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Sorghum (Sorghum bicolor L.) Growth, Productivity, Nitrogen Removal, N- Use Efficiencies and Economics in Relation to Genotypes and Nitrogen Nutrition in Kellem- Wollega Zone of Ethiopia, East Africa

Sheleme Kaba Shamme, Cherukuri V Raghavaiah, Tesfaye Balemi and Ibrahim Hamza

Sorghum is an important cereal crop, which requires high dose of nitrogen for optimum growth and productivity, specially under rainfed farming situation in tropical regions. Field experiment was conducted at Haro Sabu Agricultural Research Center during main cropping season of 2014 with an objective to investigate Nitrogen Use Efficiency (NUE) of two improved and a local sorghum cultivar in relation to graded rates of N levels and to investigate their effect on yield, N uptake and economics. The treatments comprised factorial combination of four nitrogen rates (0, 46, 92 and 138 kg N ha-1) and three sorghum genotypes (Lalo, Chemada and Local varieties) tested in a Factorial Randomized Block Design with three replications. The results revealed that there was significant effect of N rates on days to 50% flowering, days to 50% physiological maturity, Lodging percentage, leaf area at 90 and 120 DAS, leaf area index, number of green leaves plant-1, biological yield, grain yield, harvest index and nitrogen use efficiency. There was significant interaction effect of N rates and sorghum genotypes on most of parameters studied. Significantly higher grain productivity was obtained in response to the application of 92 kg N ha with Lalo variety in comparison with the rest of the genotype × N-rate combinations. Genotypic variations in N uptake, partitioning and NUE in plant parts like leaves, stems and grain were noted. Increase in the rate of applied N enhanced N uptake, nitrogen utilization efficiency, and N harvest index; while higher rates decreased N use efficiency, N uptake efficiency, N recovery efficiency, and Agronomic efficiency. Economic analysis indicated higher net return with the application of 92 kg N ha-1 and Lalo genotype accrued the highest net return and benefit: cost ratio than Local variety.