长期秸秆还田对土壤有机碳和胡敏酸结构特征的影响

Effects of Long-term Straw Returning to Field on Soil Organic Car⁃bon and Structural Characteristics of Humic Acid

针对黑土有机质老化急需培肥和解决秸秆焚烧问题,通过长期、少量、连年秸秆还田试验,研究土壤有机碳(SOC)、腐殖质组分含量和胡敏酸(HA)结构特征的变化。结果表明:与ck相比,秸秆还田配施化肥和秸秆还田处理表层、亚表层土壤有机碳含量分别增加了18.9%,20.0%和13.1%,14.7%;HA碳含量增加了17.5%,57.4%和10.7%,28.1%;胡敏素(Hu)含量分别增加了23.1%,23.0%和20.7%,16.2%。秸秆还田配施化肥处理亚表层土壤HA碳的增加量占SOC增加量的75.3%;HA占可提取腐殖质比例(PQ)从58.2%提升至63.6%。与ck相比,秸秆配施化肥处理HA的结构特征变化显著,表层和亚表层(O+S)/C比值分别降低了15.8%和17.7%;H/C比值分别增加了4.8%和5.3%;I_(2920)/I_(1720)比值分别增加了110.5%和131.2%;热量高/中比值分别降低了35.3%和28.9%;失重高/中分别降低了14.1%和12.0%。秸秆配施化肥处理使HA结构的氧化度、缩合度和热稳定性降低,脂族性增强,结构趋于简单化。

In response to the aging of organic matter in black soil and the urgent need for fertiliza⁃tion and problem solving of straw burning,the changes of soil organic carbon(SOC),humus compo⁃nent content and humic acid(HA)structure characteristics were studied by means of long-term,small amount,and continuous straw returning experiments.The results showed that compared with ck,the organic carbon content increased by 18.9%,20.0%and 13.1%,14.7%,respectively,under the treatments of straw returning combined with chemical fertilizer and straw returning in surface and subsurface soil;Carbon content of HA increased by 17.5%,57.4%and 10.7%,28.1%,respectively;Carbon content of humin(Hu)increased by 23.1%,23.0%and 20.7%,16.2%,respectively.The in⁃crease of HA carbon in subsurface soil treated with straw returning and chemical fertilizer accounted for 75.3%of the increase in SOC.The proportion of HA in extractable humus(PQ)increased from 58.2%to 63.6%.Compared with ck,the structural characteristics of HA treated with straw combined with chemical fertilizer were significantly changed,and the ratio of surface layer and subsurface layer(O+S)/C was reduced by 15.8%and 17.7%,respectively.The H/C ratio increased by 4.8%and 5.3%,respectively.I_(2920)/I_(1720) increased by 110.5%and 131.2%,respectively.The high/medium calo⁃rific ratio decreased by 35.3%and 28.9%,respectively.The high/medium weight loss decreased by 14.1%and 12.0%,respectively.The combination of straw and fertilizer treatment reduces oxidation degree,condensation degree,and thermal stability of HA structure,enhances its lipophilicity,and simplifies the structure.