Can one-time calibration of measured soil hydraulic input parameters yield appropriate simulations of RZWQM2?

Agricultural system models can help quantify soil water dynamics, crop evapotranspiration, and crop growth with a high temporal resolution to enhance soil and crop management. Simplifying the process of model calibration and validation is an important aspect for crop model use. The objective of this study was to explore the capability of using the Root Zone Water Quality Model (RZWQM2) with soil hydraulic property input parameters (SHPIPs) identified once under a given crop for other crops without recalibrating. A field experiment with soybean [Glycine max (L.) Merr.], corn (Zea mays L.), wheat (Triticum aestivum L.), and fallow soil was conducted from 2015 to 2017. The soil hydraulic property parameter calibration process was evaluated. Four model scenarios of calibrating measured SHPIPs for soybean, corn, wheat, and fallow soil were created. The RZWQM2 simulation results showed high sensitivity to the model inputs of the SHPIPs. Model input parameters of bulk density, field capacity, permanent wilting point, and saturated hydraulic conductivity showed a large effect on model simulations. Model inputs of soil water content θ at field capacity and permanent wilting point showed high impact on water holding capacity and crop development, whereas the model input parameters of saturated hydraulic conductivity and bulk density yielded a high effect on soil water dynamics. All model scenarios presented satisfactory results with regard to soil water dynamics, evapotranspiration, crop growth, and mineral nitrogen, indicating that, for a particular field, RZWQM2 calibrated for one season performs well for other seasons without recalibration.