Tillage system and fertilizer rate effects on sorghum productivity in the central rift valley of Oromiya, Ethiopia

Soil moisture and soil nutrient are the most sorghum yield limiting factors in semi-arid Oromiya. Hence, to identify appropriate crop management system for sorghum productivity, the field experiment was conducted in 2004 cropping season using factorial combination of four levels of tillage systems and four rates of fertilizer in spilt plot design at two locations. It was found that the stand count and height of sorghum varied significantly between locations, and lower stand count recorded at Wolenchity (55738 plant/ha) than at Malkassa (61548 plant/ha) while greater plant height was obtained at Wolenchity. Grain yield was significantly affected by location and fertilizer rate. Significantly (P LT= 0.05) higher grain yield was obtained at Wolenchity (2381 kg/ha) than that at Malkassa (1747 kg/ha). Grain yield achieved at the highest fertilizer rate of 57.4-64.4 kg N-P2O5/ha was significantly (P LT= 0.01) higher than that at the current rate of 41-46 kg N-P2O5/ha. The highest grain yield was recorded from tie-ridge plot but varied with fertilizer rate for each location. Harvest Index (HI) followed the same pattern as the grain yield. However, significantly (P LT= 0.05) higher stover and biomass yield of sorghum were obtained at Malkassa. These findings indicated that applications of fertilizer beyond 49.2-55.2 kg N-P2O5/ha could give no significant yield advantage and thus, would not be economicaly feasible. The tie-ridge and reduced tillage tied furrow were encouraging but need further investigation to incorporate in sorghum cropping system.