Abstract

Productivity of common bean (Phaseolus vulgaris L.) in Uganda is less than 30% of the yield of improved varieties grown on research stations. This yield gap has been attributed mainly to low soil fertility and susceptibility of local varieties saved by farmers to pest and disease infestations. This study evaluated the impact of four improved varieties and soil fertility improvement on bean yields on small-landholder farms in three agro-ecological zones in Uganda. Yields of common bean on-farm without fertilization were on average 523 kg/ha. Enhancing soil fertility on-farm with cattle manure (10 t/ha), P (60 kg/ha), or manure (5 t/ha) + P (30 kg/ha) led to average yields of 631, 615, and 659 kg/ha, respectively. On average, improved varieties produced more yield than the local farmer-saved variety, with or without soil fertility improvement. Improved variety K131 yielded 807 kg/ha, on average, in response to manure application, which was 54% greater than the yield of the local variety. P intensification up to 180 kg/ha per season, however, did not increase bean yields significantly at any of three research stations. These results confirm the yield advantage of growing improved varieties on small-landholder farms. The combination of improved genetics and fertility intensification alone, however, did not eliminate the yield gap between on-farm and potential bean yields. 

Key words: Food security, improved varieties, farmer-saved seed, soil fertility, seed quality.