BayCEER Workshop 2025

Modeling temporal soil structure changes to analyse management effects on crop-field water dynamics

P 16 in Posters

Soil is a complex system that continuously evolves under the influence of physical, biological, chemical and anthropogenic processes. These changes are manifested in the soil structure and coupled with their variability across spatial and temporal scales. They complicate the understanding and prediction of how water is retained and flows in soils, i.e. the soil hydraulic properties (SHP): the water retention and the hydraulic conductivity. Moreover, how environmental water fluxes are affected by those dynamics is still uncertain. Current models describing the soil-plant-atmosphere system do not account for the dynamics of soil structure and they assume constant SHP over time. Only very recently have some models been proposed on this topic, however they remain to a great extent theoretical.

A model that takes changes in soil structure into account is the Uppsala model of Soil Structure and Function (USSF) by Jarvis et al. (2024). However, the current representation of SHP in the USSF has several limitations. For example, the Brooks–Corey model cannot adequately describe the dry range of the water retention curve in clayey soils or capture the characteristic change in the conductivity slope. In addition, the macropore region is fixed, with a non–process-based structural pore size distribution. To address this, we extended the USSF ‘s matrix-SHP and macropore model and used the extended framework to simulate two contrasting agricultural management strategies as a case study: conventional tillage (CT) and no‑tillage (NT). Simulations were driven by 30 years of weather generated from a regional climate model, combined with a 5‑year crop rotation on a loamy soil under carbon‑rich management. The states simulated with the Daisy model drove the evolution of soil structure in the extended USSF model.

Keywords: soil hydraulic properties, soil structure, temporal changes