropriate fertilizer timing ensures synchronization between nutrient availability and crop demand during critical growth stages. Delayed or poorly timed fertilizer application may result in nutrient losses through leaching, volatilization, and runoff, especially under the high rainfall conditions typical of tropical rainforest zones. Consequently, identifying the optimal period for fertilizer application is essential for improving nutrient-use efficiency, enhancing crop productivity, and minimizing environmental losses.

Bush fallow systems traditionally play an important role in restoring soil fertility through natural vegetation regeneration and organic matter accumulation. However, increasing population pressure and land scarcity have drastically reduced fallow periods, thereby limiting the capacity of soils to recover adequately before cultivation. This has increased dependence on inorganic fertilizers for sustaining crop productivity.

Furthermore, varietal differences among maize genotypes significantly influence nutrient uptake efficiency, stress tolerance, growth duration, and grain yield. Early- and late-maturing maize varieties may therefore respond differently to fertilizer application schedules under rainforest agroecological conditions. Understanding these varietal responses is crucial for developing efficient nutrient management strategies capable of improving maize productivity in sustainable cropping systems.

It is against this background that this study was undertaken to evaluate the performance of early- and late-maturing maize varieties under varying fertilizer application timings following a bush fallow system in the tropical rainforest zone of Nigeria.

Statement of the Problem

Declining soil fertility has become a major limitation to sustainable maize production in Nigeria due to continuous cultivation, nutrient depletion, and shortened bush fallow periods. Although inorganic fertilizers are widely used to improve crop productivity, many farmers still experience low yields because fertilizer application is often poorly timed and not synchronized with crop nutrient requirements.

In tropical rainforest environments characterized by heavy rainfall, improper timing of fertilizer application can result in substantial nutrient losses through leaching and runoff, thereby reducing fertilizer-use efficiency and crop productivity. In addition, early- and late-maturing maize varieties may differ in their nutrient demand patterns and physiological responses to fertilizer timing.

Despite the importance of fertilizer management in maize cultivation, limited information exists on the comparative response of early- and late-maturing maize varieties to different fertilizer application schedules following bush fallow in the rainforest zone of Nigeria. This knowledge gap has hindered the development of efficient nutrient management recommendations for maize farmers in the region.

Therefore, there is a need to determine the most suitable timing of fertilizer application capable of optimizing the growth, development, and grain yield of different maize maturity groups under tropical rainforest conditions.

Aim of the Study

The main aim of this study is to evaluate the performance of early- and late-maturing maize varieties under varying fertilizer application timings following bush fallow in the tropical rainforest agroecology of Nigeria.

Objectives of the Study

The specific objectives of the study are to:

1. assess the growth performance of early- and late-maturing maize varieties under different fertilizer application timings;
2. determine the influence of fertilizer application timing on maize yield and yield components;
3. compare the agronomic performance of early and late maize varieties under rainforest conditions;
4. identify the most effective fertilizer application period for optimum maize productivity;
5. evaluate the interaction effects between maize maturity groups and fertilizer application timing on crop growth and yield.

Research Questions

The study seeks to provide answers to the following questions:

1. How do early- and late-maturing maize varieties respond to different fertilizer application timings?
2. What effect does fertilizer timing have on maize growth and grain yield?
3. Which maize maturity group performs better under bush fallow conditions?
4. What is the most appropriate fertilizer application timing for optimum maize productivity?
5. Is there a significant interaction between maize variety and fertilizer application timing?

Research Hypotheses

The following hypotheses were formulated and tested:

H??: Fertilizer application timing has no significant effect on the growth and yield of maize.

H??: There is no significant difference between the performance of early- and late-maturing maize varieties.

H??: There is no significant interaction effect between maize variety and fertilizer application timing on grain yield.

Significance of the Study

This study is significant because it contributes to the development of sustainable nutrient management strategies for maize production in tropical rainforest agroecosystems. The findings will provide empirical information on the appropriate timing of fertilizer application for maximizing nutrient-use efficiency and crop productivity.

The results will benefit farmers by improving maize yield and reducing fertilizer wastage, thereby increasing profitability and food security. Agricultural extension agents and policy makers will also benefit from the study through the formulation of improved fertilizer recommendations tailored to different maize maturity groups.

Furthermore, the study will serve as a valuable academic resource for researchers, students, and institutions interested in crop physiology, soil fertility management, and sustainable maize production systems.

Scope of the Study

The study focused on evaluating the growth and yield performance of early- and late-maturing maize varieties under different fertilizer application timings following bush fallow conditions. The experiment was conducted within the tropical rainforest zone of Nigeria using selected agronomic and yield parameters.

Limitation of the Study

The study was limited by environmental factors such as rainfall variability, soil heterogeneity, and seasonal climatic fluctuations which may have influenced crop performance. Financial and time constraints also limited the scope of the experiment to a single location and cropping season.

Operational Definition of Terms

Bush Fallow: A traditional land management practice in which cultivated land is left uncultivated for a period to restore soil fertility naturally.

Early-Maturing Maize: Maize varieties that complete their growth cycle within a shorter duration, usually between 90 and 95 days.

Late-Maturing Maize: Maize varieties that require a longer growth duration, generally between 100 and 120 days to attain maturity.

Fertilizer Application Timing: The specific growth stage or period at which fertilizer is applied to crops.

Grain Yield: The quantity of harvested maize grains produced per unit area.

Harvest Index: The ratio of grain yield to total biological yield produced by the crop.

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