Evaluation of Alternative Screening Criteria for Selecting Nitrogen‐Use Efficient Genotypes in Sorghum

Abstract

Development of N‐use efficient genotypes could reduce crop N fertilizer requirements; however, determining N uptake and utilization efficiencies can be costly and time consuming. The purpose of this study was to evaluate alternate screening criteria for determining relative N‐use efficiencies in sorghum [Sorghum bicolor (L.) Moench]. Different sorghum genotypes were evaluated at two soil N levels in three separate experiments on either a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) or a modified Ortello fine sandy loam soil (coarse‐loamy, mixed, mesic Udic Haplustoll). Uptake efficiency was defined as total plant N per unit soil N (PN/SN), biomass utilization efficiency as total aboveground dry matter per unit PN (NE1), and grain utilization efficiency as grain dry weight per PN (NE2). For each experiment, Spearman rank correlation coefficients were calculated for relationships between N‐use efficiency traits and alternative screening criteria. Total plant dry weight (TDW), TDW/grain N (GN) and harvest index (gram dry weight/TDW) were the best predictors of genotypic performance for PN/SN, NE1 and NE2 (r = 0.89, 0.68, 0.82), respectively. The best use of the above alternative screening criteria would be as prescreening tools to eliminate the poorest genotypes. This would alleviate the need to do wholeplant analysis on a large number of samples, yet permit a fair level of confidence in making final selections.