Effects of fertilizer and cassava-legume cropping systems on root yields in two agro-ecological zones of Ghana

Cassava is an important food crop in small-holder farming systems in Ghana. Due to the limited use of organic and inorganic inputs, soil fertility becomes a major problem in cassava production systems. A study was conducted at the Soil Research Institute, Kwadaso, in the Forest Agro-ecological zone and the Wenchi Agricultural Station in the Forest-Savannah Transitional zone. The fertilizer rates were 0:0:0, 15:15:15 and 30:30:30 N-P2O5-K2O kg/ha. Cowpea, soybean, and groundnuts were the legumes and cassava was either sole cropped or intercropped with a legume. The objective was to determine the effect of fertilizer and cassava-legume cropping systems on root and grain yields in the two agro-ecological zones. Data on soil characteristics, biomass, grain, and root yields were collected. Growth and yield data were subjected to ANOVA and mean separated using LSD (P < 0.05). Fertilizer application did not influence cassava root yields at Kwadaso but different cropping systems significantly influenced root yield. Cassava-groundnut intercrop gave the highest root yield of 70.2 t/ha. At Wenchi, both cropping system and fertilizer did not affect root yield. This study shows that intercropping cassava with groundnut or cowpea is a good option in improving cassava production.   Key words:  Agro-ecological zone, cassava-legume intercrop, fertilizer, root yield.