Abstract In response to concerns over the translocation of P from soils to P-sensitive water bodies, there is high demand for developing simple indicators for evaluating a soil’s risk of releasing P into solution. Many studies have shown that the degree of soil phosphorus saturation (DPS), calculated as the ratio of soil P concentration to soil P sorption capacity (PSC), is good predictor of a soil’s risk of releasing P in solution. In this study we compared four different DPS indices in how well they predicted dissolved P following extraction with either a 0.01 M CaCl2 (PCaCl2) solution or deionized water (PW). The first two indices were calculated from the ratio of extractable P to extractable Al and Fe using either acid ammonium oxalate (AlOX + FeOX) or ammonium lactate solutions (AlAL + FeAL). The second two DPS indices were calculated from the ratio of either Olsen-extractable P or AL-extractable P with sorption capacity estimated from the single point P sorption index (PSI). On a subset of 11 soils, we compared the different methods for estimating PSC with fitted Langmuir sorption maximum (Smax) using data from complete sorption isotherms. Both (AlOX + FeOX) and PSI were well correlated with Smax and hence regarded as good estimates for P sorption capacity. Conversely, (AlAL + FeAL) was not significantly correlated with Smax. P saturation calculated from PSI together with PAL or POls predicted PCaCl2 and PW best, whereas P saturation calculated from ammonium oxalate predicted PCaCl2 and PW the least. We did not find notable improvements in the regression models when we added a second explanatory variable (clay content, pH or total carbon) to the models. Our results show that multiple measures of P saturation provide similar predictions of a soiĺs potential for releasing dissolved P into soil solution. This provides flexibility in how P saturation indices are calculated to identify leaching prone hotspots.

中文翻译：

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比较测定磷饱和度的措施作为估算土壤溶液中溶解磷的方法

摘要 针对磷从土壤转移到对磷敏感的水体的担忧，迫切需要开发简单的指标来评估土壤向溶液中释放磷的风险。许多研究表明，土壤磷饱和度 (DPS)，计算为土壤磷浓度与土壤磷吸附能力 (PSC) 的比率，是土壤在溶液中释放磷的风险的良好预测指标。在这项研究中，我们比较了四种不同的 DPS 指数，它们在使用 0.01 M CaCl2 (PCaCl2) 溶液或去离子水 (PW) 提取后预测溶解磷的程度。前两个指数是使用酸性草酸铵 (AlOX + FeOX) 或乳酸铵溶液 (AlAL + FeAL) 根据可萃取 P 与可萃取 Al 和 Fe 的比率计算得出的。后两个 DPS 指数是根据 Olsen 可提取 P 或 AL 可提取 P 与从单点 P 吸附指数 (PSI) 估计的吸附容量的比率计算的。在 11 种土壤的子集上，我们使用完全吸附等温线的数据比较了估计 PSC 和拟合朗缪尔吸附最大值 (Smax) 的不同方法。(AlOX + FeOX) 和 PSI 都与 Smax 密切相关，因此被认为是对 P 吸附能力的良好估计。相反，(AlAL + FeAL) 与 Smax 没有显着相关性。根据 PSI 和 PAL 或 POls 计算的 P 饱和度预测 PCaCl2 和 PW 最好，而根据草酸铵计算的 P 饱和度预测 PCaCl2 和 PW 最少。当我们添加第二个解释变量（粘土含量、pH 值或总碳）到模型。我们的结果表明，磷饱和度的多种测量提供了对土壤释放溶解磷到土壤溶液中的潜力的类似预测。这为如何计算 P 饱和指数以识别易浸出的热点提供了灵活性。