Abstract:

Straw return can change the content of soil microbial biomass carbon (SMBC) in farmland, and analyzing changes in SMBC content and its related influencing factors under the conditions of straw returning is pivotal for understanding the mechanism of soil nutrient turnover and carbon cycling driven by straw returning. In this study, a database of 839 groups containing SMBC contents under straw-returned and straw-not-returned conditions was established based on 68 publicly available papers published in China Knowledge and Web of Science databases from 2001 to 2022. The data was grouped by climate type, cultivation method, tillage method, type of straw, amount of nitrogen applied, and amount of returned straw. A meta-analysis was then conducted to comprehensively analyze the variation characteristics of SMBC content under the conditions of straw returning with experimental results under the conditions of no straw returning set as controls. Results showed that 1) straw return significantly increased SMBC content by 51.4% with a confidence interval from 0.373−0.654. The improvement effect on the SMBC content in different soil layers was different, and the SMBC content in shallow and deep layers increased by 47.9% and 42.7%, respectively. 2) The content of SMBC in the temperate monsoon climate zone and subtropical monsoon climate zone increased by 71.0% and 35.8%, respectively, under straw returning, but it showed a significant negative effect on SMBC content in the temperate continental climate zone, with a decrease of 35.6%. 3) The effect of rotary tillage (99.2%) on the increase of SMBC content under different tillage methods was the most obvious, which was about 2.4 times and 4 times that of conventional tillage and no-tillage. 4) The increase of SMBC content in upland was significantly higher than that in paddy field. The response of maize straw to SMBC content was the highest, with an increase of 99.5%, followed by rice straw, with an increase of 30.8%. Wheat straw was the lowest, with a decrease of 5.8%. 5) The effect of nitrogen application rate on SMBC content increased by −34.5% to 183.9%. Under nitrogen application rates of 0−100 kg•hm⁻² and 101−225 kg•hm⁻², straw returning could significantly increase SMBC content, while under the nitrogen application rate of 226−325 kg•hm⁻² and 326−425 kg•hm⁻², straw returning showed a significant negative effect on SMBC content. 6) For the amount of straw returning, when the amount of straw returning was 9000 kg•hm⁻², the increase was 44.2%, but the increase of SMBC content showed a decreasing trend with the increase of straw returning. In conclusion, straw return has a significant influence on SMBC content in Chinese farmland, and the impact extent varies under different climatic types, planting methods, tillage methods, straw types, nitrogen application rates, and straw returning amounts.

Key words: straw returning, climate type, tillage method, amount of nitrogen applied, soil microbial biomass carbon, Meta-analysis

摘要：

秸秆还田能改变农田土壤微生物生物量碳（Soil Microbial Biomass Carbon，SMBC）含量，分析秸秆还田条件下SMBC含量变化及其相关影响因素，对理解秸秆还田下土壤养分周转与碳循环机制具有重要意义。基于中国知网和Web of Science数据库2001－2022年公开发表的68篇文献，建立了839组包含秸秆还田和秸秆不还田下SMBC含量的数据库，按照气候类型、种植方式、耕作方式、秸秆种类、施氮量、秸秆还田量进行分组，采用Meta分析对秸秆还田条件下SMBC含量变化的特征进行综合分析。结果表明，与秸秆不还田相比，1）秸秆还田显著提升SMBC含量（51.4%，置信区间为0.373－0.654），且对不同土层SMBC含量的提升效果不同，浅层和深层SMBC含量分别提升47.9%和42.7%。2）秸秆还田下温带季风气候区和亚热带季风气候区SMBC含量分别增加71.0%和35.8%，但在温带大陆气候区对SMBC含量影响表现出显著负效应，降低幅度为35.6%。3）不同耕作方式下旋耕（99.2%）对SMBC含量的增幅影响最为明显，约为常规耕作和免耕下的2.4倍和4倍。4）旱地秸秆还田SMBC含量的增幅明显高于稻田。玉米秸秆对SMBC含量的响应度最高，增幅达到99.5%，水稻秸秆次之，增幅为30.8%；小麦秸秆最低，降低幅度为5.8%。5）施氮量对SMBC含量增幅在−34.5%－183.9%之间，0－100 kg•hm⁻²和101－225 kg•hm⁻²施氮量下秸秆还田可显著提升SMBC含量，而在226－325 kg•hm⁻²和326－425 kg•hm⁻²施氮量下秸秆还田对SMBC含量的影响表现出显著的负效应；6）对于秸秆还田量而言，当秸秆还田量 <4500 kg•hm⁻²时增幅52.60%，4500－9000 kg•hm⁻²时增幅47.7%，>9000 kg•hm⁻²时增幅44.2%，但SMBC含量的增幅表现出随着秸秆还田量的增加呈递减趋势。由此可见，不同的气候类型、种植方式、耕作方式、秸秆种类、施氮量、秸秆还田量等条件下，秸秆还田对中国农田SMBC含量的影响存在显著差异。

关键词: 秸秆还田, 气候类型, 耕作方式, 施氮量, 土壤微生物生物量碳, Meta分析