On farm yield responses of soybean [Glycine max L (Merrill)] to fertilizer sources under different soil acidity status in gobu sayo district, western ethiopia

Abstract

The study was conducted on fourteen on-farm fields under rain fed in Gobu sayo district to evaluate the responses of phosphorus application with rhizobium inoculations under different soil acidity, available phosphorus and potassium. The experimental sites were purposively selected from three different peasant associations and the trials were laid out on plots of N-deficient sites that were more or less homogenous. The treatments were Didessa (+P+R), Ethio-ugozilavia (+P+R), Didessa (-P-R) and Ethio-ugozilavia (-P-R). The result of soil analysis showed that all experimental sites were strongly acidic and available phosphorus and exchangeable potassium were found to be from low to medium ranges and considerably affected yield and yield traits of the test crop. Significant variations in plant height, pods per plant, grain and husk yield due to the effect of applied inputs. However, there was significant difference between varieties in terms of nitrogen uptake, 100 seed weight and oven dry weight of husk. Even if the inputs revealed significant effects on yield traits, the responses were not consistence across each farmer's plot and resulted in considerable yield variability which ranged from less than 1t to more than 5.8 t. Variations in Soil pH, available phosphorus and exchangeable potassium across farmers' plots significantly influenced yield variability and the effects of input applications on each variety. Yield was positively and significantly correlated to initial soil pH, available phosphorus and exchangeable potassium. In conclusion, application of 50 kg ha -1 DAP in combination with rhizobium inoculation is recommended for in production in areas where soil pH is near to neutral. However, it needs more attention should be given to optimize soil pH as the majority of the farms were strongly acidic. Moreover, revision of phosphorus fertilizer rates and determination of potassium sources of fertilizer is another concern for sustainable production of soybean in the area.