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Environ Pollut. 2022 Jan 1;292(Pt B):118430. doi: 10.1016/j.envpol.2021.118430. Epub 2021 Nov 2.
To decrease the concentration of the toxic metal cadmium (Cd) in topsoil, and the human food chain, many countries have limited the Cd concentration allowed in phosphorus (P) fertilisers. However, to inform those limits we need accurate estimates of Cd leaching from established farming systems. Different soil layers were sampled to 2000 mm depth of a long-term trial that had applied 22.5 kg P ha yr for 67 years to grazed pastures that received either no irrigation or were irrigated when soil moisture fell below 10 or 20%. The annual yield of Cd leaching from the top 150 mm of soil to the 151-250 mm layer was between 1.1 and 1.8 g ha with Cd leaching increasing with the frequency of irrigation. The rate of Cd accumulation measured to 2000 mm was within the mean and standard error estimated for treatments using a mass balance approach. Estimates of annual Cd leaching loss were like those established from field trials measuring leaching events over a year (0.3-1.8 g ha) with a similar rate of P application (9-24 kg P ha yr). Using a Cd leaching rate of 1.8 g ha yr and P applications rates of 22.5 kg P ha, topsoil Cd concentrations may stop increasing if Cd concentrations in P fertiliser can be maintained at < 72 mg Cd kg P.
为了降低土壤表层和人类食物链中有毒金属镉 (Cd) 的浓度，许多国家都限制了肥料中允许的磷 (P) 浓度。然而，要确定这些限制，我们需要对已建立的农业系统中 Cd 的淋溶有准确的估计。对一个长期试验的不同土层进行了采样，该试验在 67 年的时间里，每年向放牧草地施入 22.5 公斤 P/公顷，草地要么不灌溉，要么在土壤水分降至 10%或 20%以下时灌溉。从土壤表层 150 毫米到 151-250 毫米层，每年有 1.1-1.8 克 Cd 淋溶到土壤中，且随着灌溉频率的增加，Cd 淋溶量也增加。采用质量平衡法对至 2000 毫米的 Cd 积累速率进行了测量，其结果在估计处理方法的平均值和标准误差范围内。通过对一年中淋溶事件进行测量（0.3-1.8 克/公顷），得出的年 Cd 淋溶损失估计值与使用相似 P 施用量（9-24 公斤 P/公顷）的田间试验结果相似。如果可以将肥料中 Cd 的浓度保持在 <72 毫克 Cd/公斤 P，则每年 1.8 克/公顷的 Cd 淋溶率和 22.5 公斤 P/公顷的 P 施用量，可能会阻止表层土壤中 Cd 浓度的增加。
