10a保护性耕作下轮作系统土壤碳氮磷生态化学计量特征

Ecological Stoichiometric Characteristics of Soil Carbon,Nitrogen and Phosphorus After 10 Years Conservation Tillage in a Rotation System

[目的]研究长期免耕和秸秆覆盖对轮作系统土壤质量的影响规律和机制。[方法]比较分析了10a传统耕作、免耕、传统耕作+秸秆覆盖和免耕+秸秆覆盖的玉米—冬小麦—大豆轮作系统0—200cm内土壤有机碳、全氮、全磷含量及其生态化学计量比变化。[结果]长期免耕提高土壤表层C和N的含量,仅秸秆覆盖对C和N含量的影响不大;长期保护性耕作对土壤P含量没有显著影响;保护性耕作使N和P最低含量均出现在20—30cm,而传统耕作则在30—60cm土层最低;土壤C/N,C/P和N/P均普遍低于10a前,C/P和N/P的变化量随土层深度增加均呈现出先降低后增高的趋势。[结论]10a保护性耕作对C,N,P的影响均不明显,但4种耕作模式下,土壤C/N,C/P和N/P均普遍低于10a前。

[Objective] To study the effects and mechanisms of long-term no-tillage and straw mulch on soil quality. EMethods] With comparing the soil characteristics from 2001 to 2011, the conventional tillage, no-tillage, conventional tillage ＋ straw mulch and no-tillage ＋ straw mulch were set for 10 years in a corn-wheat-soybean rotation system. Soils of 0--200 cm layers were taken for analyzing organic carbon（C）, total nitrogen（N） and total phosphorus（P）. [Results] Long-term no-tillage improved C and N contents of surface soils, and straw mulch only had little effect on them. Long-term conservation tillage had no signifi- cant effect on soil P level. Conservation tillage resulted in the lowest N and P contents at 20--30 cm soil layer, while under conventional tillage, it was at 30--60 cm layer. Soil C/N, C/P and N/P were generally lower than that of a decade ago and with soil depth increased, the variation of C/N, C/P and N/P showed a drop--rise trend. [Conclusion] Long-term conservation tillage had no significant effect on soil C, N and P. In the four tillage patterns, soil C/N, C/P and N/P were generally lower than a decade ago.