Growth and Composition of Grain Sorghum with Limited Nitrogen

Abstract

AbstractA study of N fertilization of grain sorghum [Sorghum bicolor (L.) Moench] was conducted in two fields on a Typic Xerorthent with contrasting patterns of N availability, to extend our understanding of how the partitioning of N to vegetative parts and to structural biomass influences grain yield and N‐use efficiency. The study was supported by detailed analyses of N and dry matter distribution, and proximal analyses of biochemical composition. Nitrogen accumulation differed greatly, but the patterns of N partitioning and the structural carbohydrate content of vegetative parts at equivalent developmental stages were little affected. Changes in dry weight partitioning among vegetative parts were primarily a result of the parts' differential abilities to store nonstructural compounds. In contrast, the structural carbohydrate content of panicles was affected by N availability. Low N supply resulted in leaves with a smaller N content, and lower light conversion efficiency was observed. In addition, those canopies were not able to supply as much N to panicle growth. Roughly two‐thirds of the observed effects of N deficiency on grain yield were due to structural limitations to growth; the remaining effects were associated with reduced conversion efficiency per unit leaf area.