Grain sorghum nitrogen use as affected by planting practice and nitrogen rate

Water and nitrogen supply are often the most critical factors limiting growth and yield in crop production. A study was carried out in 2006 and 2007 to determine N use efficiency of grain sorghum (Sorghum bicolor (L.) Moench) in dryland production at the University of Nebraska, Lincoln, Nebraska, South Central Agricultural Laboratory. The study evaluated three row planting arrangements (RPA) including all rows planted (s0), alternate rows planted (s1), and two rows planted alternated with two skipped rows (s2) in a complete factorial with plant populations (PP) of 75,000 and 150,000 plants ha-1 and N application rates of 0, 50, 100, and 150 kg N ha-1. The objectives of the study were to determine the optimum N rate, magnitude of N uptake, and N use efficiency (NUE) for grain sorghum under dryland conditions with different row configurations. Conventional planting out-yielded skip-row planting by 23 to 36% in each year. Percent N translocated from biomass to grain at physiological maturity at half bloom ranged from 29 to 35% in 2006 compared with 46 to 51% in 2007. The RPA x PP interaction affected internal NUE (IE N) in 2006 and 2007, and physiological NUE (PE N) in 2006. The RPA x N rate interaction affected partial factor productivity (PFP N) in 2006.