不同耕作措施对旱地土壤有机碳转化的影响

通过田间定位试验探讨了黄土高原旱地不同耕作措施下土壤有机碳的存在形式、转化过程以及有机碳各组分之间的关系。结果表明,免耕可以增加土壤有机碳含量,作物秸秆的保留与否主要影响土壤全碳（TOC）的变化。免耕秸秆覆盖（NTS）极显著提高了表层TOC含量,在干旱半干旱地区秸秆还田17个月就可使表层土壤TOC含量增加20．77％。传统耕作不覆盖（T）和传统耕作结合秸秆还田（TS）等耕作措施会破坏土壤结构,不利于土壤有机碳的积累。不同处理间的土壤焦磷酸钠提取态碳（SPPC）含量差异不显著,SPPC的含量占TOC的比例随耕作措施和土壤性质的不同变幅很大,从23．70％到50．60％不等。NTS处理的SPPC含量最高,NT处理的SPPC含量最低,说明免耕秸秆覆盖有利于改善土壤理化性质,而单纯免耕、不归还秸秆不利于土壤有机质的积累。土壤热水溶性碳水化合物（HWCC）的积累量是NTS〉NT〉TS〉T,说明免耕秸秆覆盖有利于土壤活性有机质的产生和积累,有利于土壤理化性质的改良,能够给土壤微生物提供大量能源物质,有利于土壤的健康发展。

Impact of Different Tillage Method on Changing of Soil Organic Carbon in Semi-arid Area

In order to discuss the existence forms and the conversion process of the soil organic carbon,and the relationship on different soil organic carbon components under the different tillage method in loess plateau semi-arid area,the soil in different tillage condition had be analyzed by chemical method.The results showed that no-till can increase the content of soil organic carbon.Leaving crops straw affects soil total organic carbon(TOC),no-till with straw cover(NTS)can significant improve the content of TOC on the surface of the soil,TOC content can be improve 20.77% in semi-arid area after return straw for 17 months.Conventional tillage with no straw(T)and conventional tillage with straw incorporated(TS)can destroy soil construction,go against accumulation of soil organic carbon.There is no significant discrepancy in soil sodium pyrophosphate-extractable carbon(SPPC)among different soil treatments.There is big range of variation on the rate of SPPC in TOC,from 23.70% to 50.60%.NTS has the highest SPPC content,NT has the lowest SPPC content,that is no-till with straw cover is benefit to improve the soil physical chemistry property,but only no-till,doesn't return straw go against the accumulation of the soil organic matter.The content of hot water-extractable carbohydrate(HWCC)accumulation is NTS>NT>TS>T,that is no-till with straw cover benefit to the active organic matter accumulation,to improve the soil physical chemistry property,to provide lots of energy resource to soil microorganism and to benefit soil development.