A PRELIMINARY STUDY ON EVALUATING HYDRAULIC PROPERTIES CALCULATOR TO PREDICT SOIL AVAILABLE WATER OF SELECTED TROPICAL MONSOON SOIL, INDONESIA

Abstract

Background: Hydraulic properties calculator had been employed by many researchers worldwide, as it is simplified soil water properties prediction by resulting a model. However, the model was formulated by investigating soil samples from all over the USA, which are not similar with Indonesian soil due to different climatic zone. Objective: To evaluate the accuracy of Hydraulic Properties Calculator for Indonesian soil, which is categorized developed under the tropical monsoon climate. Methodology: Undisturbed soil samples were collected from 36 land units of 4 soil types surrounding Karanganyar Regency, Indonesia. Soil properties data included soil permeability, pH (soil reaction), pF, organic matter, particle density, bulk density, porosity, and texture were analyzed using Pearson’s correlation, regression analysis, multiple linear regression, and pair T-Test (α=0.05). Results: The results showed the coefficient of determination (R2) of soil available water using laboratory analysis and hydraulic properties calculator was 0.959, but paired t-test resulted P<0.01. This means despite high value of R2, both methods produced different soil available water results. Implications: Further study is required to formulate new model is to predict soil available water of Indonesian soil. Conclusion: The hydraulic properties calculator is less accurate to predict soil Available Water (AW) of selected Indonesian soil.