Abstract:
Agroforestry using coppicing legume trees and shrubs is a way to improve livestock fodder quality and soil fertility in the tropics. However, tree establishment and appropriate management are challenging, hampering their integration into agriculture and livestock systems. This thesis evaluates the biomass production by Acacia angustissima, Leucaena pallida and Mimosa scabrella legume tree species grown on a Ferralsol in Southern Rwanda, determines their effects on fodder quality and assesses the fertiliser quality of the resulting manure and its effect on a maize crop yield and the fertility status of a Rwandan Ferralsol.
In field studies, biomass production and nutritive value of the three agroforestry species when subjected to 0.3 and 1.0 m cutting height were determined and the effects of micro-dosing manure, fertiliser and lime on soil properties and maize yield were examined. Higher biomass production was generally found at lower cutting height. Acacia angustissima had the highest biomass production, whereas M. scabrella was sensitive to repeated harvests. Crude protein (CP) was not affected by cutting height, but neutral detergent fibre (NDF), acid detergent fibre (ADF) and total polyphenols were higher at grater (1.0 m) cutting height. The highest CP was found in A. angustissima and the highest NDF and ADF in M. scabrella. Mixing legume leaves with Chloris gayana grass improved feed CP content, dietary mineral content and digestibility.
Adding A. angustissima into C. gayana grass based feed increased the total nitrogen, organic carbon and base cation content in the manure produced. Manure application increased soil pH, soil nutrient content, soil organic carbon, soil cation exchange capacity and water-holding capacity at maize planting stations. Maize agronomic parameters and yield increased with manure micro-dosing method.
Thus A. angustissima and L. pallida appear to be robust species for use in agroforestry systems with similar biophysical conditions and cutting methods to those tested in this thesis, and can be recommended to improve low-quality forage. Manure micro-dosing is a promising practice for soil fertility replenishment in crop production by smallholder farmers with limited income and access to manure.
