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Crop-livestock interactions: considerations of direct and indirect utilisation of MPTs and/or herbaceous biomass in soil fertility management.

L.R. Ndlovu


In smallholder farming systems, crops and livestock complement and compete with each other in terms of natural resource use. Supply of manure to the cropping system and use of resultant crop residues are an example of this interaction. Tree forages are valuable sources of nutrients for livestock and they are also important in soil amendment. The dilemma is whether to apply the tree forages directly to the soil or to pass them through animals ( as feed) and apply the manure to the soil. Legume tree foliage tends to contain tannins that regulate nutrient release and affect distribution of nitrogen (N) in animal excreta. Most urine N is lost through volatilisation whilst N excreted in faeces could be mobilised for plant uptake. Manure has been shown to be higher in content of phosphorus (P), lignin and nitrogen and to result in faster mineralisation of N and P than leaves. However this is based on a limited number of studies and there is a need for well-designed studies that compare manure from animals fed specified tree forages of the same plants incorporated directly into the soil as part of the same experiment.

Transactions of the Zimbabwe Scientific Association Volume 72 (Supplement) 1998, pp. 27-30

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