Effects of controlled drainage on soil water and nitrogen changes in greenhouse

The controlled drainage is beneficial to avoiding the secondary salinity in the greenhouse. In order to analysis the soil water and nitrogen dynamics in the greenhouse, the RZWQM (Root Zone Water Quality Model) model was calibrated and validated based on the field experiment and used to analyze the soil water and nitrogen distributions in greenhouse. The root mean standard errors (RMSE) of predicted soil water contents were within the range of 0.038 to 0.050 cm3/cm3 during the calibration and the range of 0.040 to 0.081 cm3/cm3 during the validation. The results indicated that the RZWQM model could be used for the study of water and nitrogen changes in greenhouse field. The controlled drainage had significant effect on the water table depth, the tile drainage volume, tile drainage nitrogen and the seepage nitrogen by the different spacing and depth of underground pipe, on the contrary, the crop uptake was not affected by the controlled drainage.