Professor Indian Institute of Technology Roorkee Indian Institute of Technology Roorkee
Knowing the amount and timing of irrigation is critical for irrigation water management. In this study, a numerical model is used to predict the irrigation schedules for wheat crop grown in sandy-loam soil in humid subtropical climate type. Irrigation schedules are simulated for four different soil moisture depletion levels (referred here as MAD level): 40%, 45%, 50% and 55%. For each of the four MAD levels; three levels of deficit irrigation: 70%, 80% and 100% of the irrigation water required to attain field capacity, are considered. Irrigation is provided by the model when the average soil moisture depletion in the effective root zone reaches the MAD value and amount of irrigation for each MAD value is governed by level of deficit irrigation. The numerical model uses Richards equation with sink term as the governing equation. A non-linear root water uptake model is used to account for the sink term. Neumann type upper and lower boundary conditions are considered in the numerical model. Inputs to the numerical model include crop and soil parameters and daily crop water requirements.
The simulation results show that the number of irrigations and amount of total irrigation decreased with the increase in MAD level. Overall, the highest amount of irrigation is found corresponding 40% MAD and lowest amount of irrigation is found corresponding to 55% MAD. No definite trend of water saving was however found with the variation in level of deficit irrigation. The simulated irrigation schedules can provide an estimate about the frequency and amount of irrigation at different levels of water availability and will be helpful in the planning and management of irrigation water.
