Evaluating sustainable cropping sequences with cassava and three grain legume crops: Effects on soil fertility and maize yields in the semi-deciduous forest zone of Ghana

Abstract

Declining soil fertility has become a major constraint to crop productivity in the semi-deciduous forest agro-ecological zone of Ghana. We evaluated six crop sequences: pigeonpea, cassava variety ‘Ex-Subi’, cassava variety ‘Boakentemma’, cowpea-maize, groundnut-maize and maize-maize in 2007/2008 and 2008/2009 cropping seasons to determine their effects on soil chemical properties and the productivity of subsequent maize. Maize grain yield was significantly (p < 0.001) influenced by crop sequence. In the 2007/2008 cropping season, maize grain yield ranged from 2.0 t ha-1 with the continuous maize plot to 7.0 t ha-1 on plot previously cropped to pigeonpea. In the 2008/2009 cropping season, maize grain yield ranged from 1.3 t ha-1 with the continuous maize cropping to 2.3 t ha-1 with the plot previously under pigeonpea. High maize grain yield associated with crop sequences involving cassava and pigeonpea were more related to faster decomposition and nitrogen release of the biomass compared with the slower release of N by lower quality materials like maize stover. The study suggests that under the low input production systems of the smallholder farmers, rotation of maize with cassava and grain legumes, particularly pigeonpea, could be considered as an alternative cropping system that returns large quantities of crop residues to the soil and sustains maize yield. Key words: Soil chemical properties, pigeonpea, cassava, organic carbon.