فهرست نشریات علمی دسترسی آزاد ایران

Researchers estimate hydraulic properties by indirect methods using various procedures. The objective of this study was to evaluate the effect of using the free swelling index as an estimator to improve the precision of soil moisture curve (SMC) estimation. In this study, 147 soil samples were taken from West Azarbaijan, East Azarbaijan, Mazandaran, Hamedan and Kermanshah provinces, and their particle size distribution, bulk density, free swelling index, cation exchange capacity and SMC were determined. Then, the Groenevelt & Grant’s model was fitted to the experimental data of SMC. Free swelling index and other variables were used as estimators to predict the parameters of Groenevelt & Grant’s model by multiple regression method. All samples were divided into several groups based on textural classes and SMC was estimated for them in four steps. Grouping the data improved the estimation of SMC. In soil textural groups of the numbers 3 (silty clay loam and clay loam classes), 7 (sandy loam class) and 8 (sand, loamy sand and sandy loam) the IRMSE and AIC values were decreased from 0.07 and 77.85 to 0.06 and 72.28, from 0.05 and 1.63 to 0.04 and -61.78 and from 0.06 and 86.11 to 0.05 and 2.97, respectively. Therefore, using the free swelling index as an estimator, significantly improved the estimates of SMC through the Groenevelt and Grant’s model.