Estimation of Soil Clay Content using Hygroscopic Water Content at an Arbitrary Humidity

Abstract

Clay content has a significant influence on soil physical, chemical, and biological properties. The objectives of this study are to develop a linear model that predicts clay content of soils dominated by 2:1 minerals from easily measured hygroscopic water content (θ) at an arbitrary relative humidity (RH), and to compare the performance of the new model versus two previous models: the Resurreccion model (R model) and the Schneider-Goss model (SG model). The new linear model (New model) was established by integrating with the Campbell and Shiozawa model and the Kelvin equation. A total of 114 soil samples were collected from 14 soil profiles (0 to 2 m) near Tai'an city of China. Soil clay content (fCL) and θ at three different RHs (21, 45, and 60%) were measured and used to validate the New model, separately. The θ values varied from 0.23 to 4.86%, and fCL ranged from 2.84 to 37.3%. The results showed that the values predicted by the New model agreed well with measured data. The further comparison using measured and literature data indicated that the root mean squared errors (RMSE) of the New model, the R model, and the SG model were in the ranges of 2.3 to 6.6%, 3.1 to 8.8% and 4.4 to 9.2%, respectively, with the New model having the least prediction error. The New model will provide a useful method to estimate clay content of soils dominated by 2:1 minerals using θ at an arbitrary RH.