关键词: 冬小麦, 春季追氮, 分蘖成穗, 产量及构成, 因蘖追肥

Abstract:

【Objective】To clarify the precise management of water and fertilizer based on spring growth stages, and to reveal the mechanism of optimizing yield components through efficient light energy utilization, thereby contributing to the increase in grain yield of winter wheat.【Method】The field experiment was conducted at the TaiGu Winter Wheat Experimental Station in Jinzhong, Shanxi Province, from 2021 to 2023. A split-plot design was adopted, with two spring nitrogen top-dressing rates (90 kg·hm^-2, N90; 120 kg·hm^-2, N120) as main plots, and four top-dressing times after regreening (10 d, 20 d, 30 d, and 40 d) as sub-plots. Through systematic surveys of tillering dynamics and measurements of canopy photosynthetic active radiation interception, combined with the fitting of the grain-filling process using the Richards model, we systematically analyzed the effects of different nitrogen topdressing treatments on the winter wheat population structure, canopy light distribution, and grain-filling characteristics. Correlation analysis was conducted to clarify the intrinsic relationships among population photosynthetic performance, tillering dynamics, and yield components.【Result】Compared with other treatments, applying 120 kg·hm^-2 of nitrogen at 30 days after regreening reduced the peak tiller number, delayed the occurrence of the tillering peak, and decreased the tiller senescence rate by 28%-43%. It also decreased the number of ineffective tillers (50-70 days after regreening) by 15%-30%, thereby significantly increasing the tiller-to-spike ratio by 10%-23%. Significantly increased the canopy PAR interception rate and extinction coefficient during the anthesis and mid-grain-filling stages, while significantly reducing the decline rate of lower-layer PAR interception during the anthesis-to-grain-filling period. Significantly increased the theoretical maximum 1000-grain weight, initial filling potential, average and maximum grain-filling rates, the time to reach maximum grain-filling rate, the duration of the gradual-increasing phase, and the grain-filling rates during the rapid-increasing and slow-increasing phases; significantly increased spike length by 3%-10%, spike weight by 8%-14%, and seed setting rate by 2%-12%.Significantly increased the number of spikes by 4%-10%, the number of grains per spike by 3%-10%, and the 1000-grain weight by 5%-10%, resulting in an increase in grain yield of 7%-20%.The Population Photosynthetic Potential during the booting-anthesis period showed a significant positive correlation with the tiller number at 45-70 days after regreening; meanwhile, the tiller number at 45-70 days after regreening was significantly and positively correlated with the spike number at maturity.The radiation interception rate in the lower layer of the canopy at the mid-grain-filling stage showed a significant positive correlation with the tiller number at 50-55 days after regreening; meanwhile, the tiller number at 50-55 days after regreening was significantly and positively correlated with the number of grains per spike. The PAR interception rate in the canopy at anthesis and mid-grain-filling stages showed a positive correlation with the tiller number at 50-55 days after regreening; meanwhile, the population photosynthetic potential during the booting-anthesis period was significantly and positively correlated with the tiller number at 50-55 days after regreening, and the tiller number at 50-55 days after regreening was significantly and positively correlated with the 1000-grain weight.【Conclusion】Application of 120 kg·hm^-2 nitrogen topdressing 30 days after regreening achieved a synergistic improvement in the number of effective spikes, grains per spike, and 1000-grain weight, thereby significantly increasing grain yield. This was realized by suppressing and delaying the tillering peak, optimizing the post-anthesis canopy light distribution, and enhancing the grain-filling process. Furthermore, correlation analysis further confirmed that the population photosynthetic potential before anthesis and the canopy photosynthetic performance after anthesis, by influencing spikelet formation and grain filling, jointly determined the final grain yield. This study provides a critical nitrogen management strategy for achieving high-yield and efficient cultivation of winter wheat in the irrigation area of the Loess Plateau by improving the population photosynthetic efficiency through integrated water and fertilizer management.

Key words: winter wheat, spring nitrogen topdressing, tiller-to-spike ratio, yield and its components, fertilization based on tiller number