Abstract:

Nitrogen (N) and sulphur (S) are essential plant nutrients, both of them are constituents of protein. About 70% of N and 1/3 of S in vegetative organs were redistributed to the ears after anthesis. The proportion of ear N and S allocated from the redistribution of vegetative organs are 70% and 48%, respectively. The N and S accumulated in vegetative organs before anthesis then redistributed to grains after anthesis are important for the grain quality of wheat. The objectives of this study were to determine the effect of nitrogen application rate on the accumulation and redistribution of N and S, and grain quality of wheat, for providing a theoretical basis on appropriate amount of nitrogen application in production. In the present study, field experiments were carried out using the winter wheat cultivar “Jimai 20”, on two locations, one with alkalihydrolysable nitrogen of 85.87 mg kg^-1 and available sulphur of 18.91 mg kg^-1 in 0–20 cm soil layer, and treatments of 0, 105, 195, 285 kg ha^-1 nitrogen applications, another with alkalihydrolysable nitrogen of 84.00 mg kg^-1 and available sulphur of 16.74 mg kg-1 in 0–20 cm soil layer, and treatments of 0, 132, 204, 276 kg ha^-1 nitrogen applications, using urea as the nitrogen fertilizer. Half of the nitrogen fertilizer was applied before sowing, the other half topdressed at jointing stage. The treatments were applied also with105 kg P₂O₅ ha^-1 and 135 kg K₂O ha^-1 before sowing. Each treatment had three replicates, and the plot area was 3 m×8 m =24 m². The basic seedlings were 150 plant m^-2. The results showed that the amount of N and S accumulated in vegetative organs before anthesis and the amount of N and S in grains from the absorption after anthesis, the amount of N redistributed from vegetative organs to grains, the amount of S redistributed from leaves and spike axis + glume to grains increased, the contents of N and S, the proportion of glutenin in grains increased and the grain quality improved, the N/S ratio in grains decreased from16.38–16.98 to 14.22–14.48 with nitrogen applied from 0 to 195–204 kg ha^-1. The residual N in stem + sheath increased and the S redistribution was inhibited, the amount of N accumulated in plant were not affected significantly by excessive nitrogen applications of 276–285 kg ha^-1, and consequently, resulted in the decrease of sulphur accumulation amount, sulphur content, the proportion of glutenin in grains and the grain quality, and the increase of N/S ratio (increased to 15.20–15.27) in grains. It was suggested that the regulation of nitrogen application rate on protein compositions and grain quality is based on the changes of N and S contents and N/S ratio in grains due to the accumulation and redistribution of N and S. The optimal N/S ratio in grains for quality improvement was 14.22–15.27. The appropriate amount of nitrogen application for high yield and high quality was 195–204 kg ha^-1.

Key words: Winter wheat (Triticum aestivum L.), Nitrogen application rate, Sulphur, Redistribution, Grain quality