Composted shrub-prunings and other organic manures for smallholder farming systems in southern Rwanda

Abstract

Organic manures are the primary source of crop nutrients in many African farming systems. The quantity of such materials that are available on farms and their quality are therefore important issues, especially in countries with limited land resources, such as Rwanda. In this study, different types of compost (including composted shrub-prunings) were compared with farmyard manure (FYM) and green manure (Calliandra calothyrsus) using beans (Phaseolus vulgaris) as test crops. The study confirmed the farmers’ general opinion that FYM has high manurial value for crop yields. Composts with P- and Ca-rich Tithonia diversifolia prunings were of similar quality as FYM or dung composts and had a higher fertilizer value than Calliandra ‘green manure’ (biomass transfer). However, the farmers’ perception of trees and shrubs as biomass and nutrient sources is still very low in Rwanda.