玉米秸秆覆盖冬小麦免耕播种对土壤微生物量碳的影响

Effects of sowing winter wheat under no-till with maize straw mulching on soil microbial biomass carbona

土壤微生物量碳（SMBC）是土壤有机碳的一部分，在养分循环中起着重要作用。本研究目的在于揭示我国华北平原玉米秸秆覆盖冬小麦免耕对土壤微生物量碳的影响。4-5年的试验结果表明，不同耕作方式对农田SMBC含量的时空变异具有显著的影响。玉米秸秆覆盖免耕播种处理上层（0-10cm）的含量比下层（10-20cm）增加47．4％，而清茬翻耕和还田翻耕处理的含量在土壤中的分层不显著。不同的耕作方式的SMBC含量均随气温降低而减少。全年平均来看，在0-10cm土层，不同耕作方式的SMBC含量大小表现为覆免〉还翻〉清翻，在10-20cm土层则表现为还翻〉覆免=清翻。整个耕层（0-20cm）表现为还翻〉覆免〉清翻。在气温较低时，覆盖免耕的SMBC含量比清茬翻耕和还田翻耕低。在土壤表层，不同耕作方式SMBC含量的稳定性大小表现为还翻〉覆免〉清翻；在下层，不同耕作方式之间差异不显著。

Soil microbial biomass carbon （SMBC）, as a part of soil organic C, places an important role in global carbon cycling. The purpose of the study was to reveal the effects of the practice of winter wheat seeding under the condition of no - tillage with maize straw mulching （NTS）, on SMBC in North China Plain. The results of 4 - 5 years field experiment showed that tillage management significantly influenced the spatio - temporal changes of SMBC. The content of SMBC in upper layer of soil （0 -10 cm） increased by 47.4% compared with that in lower layer of soil （10- 20 cm） in treatment of NTS, and no significant stratification was found in treatments of tillage with maize straw return （TS） and tillage with no maize straw return （TNS）. The content of SMBC decreased while air temperature decreased in all of treatments. Monthly average content of SMBC of different tillage measures significantly showed different changing sequences as follows： NTS〉 TS〉 TNS in upper soil （0- 10 cm）, TS〉 NTS= TNS in subsoil （ 10 - 20 cm） and TS 〉 NTS 〉 TNS in arable soil layer. The content of SMBC in NTS significantly decreased compared with other two treatments in low temperature seasons. The effect of different treatments on stabihty of SMBC in topsoil showed as follows： TS 〉 NTS 〉 TNS, and there was no significantly difference between different treatments in subsoil layer.