玉米秸秆在土壤中的分解速率及其对腐殖质组成的影响

Decomposition Rate of Corn Straw in Soil and Its Effects on Soil Humus Composition

为研究秸秆还田后玉米秸秆在土壤中的分解速率及其对土壤腐殖质组成的影响，采用室内培养试验，以黑土和暗棕壤为研究对象，每种类型土壤分别模拟设置：ck（未施用秸秆）、12（2倍量秸秆与土混合）、I（全量秸秆与土混合）、II／2（1／2量秸秆与土混合）、C（全量秸秆覆盖）和D（全量秸秆埋置）共6种处理。利用碱液吸收法测定秸秆分解过程中CO：一C释放量，腐殖质组成修改法提取土壤腐殖质，富里酸（Fulvic acid，FA）、胡敏酸（Humic acid，HA）和胡敏素（Humin，HM）。研究结果表明：玉米秸秆分解过程中其分解速率迅速增加，在第4天各处理秸秆分解速率达到顶峰为194—1103mg／（kg·d），随后迅速下降；在第24天到第260天各处理秸秆分解速率缓慢下降趋于稳定，平均在40—160mg／（kg·d）。不同秸秆用量下，秸秆分解速率表现为12〉I〉Ⅱ／2；等量秸秆不同处理方式下，秸秆分解速率表现为I〉D〉C；黑土中秸秆分解速率高于暗棕壤中相对应处理。培养260d后，各处理秸秆分解率为43％-78％；黑土中全量秸秆-9混合处理的秸秆分解率最高（78％）；不同土壤类型下，黑土各处理的秸秆分解率高于暗棕壤相对应处理4％～13％。相对于ck，各处理下土壤有机碳及腐殖质含量显著增加，2倍量秸秆与土壤混合后累积效果更显著，黑土中秸秆还田的培肥效果优干暗棕壤。各处理下土壤PQ值略有增加，无显著差异。

To study decomposition rate of corn straw in soil and its effects on soil humus composition after straw returning to field, by indoor cultivation experiments, with black and dark brown soil as research object, six treatments were designed for different types of soil： ck （no corn straw applica- tion）, 12 （mixture of doubled corn straw with soil）, I （mixture of corn straw with soil） ,I1/2 （mix- ture of one-half corn straw with soil）, C （ covering of soil with corn straw） and D （ burying of corn straw）. Alkali absorption method was applied to determine soil CO2- C, and humus composition modification method was used to extract soil humus, fulvic acid （FA） , humic acid （HA） and hu-min （ HM）. The results show that the decomposition rate of corn straw with different treatments in- creased rapidly and all reached their peak at 194-1 103 mg/（kg · d） on the fourth day, then pres- ented a sharp deerease, in 24-260 days＇ incubation, and the deerease tended to be slow and steady at average 40-160 mg/（kg ·d）; with different amounts of corn straw, corn straw decomposition rate of different treatments showed an order of Ⅰ2 〉Ⅰ〉 Ⅱ/2; with the same amount of corn straw, eorn straw deeomposition rate of different treatments showed an order of I〉D〉C ; with different soil types, corn straw deeomposition rate of blaek soil was higher than dark brown soil. After 224 days＇ incubation, eorn straw decomposition rate was about 43%-78% for different treatments; when full- amount corn straw was mixed with black soil, eorn straw deeomposition rate was the highest （78%） ; with different soil types, corn straw decomposition rate in black soil was 4%-13% higher than in dark brown soil. Compared with ck, soil organic carbon and humus content of each treatment increased significantly, and when doubled eorn straw was mixed with soil, cumulative effeet was more obvious, and fertilizing effect of corn straw returning into the blaek soil was better than the dark brown soil. PQ value with the different treatments increased slightly, and no significant differ- enee was found.