Why We Should Include Soil Structural Dynamics of Agricultural Soils in Hydrological Models

Abstract

Surface soil structure is sensitive to natural and anthropogenic impacts that alter soil hydraulic properties (SHP). These alterations have distinct consequences on the water cycle. In this review, we summarized published findings on the quantitative effects of different agricultural management practices on SHP and the subsequent response of the water balance components. Generally, immediately after tillage, soils show a high abundance of large pores, which are temporally unstable and collapse due to environmental factors like rainfall. Nevertheless, most hydrological modeling studies consider SHP as temporally constant when predicting the flow of water and solutes in the atmosphere-plant-soil system. There have been some developments in mathematical approaches to capture the temporal dynamics of soil pore space. We applied one such pore evolution model to two datasets to evaluate its suitability to predict soil pore space dynamics after disturbance. Lack of knowledge on how dispersion of pore size distribution behaves after tillage may have led to over-estimation of some values predicted by the model. Nevertheless, we found that the model predicted the evolution of soil pore space reasonably well (r2 > 0.80 in most cases). The limiting factor to efficiently calibrate and apply such modeling tools is not in the theoretical part but rather the lack of adequate soil structural and hydrologic data.

Estimates of Tillage and Rainfall Effects on Unsaturated Hydraulic Conductivity in a Small Central European Agricultural Catchment

“…A similar conclusion was presented by Moret and Arrue [54] who observed a significant impact of tillage on soil hydrophysical properties in both short-term and seasonal scales, which outweighed the effects of spatial variability. The main driver of K h0 temporal variability on the tilled soil studied is attributed to the actual state of the topsoil structure; namely the macropores, mesopores and large inter-aggregate void proportion and connectivity changes, as also suggested by, for example, [10,41,55,56]. Additional explanations for the increase of the hydraulically active pores during the season are biological activity, carbon content, root growth, and wetting/drying cycles [57].…”

SPorDyn: A Python code for modeling the evolution of soil pore size distribution after tillage

“…rainfall). The need for inclusion of soil pore dynamics in hydrological models to improve their reliability and accuracy has been stressed in recent times [[1], [2], [3]]. In this context, Or et al [4] proposed to use a partial differential equation (PDE) known as the Fokker-Planck Equation to capture the dynamics of soil pore size distribution (PSD) following tillage with respect to time and pore radius.…”

Special Issue “Soil Hydrology in Agriculture”

“…The main outcome was that the temporal k(h) variability was higher than the spatial variability. Similarly, the study by Chandrasekhar et al [14] reviewed the quantitative effects of different agricultural management practices on SHP and the subsequent response of the water balance components. With the objective of overcoming the limitations of using SHP constant over time, they applied a pore evolution model to two datasets to evaluate its suitability to predict soil pore space dynamics after disturbance.…”