EFFECT OF CROP RESIDUE ON SOIL CHEMICAL PROPERTIES AND RICE YIELDS ON AN ULTISOL

CHAPTER ONE
INTRODUCTION
1.1       Background of the Study
Soils of Southeast Nigeria are acidic, sandy and physically fragile and are deficient in organic matter, nitrogen and basic cations (Ohiri and Ano, 1989). Because of high cost of chemical fertilizers it becomes necessary to intensify studies into locally available and acceptable soil management strategies to stabilize and improve condition of the soil, their fertility and productivity. In this part of Nigeria huge amount of crop residues are generated through manual preparation of land for crop production. The residues traditionally viewed as nuisance are associated with mechanical planting difficulties, decreased efficacy of herbicides, release of growth inhibitory allelopathic compounds and ultimately decreased yield (Sandford, 1982). There is need to avoid these problems through proper management of the residues.
Ojeniyi and Ighomrore (2004) as well as Owolabi et al. (2003) observed that some of the residue management techniques had varied effects on soil organic matter (SOM) contents. Similarly, Adetunji (1997) as well as Kuku and Omoeti (2003) observed that the management of residues after land clearing influences the fate of soil organic matter (SOM). However, soil fertility can be maintained through maintenance of appropriate levels of SOM (Opara-Nadi et al., 2003; Onofiok, 1993). The addition of residues into the soil environment and the study of the changes associated with their addition according to Azzez et al. (2007) are important in planning cultural operations and developing appropriate soil management systems. This study aimed at evaluating the effects of different crop residue management techniques, such as surface mulch(SM), slash and incorporation (SAI), burning and incorporation (BAI) and control on the properties and grain yield of maize in a Typic Haplustult in Nigeria.
The soils of the Abakaliki area are low in fertility. The soils have been noted to be acidic, low in organic matter status, cation exchange capacity and other essential nutrients, (Emoezor et al., 1988, Asadu and Akamigbo, 1990, Nnabude and Mbagwu 1999 and Ogbodo and Nnabude, 2004). The use of organic amendments could be a viable means of improving the productivity of the soils. Recycling of crop residue has demonstrated to be one of the ways of improving soil nutrient content and maintaining soil productivity (Kang and Juo 1986, Iwuafor et al., 1991, Salim, 1991 and Mbagwu et al., 1994). Large quantities of rice straw and husk are produced in Abakaliki annually. These materials are