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ABSTRACT

This study was carried out at the Research Farm of the University of Benin during the early growing season (April to July) of 2014 to investigate the performance of early and late maize variety under varying times of fertilizer application. The experiment was laid out as a Randomized Complete Block Design (RCBD) with a split-plot arrangement with four replications. Early and Late maize were used. Fertilizer application times included 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. The traits evaluated include the plant and ear height, days to 50% tasselling and silking, days to 95% maturity, harvest index, the total dry matter plant-1, 1000-grain yield and the grain yield ha-1. The result obtained showed that these characters were significantly influenced by time of fertilization and maize variety. Early maize had significantly higher grain yield than late maize. Time of fertilization influenced total dry matter and grain yield. Therefore, early maize may be recommended for optimal yield under bush fallow in the Rainforest zone of Nigeria.

CHAPTER ONE
INTRODUCTION

Maize (Zea mays L.) is an important staple food crop and provides bulk of raw materials for the livestock and many agro-allied industries in the world (Bello et al, 2010; Randjelovic et al, 2011). It is the third most important grain crop in the world after wheat and rice (USDA and FAS Grain, “Zea production maps and statistics,” 2010). Maize is of significant importance for developing countries like Nigeria, where rapid increase in population have already out stripped the available food supplies in which maize serve to ameliorate due to its high productivity and diversified use. More maize is produced annually than any other grain (IITA 2016). 

Worldwide production of maize is 785 million tons, with the largest producer, the United States, producing 42%. Africa produces 6.5% and the largest African producer is Nigeria with nearly 8 million tons, followed by South Africa. Africa imports 28% of the required maize from countries outside the continent (IITA 2016). 158 million hectares of maize are harvested worldwide. Africa harvests 29 million hectares, with Nigeria, the largest producer in Sub Sahara Africa (SSA) harvesting 3%, followed by Tanzania (FAO, 2017). Worldwide consumption of maize is more than 116 million tons, with Africa consuming 30% and SSA 21%. 

The tropical rainforest agro-ecology of Nigeria has a great potential for its production because of its high solar radiation coupled with much precipitation that favours maize production. In the southern rainforest belt of Nigeria, maize is grown twice due to bimodal rainfall pattern (a short early growing season followed by fairly long late season). Early maize varieties are usually planted at the onset of rainy season before it’s fully established (March/April), and matured sooner than the traditional crops. This succours in filling the hunger gap in July when all food reserves have been depleted after the long dry period in the zone. On the other hand, the late season crop is planted during the second cycle of rains (July/August). While the short early season is usually characterised by abrupt cessation of rains during crop cycle, the late season is normally affected by terminal drought. The occurrence of extreme environmental events impose different degrees of drought stresses on maize thereby affecting growth duration, plant size, dry matter accumulations, assimilate reserves and grain yield . Efforts aimed at obtaining high yield of maize would necessitate the augmentation of the nutrient status of the soil to meet the crop’s requirements for optimum productivity and maintain soil fertility. 

In spite of the increase in land areas under maize production, yield is still low. Some of the major causes of low maize yield are declining soil fertility and insufficient use of fertilizers resulting in severe nutrient depletion of soils (Buresh et al, 2017). Maize requires adequate supply of nutrients particularly nitrogen, phosphorus and potassium for good growth and high yield. Evaluation of early (90-95 days)and late (100-105 days) maturing maize have formed part of the varietal trials in the marginal environments of the region under the auspices of International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria (Badu-Apraku et al, 2003; Sallah et al, 2004; Olaoye and Omueti,2006; Oluwaranti et al, 2014). Base on maize Investigations carried out, the crop has been observed to produce well under high soil fertility condition (Yusuf and Iwuafor, 2015). The nutrient supply to each crop is observed to be influenced by fertilizer supply to previous crop (Negassa et al, 2011; FAO, 2006; Rutunaa and Neel, 2016).

Notwithstanding, the yield of maize varies among varieties, planting site coupled with availability of integral factors such as soil nutrient status and fertilizer application. Nitrogen is a vital plant nutrient and a major yield-determining factor required for maize production (Adediran and Banjoko, 1995; Shanti et al, 2017). Low N availability has limited cereal crop growth more than deficiencies in any other minerals (Carsky and Iwuafor, 2015). Thus maize yield has been dangerously reduced especially in developing countries of the world where maize production is carried out under low soil fertility condition (McCown et al, 2012; Oikeh and Horst, 2011).  It was in view of the above that this study was conducted to evaluate the performance of early and late maize varieties under varying times of applied fertilizer following a bush fallow. The following objectives where conceived:

(1). Evaluate the growth and yield of early and late varieties of maize in tropical rainforest environment.

(2). Determining the appropriate time of fertilizer application that would support optimal growth, yield and development of early and late maturing maize varieties.