This study investigated the effect of cutting height (30 and 100 cm) on chemical composition and in vitro digestibility in field-grown Acacia angustissima (Mill.) Kuntze. (Prairie acacia), Leucaena pallida Britton & Rose (guaja) and Mimosa scabrella Bentham. (bracatinga) legumes and their value in supplementing a basal diet of Chloris gayana Kunth. (Rhodes grass). Cutting height did not affect major chemical composition. Crude protein (CP) was highest in A. angustissima and lowest in M. scabrella, while neutral detergent fibre (NDF) and acid detergent fibre (ADF) were highest in M. scabrella. Degradation parameters were greater at 100 cm cutting height. L. pallida showed high in vitro organic matter digestibility but A. angustissima had the highest metabolisable energy. Addition of A. angustissima, L. pallida and M. scabrella to the basal diet increased improved the nutritional value and increased the CP content from 8.4 to 19.8% and 18.1 and 16.1%, respectively. Cutting height of A. angustissima, L. pallida and M. scabrella had no effect on their nutritional value. Their other functions and benefits will determine choice of cutting height as management practice when used on farms.

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Combined use of lime, animal manure and inorganic fertilisers is effective in replenishing the fertility of degraded acid soils. However, many smallholder farmers lack access to sufficient amounts of these inputs to improve the fertility and reduce the aluminium toxicity of Ferralsols. Organic manures are available but often have low nutrient content, which limits their ability to supply nutrients to soils. In a two-factor field experiment over four seasons on an Anthropic Ferralsol in Southern Province, Rwanda, we assessed (i) the effect of cattle manure on soil properties at a reduced rate affordable to smallholder farmers compared with that of NPK fertiliser applied, with and without lime also at a reduced rate, and (ii) the effect of supplementing grass in a basal cattle diet with legume leaves on manure quality and its effect on soil properties. Manure from cattle fed only the grass Chloris gayana (grass-only manure) and from cattle fed C. gayana supplemented with Acacia angustissima leaves (grass+legume manure) was applied at 5 t dry matter ha-1 (25% of the recommended rate) at the beginning of each growing season. NPK was applied as split doses supplying a total rate of 70 kg N ha-1. Lime was applied annually at a rate of 2.0 t CaO ha-1, which was 25% of the rate required to neutralise total acidity at the site. All amendments were applied only to the soil surrounding the maize plants (planting stations), which is estimated at 25% of the plot area. Maize stover was left on plots after harvest and planting stations were retained over all growing seasons. All treatments altered soil properties at the planting stations. Lime generally increased pH but there was no significant difference between lime plus manure treatments and non-limed manure treatments. Soil organic carbon concentration and cation exchange capacity were higher in manure and NPK treatments than in non-fertilised treatments. The manure treatment increased soil water-holding capacity compared with the NPK and non-fertilised treatments. There was no significant difference in total N, Ca2+, Mg2+ and K+ between the NPK and manure treatments. Micro-dosing animal manure can thus replace mineral fertiliser plus lime for soil fertility replenishment in smallholder farming. Grass+legume manure contained higher concentrations of total N, Ca, Mg, K and Na than grass-only manure, but its effect on soil properties did not differ significantly from that of grass-only manure.