Understanding maize/beans intercropping yield distributions from water conservation measures in a hedged agroforestry system in semi-arid Laikipia District, Kenya

Cropping systems in semi-arid Laikipia district are more weather sensitive than those in medium to higher potential areas of Kenya. Water, and to a certain extent, wind are major climatic constraints. Agroforestry (AF) farms surrounded by Coleus barbatus hedges as live-fences are being introduced by demonstrations into this fragile environment, in which Grevillea robusta trees are combined with an intercrop of maize and beans. In this demonstration plot research with a six-year-old tree system, root pruning of trees and live-fences diminished competition with crops. When combined with mulching and minimum tillage as additional water conservation measures, this was successful for maize biomass and for low bean seed and biomass yields under very low rainfall conditions. Under ample rainfall, pruning remained useful for maize and both mulching and pruning for beans. Partitioning of assimilates among stover biomass, grain and cobs was found to occur in a ratio of close to 6:3:1. This implies that the photosynthates are proportioned such that 10% goes to build cob dry matter, 30% grain dry matter and 60% to the biomass. However, under unfavourable on-farm conditions the stover accumulated more biomass while other parts had very little. Although some farmers have adopted the use of AF, tree spacing in their farms had not taken care of necessary conditions for understory crops. This way, water conservation measures such as root pruning, mulching and minimum tillage could not yield the desired results on these farms, although pruning was observed to influence maize height and biomass weight. The objective of this article is to articulate methods that were used in water conservation for enhanced maize and beans intercrop yields in the semi-arid and arid areas of Kenya. The specific objectives included the role of root pruning of agroforestry trees, tillage modes and soil mulching in amelioration of intercrop environment.