Effects of Different Humic Acid Replacement Ratios of Nitrogen Fertilizer on Yield, Quality and Nitrogen Utilization of Weak-gluten Wheat

To clarify the regulatory effects of different replacement ratios of humic acid urea on growth and development, nitrogen utilization, yield and quality of weak-gluten wheat, a field experiment was conducted with weak-gluten wheat variety Yangmai 13 in the main weak-gluten wheat production area of southern Henan from 2023 to 2025. Five replacement ratios of humic acid urea for conventional urea (0%, 40%, 60%, 80% and 100%) were set up. The SPAD value of functional leaves, stem and tiller dynamics, nitrogen use efficiency, yield components and processing quality were systematically analyzed. The results showed that humic acid urea substitution significantly delayed chlorophyll degradation of flag leaves after anthesis, increased tiller number at over-wintering stage and optimized population structure. Compared with conventional urea treatment, all substitution treatments significantly increased nitrogen uptake, agronomic nitrogen use efficiency and apparent nitrogen recovery efficiency, among which the 80% substitution treatment performed the best. In two growing seasons, the yields of all substitution treatments were higher than the control. The 80% substitution treatment obtained the highest yield, with an increase of 7.66%~14.84% compared with the control, mainly by increasing spike number and 1000-grain weight. Meanwhile, substitution treatments significantly reduced grain protein content and hardness index, making quality more in line with the standard of weak-gluten wheat, without negative effects on wet gluten content, sedimentation value and flour yield. In conclusion, 80% humic acid urea replacing conventional urea can synchronously achieve high yield, good quality and high nitrogen use efficiency of weak-gluten wheat, which is suitable for popularization in southern Henan and similar ecological regions.