Field testing and evaluation of a two layer soil water balance model

Abstract

A two layer soil water balance model was tested in the field with bhindi as the test crop. The model considers the dynamics of soil water balance by incorporating an empirical model of root growth and an empirically established result of plant response to available soil water. The input data of the model were daily values of rainfall, irrigation and reference crop evapotranspiration. The model calculated the values of root depth, potential evapotranspiration, actual evapotranspiration, percolation and soil moisture content at the end of each day. The root depth computed by the model was compared with that measured in the field. Maximum root depth of 39.0 cm was attained at 53rd DAS. Total amount of water percolated down the active root zone during the entire crop season was 8.15 mm. The actual evapotranspiration was less than the potential evapotranspiration, whenever the soil moisture content in the active root zone dropped below the critical soil moisture. Totally, AET was less than PET for 6 days durinq the period of study. The computed and observed values of soil moisture content were in close agreement with correlation coefficients 0.976, 0.971 and 0.965 for gravimetric, tensiometer and electrical resistivity methods respectively.