A Brief Study on Using pH H 2 O to Predict pH KCl for Acid Soils

Abstract

pHKCl and are two basic necessary indexes to reflect the acidity of asoil. Predicting pHKCl directly from could save the cost of laboratory work. In this study, the values of pHKCl and of 442 and 310 horizon samples from 126 and 98 soil profiles (0 - 120 cm in depth) surveyed from 2014 to 2015 in Guangxi and Yunnan were used to establish the optimal correlation model between pHKCl and . The results showed that: 1) pHKCl is lower than , pHKCl was 0.07 - 1.99 units with a mean of 0.99 units lower than for Guangxi, while 0.03 - 1.90 units with a mean of 0.89 lower than pHH2O for Yunan. 2) There is significant positive correlation between pHKCl and , the optimal correlation models between pHKCl (y) and (x) for Guangxi and Yunnan are y = 0.1963x2 − 1.0512x + 4.338, R2 = 0.836, p < 0.01 and y = 1.5882e0.1859x, R2 = 0.769, p < 0.01, respectively, and the values of MAE and RSME of the models are 0.13 and 0.36 for Guangxi, 0.08 and 0.28 for Yunnan, respectively. There are significant negative correlations between pHKCl with exchangeable H+ and Al3+ (R2 = 0.487, 0.716, p < 0.01), and pHKCl is dominated by exchangeable Al3+, followed by exchangeable H+, and their contribution to pHKCl were 71.1% and 28.7%, respectively.