Below- and aboveground pigeonpea productivity in on-farm sole and intercrop systems in central Malawi

Smallholder farmers in Malawi face many challenges which include a degrading soil resource base. Pigeonpea is one legume that has shown promise in Malawi in terms of improving soil fertility but its below and aboveground productivity is not fully understood. On-farm trials were set-up in 2013/14 across three agro-ecologies in central Malawi. Pigeonpea was planted as a sole crop or in an additive intercrop system with soyabean, groundnut or maize (the farmer check system). The objectives of this study were to (1) assess the effect of cropping system and soil texture on pigeonpea root and shoot biomass and (2) to evaluate variability of pigeonpea growth within a smallholder farm context. Destructive harvest was conducted six months after planting to evaluate shoot parameters, and roots of the same plants were excavated from 0-- 60 cm. Cropping system and soil texture effected shoot and root biomass (alpha=0.05). Sole pigeonpea had the highest shoot biomass at 11.83 Mg ha-1, root at 1.56 Mg ha-1 and pigeonpea/maize had the lowest shoot at 3.57 Mg ha-1 root at 0.53 Mg ha-1. Root biomass was largely confined to the topsoil, with trends similar to that for aboveground biomass. The results confirm that intra-specific competition in a pigeonpea/maize intercrop is large, while pigeonpea productivity in pigeonpea/groundnut intercrop is comparable to sole cropped pigeonpea, with additional groundnut grain benefits. Promoting the later cropping system can enhance land productivity on smallholder farms in Malawi.