Subsurface organic ameliorant plus polyethylene mulching is a novel strategy for saline soil improvement and utilization in China. However, little is known about how this strategy impacts soil organic carbon (SOC) both directly (carbon input) and indirectly (soil aggregates protection and microbial regulation). Therefore, a field experiment was arranged and sampled after 3 years, including four treatments, i.e., no ameliorant with and without polyethylene mulching, and subsurface (10–30 cm soil depth) organic ameliorant with and without polyethylene mulching. Subsurface organic ameliorant raised the SOC content in the 0–40 cm by 70% and 90% with and without mulching, respectively. Subsurface organic ameliorant converted the major aggregation size from <0.053 to 0.25–2 mm, indicating that both direct carbon (C) input and indirect soil aggregates protection contributed to the increase in SOC content. In contrast, polyethylene mulching reduced the SOC content by 16% and 6% with and without organic ameliorant respectively. This was due to lower fungal diversity by 9%–14% and supported by the positive effect from fungal diversity to SOC. Further, the subsurface organic ameliorant plus polyethylene mulching increased SOC by 61% through direct C input, indirect soil aggregates protection and microbial regulation. Meanwhile, the contribution of physical protection standardized total effect (STE) = 0.223–0.294] was higher than microbial regulation (STE = 0.040–0.162) according to a structural equation model. Consequently, subsurface organic ameliorant plus polyethylene mulching represents a feasible agricultural practice to increase the SOC content for saline soil amelioration.

中文翻译：

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地下有机改良剂加聚乙烯覆盖通过改变盐渍土团聚体结构和调节真菌群落来强化土壤有机碳

地下有机改良剂加聚乙烯覆盖是我国盐渍土改良利用的新策略。然而，关于这种策略如何直接（碳输入）和间接（土壤聚集体保护和微生物调节）影响土壤有机碳 (SOC) 知之甚少。因此，在3年后安排了一次田间试验并取样，包括四个处理，即无改良剂有和没有聚乙烯覆盖，以及地下（10-30 cm土壤深度）有机改良剂有和没有聚乙烯覆盖。在覆盖和不覆盖的情况下，地下有机改良剂分别将 0-40 cm 的 SOC 含量提高了 70% 和 90%。地下有机改良剂将主要聚集体尺寸从 <0.053 转变为 0.25-2 mm，表明直接碳 (C) 输入和间接土壤团聚体保护都有助于 SOC 含量的增加。相比之下，聚乙烯覆盖在使用和不使用有机改良剂的情况下，SOC 含量分别降低了 16% 和 6%。这是由于真菌多样性降低了 9%–14%，并且得到了真菌多样性对 SOC 的积极影响的支持。此外，通过直接碳输入、间接土壤团聚体保护和微生物调节，地下有机改良剂加聚乙烯覆盖使 SOC 增加了 61%。同时，根据结构方程模型，物理保护标准化总效应（STE）= 0.223-0.294]的贡献高于微生物调节（STE = 0.040-0.162）。最后，