Abstract

Intensive tractorised tillage practices especially in the tropical and subtropical climate produces compaction in crop root zone (20 to 30 cm depth), degradation of soil quality, loss of organic matter and declining soil and crop productivity. The effects of tillage and manure application on soil physical and chemical properties, growth and yield of maize grown on an intensively mechanized and degraded Alfisol was investigated on the field in 2006 and 2007.  The treatments consisted of 3 x 3 factorial combinations of tillage methods and manure application rates arranged in a split-plot design. The three tillage methods were: manual clearing (M_c), ploughing at 10 cm followed by harrowing (P₁H₁) and ploughing at 20 cm followed by harrowing (P₂H₁) while manure application at 10 t. ha^-1 farm yard manure (FYM) and 200 kg.ha^-1 NPK fertilizer (a compound mineral fertilizer which contain N, P and K in the ratio 20:10:10). The tillage constituted the main plot while farm yard manure and NPK fertilizer were the subplots. There was an unmanured control. Ploughing was carried out using mouldboard plough mounted on a tractor and harrowing was carried out after ploughing. There were no significant differences (P < 0.05) in soil moisture contents and bulk densities (0 to 60 cm depth) between tillage alone and tillage systems combined with manure application at 4 and 10 weeks after planting. The tillage-manure combination produced higher values of soil organic matter (1.3, 1.6%), total N (0.08, 0.11%) and available P (14.5, 18.9 mg/g) over tillage alone. Compared with tillage systems alone, application of manure significantly increased (P = 0.05) root and shoot dry weights, leaf area (0.11and 0.25 m²), cob and seed yield of maize. The increases in grain yield due to manure (10 tha^-1 FYM) and 200 Kgha^-1 NPK fertilizers were 10, 13 and 12%, respectively.

Key words: Alfisol, degradation, tillage, manure, soil, physico-chemical, maize.