Modelling soil water dynamics and crop water use in a soybean-wheat rotation under chisel tillage in a sandy clay loam soil

Mechanical chiseling disrupts the sub-surface compaction often found in agricultural soils, and modifies soil physical condition conducive to root growth. However, the effect is transitory and therefore, the impact on soil hydraulic characteristics and consequently on water dynamics must be precisely quantified for effective technology-targeting. In this study, Hydrus-2D was used to describe the soil water change, root water uptake and profile water balance components under different time lags after chiseling. The input parameters were collected from a 2-year field experiment with soybean-wheat crops in rotation on a sandy loam soil in the experimental farm of the ICAR-Indian Agricultural Research Institute, New Delhi. The chisel treatments were residual (RS), repeated (RC) and no chisel (NC). Greater root water uptake in RS and RC compared to the NC could be attributed to marginally higher leaf area index and fIPAR in chiseled plots along with greater depth and spread of roots. Model simulated soil water content was in good agreement with observed data in the first year of rotation. The model was further validated by comparing the simulated and observed values of crop transpiration with R-2 = 0.85 and 0.72 (p < 0.001) in soybean and wheat crop, respectively in the following year. Simulated field water valance components indicated 50-70 mm higher seasonal transpiration by the crops. Chisel plots had significantly higher yield and water use in 1st year soybean-wheat rotation, but the effect of chisel became marginal in the 2nd year rotation. Soil water content profile indicates higher plant-available water in chiseled plots. In view of the cost of chiseling and the marginal benefits obtained till 2nd tear of crop rotation, chiseling once in 2-3 years may be recommended for the sandy loam soils under the semi-arid climate condition.