The low organic C (OC) sequestration and low water and nutrient holding capacities of sandy soils can be improved by amendment with clay soils. However, the effect of clay soils may depend on clay soil properties, including cation exchange capacity (CEC) and clay and OC contents. Two experiments were carried out. In the first experiment, sandy soil was mixed with two high clay content soils (Sodosol and Vertosol) at 10% and 40% (w/w). The soil was left unamended or amended with wheat straw, to assess if the effect of clay soil addition was influenced by OC addition. In the second experiment, sandy soil was mixed with two low-clay content soils which differed in CEC without wheat straw amendment. In experiment 1, compared with sandy soil alone, amendment with Sodosol (low OC) reduced cumulative respiration more strongly than addition of Vertosol. Without wheat straw addition, both clay soils increased microbial biomass C (MBC), whereas with wheat straw, they reduced microbial biomass C (MBC) compared with sandy soil alone. Sodosol amendment reduced water-extractable OC (WEOC) without wheat straw but increased it with wheat straw. In experiment 2, only the high CEC clay soil reduced cumulative respiration, MBC and WEOC compared with sandy soil alone. Clay soil addition to sandy soil will result in the greatest OC sequestration if the added soil has high clay but low OC content and its CEC is high.

中文翻译：

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用粘土改良的沙质土壤：粘土特性对土壤呼吸、微生物生物量和水可提取有机碳的影响

砂质土壤的低有机碳 (OC) 封存和低水和养分保持能力可以通过用粘土进行改良来改善。然而，粘土的影响可能取决于粘土的特性，包括阳离子交换容量 (CEC) 以及粘土和 OC 含量。进行了两个实验。在第一个实验中，沙土与两种高粘土含量的土壤（Sodosol 和 Vertosol）以 10% 和 40% (w/w) 混合。土壤未经改良或用麦秸改良，以评估粘土添加的效果是否受 OC 添加的影响。在第二个实验中，沙土与两种低粘土含量的土壤混合，这些土壤在没有小麦秸秆改良剂的情况下具有不同的 CEC。在实验 1 中，与单独的沙质土壤相比，添加 Sodosol（低 OC）的改良剂比添加 Vertosol 更能降低累积呼吸。与单独的沙土相比，没有添加小麦秸秆，两种粘土都增加了微生物生物量 C (MBC)，而添加小麦秸秆后，它们降低了微生物生物量 C (MBC)。Sodosol 修正剂在没有小麦秸秆的情况下降低了水可萃取 OC (WEOC)，但在小麦秸秆的情况下增加了它。在实验 2 中，与单独的沙质土壤相比，只有高 CEC 粘土土壤降低了累积呼吸、MBC 和 WEOC。如果添加的土壤具有高粘土但低 OC 含量且其 CEC 高，则将粘土添加到沙质土壤中将导致最大的 OC 封存。在实验 2 中，与单独的沙质土壤相比，只有高 CEC 粘土土壤降低了累积呼吸、MBC 和 WEOC。如果添加的土壤具有高粘土但低 OC 含量且其 CEC 高，则将粘土添加到沙质土壤中将导致最大的 OC 封存。在实验 2 中，与单独的沙质土壤相比，只有高 CEC 粘土降低了累积呼吸、MBC 和 WEOC。如果添加的土壤具有高粘土但低 OC 含量且其 CEC 高，则将粘土添加到沙质土壤中将导致最大的 OC 封存。