ABSTRACT

Conversions of soil pH values between different methods are required for the standardization of data from international scientific literature, soil test reports and soil databases. All commonly employed matrices (H₂O, 0.01 M CaCl₂ and 1 M KCl) and relevant soil:solution ratios (1:1, 1:2.5, 1:4 and 1:5) used for pH measurement have yet to be compared using the same sample dataset. The combined effects of soil physiochemical properties on the accuracy and parsimony of soil pH conversions have also not been thoroughly examined. Therefore, the aim of this study was to investigate the mathematical relation between the most common methods of pH determination. A diverse set of soil samples (n = 57) dominated by low-activity clays were used to calibrate simple and multilinear pH conversion models. The combined effects of soil texture, carbon content and salinity on model parsimony and accuracy were critically evaluated. All pH determination methods were found to be highly reproducible and relatable to one another. It was found that simple linear equations are the most effective means of converting pH values (r² = 0.77–0.97; RMSE = 0.12–0.32), considering the trade-off between model complexity and accuracy. Simple direct conversion factors are not deemed sufficiently accurate for the purpose of agricultural management recommendations.

摘要

国际科学文献、土壤测试报告和土壤数据库数据的标准化需要不同方法之间的土壤 pH 值转换。所有常用的基质（H ₂ O、0.01 M CaCl ₂和 1 M KCl）以及用于 pH 测量的相关土壤：溶液比（1:1、1:2.5、1:4 和 1:5）尚未使用相同的样本数据集进行比较。土壤理化性质对土壤 pH 转换的准确性和简约性的综合影响也尚未得到彻底研究。因此，本研究的目的是研究最常用的 pH 测定方法之间的数学关系。以低活性粘土为主的一组不同的土壤样品 (n = 57) 用于校准简单的多线性 pH 转换模型。严格评估了土壤质地、碳含量和盐度对模型简约性和准确性的综合影响。发现所有 pH 测定方法都具有高度的可重复性和相互关联性。²  = 0.77–0.97；RMSE = 0.12–0.32），考虑模型复杂性和准确性之间的权衡。就农业管理建议而言，简单的直接转换因子被认为不够准确。