Effects of seedbed type N fertilizer and cultivar on the yield and N use efficiency of sorghum insemiarid Ethiopia 47

Moisture deficiency, poor soil fertility, and lack of improved varieties are major factors constraining sorghum [Sorghum bicolor (L.) Moench] production in semi-arid Ethiopia. An investigation was conducted at two semi-arid locations in north-eastern Ethiopia to determine the effect of combining seedbed type, N fertilizer, and cultivar on the yield and N use efficiency (NUE) attributes of sorghum. The experimental design was split-split plot with seedbed type (tied-ridge vs flatbed planting) as main plots, N fertilizer levels (0, 40, and 80 kg N ha-1) as sub-plots, and sorghum cultivars (Jigurti, ICSV111, and 76 T1#23) as sub-sub plots, with three replications. At Kobo, the interaction effect of seedbed type by cultivar affected all parameters where planting ICSV111 and 76 Tl#23 under tied-ridging, gave significantly higher above-ground biomass, grain yield, and NUE attributes. Nitrogen fertilization also increased biomass yield and NUE attributes at both locations and grain yield at Sirinka. Cultivars performed differently where ICSV111 and 76 T1#23 were superior in grain yield, grain and stover N concentration and uptake, N harvest index, and grain NUE (NUEg). Thus, planting ICSV111 and 76 T1#23 under tied-ridging and with N fertilization at Kobo and under flatbed and with N fertilization at Sirinka is recommended. From this study, it could be concluded that tied ridging is not a solution in all areas where moisture deficiency is a problem. Its effectiveness could be affected by rainfall amount and soil type. Thus, tied-ridging is not recommended at Sirinka. Cultivars ICSV111 and 76 T1#23 were found to be NUEg and gave higher yields on N poor soils, and thus, are important cultivars in north-eastern Ethiopia, where farmers cannot afford to apply large amounts of inorganic fertilizers.