Abstract:

Improving grain quality based on high yield is still a substaintial target in wheat production. It has been proved that the key factors contributing to high yield are the dry matter accumulation from flowering to maturity, the biomass at maturity, the optimal leaf area index (LAI), and the proper spike rate. These factors also act as the indexes to evaluate wheat population quality. However, the optimal population quality indexes vary in different specific wheat populations, and optimal cultivating techniques are unavailable due to lack of reliable population regulation indexes in weak-gluten wheat practice. It is very important to establish the optimal population quality index and develop corresponding nitrogen fertilization strategy for high-quality and high-yield production in weak-gluten wheat. In the present study, we employed two weak-gluten wheat cultivars, Yangmai 9 and Ningmai 9, to investigate the effects of nitrogen rates (0, 60, 120, 180, 240, and 300 kg ha^-1) and dressing ratios (8:2, 7:3, 6:4, 5:5, and 7:2:1 under nitrogen rate of 180 kg·ha^-1) on population index, grain yield, protein and gluten contents in 2003–2004. The results showed that leaf area index (LAI) at booting increased with increasing nitrogen rates. Grain yield, post-anthesis dry matter accumulation and biomass at maturing were parabolically related to nitrogen rates. The contents of protein and wet gluten in grains were positively correlated with nitrogen rates. While under the same nitrogen rate of 180 kg ha^-1, post-anthesis dry matter accumulation, biomass at maturity, spike number, spike rate, LAI at booting, grain yield, and contents of crude protein and wet gluten were enhanced with increasing dressing percentages, especially with dressing twice with the same percentage. Also, post-anthesis dry matter accumulation, biomass at maturity, spike number and spike rate were significantly correlated with grain yield. LAI at jointing, booting, anthesis and filling showed close relationships with grain yield. The results indicated that grain yield and quality could be improved synchronously under nitrogen rate of 200 kg ha^-1 based on dressing ratio of 7:2:1 in weak-gluten wheat. The corresponding population indexes for high-quality and grain yield in weak gluten wheat were 6.9 of the highest LAI at booting, 5 300 kg ha^-1 of post-anthesis dry matter accumulation, 16 500 kg ha^-1 of biomass at maturity, 466×10⁴ ha^-1 of spike number and 50% of spike rate.

Key words: Weak-gluten wheat, Nitrogen strategy, Grain yield, Protein content, Wet gluten content, Population quality index