Improving local technologies to manage speargrass ( Imperata cylindrica ) in southern Benin

Abstract

Speargrass (Imperata cylindrica) is difficult to control in the tropics. Farmers allocate most of their time and labour to weedingspeargrass. We investigated in a joint experiment concluded with farmers, how effectively grain legumes suppress speargrass,and the relationships between speargrass suppression, legume grain yield, and subsequent maize yield. Without management,speargrass shoots and rhizomes increased with 31 and 17% per month, respectively. The integration of deep ridging, deephoe weeding and shading suppressed speargrass more effectively than farmers’ practices. Creeping varieties of cowpea thatproduced most biomass were most successful in suppressing speargrass and in enhancing subsequent maize yields, but erectcowpea cultivars produced more grain. Farmers traded off cowpea yield against speargrass suppression to bridge the hungrygap. They preferred the erect cowpea cultivar wan. The need to forego a harvest and the fact that pigeonpea is not consumedin the area makes pigeonpea presently unsuitable for integration into the cropping system.