长期秸秆还田对塿土耕层土壤有机碳库的影响

在关中平原塿土(土垫旱耕人为土)上施用化肥的条件下,进行不同用量玉米秸秆直接还田(低秸9 375 kg·hm^-2,中秸18 750 kg·hm^-2,高秸37 500 kg·hm^-2)、间接还田(厩肥,37 500 kg·hm^-2)的长期定位试验21 a,观测和分析了耕层土壤有机碳的储量及氧化稳定性等的变化。结果显示,与单施化肥相比,秸秆直接或间接还田均可显著提高土壤有机碳含量,耕层土壤有机碳储量分别增加了12%(低秸)、24%(中秸)、41%(高秸)和39%(厩肥)。施用秸秆和厩肥21 a,土壤有机碳累积系数平均分别为5.6%和7.2%。秸秆直接还田和厩肥均使土壤有机碳的氧化稳定性降低,胡敏酸的能态升高且保持相对稳定。以上结果表明,秸秆直接或间接还田不仅能显著提高土壤有机碳储量,也能明显改善土壤有机碳的活性和质量,是提高农田固碳能力、促进农业可持续性的重要措施。

Effect of Long-Term Residue Return on Soil Organic Carbon Storage

To investigate the effect of maize residue return on soil organic carbon(SOC) maintenance,soil samples were collected from a long-term field experiment site after 21-year treatments involving three rates of residue return(9 375,18 750,37 500 kg·hm-2),yard manure application(37 500 kg·hm-2),chemical fertilizer and unfertilized control.The study was conducted in Guanzhong Plain on clay loam soil,classified as Eum-Orthic Anthrosols.Compared to the chemical fertilizer treatment,the low,middle and high levels of residue incorporation increased SOC storage by 12%,24% and 41%,respectively,while 39% increase was found for yard manure application.The SOC accumulative coefficient after 21 years was about 5.6% for residue,and 7.2% for yard manure.The annual rate of SOC accumulation was 413 kg·hm-2,265 kg·hm-2 and 155 kg·hm-2 for residue return at the high,middle and low levels,respectively,and 397 kg/hm2 for yard manure application.Residue and yard manure application reduced the oxidation stability of SOC and enhanced the energy state of humic substances,which means the decrease of SOC decomposition.The results indicate that residue return,both directly and indirectly(yard manure application),would significantly increase the SOC level relative to chemical fertilizer treatment and unfertilized control on clay loam soil with benefits for soil productivity and agricultural sustainability.