To investigate the impact of integrating ley grassland in crop rotations on soil C changes at depths of 0–30 and 0–60 cm, field data regarding C input, soil C and crop production were collected during 2005–2016 from a long-term experimental site in Lusignan, southwestern France. Root biomass C was sampled annually, and the stable C isotope signature (δ¹³C) was determined to quantify the amount of C input from the root biomass. The results showed that integrating ley grassland in crop rotations increased the C input in the 0–30 and 0–60 cm soil layers. Carbon stocks also increased in the 0–30 cm soil layer but not always in the 0–60 cm layer. However, during the first full rotation (2005–2013), treatments involving 3-year and 6-year grasslands showed 37.5% and 62.5% losses of their crop production, respectively. In crop rotations, integrating ley grassland together with high-nitrogen (N) or low-N fertilisation did not impact the C input, changes in soil C in either the 0–30 or 0–60 cm soil layer, or even crop production, while grass production decreased by 22.2–66.6% under low-N fertilisation. Compared with cropland, permanent grassland did not show a greater C input, whereas the latter showed a C stock increase of 0.6–1.4 Mg C ha⁻¹ yr⁻¹. The analysis of 2005–2013 crop rotation data suggested that both above- and belowground C inputs should be considered as a single total C input. An estimated baseline C input rate of 1.9 Mg C ha⁻¹ yr⁻¹ was suggested to maintain soil C stocks for some of the crop rotations at the site. Considering the balance of food production and soil C stocks, crop rotation in conjunction with 3 years of high-N-fertilised grassland is recommended.

为了研究将麦草纳入轮作对 0-30 厘米和 0-60 厘米深度土壤碳变化的影响，从长期试验中收集了 2005-2016 年有关碳输入、土壤碳和作物产量的田间数据。位于法国西南部的吕西尼昂。每年对根生物量 C 进行采样，稳定 C 同位素特征 (δ ¹³C) 被确定为量化来自根生物量的 C 输入量。结果表明，在作物轮作中整合麦草增加了 0-30 和 0-60 厘米土层的碳输入。0-30 厘米土壤层的碳储量也增加，但在 0-60 厘米土壤层中并非总是如此。然而，在第一个完整轮作期间（2005-2013），涉及 3 年和 6 年草地的处理分别显示其作物产量损失 37.5% 和 62.5%。在轮作中，将麦草与高氮 (N) 或低氮施肥结合起来，不会影响碳输入、0-30 或 0-60 厘米土层中土壤碳的变化，甚至作物产量，而在低氮施肥下，草产量下降了 22.2-66.6%。与耕地相比，永久草地并没有表现出更大的碳输入，^-1年^-1 . 对 2005-2013 年作物轮作数据的分析表明，地上和地下碳输入均应视为单一的总碳输入。建议估计基准碳输入率为 1.9 Mg C ha ^-1 yr ^-1以维持该地点某些作物轮作的土壤碳库。考虑到粮食产量和土壤碳储量的平衡，建议轮作结合 3 年高氮肥草地。