6. Influence of Tillage, Crop Rotation and Crop Residue Management on Soil Erosion and Maize Yield
An experiment was conducted in 2014 and 2015 in the forest zone of Ghana to evaluate the effects of tillage, maize-cowpea rotation, and residue management on runoff, soil erosion and maize grain yield. Four treatments consisting of full tillage with continuous maize cropping and removal of crop residue (T1), full tillage with maize-cowpea rotation with incorporation of plant residues (T2), minimum tillage with maize-cowpea rotation and plant residues applied as mulch (T3), and minimum tillage with continuous maize cropping with residue mulch (T4) were imposed on a randomized complete block design with three replications. Results showed a very high runoff coefficient (15.53%) for T1, while runoff was significantly lower for T2 followed by T3 and T4. This translated into very high total suspended sediments (5.7 t ha-1) and subsequently higher (p = 0.007) total eroded soil (9.2 t ha-1). There seem to be a synergy between the presence of plant cover/mulch and residue incorporation resulting in the lowest runoff for T2, as the combined effect probably improved infiltration and soil permeability. In 2014, maize grain yield was lowest in the T1 (2.3 t ha-1) which was similar to T4 (2.4 t ha-1). Grain yields for T3 (4.2 t ha-1) and T2 (4.1 t ha-1) were also similar but higher than the other two treatments. In 2015, however, maize grain yields were significantly different among the various practices in the following order: T1 (1.2 t ha-1) < T4 (2.2 t ha-1) < T3 (3.4 t ha-1) < T2 (4.0 t ha-1). The inclusion of a legume in T2 and T3 probably enhanced the soil fertility status resulting in higher grain yields. Hence, tillage practices including cereal-legume rotation systems, coupled with effective management of crop residue is a promising strategy to address soil and nutrient loss to water erosion and increase crop yield.