Zhang Zihan, Dong Yubing, Yang Dongqiao, Lu Mengya, Zhang Wei, Ding Xueli, He Hongbo
Key Laboratory of Ecosystem Carbon Source and Sink-China Meteorological Administration (ECSS-CMA), School of Ecology and Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Huaiyin Institute of Agricultural Sciences of Xuhuai Region, Jiangsu Academy of Agricultural Sciences, Huaian, 223001, China.
J Environ Manage. 2025 Aug;389:126181. doi: 10.1016/j.jenvman.2025.126181. Epub 2025 Jun 13.
Legume cover crops are widely used to increase soil organic carbon (SOC) sequestration in agricultural ecosystems. Microbial necromass play important roles in SOC buildup and sequestration. However, how legume cover crops impact microbial necromass accumulation and its contribution to SOC remain poorly understood in paddy soils, particularly in deeper subsurface soils. Here, we conducted a three-year field experiment to evaluate the effect of different legume cover crops (milk vetch (RM) and hairy vetch (RH)) on microbial necromass accumulation at three depth increments down to 60 cm. We used amino sugar as microbial necromass biomarker. Our results showed that legume cover crops increased microbial necromass accumulation in surface layer (0-20 cm) by 1.4 % and 20.8 % in RH and RM treatments, respectively. However, this positive effect diminished with soil depth and became negative in the 40-60 cm layer, with 22.8 % and 48.0 % lower in RH and RM treatments than fallow control, respectively, possibly due to intensified N limitation in subsurface soils. This was supported by the observation that cover crops combined with N fertilizer promoted greater necromass accumulation at both 20-40 cm and 40-60 cm layers as compared with no-fertilizer cover crop treatment. Our findings demonstrate that cover crops exerted contrasting effect on microbial necromass accumulation along soil depth with stronger depletion in deeper subsurface soils. Our work underscores the need for full considering microbial necromass and SOC changes throughout a certain soil depth when evaluating the potential of crop management practices to optimize soil C sequestration.
豆科覆盖作物被广泛用于增加农业生态系统中的土壤有机碳（SOC）固存。微生物残体在SOC的积累和固存中发挥着重要作用。然而，在稻田土壤中，特别是在较深的表层土壤中，豆科覆盖作物如何影响微生物残体的积累及其对SOC的贡献仍知之甚少。在此，我们进行了一项为期三年的田间试验，以评估不同豆科覆盖作物（紫云英（RM）和毛苕子（RH））对深度达60厘米的三个深度增量处微生物残体积累的影响。我们使用氨基糖作为微生物残体生物标志物。我们的结果表明，豆科覆盖作物使表层（0-20厘米）的微生物残体积累分别在RH和RM处理中增加了1.4%和20.8%。然而，这种积极影响随着土壤深度的增加而减弱，并在40-60厘米层变为负面影响，RH和RM处理分别比休闲对照低22.8%和48.0%，这可能是由于表层土壤中氮限制加剧所致。与不施肥的覆盖作物处理相比，覆盖作物与氮肥结合促进了20-40厘米和40-60厘米层更大的残体积累，这一观察结果支持了上述观点。我们的研究结果表明，覆盖作物对微生物残体积累沿土壤深度产生了不同的影响，在较深的表层土壤中消耗更强。我们的工作强调，在评估作物管理措施优化土壤碳固存潜力时，需要充分考虑整个特定土壤深度内微生物残体和SOC的变化。
