Effect of Tillage on Soil Properties and Yield of Sorghum (Sorghum Bicolor (L.) Moench) in Southwest Nigeria

Abstract

Field experiments were carried out at two locations in late-season 2004, early-season 2005 and lateseason 2006 on an Alfisol of southwest Nigeria to assess the effect of five tillage methods on soil properties and yield of sorghum. The tillage treatments were zero tillage, manual clearing, ploughing, ploughing plus harrowing and ploughing plus harrowing twice. The surface soils (0-15 cm) were chemically analysed before and after second and third experiments and selected soil physical properties were determined. Zero tillage and manual clearing reduced soil temperature and conserved more soil water better than mechanized tillage systems. Soil pH, organic matter, N, P, K, Ca and Mg were significantly influenced (p=0.05) by tillage with zero tillage being the most effective treatment in conserving fertility of the surface soil (0-15 cm). Soil fertility, as indicated by soil pH, organic matter, N, P, K, Ca and Mg declined significantly (p=0.05) over time in all tillage systems, but this decline was more pronounced in the ploughing plus harrowing twice. Zero tillage followed by manual clearing resulted in higher grain yield of sorghum compared with mechanized tillage systems. Average over the years, zero tillage, manual
clearing, ploughing and ploughing plus harrowing out-yielded ploughing plus harrowing twice by 33.7, 30.5, 18.9 and 17.9%, respectively in grain yield. Soil bulk density ranging from 1.28-1.58 Mg m-3 correlated positively with yield. Sorghum can be grown successfully on zero tillage and manually cleared Alfisol of the humid tropics.