Effect of Tillage Practices on Selected Soil Properties in Sudan Savanna Agro-Ecology of Nigeria

Tillage is performed to loosen the soil and produce a good tilth. Tillage requirement of a crop is site, environment and soil type specific (Ojeniyi and Agboola, 1995). Tillage contributes up to 20 % amongst crop production factors (Adekiya and Ojeniyi, 2011). Tillage operations in various forms have been practiced from the very inception of growing crop plants (Sharma and Behera, 2008). To prepare a virgin or fallow land and use it for growing crops, tillage in any form is an indispensable practice even today. Tillage is one of the forms of management practices of soil, water, nutrient, crop and pests. Tillage helps to replace natural vegetation with useful crops and is necessary to provide a favourable edaphic environment for the establishment, growth and yield of crop plants (Sharma et al., 2002). After harvest of the crop, soil becomes hard and compact. Beating action of rain drops, irrigation and subsequent drying, movement of inter-cultivation implements and labour cause soil compaction. Seeds need loose, friable soil with sufficient air and water for good germination. The field should be free from weeds to avoid competition with the crop. It should also be free from stubbles to facilitate easy and smooth movement of sowing implements. There have been conflicting reports on the influence of tillage on soil chemical properties; likewise contradictory reports as to the superiority of crops on tilled plots to those of no-till plots have been documented (Adekiya and Ojeniyi, 2011). Ridge tillage was found to increase growth of okra on ultisol of central Southwest, Nigeria relative to no-tillage (Ojeniyi and Adekayode, 1999).

However, manual tillage systems including ridges, heaps and flatbeds have been reported to degrade soil quality and reduce chemical and biological qualities especially on alfisols in the rainforest areas of Southwest, Nigeria (Busari and Salako, 2013). The study of relative effect of ridging and no-tillage on soil properties and yield of sweet potato in guinea savanna zone (middle belt) of Nigeria showed that no-till gave higher tuber yield of sweet potato compared to ridging, which was adduced to have higher moisture content, N, P, K, Ca and Mg status (Ojeniyi, 1993). In Nigeria, farmers commonly till the soil to improve its physical, chemical, and biological characteristics that alter plant growth and yield (Agber et al., 2017). Crops grown without tillage are stunted and show symptoms of water and nutrient deficiencies because of high surface bulk density, low porosity, retarded infiltration, and low water holding capacity of the soil (Ali et al., 2015). However, the conventional and traditional tillage methods have negative effects on soil life and increase mineralization of organic matter. A zero tillage system, on the other hand, is a conservation method that involves the use of crop residues that aid water infiltration, prevent erosion, and increase organic matter content and agricultural productivity (Ali et al., 2015). Soil properties describe the physical and chemical characteristic behaviour of soils including the nutrient status (Usman, 2017). The need for basic knowledge and assessment of changes in soil properties and their fertility status with time to evaluate the impact of various tillage practices has become necessary for sustainable agriculture in Nigerian savanna zones. Similarly, for sustainable soil nutrient management in these zones, there is also need for an understanding of how soil responds to tillage practices overtime (Oyedele et al., 2014). One of the major important components of agricultural management and sustainability as well, a goal of most farmers in the tropics is the maintenance of soil nutrients and qualities. This according to Mallo (2010) provides avenue for measuring levels of crop productivity. Soil properties reveal soil quality which measures the levels of soil fertility. This means that assessing soil quality also involves measuring and evaluating soil properties for optimum crop yield. Soil properties may have influence on various processes that are suitable for agricultural practices, though the dynamic soil nature describes the condition of a specific soil due to management practices. However, for sustainable crop production, there is need for adoption of improved tillage practices and proper soil management that would ensure optimum crop yield. The knowledge of tillage and soil properties in Nigerian savanna is necessary in addressing the problem of low crop productivity and to ensure optimum food production. Thus, the objective of this study was to provide documented information on the effect of tillage practices on post harvest soil properties of sesame fields in the study area.