The objective of this study was to obtain sufficient estimates of quantity-intensity (Q/I) parameters using a single-point method, and to evaluate the role of cation exchange capacity (CEC) and Gapon selectivity coefficient (K G ) as parameters that improve prediction model’s estimation accuracy or explain its limitations under conditions of K deficiency. Regression models were applied on raw data derived from previews Q/I experiments conducted on 20 soils of northern Greece at initial and K-depleted treatment states. Relationships between soil K adsorbed or released (ΔΚ), or K activity ratios at each K addition (AR K ) and respective values at equilibria (-ΔΚ 0 , AR e K ) were tested to find the best fitting models. CEC was included in regression models to improve their performance, while K G parameter was assessed for initial and K-depleted soils. The study showed that Q/I parameters were well predicted with the single-point method for a wide range of K saturation ratios, by applying 0.01 M CaCl 2 and 10 mg L −1 K addition. Furthermore, CEC significantly improved model’s estimation accuracy. Under the ΔG breakpoint of − 14.67 kJ mol −1 , specific adsorption sites of the soil inner-sphere region weaken the single-point prediction efficacy, as was clearly indicated by the K G formation under conditions of K depletion. The study suggests that the proposed method is applicable for estimating Q/I parameters for soils covering a wide range of K activity ratios. Moreover, CEC and K G parameters constitute useful tools in improving prediction model’s estimation accuracy, or explaining their limitations under conditions of K deficiency.

中文翻译：

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使用单点方法估算不同钾饱和度土壤中钾的数量-强度参数

本研究的目的是使用单点方法获得对数量-强度 (Q/I) 参数的充分估计，并评估阳离子交换容量 (CEC) 和 Gapon 选择性系数 (KG) 作为改善预测模型的估计精度或解释其在 K 不足条件下的局限性。回归模型应用于原始数据，这些原始数据来自在希腊北部的 20 个土壤上进行的初始和缺钾处理状态下的预览 Q/I 实验。测试吸附或释放的土壤钾 (ΔΚ) 或每次添加钾时的钾活性比 (AR K ) 与各自平衡值 (-ΔΚ 0 , AR e K ) 之间的关系以找到最佳拟合模型。CEC 包含在回归模型中以提高其性能，而 KG 参数则是针对初始土壤和贫钾土壤进行评估的。研究表明，通过应用 0.01 M CaCl 2 和 10 mg L -1 K 添加物，使用单点方法可以很好地预测 Q/I 参数，适用于各种 K 饱和比。此外，CEC 显着提高了模型的估计精度。在-14.67 kJ mol -1 的ΔG 断点下，土壤内球区域的特定吸附位点削弱了单点预测效果，K 耗尽条件下的KG 形成清楚地表明了这一点。该研究表明，所提出的方法适用于估计涵盖广泛 K 活度比的土壤的 Q/I 参数。此外，CEC 和 KG 参数构成了提高预测模型估计精度的有用工具，