Enhancing maize productivity in agroforestry systems through managing competition: lessons from smallholders' farms, Rift valley, Kenya

Understanding crop performance and productivity in relation to intercropped tree species, tree management and prevailing environmental conditions may assist farmers in managing agroforestry systems appropriately. Our study evaluated the management and spatial effect of six dominant tree species (Eucalyptus spp., Sesbania sesban, Grevillea robusta, Calliandra calothyrsus, Markhamia lutea and Croton macrostachyus) on water availability and crop performance in smallholders' maize fields in Rift valley, Kenya. Maize performance under C. macrostachyus and M. lutea was also evaluated at on-station experiment in the same area. The smallholder farmers in the study area remain important maize producers in Kenya with an average maize yield of 6.5tonsha(-1) recorded. Maize yield under the dominant tree species in studied smallholder farms showed significant differences (P<0.001) with leguminous species (C. calothyrsus and S. sesban) recording the highest amount of grain weight. Farmers selectively prune tree they perceive as competitive but still want to maintain them in the farms such as Eucalyptus spp. and G. robusta but miss to equally prune M. lutea and C. macrostachyus which would greatly improve performance of associated crops. In addition to presence of great tree management diversity, the study clearly showed that tree in smallholder farms either have competitive, complementary or balanced-off interaction with crops. Lastly, despite the adequate rainfall throughout the cropping season, dominant tree species in smallholder farms were shown to significantly (P<0.0001) influence the spatial distribution of soil water.