保护性耕作对麦-豆轮作土壤有机碳全氮及微生物量碳氮的影响

通过设置在甘肃省定西市李家堡镇的保护性耕作措施长期定位试验，共设4个处理（T：传统耕作；NT：免耕无覆盖；TS：传统耕作＋秸秆还田；NTS：免耕＋秸秆覆盖），采用春小麦豌豆双序列轮作（即小麦→豌豆→小麦和豌豆→小麦→豌豆，本文中所指春小麦地、豌豆地分别指2008年种植春小麦、豌豆的轮作次序），于2008年3月中旬对春小麦、豌豆双序列轮作下的土壤有机碳、全氮、土壤微生物量碳及土壤微生物量氮含量进行了采样测定。结果表明，经过7a的轮作后，两种轮作次序下，0-30cm土层中土壤有机碳、全氮、土壤微生物量碳、土壤微生物量氮含量均有在免耕＋秸秆覆盖、传统耕作＋秸秆还田处理较免耕不覆盖、传统耕作处理高的趋势，且其含量均随着土壤深度的增加而降低。其中，土壤微生物量碳含量在两种轮作次序下的排序均为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）；而土壤微生物量氮含量在春小麦地和豌豆地的排序则分别表现为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉传统耕作（T）〉免耕不覆盖（NT）和免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）。同时，微生物量碳、微生物量氮与有机碳和全氮均呈显著正相关，说明提高土壤有机质、全氮含量的保护性耕作模式有利于土壤微生物量碳与氮的积累。

Effects of Conservation Tillage on the SOC,TN,SMBC and SMBN in Two Sequence Rotation Systems with Spring Wheat and Pea

Soil microbial biomass has been identified as an appropriate index to denote the soil quality by many researchers because of its good indicative function. The effects of conservation tillage on soil organic carbon （SOC）, total nitrogen （TN）, soil microbial biomass carbon （SMBC） and microbial biomass nitrogen（SMBN ） were investigated in a field experiment ,which consisted of four treatments（T：conventional tillage; NT： no-tillage with no straw cover; TS： conventional tillage with straw; NTS： no-tillage with stubble retention ） and two sequence rotation systems with spring wheat and pea at the Gansu Agricultural University＇s farm in Dingxi. ＂The spring field＂ and ＂the pea field＂ represented the order of rotation spring wheat and pea had been planted in 2008. The results showed that after 7 years, SOC, TN, SMBC and SMBN of 0-30 cm soil layer which under no-tillage with stubble retention（ NTS ） and conventional tillage with straw（TS ） treats all had been higher than the ones under no-tillage with no straw cover（NT） and conventional tillage（T） treats. Moreover, the contents of SOC, TN, SMBC and SMBN were decreasing with soil layer being deepened. In the 0-30 cm soil layer of the spring wheat field the contents of SMBC and SMBN followed the order in the treatments ： NTS〉TS〉NT〉T while NTS〉TS〉NT〉T, NTS〉TS〉NT〉T in the pea field. Moreover, there were significant positive correlations among SMBC, SMBN, SOC and TN. It proved that conservation tillage which could improve the contents of SOC and TN were also beneficial to SMBC and SMBN＇s accumulations.