Abstract Soil organic matter dynamics in terrestrial ecosystems are controlled by complex interactions between various factors such as climate, soil, and agricultural management practices. We utilized a process-based crop model, APSIM, to simulate long-term soil organic carbon (SOC) dynamics for a soybean-wheat cropping system under nitrogen (N) and farmyard manure management (FYM) practices for a 43-year old experimental dataset in India. The APSIM was parameterized and validated to predict grain yield and SOC stock. The validated model was then used to evaluate the impacts of different management practices on SOC dynamics in the top 30 cm of soil through scenario modeling. The results of the APSIM simulations demonstrated that improved N and FYM management practices had great potential to increase SOC sequestration in these Vertisols. The equilibrium SOC concentration under different N management practices increased with a higher N application rate, with the integrated application of N with FYM showing the maximum rate. The optimum N (Nopt) rate for maximum SOC sequestration was estimated to be 155 kg ha−1 for wheat in the studied Vertisol and the time to reach steady-state of the site was 104 years. The Nopt increased SOC by about 28.6% over the initial concentration. We found that the APSIM was robust in predicting long-term changes in SOC stock (Index of agreement = 0.79 and root mean square error = 3.33 Mg ha−1, R2 = 0.92, mean bias error = −1.08) for a Vertisol soil of central India, in this case under a soybean-wheat cropping system. The study results highlighted that balanced fertilization is the key to sustaining SOC stock in the long-term for Vertisols.

中文翻译：

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印度中部 Vertisol 土壤碳封存潜力 - 来自 43 年长期实验和 APSIM 建模的结果

摘要 陆地生态系统中的土壤有机质动态受气候、土壤和农业管理实践等各种因素之间复杂的相互作用控制。我们利用基于过程的作物模型 APSIM 来模拟大豆 - 小麦种植系统在氮 (N) 和农家肥管理 (FYM) 实践下的长期土壤有机碳 (SOC) 动态，用于 43 年的实验印度的数据集。APSIM 被参数化和验证以预测谷物产量和 SOC 储量。然后使用经过验证的模型通过情景建模评估不同管理实践对土壤表层 30 cm 中 SOC 动态的影响。APSIM 模拟的结果表明，改进的 N 和 FYM 管理实践具有增加这些 Vertisol 中 SOC 封存的巨大潜力。不同氮肥管理措施下的平衡SOC浓度随着施氮量的增加而增加，其中氮肥与FYM的综合施用表现出最大比率。在所研究的 Vertisol 中，小麦的最大 SOC 封存的最佳 N (Nopt) 速率估计为 155 kg ha-1，达到该地点稳态的时间为 104 年。与初始浓度相比，Nopt 使 SOC 增加了约 28.6%。我们发现，对于 Vertisol 土壤，APSIM 在预测 SOC 储量的长期变化（一致性指数 = 0.79 和均方根误差 = 3.33 Mg ha−1，R2 = 0.92，平均偏差误差 = -1.08）方面是稳健的印度中部，在这种情况下是在大豆-小麦种植系统下。研究结果强调，平衡施肥是长期维持 Vertisols SOC 存量的关键。