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

摘要

pH_(KCl) and pH_(H_(2)O) are two basic necessary indexes to reflect the acidity of asoil. Predicting pH KCl?)directly from pH H_(2)O?)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 pH KCl) and pH H_(2)O). The results showed that: 1) pH KCl) is lower than pH H_(2)O), pH KCl?)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 pH H_(2)O?)for Yunan. 2) There is significant positive correlation between pH KCl) ?and pH H_(2)O), the optimal correlation models between pH KCl?)(y) and pH H_(2)O?)(x) for Guangxi and Yunnan are y = 0.1963x~(2) &minus; 1.0512x + 4.338, R2 = 0.836, p < 0.01 and y = 1.5882e~(0.1859x), 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 pH KCl?)with exchangeable H~(+ )and Al~(3+) (R2 = 0.487, 0.716, p < 0.01), and pH KCl?)is dominated by exchangeable Al~(3+), followed by exchangeable H~(+), and their contribution to pH KCl?)were 71.1% and 28.7%, respectively.