ABSTRACT Biosolids are an important potential source of plant-available nutrients and also contain valuable quantities of stable organic matter, which can provide long-term benefits to soil structure and fertility. In this study, the long-term impacts of biosolids recycling to agricultural land on soil quality and fertility were assessed using established experimental platforms at four sites in England with contrasting soil types and agroclimatic conditions. At each site, treatment plots that had received 20 annual additions of biosolids (i.e., three types of digested sludge cake) at rates of 2.9 to 3.4 t ha−1 y−1 since 1994 were used in comparison with an untreated control treatment (which had received inorganic fertilizers only) to quantify the effects of biosolids on soil physical, chemical, and biological properties. Significant increases (P < 0.05) in soil organic matter (SOM) of 10% to 17% and in “light fraction” SOM (up to 2.9 mg kg−1 on the biosolids treatment compared with 1.8 mg kg−1 on the untreated control), along with a significant (P < 0.01) increase of up to 10% in available water capacity and numerical increases in water infiltration rate and aggregate stability, were found in plots that received biosolids. These plots also had significant (P < 0.05) increases of up to 20%, 48%, and 30% in soil total nitrogen, extractable phosphorus, and total sulfur, respectively. Earthworm numbers and weights were approximately doubled relative to the untreated control (P < 0.05) where low-metal biosolids had been applied. These results indicate that applying biosolids to agricultural land is an important means of replenishing and maintaining SOM levels. Importantly, no adverse effects on crop quality were observed. The results from this study provided valuable evidence toward maintaining a sustainable agricultural landbank for biosolids recycling in the United Kingdom.

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生物固体对土壤质量和肥力的长期影响

摘要 生物固体是植物可利用养分的重要潜在来源，还含有大量稳定的有机物质，可为土壤结构和肥力提供长期效益。在这项研究中，使用在英格兰四个地点建立的实验平台评估了生物固体循环到农业用地对土壤质量和肥力的长期影响，这些地点具有对比的土壤类型和农业气候条件。在每个地点，自 1994 年以来每年以 2.9 到 3.4 t ha−1 y−1 的速率添加 20 次生物固体（即三种消化污泥饼）的处理地块与未处理的对照处理（即仅接受无机肥料）以量化生物固体对土壤物理、化学和生物特性的影响。土壤有机质 (SOM) 显着增加 (P < 0.05) 10% 至 17% 和“轻质部分”SOM（生物固体处理高达 2.9 mg kg-1，而未处理对照为 1.8 mg kg-1） )，同时在接受生物固体的地块中发现可用水容量显着增加 (P < 0.01)，并且水渗透率和聚集体稳定性的数值增加高达 10%。这些地块的土壤总氮、可提取磷和总硫含量也分别显着 (P < 0.05) 增加了 20%、48% 和 30%。蚯蚓的数量和重量相对于应用了低金属生物固体的未处理对照（P < 0.05）大约翻了一番。这些结果表明，将生物固体应用于农田是补充和维持 SOM 水平的重要手段。重要的是，没有观察到对作物质量的不利影响。这项研究的结果为维持英国生物固体回收利用的可持续农业土地库提供了宝贵的证据。