Subsoil carbon (C) stocks are a prime target for efforts to increase soil C storage for climate change mitigation. However, subsoil C dynamics are not well understood, especially in soils under long-term intensive agricultural management. We compared subsoil C storage and soil organic matter (SOM) composition in tomato–corn rotations after 25 years of differing C and nutrient management in the California Central Valley: CONV (mineral fertilizer), CONV+WCC (mineral fertilizer and cover crops), and ORG (composted poultry manure and cover crops). The cover crop mix used in these systems is a mix of oat (Avena sativa L.), faba bean (Vicia faba L.), and hairy vetch (Vicia villosa Roth). Our results showed a ∼19 Mg ha⁻¹ increase in soil organic C (SOC) stocks down to 1 m under ORG systems, no significant SOC increases under CONV+WCC or CONV systems, and an increased abundance of carboxyl-rich C in the subsoil (60–100 cm) horizons of ORG and CONV+WCC systems. Our results show the potential for increased subsoil C storage with compost and cover crop amendments in tilled agricultural systems and identify potential pathways for increasing C transport and storage in subsoil layers.

中文翻译：

---

地中海行作物系统中堆肥和覆盖作物之间的协同作用导致地下土壤碳储存增加

底土碳 (C) 储量是努力增加土壤碳储存以缓解气候变化的主要目标。然而，地下土壤 C 的动态尚不清楚，特别是在长期集约化农业管理下的土壤中。我们比较了加利福尼亚中央山谷 25 年不同碳和养分管理后番茄-玉米轮作中的底土碳储存和土壤有机质 (SOM) 组成：CONV（矿物肥料）、CONV+WCC（矿物肥料和覆盖作物）、和 ORG（堆肥的家禽粪便和覆盖作物）。这些系统中使用的覆盖作物混合物是燕麦 ( Avena sativa L.)、蚕豆 ( Vicia faba L.) 和毛紫云英 ( Vicia villosa Roth) 的混合物。我们的结果显示~19 Mg ha ^-1在 ORG 系统下土壤有机碳 (SOC) 储量增加至 1 m，在CONV+WCC或 CONV 系统下 SOC 没有显着增加，并且底土中富含羧基的 C 丰度增加（60-100 cm ) ORG 和CONV+WCC系统的视野。我们的研究结果表明，在耕作的农业系统中通过堆肥和覆盖作物改良剂增加地下土壤碳储存的潜力，并确定了增加地下土壤层中碳运输和储存的潜在途径。