腐殖酸对盐胁迫下紫花苜蓿生长及土壤酶活性的影响

Effects of Humic Acid on Alfalfa Growth and Soil Enzyme Activity under Salt Stress

摘要: 为探究腐殖酸(Humic Acid, HA)对盐胁迫的缓解效应及作用机制。本研究通过盆栽试验，以NaCl模拟盐胁迫，设置空白对照(CK)、盐胁迫组(ST)及不同浓度腐殖酸(10，25，50和100 mg/kg，T1~T4)处理，系统探究HA盐胁迫下紫花苜蓿生长和土壤微环境的调控效应。结果表明：ST处理显著抑制了紫花苜蓿的生长并导致土壤环境劣化。与CK相比，ST处理组植株地上部和地下部生物量分别降低49.37%和52.14%；叶片可溶性糖和可溶性蛋白含量分别下降45.21%和31.98%。同时，ST处理降低了土壤氮素的有效性，硝态氮和铵态氮含量分别降低57.56%和49.69%；土壤蔗糖酶、淀粉酶、纤维素酶、脲酶和过氧化氢酶活性分别下降了41.37%、72.31%、86.37%、74.01%和44.69%。施用腐殖酸可有效缓解盐胁迫的负面效应，其中T3处理效果最佳。与ST相比，T3处理地上部和地下部生物量分别提高179.86%和312.79%；叶片可溶性糖和可溶性蛋白含量分别提高139.95%和49.88%；土壤硝态氮和铵态氮含量分别提高172.05%和121.22%；蔗糖酶、淀粉酶、纤维素酶、脲酶和过氧化氢酶活性较ST分别提高67.26%、231.75、697.26%、327.82%和79.77%。综上所述，适宜浓度腐殖酸(50 mg/kg)通过改善土壤氮素供应、提升碳氮转化相关酶活性、促进渗透调节物质积累，有效缓解盐胁迫对紫花苜蓿生长的抑制作用，研究结果为盐碱地改良及优质苜蓿栽培提供了理论依据与实践指导。

Abstract: This study aimed to investigate the alleviating effects and underlying mechanisms of Humic Acid (HA) on salt stress in alfalfa. A pot experiment was conducted with NaCl-stimulated salt stress, including a control (CK), a salt stress group (ST), and different concentrations of HA treatments (10, 25, 50, and 100 mg/kg, T1~T4). The effects of HA on alfalfa growth and the soil micro-environment under salt stress were systematically examined. The results showed that ST treatment significantly inhibited alfalfa growth and deteriorated the soil environment. Compared with CK, ST treatment reduced aboveground and belowground biomasses by 49.37% and 52.14%, respectively; soluble sugar and soluble protein contents in leaves decreased by 45.21% and 31.98%, respectively. Simultaneously, ST treatment reduced soil nitrogen availability, with nitrate and ammonium contents decreasing by 57.56% and 49.69%, respectively. The activities of soil sucrase, amylase, cellulase, urease, and catalase decreased by 41.37%, 72.31%, 83.60%, 74.01%, and 44.69%, respectively. Application of HA effectively mitigated the negative effects of salt stress, with the 50 mg/kg HA treatment (T3) showing the most pronounced effect. Compared with ST, the T3 treatment increased aboveground and belowground biomasses by 179.86% and 312.79%, respectively; soluble sugar and soluble protein contents in leaves increased by 139.95% and 49.88%, respectively; soil nitrate nitrogen and ammonium nitrogen contents increased by 172.05% and 121.22%, respectively; and the activities of soil sucrase, amylase, cellulase, urease, and catalase increased by 67.26%, 231.75%, 697.26%, 327.82%, and 79.77%, respectively. In conclusion, an appropriate concentration of humic acid (50 mg/kg) effectively alleviated the inhibitory effects of salt stress on alfalfa growth by improving soil nitrogen availability, enhancing the activities of enzymes involved in carbon and nitrogen transformations, and promoting the accumulation of osmotic adjustment substances. These findings provide both a theoretical basis and practical guidance for the remediation of saline-alkali soils and the cultivation of high-quality alfalfa.