Effects of Tillage and Residue Retention on Maize (Zea Mays L.) Yield and Soil Water Content of Humic Nitisols in the Central Highlands of Kenya

To achieve sustainable agricultural production in Kenya, there is need to enhance the yields per unit of land while still conserving the soil resources. In the Central Highlands of Kenya, agriculture is rain fed and besides poor soil nutrient status, water is also a limiting factor to food production. There is therefore a need to address the poor soil nutrient status alongside soil water stresses, through appropriate tillage and crop residue management practices to increase crop productivity. Knowledge on the appropriate tillage and crop residue management for increased productivity is only partial in the region. As such, this research focused on addressing the knowledge gap by assessing the effects of tillage and mulching on maize (Zea Mays L.) yield and soil water content of Humic Nitisols in the central highlands of Kenya. Two mulch levels [removal (W) and retention (R) of crop residue] were applied randomly to plots measuring 7 m × 7 m under two tillage methods [conventional tillage (CT) and minimum tillage (MT)]. Special attention was given to the effects of these treatments to the maize yields and soil moisture content. There was significant treatment effect for grain yields under minimum tillage without residues (MTW), conventional tillage with residues (CTR) and minimum tillage with residues (MTR) treatments. For CTR, a significant (P<0.0029) increase in grain yield of 38% was recorded. There was significant (P<0.017) response to MTW in terms of grain yield and on average MTW yielded 87% higher than the control. In SR13 and LR14, significant (P<0.007 and P<0.003 respectively) grain response to MTR was observed. A significant yield increase in SR13 and 32% in LR14 was recorded in MTR plots compared to the control. A significant (P<0.05) treatment effect on soil moisture was observed within the top 10 cm depth, whereby the total amount of soil moisture stored within the 10-cm depth of the soil profile, was highest for MTR and MTW treatments. The results of the experiment show significant effects of MT and mulching on maize yields, soil moisture content of the Humic Nitisol in the Central Highlands of Kenya. Therefore, short-term implementation of MT and mulching under the soil and climate conditions prevailing in the Central Highlands of Kenya, enhances production in the already good seasons (high and well distributed rainfall) while maintaining a long-term prospect of stabilising yields and overcoming crop failure during poor rainfall seasons. (author)