Simulation of salt dynamics in the root zone and yield of wheat crop under irrigated saline regimes using SWAP model

Crop modelling has played an important role in formulating agricultural policies and measures to reduce yield losses. In this study, an effort was made to evaluate the SWAP (Soil Water Atmosphere Plant) model to assess its capability to simulate the salt dynamics and yield of three salt tolerant and one salt non-tolerant wheat varieties under varying saline water irrigation regimes. The experiment was conducted at the research farm of Water Technology Centre, Indian Agricultural Research Institute, New Delhi, India located in a semiarid monsoon climatic region. Four irrigation treatments viz. ground water (S-1) salinity varying from 1.45 to 1.7 dS m(-1), and saline water levels of 4 dS m(-1) (S-2), 8 dS m(-1) (S-3), 12 dS m(-1) (S-4) were used for irrigating the crop. The model was calibrated and validated using the experiment generated data of rabi 2009-2010 and 2010-2011 cropping seasons, respectively. The model performance indicators i.e. model efficiency (ME) and degree of agreement (d) was 0.76 and 0.93 for root zone soil salinity and 0.96 and 0.99 for relative wheat yield of calibrated model, respectively. Furthermore, root mean square error (RMSE) and mean absolute error (MAE) for prediction of relative yield during calibration was 4% and 3% and during validation was 9.6% and 8.3%, respectively. The validated model performed well for salt dynamics in root zone and relative yields that were corroborated by prediction error statistics R-2 of 0.96 and 0.95, ME of 0.95 and 0.75 besides degree of agreement (d) of 0.98 and 0.93, respectively. It was observed that the model performed better for prediction of relative yield of salt tolerant varieties as compared to the salt non tolerant variety under different saline irrigation water regimes. Overall, the SWAP model could be used to simulate the salt dynamics in the crop root zone and yield of wheat with acceptable accuracy under irrigated saline environment. (C) 2014 Elsevier B.V. All rights reserved.