Organic C has many benefits for soil, but it is depleted by tillage and crop harvest, and especially so for biofuel crops. Accordingly, strategies such as partially retaining stover or planting a cover crop can help ameliorate the negative effect of C removal. We used a long-term field experiment to study the impacts of stover retention and planting a cover crop on soil organic matter (SOM), its extractable components, and the soil microbial community. SOM chemical composition characterization was determined by electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in sequential water, methanol (MeOH), and chloroform (CHCl₃) extracts. The characteristics of the soil bacterial community were measured by phospholipid fatty acid (PLFA), real-time quantitative PCR, and 16S rRNA gene sequence. The variations in total SOM content, total microbial biomass, and bacterial population were slight among treatments, but SOM chemical compounds, arbuscular mycorrhizal fungi (AMF) biomass, and bacterial structure changed significantly, and especially so in the coupled application of stover retention and cover crop. Specifically, stover retention enriched more lignin-like compounds in soil, whereas cover crop enriched more condensed hydrocarbons, and had more compounds with an aromaticity index (AI) > 0.5. The bacterial community was not altered by the cover crop, but the corn stover retention increased the relative abundances of Myxococcales (Deltaproteobacteria) and decreased that of Actinobacteria. Redundancy analysis (RDA) further revealed that the bacterial community in the stover treatments had a significant positive association with CHCl₃-extracted chemical classes, i.e. unsaturated hydrocarbons and lipids, with the coupled application (stover and cover crop), and lignin and proteins with the corn stover only treatment. Taken together, our study shows how different C addition practices influence the molecular composition of SOM and the structure of soil microbial communities.

有机碳对土壤有很多好处，但耕作和农作物收成却特别是生物燃料作物，因此它被消耗了。因此，采取诸如部分保留秸秆或种植农作物的策略可以帮助减轻碳去除的负面影响。我们使用了长期的田间试验来研究秸秆还田和种植覆被作物对土壤有机质（SOM），其可提取成分和土壤微生物群落的影响。通过电喷雾电离（ESI）结合傅里叶变换离子回旋共振质谱（FT-ICR-MS）在顺序的水，甲醇（MeOH）和氯仿（CHCl ₃）中确定SOM的化学成分）提取物。通过磷脂脂肪酸（PLFA），实时定量PCR和16S rRNA基因序列测量了土壤细菌群落的特征。在处理中，总SOM含量，总微生物生物量和细菌种群的变化很小，但是SOM化学化合物，丛枝菌根真菌（AMF）生物量和细菌结构发生了显着变化，尤其是在秸秆保留和覆盖结合使用时作物。具体来说，秸秆保留能使土壤中更多的木质素样化合物富集，而表层作物则富集更多的冷凝碳氢化合物，并具有更多的芳香指数（AI）> 0.5的化合物。覆盖作物没有改变细菌群落，但是玉米秸秆的保留增加了粘球菌（Deltaproteobacteria）的相对丰度，而放线菌的相对丰度降低。冗余分析（RDA）进一步表明，秸秆处理中的细菌群落与CHCl呈显着正相关_3-提取的化学类别，即不饱和烃和脂质，结合应用（秸秆和覆盖作物），以及仅玉米秸秆处理的木质素和蛋白质。两者合计，我们的研究表明不同的碳添加方式如何影响SOM的分子组成和土壤微生物群落的结构。