There is insufficient evidence for how cover crop-driven changes to the soil microbial community affect soil organic carbon (SOC) accumulation. One mechanism by which enhanced microbial activity can contribute to SOC accrual is through the conversion of plant inputs to microbial biomass and ultimately necromass that may form organo–mineral associations with soil particles. Here we investigated the effects of winter rye as a cover crop and winter rye harvested as a forage double crop on SOC, chemically labile and complex C fractions, microbial necromass biomarkers (amino sugars), and potential extracellular enzyme activities following a seven–year continuous corn silage trial in southern Wisconsin, North Central US. Whereas SOC increased when winter rye was used as a cover crop compared to no cover, there were no changes to SOC when winter rye was harvested as a forage crop. A positive relationship between chemically labile aliphatic soil–C and total SOC indicates that higher SOC stocks may result from persistence of simple compounds rather than chemically complex, aromatic materials. However, the accumulation of microbial necromass, as inferred from amino sugar biomarker concentrations, was largely unaffected by winter rye use, despite a positive relationship between SOC and amino sugar residue concentrations. Greater potential extracellular enzyme activities indicate increased microbial activity with winter rye. Together, these results suggest that despite some microbial stimulation and potential soil health benefits, winter rye did not increase the contribution of microbial necromass to SOC accrual in this seven–year continuous corn silage field trial.

没有足够的证据表明农作物驱动的土壤微生物群落的变化如何影响土壤有机碳（SOC）的积累。增强微生物活性可以促进SOC累积的一种机制是通过将植物投入转化为微生物生物量，最终转化为可能与土壤颗粒形成有机矿物联系的坏死生物。在这里，我们调查了连续七年连续生长的冬季黑麦（作为覆盖作物）和冬季黑麦（作为饲草双季作物）对SOC，化学不稳定和复杂的C组分，微生物坏死生物标志物（氨基糖）以及潜在的细胞外酶活性的影响。美国中北部威斯康星州南部的玉米青贮饲料试验。冬季黑麦用作遮盖作物的SOC比无遮盖的有所增加，冬季黑麦作为饲料作物收获时，SOC没有变化。化学不稳定的脂族土壤C与总SOC之间呈正相关关系，这表明较高的SOC储量可能是由于简单化合物的持久性而非化学复杂的芳族材料的持久性所致。然而，尽管SOC和氨基糖残留浓度之间存在正相关关系，但从氨基糖生物标记物浓度推断出的微生物坏死积累在很大程度上不受冬季黑麦使用的影响。潜在的细胞外酶活性越高，表明冬季黑麦的微生物活性越高。总之，这些结果表明，尽管有一些微生物刺激作用和潜在的土壤健康益处，