Penentuan Kurva Retensi Air dan Konduktivitas Hidraulik pada Kolom Tanah Inceptisol di Laboratorium dengan Tensiometer Gips

Abstract

The gypsum tensiometer is a gypsum (CaSO4.nH2O) sensor that converts changes in electrical conductivity into soil water tension values (hPa). The purpose of this research is to assess the reliability of gypsum tensiometers compared to Granular Matrix Sensors (GMS) and empirical Mualem van Genuchten (MvG) tests for measuring the pF curve and unsaturated hydraulic conductivity (Kh) of soil. Four gypsum tensiometer sensors, three GMS sensors, and one GP2 profile probe were vertically installed in a column of Inceptisols. Measurements of soil water tension (Ψ) and soil moisture content (θ) were collected weekly. The research results indicate that the gypsum tensiometers fit the MvG model with values of n ranging from 1.209 to 1.383, m from 0.173 to 0.277, and alpha from 0.021 to 0.545. The measurement discrepancies with this model resulted in a Normalized Root Mean Square Error (NRMSE) ranging from 6.8% to 12.2% (low) and Nash-Sutcliffe Efficiency (NSE) values between 0.898 and 0.902 (good fit). The calculation of Kh from the measurements generated a value of 3.54 x 10-4 cm.day-1 at a soil moisture content of 0.284 cm3.cm-3. However, the MvG model with values of n between 1.101 and 1.500, m between 0.092 and 0.333, and alpha between 0.075 and 0.500 provided a less accurate fit to the measurement results. The measurement discrepancies showed NRMSE values between 27.9% and 30.6% (high) and NSE values ranging from -0.138 to -25.56 (unsatisfactory fit). In conclusion, this research indicates that determining the retention curve with gypsum tensiometers yields results close to the MvG model predictions but shows significant inconsistencies in the measurement of unsaturated hydraulic conductivity (Kh).