Mulching effects on soil physical quality of an alfisol in western Nigeria

Degradation of soil physical quality, following deforestation and cultivation, is a major soil-related constraint to an intensive use of soil for crop production in subhumid regions of subSaharan Africa. Use of crop residue mulch is an important strategy to minimize the risks of soil degradation. Therefore, a three-year experiment was conducted to study the effects of five rates of mulch application (0, 2, 4, 6 and 8 Mg ha−1 season−1) on soil physical properties and growth and yield of maize (Zea mays). Mulch rate of rice straw significantly increased maize grain and stover yields during the first season, and the stover yield during the second season. In comparison with the control, the grain yield increased by 20 per cent at 2 Mg ha−1 of mulch rate and by 33 per cent at 8 Mg ha−1 of mulch rate. The rate of increase was 0·16 Mg ha−1 for grain yield and 0·38 Mg ha−1 for stover yield for every Mg of mulch applied. The increase in stover yield during the second season was 67 per cent for 8 Mg ha−1 mulch rate compared with the unmulched control. Effects of mulch rate on soil physical properties were confined mostly to the surface 0–5 cm depth. For this depth, mulching decreased bulk density from 1·17 Mg m−3 for control to 0·98 Mg m−3, and penetration resistance from 1·54 kg cm−2 to 1·07 kg cm−2 for 8 Mg ha−1 of mulch rate. Application of mulch up to 16 Mg ha−1 yr−1 for three consecutive years had no effect on soil physical properties below 5 cm depth. Experiments were probably not conducted for a long enough period. For mulch farming to be adopted by farmers of West Africa, it must be an integral part of the improved farming system. Copyright © 2000 John Wiley & Sons, Ltd.