Effect Of Nitrogen Fertilizer On Growth, Yield and Nitrogen Use Among Grain Sorghum.

Grain sorghum is an important crop in the semi-arid regions of Africa, Asia and United States. Productivity of grain sorghum is limited by soil fertility, especially nitrogen (N). Sorghum genotypes are known to vary in their response to nitrogen, however, the information on nitrogen use efficiency is limited. The objectives of this research were to (a) determine the response of sorghum genotypes (hybrids and inbred lines) to nitrogen fertilizer; and (b) quantify genotypic differences in nitrogen use efficiency (NUE). Field experiments were conducted at three locations (Hays, Ottawa and Manhattan in; Kansas) in 2010 and 2011. Six hybrids and six inbred lines of grain sorghum were grown with 0N, 45N and 90kg N ha-1. The experimental design was a split-plot arranged in randomized complete block design with nitrogen regimes as main plots and genotypes as sub-plot, with four replications. Urea N (46% N), was applied at emergence. There were significant effects of genotypes (P<0.05) and nitrogen (P<0.05) on leaf chlorophyll content, biomass and grain yield across all locations. Leaf chlorophyll content was higher among the inbred lines than the hybrids. Hybrids 26056 and 99480 produced maximum grain yield across all locations. While, inbreds SC35 and B35 had the lowest grain yield. Maximum biomass and grain yield was obtained at 90 kg N ha-1, followed by 45 kg N ha-1, and lowest in 0N kg ha-1.There were significant differences among genotypes for all NUE traits. Across genotypes N uptake efficiency ranged from 26 to 75 percent, utilization efficiency from 25 to 60 kg grain/kg N uptake, N recovery from 2 to 52 percent and total NUE from 17 to 43 kg grain/kg N supplied. Overall, this data suggest that there were significant differences for yield and NUE traits in sorghum hybrids and inbred lines.