Cadmium (Cd) can accumulate in soil from the application of phosphorus fertilizer. However, there is little information on what happens to soil Cd concentrations when Cd inputs stop. This study used soil and pasture samples collected from a long-term field trial to measure changes in Cd concentrations in soil for 22 yr after Cd inputs from fertilizer had stopped and assessed whether the application of nitrogen (N) (50 kg ha-1 yr-1 ) could increase plant uptake of Cd and reduce soil Cd concentrations. It was found that there was no significant change in total or labile soil Cd (1 M CaCl2 extractable) concentrations after Cd inputs stopped. The application of N did not significantly (P < .05) increase dry matter yield or increase Cd solubility. As a result, N did not enhance plant uptake of Cd. A mass balance that included Cd loss via plant uptake and Cd leaching confirmed they were insufficient to result in a detectable decrease in soil Cd concentration over the 22-yr interval of the trial. It appears that even an acid soil with low amounts of carbon (2.67%), iron/aluminum oxides, and clay can still strongly retain Cd, preventing Cd depletion from the soil, despite stopping Cd inputs and trying to enhance plant uptake of Cd from the application of N fertilizer.

中文翻译：

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停止施磷肥后土壤镉浓度随时间的变化

镉（Cd）可以通过施用磷肥在土壤中积累。然而，关于当 Cd 输入停止时土壤 Cd 浓度会发生什么变化的信息很少。本研究使用从长期田间试验中收集的土壤和牧场样品来测量停止从肥料中输入 Cd 后 22 年土壤中 Cd 浓度的变化，并评估施氮（N）（50 kg ha-1 yr -1 ) 可以增加植物对 Cd 的吸收并降低土壤 Cd 浓度。结果表明，停止 Cd 输入后，土壤中总的或不稳定的 Cd（可提取 1 M CaCl2）浓度没有显着变化。施氮并没有显着（P < .05）增加干物质产量或增加 Cd 溶解度。因此，N 并没有增强植物对 Cd 的吸收。包括通过植物吸收和 Cd 浸出导致的 Cd 损失在内的质量平衡证实，它们不足以导致在 22 年的试验间隔内土壤 Cd 浓度出现可检测的下降。似乎即使是含有少量碳 (2.67%)、铁/铝氧化物和粘土的酸性土壤仍然可以强烈保留 Cd，防止土壤中的 Cd 耗竭，尽管停止了 Cd 输入并试图提高植物对 Cd 的吸收。施氮肥。