The sustainability of a groundnut plus maize rotation over 12 years on smallholder farms in the sub-humid zone of Zimbabwe

Abstract

An experiment was conducted on four smallholder farms and on-station in the sub-humid zone of northeast Zimbabwe for 12 years to assess how the rotation of groundnut with NPK-fertilized and unfertilized maize affected the productivity and sustainability of this common smallholder cropping system. At the sandy-soil Domboshava station, maize grain yield declined over 12 years of continuous maize cropping, and the rate of decline was larger when fertilizer was used. Maize grain yield was already low (around 0.7 t ha -1 without fertilizer) on the smallholder farm fields when the experiment began, and there was little evidence of further decline. A 3-year groundnut plus maize plus maize rotation raised maize grain yield on station both when fertilizer was used on maize and when not, with some benefits persisting into the second year of maize after groundnut. Three cycles of the rotation with fertilizer at Domboshava increased maize yields by 0.21, 2.92 and 2.26 t ha -1