We conducted field experiments in nine managed grassland sites spanning annual temperatures of 5.8–16.3 °C for 5 years to investigate the effects of farmyard manure (FYM) application and environmental conditions on soil organic carbon (SOC) stock changes. Experimental plots were established with three (zero, low, and high) levels of continuous FYM application at each site, and soil samples down to 30 cm depths were annually collected to determine SOC stocks. Annual changes in SOC stocks were analyzed by fitting a linear mixed-effect model, including the sites as random-effects. Based on the model, low and high level FYM application lead to 1.9–10.4 (4.8 on average) and 3.4–15.1 (8.4 on average) Mg C ha⁻¹ year⁻¹ of SOC increase across the sites, respectively. The random-effects for annual changes in SOC stocks were not correlated with soil type (andic vs. non-andic) but positively correlated with the duration, implying that the grassland maintenance without renovation contributed more to SOC sequestration than soil type. Simple simulations using the model showed that SOC stocks increased at all nine sites with recommended (low) level of FYM application. The simulation also revealed that SOC sequestration with the recommended level FYM application can be maintained even under a global change scenario with temperature rise of up to 2.8 °C above the current level. These results indicated that managed grasslands in Japan with the recommended level FYM application can contribute to climate change mitigation via SOC sequestration even under future climate change.

我们在 9 个受管理的草地场地进行了为期 5 年的田间试验，这些场地的年温度为 5.8-16.3 °C，以研究农家肥 (FYM) 施用和环境条件对土壤有机碳 (SOC) 储量变化的影响。在每个地点建立了三个（零、低和高）连续 FYM 应用水平的试验小区，每年收集深度达 30 厘米的土壤样品以确定 SOC 储量。通过拟合线性混合效应模型来分析 SOC 储量的年度变化，包括作为随机效应的站点。基于该模型，低水平和高水平的 FYM 应用导致 1.9-10.4（平均 4.8）和 3.4-15.1（平均 8.4）Mg C ha ^-1年^-1的 SOC 分别在不同地点增加。SOC 储量年度变化的随机效应与土壤类型（andic vs. non-andic）无关，但与持续时间正相关，这意味着未经整修的草地维护对 SOC 封存的贡献大于土壤类型。使用该模型的简单模拟表明，所有九个地点的 SOC 储量均增加，推荐（低）水平的 FYM 应用。模拟还表明，即使在温度比当前水平高出 2.8°C 的全球变化情况下，也可以维持采用推荐水平 FYM 应用的 SOC 封存。