Atmospheric C sequestration in agricultural soils is viewed as one of the most promising negative emission technologies currently available. Nonetheless, it remains unclear how strongly soil organic carbon (SOC) stocks respond to agricultural practices, especially for subsoil. Here, we assess the SOC storage potential in croplands and how the presence of temporary grasslands (TG) in the crop rotation affects SOC stocks. We developed a new approach to correct for bias in bulk density (BD) induced by sampling conditions and land-use effects with a data-driven model to predict the BD of fine soil (<2 mm) for reference condition. Using 54 permanent grassland and cropland sites with various proportions of TG from a monitoring network in Switzerland, we showed that SOC stock differences down to 50-cm depth between cropland and permanent grasslands (maximum: 3.0 ± 0.8 kg C m⁻²) depend on the TG proportion in the crop rotation, regardless of clay content and pH. An increase of the TG proportion by 10% would induce a SOC gain of 0.40 ± 0.13 kg C m⁻². The responses of topsoil (0–20 cm) and subsoil (20–50 cm) SOC stocks to TG proportion were linear and equivalent. The effect of TG on SOC storage would have been underestimated by 58% without accounting for subsoil stocks response and by 16% without BD corrections. The conversion of all croplands to permanent grasslands in the study region would potentially store a quantity of SOC equivalent to the anthropogenic greenhouse gas emissions generated by the same region during one year. Although the potential of agricultural soils as negative emission technology is relatively modest compared to former expectations, the findings demonstrate the potential to manage SOC and its associated ecosystem services at large scales and down to deep soil layers.

农业土壤中的大气碳封存被认为是目前可用的最有前途的负排放技术之一。尽管如此，仍不清楚土壤有机碳 (SOC) 储量对农业实践的反应有多强烈，尤其是对底土。在这里，我们评估了农田中 SOC 的储存潜力，以及轮作中临时草地 (TG) 的存在如何影响 SOC 库存。我们开发了一种新方法来校正采样条件和土地利用效应引起的容重 (BD) 偏差，使用数据驱动模型来预测参考条件下细土 (<2 mm) 的 BD。使用来自瑞士监测网络的 54 个具有不同 TG 比例的永久性草地和农田站点，^-2 ) 取决于轮作中的 TG 比例，与粘土含量和 pH 值无关。TG 比例增加 10% 将导致 0.40 ± 0.13 kg C m ^{-2的 SOC 增益}. 表土（0-20 厘米）和底土（20-50 厘米）SOC 储量对 TG 比例的响应是线性且等效的。如果不考虑底土储量响应，TG 对 SOC 储存的影响会被低估 58%，如果不考虑 BD 修正，则会被低估 16%。将研究区域内的所有农田转变为永久性草地可能会储存相当于同一区域一年内产生的人为温室气体排放量的 SOC。尽管与以前的预期相比，农业土壤作为负排放技术的潜力相对较小，但研究结果证明了在大范围和深层土壤层管理 SOC 及其相关生态系统服务的潜力。