Astudy was conducted in three agroecosystems in California (Sacramento, Solano, and Merced counties) that received biosolids applications for 20 yr. Management varied in application rates and frequencies, resulting in average cumulative amount of biosolids applied of 74 (Solano), 105 (Merced), and 359 (Sacramento) Mg biosolids_dry ha^–1, resulting in the addition of 26 (Solano), 36 (Merced), and 125 (Sacramento) Mg biosolids-C ha^–1. Measurements included soil organic carbon (SOC) and total nitrogen (N) concentrations from 0 to 100 cm and microbial biomass C (MBC) and microbial biomass N (MBN) from 0 to 30 cm in biosolids-amended and control sites. Biosolids treatments had greater amounts of SOC and total N at all sites, and MBC and MBN were greatest at Sacramento and Solano. The largest increases in SOC were at the site that received the lowest cumulative loading rate of biosolids (Solano), where SOC content to 100 cm was 50% greater in amended soils (p < .001). Net changes in soil C stocks to 30 cm were 0.4 ± 0.1 (Solano), −0.04 ± 0.1 (Merced), and 0.3 ± 0.2 (Sacramento) Mg C ha^–1 yr^–1. These values change when considering deeper soil depths (0–100 cm) to 0.5 ± 0.1 (Solano), 0.2 ± 0.2 (Merced), and 0.216 ± 0.2 (Sacramento) Mg C ha^–1 yr^–1, reflecting differences in C stocks changes in surface and subsurface soils across sites. Rates of C storage per dry Mg of biosolids per year applied were 1 ± 0.2 (Solano), 0.5 ± 0.4 (Merced), and 0.04 ± 0.1 (Sacramento). Our results suggest that local controls on soil C stabilization are more important than amendment application amount at predicting climate benefits and that accounting for soil C changes below 30 cm can provide insight for sequestering C in agroecosystems.

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土壤碳对长期生物固体应用的响应

Astudy 是在加利福尼亚州（萨克拉门托、索拉诺和默塞德县）的三个农业生态系统中进行的，这些系统收到了 20 年的生物固体申请。管理部门的施用率和频率各不相同，导致平均累计施用的生物固体量为 74 (Solano)、105 (Merced) 和 359 (Sacramento) Mg 生物固体_干ha ^–1，导致增加了 26 (Solano)、36 (Merced) 和 125 (Sacramento) Mg biosolids-C ha ^–1. 测量包括 0 至 100 cm 的土壤有机碳 (SOC) 和总氮 (N) 浓度，以及生物固体修正和控制地点的 0 至 30 cm 的微生物生物量 C (MBC) 和微生物生物量 N (MBN)。生物固体处理在所有地点都有更多的 SOC 和总 N，而 MBC 和 MBN 在萨克拉门托和索拉诺最大。SOC 增加最大的是在生物固体累积负载率最低的地点 (Solano)，其中 100 cm 的 SOC 含量在改良土壤中增加了 50% ( p  < .001)。土壤碳库到 30 cm 的净变化为 0.4 ± 0.1 (Solano)、-0.04 ± 0.1 (Merced) 和 0.3 ± 0.2 (Sacramento) Mg C ha ^–1 yr ^–1. 当考虑更深的土壤深度 (0–100 cm) 到 0.5 ± 0.1 (Solano)、0.2 ± 0.2 (Merced) 和 0.216 ± 0.2 (Sacramento) Mg C ha ^–1 yr ^{–1 时}，这些值会发生变化，反映了碳库的差异不同地点地表和地下土壤的变化。每年应用的每干 Mg 生物固体的 C 储存率为 1 ± 0.2 (Solano)、0.5 ± 0.4 (Merced) 和 0.04 ± 0.1 (Sacramento)。我们的结果表明，在预测气候效益方面，对土壤碳稳定的局部控制比修正剂施用量更重要，并且考虑到低于 30 厘米的土壤碳变化可以为在农业生态系统中固碳提供洞察力。