Leucaena hedgerow intercropping and cattle manure application in the Ethiopian highlands - III. Nutrient balances

Balances between nutrients applied or mineralized and nutrients removed in maize grain and stover were calculated in a hedgerow intercropping experime nt in which Leucaena leucocephala and L. pallida prunings and cattle manure were applied. Hedgerow intercropping (also called alley cropping) is an ag roforestry system in which trees are grown in dense hedges between alleys w here short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure . In control treatments, nutrient depletion per season was in the order of 7-19 kg N ha(-1), 4-12 kg P ha(-1), 10-26 kg K ha(-1), 0-2 kg Ca ha(-1) and 3-6 kg Mg ha(-1). N fertilizer reversed the depletion of N, but it acceler ated the depletion of the other nutrients. Manure and at least two applicat ions of leucaena prunings resulted in net positive balances of N, It, and C a between amounts applied or mineralized and amounts removed by maize. The amounts of P and Mg applied with, or mineralized from, prunings or manure w ere insufficient to offset the negative balances of these nutrients.