The effects of alley cropping with Leucaena leucocephala and of different management practices on the productivity of maize and soil chemical properties in lowland coastal Kenya.
The effects were assessed of leucaena hedgerows (established in 1989), mulching with leucaena foliage (0, 50 and 100% of harvested foliage), cowpea intercropping and addition of dairy cattle slurry (55 t/ha of maize crop) on the yield of maize grown on a sandy soil at the KARI Regional Research Centre at Mtwapa. Four-year results from 5 maize crops are reported, and data are also given on soil chemical properties under the different treatments. Except in the first year, yields of maize grains and stover were significantly reduced (by 30%) in the presence of leucaena hedgerows. Use of leucaena mulch eliminated this effect; application of all the harvested leucaena mulch increased the total maize grain yield of the 5 crops by 44% over sole maize. Hedgerow and mulching management required an additional 36 man days labour/ha but this was more than compensated for by the increased maize yields. Furthermore, the leucaena hedgerows substantially reduced the growth of weeds between cropping seasons. Intercropping with cowpeas significantly reduced yields of maize grain and stover when both crops were sown together, but not in later seasons when cowpeas were sown 4 weeks after the maize. Application of cattle slurry increased the total yields of maize grain and stover by 35 and 37%, respectively. The grain yield of maize in the leucaena hedgerow treatments fertilized with slurry did not respond to application of more than half of the leucaena foliage, which suggested that half of the foliage could be spared for feeding to livestock. The cumulative yield of maize grain from the highest yielding organic system was 85% of the yield from the fertilizer treatment. The study (which is continuing), demonstrates that large increases in agricultural productivity are possible through the intercropping of maize with woody forage and grain legumes and the integration of dairy cattle production into the system, and shows the importance of exploiting crop/livestock interactions.