CALIBRATION OF A WATER-UPTAKE SIMULATION-MODEL UNDER VARYING SOIL-MOISTURE REGIME AND NITROGEN LEVEL FOR WHEAT CROP

Crop production is directly related to the time-depth status of soil w ater which is often predicted with the help of a simulation model avoi ding time-consuming deterministic procedures. In the present study, th e accuracy of a mathematical simulation model has been tested by compa ring the simulated profile water content with its measured counterpart in a field experiment conducted with winter wheat on a sandy loam soi l (Typic Ustipsamment). Wheat crop was grown under two soil water regi mes, monitored by applying irrigation at 1.2 (wet, W) and 0.6 (dry, D) ratios of irrigation water to cumulative pan evaporation and at two l evels of nitrogen: high, (120 kg ha(-1), N) and low (60 kg ha(-1), N). The calibration studies indicated high dependency of the simulation m odel on the depth of rooting used as an input parameter. The matching between simulated and measured profile water content was better when p enetration depth of wheat roots was less than 0.6 m. Predictability of the model was found to be high under wet soil moisture regime and at low level of fertilizer nitrogen.