Evaluating Drainmod-s to Predict Drainage Water Salinity and Groundwater Table Depth During Winter Cropping in Heavy-Textured Paddy Soils

Simulation models can quickly and cost-effectively describe various aspects of management practices in newly reclaimed agricultural soils. In this research, the capability of the DRAINMOD-S model was evaluated to predict the salinity of the subsurface drainage effluents in a newly subsurface drained paddy field during winter cropping. Measurements of groundwater table depths and drainage water salinity were taken in three conventional subsurface drainage systems at the Sari Agricultural Sciences and Natural Resources University, northern Iran, during three canola growing seasons (2011-2012, 2015-2016 and 2016-2017). The data were used to calibrate and validate the model. The model provided better predictions of groundwater table depths in shallower drainage systems. Measured and simulated drainage water salinities varied, respectively, from 620 to 1580 and 790-1430 mg l(-1) in the calibration process and from 441 to 1640 and 656-1820 mg l(-1) in the validation process. The differences between measured and simulated salt loads were in the range of 59-174 and 43-586 kg ha(-1) in calibration and validation, respectively. The results indicated that DRAINMOD-S can be used as a management tool to diminish environmental issues in heavy paddy soils from the viewpoint of salt load. (c) 2019 John Wiley & Sons, Ltd.