Xu Yaxin, Gao Quantong, Xue Lihua, Zhang Jianxin, Wang Cong
College of Agriculture, Xinjiang Agricultural University, Urumqi, China.
Research Institute of Food Crops, Xinjiang Academy of Agricultural Sciences, Urumqi, China.
Front Plant Sci. 2025 Jul 2;16:1604251. doi: 10.3389/fpls.2025.1604251. eCollection 2025.
Although the mulched drip irrigation system combined with high nitrogen input (240∼310 kg ha) in Xinjiang, China, frequently achieves record-high soybean yields (6855 kg ha), this practice is not conducive to symbiotic nitrogen fixation and compromises agricultural sustainability.
Under the mulched drip irrigation, this study evaluation four nitrogen application treatments (N: 0 kg ha, N: 120 kg ha, N: 180 kg ha, and N: 240 kg ha) were evaluated over two consecutive growing seasons to investigate their effects on nodule morphological and physiological traits, stem ureide content, and the percentage of nitrogen derived from the atmosphere (%Ndfa) during the reproductive growth stage.
The application of 180 kg ha nitrogen significantly increased nodule number, nodule dry weight, nodule sucrose content, and nodule starch content, while improving soybean yield and nitrogen agronomic use efficiency. Conversely, the application of nitrogen exceeding 180 kg ha inhibited nitrogenase activity, suppressed leghemoglobin synthesis, disrupted the glutamine synthetase/glutamate synthase metabolic pathway, and reduced ureide translocation from nodules to stems, leading to significant accumulation of ureides in nodules. Correlation and path analyses indicated that nitrogenase activity, leghemoglobin content, urate oxidase activity, and stem ureide content were significantly positively correlated with %Ndfa, whereas nodule ureide content showed a significant negative correlation with %Ndfa. Stem ureide content exhibited a strong direct positive effect on %Ndfa (path coefficient = 0.95), confirming its validity as a robust indicator for assessing SNF capacity.
In conclusion, mulched drip irrigation, applying 180 kg ha nitrogen at the beginning pod stage (R) effectively enhances root nodulation, promotes carbohydrate allocation to nodules, sustains symbiotic nitrogen fixation activity, and ultimately increases soybean yield and nitrogen use efficiency. Thus, under mulched drip irrigation system, applying the correct rate of nitrogen fertilizer is beneficial for enhancing soybean yield and mitigating environmental risks, which holds significant importance for promoting sustainable agricultural development.
在中国新疆，尽管覆盖滴灌系统结合高氮投入（240∼310千克/公顷）常常能实现创纪录的大豆高产（6855千克/公顷），但这种做法不利于共生固氮，有损农业可持续性。
在覆盖滴灌条件下，本研究在连续两个生长季评估了四种施氮处理（氮：0千克/公顷、氮：120千克/公顷、氮：180千克/公顷和氮：240千克/公顷），以研究它们对生殖生长阶段根瘤形态和生理特征、茎部酰脲含量以及来自大气的氮百分比（%Ndfa）的影响。
施用180千克/公顷氮显著增加了根瘤数量、根瘤干重、根瘤蔗糖含量和根瘤淀粉含量，同时提高了大豆产量和氮农学利用效率。相反，施氮量超过180千克/公顷会抑制固氮酶活性，抑制豆血红蛋白合成，扰乱谷氨酰胺合成酶/谷氨酸合酶代谢途径，并减少酰脲从根瘤向茎部的转运，导致酰脲在根瘤中大量积累。相关性和通径分析表明，固氮酶活性、豆血红蛋白含量、尿酸氧化酶活性和茎部酰脲含量与%Ndfa显著正相关，而根瘤酰脲含量与%Ndfa呈显著负相关。茎部酰脲含量对%Ndfa表现出强烈的直接正向影响（通径系数 = 0.95），证实了其作为评估共生固氮能力的可靠指标的有效性。
总之，覆盖滴灌，在始荚期（R）施用180千克/公顷氮能有效增强根瘤形成，促进碳水化合物向根瘤分配，维持共生固氮活性，并最终提高大豆产量和氮利用效率。因此，在覆盖滴灌系统下，施用正确比例的氮肥有利于提高大豆产量并降低环境风险，这对促进可持续农业发展具有重要意义。
