A comparison of the HYDRUS (2D/3D) and SALTMED models to investigate the influence of various water-saving irrigation strategies on the maize water footprint

Abstract

In this comparative research, we applied the HYDRUS (2D/3D) and SALTMED models to investigate the influence of various water-saving irrigation strategies on maize water footprints (WFs). The models were first calibrated and validated based on data collected in a two-year field investigation under five water-saving irrigation treatments: full irrigation (FI), partial root-zone drying at water deficit levels of 55% (PRD55) and 75% (PRD75), and deficit irrigation at the same levels (DI55 and DI75). While the SALTMED model performed well when simulating crop growth parameters, with absolute relative error (RE) of 3.5–12%, the HYDRUS (2D/3D) model was more accurate when simulating soil water and solute transport, with the normalized values of the root mean square error (nRMSEs, 6.7–31.8%) and the mean bias error (nMBEs, 7.7–34.3%) lower than by SALTMED. This better performance of HYDRUS (2D/3D) resulted in 0.6–3.0% and 5.3–30.2% lower values of estimated consumptive and degradative WFs, respectively, compared to values estimated by SALTMED. While no considerable differences were observed among various irrigation treatments regarding their consumptive WFs for the maize production, PRD75 may represent a safer option under the water crisis, since its grey WF was 17.1–77.2% lower than those estimated for the other water-saving irrigation treatments. This WF reduction was accompanied by an insignificant reduction in crop yield and improved N uptake. Based on our results, while HYDRUS (2D/3D) provides more reliable results, both the HYDRUS (2D/3D) and SALTMED models may be applied for the evaluation of new targets implemented for achieving sustainable agriculture in water-scarce regions.