Shu Xin, Zou Yiran, Shaw Liz J, Todman Lindsay, Tibbett Mark, Sizmur Tom
Soil Research Centre, Department of Geography and Environmental Science University of Reading Reading UK.
Soil Research Centre, Department of Sustainable Land Management, School of Agriculture, Policy and Development University of Reading Reading UK.
Eur J Soil Sci. 2022 Mar-Apr;73(2):e13232. doi: 10.1111/ejss.13232. Epub 2022 Mar 25.
Increasing the diversity of crops grown in arable soils delivers multiple ecological functions. Whether mixtures of residues from different crops grown in polyculture contribute to microbial assimilation of carbon (C) to a greater extent than would be expected from applying individual residues is currently unknown. In this study, we used C isotope labelled cover crop residues (buckwheat, clover, radish, and sunflower) to track microbial assimilation of plant residue-derived C using phospholipid fatty acid (PLFA) analysis. We also quantified microbial assimilation of C derived from the soil organic matter (SOM) because fresh residue inputs also prime the decomposition of SOM. To consider the initial stages of residue decomposition, and preclude microbial turnover, we compared a quaternary mixture of residues with the average effect of their four components 1 day after incorporation. Our results show that the microbial biomass carbon (MBC) in the treatment receiving the mixed residue was significantly greater, by 132% (3.61 μg C g), than the mean plant residue-derived MBC in treatments receiving the four individual components of the mixture. However, there was no evidence that the mixture resulted in any additional assimilation of C derived from native SOM than the average observed in individual residue treatments. We surmise that, during the initial stages of crop residue decomposition, a greater biodiversity of residues increases microbial assimilation to a greater extent than would be expected from applying individual residues either due to faster decomposition or greater carbon use efficiency (CUE). This might be facilitated by functional complementarity in the soil microbiota, permitted by a greater diversity of substrates, reducing competition for any single substrate. Therefore, growing and incorporating crop polycultures (e.g., cover crop mixtures) could be an effective method to increase microbial C assimilation in the early stages of cover crop decomposition.
The effect of mixing crop residues on assimilation of C by soil microbial biomass was investigated.The study is important due to recent interest in diverse cover crop mixtures for arable systems.Mixing crop residues enhanced the assimilation of plant residue-derived C into microbial biomass.Growing and incorporating cover crop polycultures may enhance C storage in arable soils.
增加耕地土壤中种植作物的多样性可提供多种生态功能。目前尚不清楚，与单一种植作物残茬相比，混作条件下不同作物残茬混合物是否能在更大程度上促进微生物对碳（C）的同化作用。在本研究中，我们使用碳同位素标记的覆盖作物残茬（荞麦、三叶草、萝卜和向日葵），通过磷脂脂肪酸（PLFA）分析追踪植物残茬来源碳的微生物同化作用。我们还对土壤有机质（SOM）来源碳的微生物同化作用进行了量化，因为新鲜残茬输入也会促进土壤有机质的分解。为了研究残茬分解的初始阶段，并排除微生物周转的影响，我们在残茬掺入1天后，将残茬的四元混合物与其四个组分的平均效应进行了比较。我们的结果表明，接受混合残茬处理的微生物生物量碳（MBC）显著高于接受混合物四个单一组分处理的平均植物残茬来源的MBC，增幅为132%（3.61μg C/g）。然而，没有证据表明混合物比单个残茬处理中观察到的平均值导致更多来自天然土壤有机质的碳同化。我们推测，在作物残茬分解的初始阶段，残茬的更高生物多样性比单一种植作物残茬在更大程度上促进微生物同化，这可能是由于分解速度更快或碳利用效率（CUE）更高。土壤微生物群的功能互补可能有助于此，更多样化的底物允许这种互补，减少了对任何单一底物的竞争。因此，种植和掺入作物混作（如覆盖作物混合物）可能是在覆盖作物分解早期增加微生物碳同化的有效方法。
研究了混合作物残茬对土壤微生物生物量碳同化的影响。由于最近对适用于耕地系统的多样化覆盖作物混合物感兴趣，该研究具有重要意义。混合作物残茬增强了植物残茬来源碳向微生物生物量的同化。种植和掺入覆盖作物混作可能会增强耕地土壤中的碳储存。
