Advancing the selection of soil hydraulic property models for soil-crop modelling

<p>From hypothesis testing to impact assessment, soil-crop models serve a multitude of purposes in researching climate change impact on the water cycle in cropping systems. As such, model complexity undeniably differs amongst approaches and intended purpose but must include the full range of soil-water states. Climate change is predicted to increase prolonged periods of dry conditions, however, soil-crop models, often misrepresented drying of soils, inducing misquantifications in root water uptake, evapotranspiration, and concomitantly, water use efficiency and ground water recharge rates. While in soil hydrology, this has been recognised and effective solutions exist, soil-crop models typically neglect these more comprehensive approaches.</p><p>Our study serves two aims: For one, we shed light into the chaotic multitude of soil hydraulic property models, by representing the models in a systematic framework, of sub-models and processes. This model is called the Brunswick Soil Hydraulic Property Model Framework. With this we hope to make soil hydrology more tangible, for non-experts. Secondly, we i) demonstrate that representing soil hydraulic properties over the entire moisture range, i.e. from fully saturated to completely dry soils, changes simulated root water uptake under dry soil conditions, which sensitively affects crop yields. We quantify these effects by simulating root water uptake using the agro-ecosystem models Expert-N and Daisy, comparing the standard as well as oversimplified approach to a comprehensive model (of the Brunswick model framework). This was possible by using new pedotransfer functions to obtain all required model parameters. The framework and pedotransfer functions are available in the R package spsh on CRAN.</p>