Genotypic differences in yield and nitrogen use efficiency of 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 90 kg N ha-1. The experimental design was a split-plot design with nitrogen regimes as main plots and genotypes as sub-plot, with four replications. Planting was done in May and June across all the locations, and nitrogen fertilizer (Urea, 46% N) was applied at emergence. Nitrogen concentrations in the grain and component of NUE were determined for Ottawa and Manhattan. There were significant effects of genotypes (P