保护性耕作对土壤结构体有机碳氧化稳定性的影响

以7年不同耕作的定位试验为研究对象，研究了深松、旋耕、免耕等保护性耕作措施对关中塿土小麦-玉米轮作条件下结构体有机碳氧化稳定性的影响。结果表明，与传统耕作相比，深松、旋耕、免耕及秸秆还田+传统耕作均提高了各粒级结构体的有机碳和易氧化有机碳含量，且深松和旋耕效果达到显著水平，免耕作用不显著；深松、旋耕、免耕对难氧化有机碳含量的影响均不明显。由此可见，各保护性耕作对土壤结构体总有机碳含量的提高主要是通过结构体中易氧化有机碳含量的提高来实现。各保护性耕作降低了结构体有机碳的氧化稳定系数（Kos），但未达到显著水平。土壤较小粒级（0.5～0.25mm和<0.25mm）结构体中的总有机碳，易氧化、难氧化有机碳含量均比大粒级结构体中（>0.5mm）的高，且其氧化稳定系数（Kos）较低。相关分析表明，除5～2 mm粒级结构体外，各粒级结构体的总有机碳之间、易氧化有机碳之间、总有机碳和易氧化有机碳之间均相关极显著，且以<0.25mm结构体的总有机碳、易氧化有机碳和各粒级结构体的总有机碳、易氧化有机碳之间的相关系数较大。关键词：保护性耕作，结构体，有机碳，氧化稳定性

Effect of Conservational Tillage Measures on the oxidation stability of soil Organic Carbon in Soil Aggregates

A sven years＇ location experiment of wheat-corn rotation in Guanzhong plain was conducted for of sub-soiling, rotary tillage and no-tillage on the oxidation stability of soil organic carbon The results showed that compared with conventional tillage, sub-soiling, rotary tillage, entional tillage with straw incorporated all increased the content of total organic carbon and readily oxidizable organic carbon in soil aggregates. The effects of sub-soiling and rotary significant, but no-tillage have a little effect, Effects o of difficultly oxidizable organic in soil aggregates were carbon in soil aggregates by conservational were f sub-soiling, rotary tillage and no-tillage on the content insignificant. It implied that the increase of total organic measures was mainly by enhancing the content of readily oxidizable organic carbon. The oxidation stablility coefficient （Kos） of organic carbon in soil aggregates was decreased by conservational tillage measures, but the effect was insignificant. The content of total organic carbon, readily oxidizable organic carbon and difficultly oxidizable organic carbon in smaller sizes （0.5- 0.25mm and〈0.25mm） of soil aggregates were higer than that in lager sizes （〉0.5mm） of soil aggregates. But the oxidation stablility coefficients （Kos） of organic carbon in smaller sizes of soil aggregates were lower than that in lager sizes of soil aggregates. The correlation analysis demonstrated that except for 5-2mm soil aggregates,correlation between soil organic carbon in different size of soil aggregates all were very significant, as well as the readily oxidizable organic carbon between different sizes of soil aggregates. The correlations between readily oxidizable organic carbon and total organic carbon in different sizes aggregates were very significant. The correlations coefficients of total organic carbon, readily oxidizable organic carbon between 〈0.25ram aggregates and the other sizes of soil aggregates were higher .