Effects of nitrogen application strategy and planting density optimization on sorghum yield and quality

Abstract

AbstractNitrogen and planting density are two key factors affecting sorghum [Sorghum bicolor (L.) Moench] yield. In this study, two dwarf sorghum cultivars were used to analyze the effects of nitrogen and planting density on the yield and quality of sorghum in northern China. The experiment adopted a two‐factor, split‐zone design with the main plots assigned to three nitrogen application strategies, including all nitrogen applied at the sowing stage (N1), one‐third nitrogen applied at the sowing stage and two‐thirds nitrogen applied at the jointing stage (N2), and all nitrogen applied at the jointing stage (N3). The subplots were assigned to four planting densities of 20 × 104 (D1), 25 × 104 (D2), 30 × 104 (D3), and 35 × 104 plants ha−1 (D4). The results showed that N2 improved significantly the leaf area index, chlorophyll content, and net photosynthetic rate, and the number of grains per panicle and yield were significantly higher than that of the N1 and N3 treatments. Under the same density, the N2 and N3 increased the plant height. Under the same nitrogen, D3 significantly increased the yield. The combination of density and nitrogen was significantly correlated with grain number per panicle and yield. The protein content increased, and the starch content decreased by applying N3 at the jointing stage. The grain yields and grain number per plant were significantly affected by nitrogen application strategy, planting density, and their interaction. The N2D3 was the recommended planting density and nitrogen combination.