Long-Term Impact of Cover Crop and Reduced Disturbance Tillage on Soil Pore Size and Soil Water Storage

Abstract. Using laboratory measurements and numerical simulations, we studied the long-term impact of contrasting tillage and cover cropping systems on soil structure and soil hydraulic properties. Complete water retention and conductivity curves for top (0–5 cm) and subsurface (20–25 cm) samples were characterized and contrasted. Plot-level properties of water storage and retention were evaluated using numerical simulations in HYDRUS-2D software. Soils under no-till (NT) and cover cropping (CC) systems showed an improved soil structure in terms of pore size distribution (PSD) and the hydraulic conductivity (K) under these systems led to increased infiltration rate and water retention. The conventional measurement of water content at field capacity (water content at −33 kPa suction) and the associated plant available water (PAW) showed that NT and CC plots had lower water content at field capacity and lower PAW compared to standard-till (ST) and plots without cover crop (NO). The numerical simulations, however, showed that NT and CC plots have higher profile-level water storage (albeit marginal in magnitude) and water availability following irrigation. Because the numerical simulations consider retention and conductivity functions simultaneously and dynamically through time, they allow the capture of hydraulic properties that are arguably more relevant to crops. The changes in PSD, water conductivity, and water storage associated with NT and CC systems observed in this study suggest that these systems are beneficial to general soil health and improve water retention at the plot scale.