CORN RESPONSE TO SULFUR AND ZINC STUDY

CORN RESPONSE TO SULFUR AND ZINC STUDY

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CHAPTER ONE

INTRODUCTION

• Background to the study

Maize is one of the major cereal crops cultivated extensively in all agro-ecological zones of Nigeria. It ranks second both in total production and utilization after sorghum, followed by millet and rice (National Bureau of Statistics, 2010).

Extensive studies have been conducted in the Nigerian savannas on nitrogen and phosphorus considered as most limiting nutrients for crop production (Ogunlela et al., 1988), but not much on S nutrition, especially when in combination with organic manures. Organic manure is a good contributor of N in soils, though the amount of N contained in manure varies with source, quality of the substrate, age, management and ease of mineralization, therefore its co-application with readily soluble inorganic N and S becomes necessary and offers a realistic approach towards sustainable soil productivity, while at the same time improving the soil physical conditions for nutrient retention and uptake by plants.

Fertilizer regime for cereal crops in the savanna of Nigeria emphasises on the continuous application of high rates of N, fairly high rate of P and K, with no attention given to sulphur and micronutrients (Chude et al., 2012). In view of this, crop exploitation of soil available nutrients often leads to the deficiency of S and micronutrients, thereby resulting in poor crop yields. Incidental inclusion of sulphur and micronutrients in fertilizers has been effective in masking soil depletions in the past, such that deficiency symptoms were not of any serious concern. But increased cropping intensity, higher crop yields per hectare of cultivated lands, use of high analysis fertilizers such as urea and triple super phosphate (TSP) with no sulphur content, coupled with a low soil organic matter (SOM) content, has contributed to the greater incidence of S deficiency observed in the soils.

Studies on maize response to sulphur fertilizer application in the Northern Guinea savanna of Nigeria revealed that yield was reduced by about 20% due to sulphur deficiency (IITA, 2005) even when the full recommended rates of N-P-K were applied. It is therefore expected that application of S in combination with N and cowdung will enhance availability and efficient use of these essential nutrients and equally increase yield of maize.

Although organic matter provides a retention base for plant major and micronutrients (Sing et al., 1995; Syers and Craswell, 1995), the slow rate of mineralization often hinders its short term efficiency relative to long term benefits. Still, many workers have recorded increased and significant yield of crops from organic and inorganic fertilizer application (Adeleye and Ayeni, 2010; Ukem et al., 2005). There is therefore the need to incorporate organic residues to boost plant nutrient base while pegging down on excessive mineral fertilizer application in view of its deleterious effect on soil properties.

Studies have shown that zinc and sulphur play a vital role in plant nutrition, being components of proteins, nucleic acid, auxins and chlorophyll and promoting a healthy crop performance. Sulphur is also an important element involved in plant biochemistry; being a major constituent of amino acids and in the formation of enzymes and vitamins (Havlin et al. 2006; Ceccotti, 1996). Efficient crop response to N fertilization in the savanna of Nigeria especially on cereals is available in literature (Chude et al., 2012, Ukem, 2011), but information on the performance of maize to N and S combination amended with cowdung and their effect on soil properties is scarce. Also, the potentials of cowdung, inorganic Z and S combinations on maize performance influenced by environmental factors and the resultant impact on soil fertility have not been fully understood in the savanna. Therefore, farmers and other workers need adequate information regarding Z availability from organic residues as a guide towards the determination of the optimum inorganic Z fertilizer application rate for improved maize yield especially in combination with sulphur.

1.2 Statement of the Problem

Due to intensification of agriculture in the savanna zone of Nigeria, available soil nutrients are constantly exploited by crops, leading to deficiency of essential plant nutrients. Also, shortened fallow periods and adverse cultural practices of farmers such as bush burning, crop residue removal and the acute low organic matter content of the soil, contribute to the continuous decline of essential plant nutrients in soils. Application of inorganic fertilizers as intervention measures benefits mainly N, P and K with a disproportionate amount of sulphur input; though it constitutes 12% of Single Super Phosphate (SSP), and which might not be sufficient to meet crops nutritional needs. In view of this, sulphur deficiency becomes significant, coupled with the already low soil organic matter content. Workers in the past had erroneously overlooked complementary role of N and S in maize cultivation in the savanna. This has caused nutritional imbalance for the crop and resulted in yield reductions. There is therefore the need to include sulphur along with inorganic N and organic matter for increased maize production.

• Justification of the Work

It is increasingly recognized that maize production in some locations of the world has improved by introduction of sulphur along with the practice of applying nitrogen, phosphorus and potassium (Khan et al., 2011; Bharathai and Poongothai, 2008; Ceccotti, 1996; Friesen, 1991). This approach has therefore intensified further research efforts aimed at addressing maize response to sulphur fertilization and equally determining optimum sulphur levels for maize production in combination with nitrogen. However, not much was reported to have been done about nitrogen and sulphur interactions on maize cultivation in the tropical savannas of Nigeria, perhaps due to the dependence on SSP for plant sulphur requirements or on the assumption that the absence of sulphur is not a serious cause for concern by farmers in the area. Years of crop cultivation and considering the already low soil sulphur status in the savanna soils (Kayode, 1990), in addition to human activities that tend to limit soil fertility, the incidental application of sulphur as SSP cannot be considered sufficient. There is therefore the necessity to incorporate sulphur in fertilizer programme based on actual crop needs, if improvement in maize yield in the savanna is to be achieved.

• Objectives

The objectives of the study are as follows:

1. To determine the effect of complementary role of N, S and cowdung on growth and yield of maize in a savanna soil.
2. To determine the interactive effects of N, S and CD combination on soil chemical properties.
3. To test the efficiency of QUEFT model in simulating growth and yield of maize and determine optimum inorganic fertilizer recommendation for maize in the Guinea savanna of Nigeria.

CORN RESPONSE TO SULFUR AND ZINC STUDY

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