Crop rotations influence soil hydraulic and physical quality under no-till on the Canadian prairies

Cropping system sustainability is dependent on the conservation of soil hydraulic and physical quality over time. This study examined the effects of crop rotations on soil hydraulic and physical quality on the Canadian prairies, emphasizing choices of crop species and sequence to preserve or improve soil quality under no-till management. Field experiments were initiated in spring 2018 at three sites: Lethbridge (Alberta), and Swift Current and Scott (Saskatchewan) to evaluate six crop rotations, consisting of (i) conventional (control), (ii) pulse/oilseed intensified, (iii) diversified, (iv) market-driven, (v) high-risk and high-reward, and (vi) soil health-enhanced. Undisturbed soil cores were collected from 5-10 and 15-20 cm soil depth increments in 2021 after crop harvest, to determine bulk density (BD), total (TP) and effective porosity (EP), pore size distribution, soil water retention, and unsaturated hydraulic conductivity. Results revealed that crop rotations did not significantly impact BD, TP, or EP in the 5-10 and 15-20 cm soil depth increments across the three sites. Depending on the site and soil layer, the pulse/oilseed intensified, diversified, high-risk and high-reward, and soil health-enhanced rotations improved macroporosity by 13-127% and mesoporosity by 1-36% compared to the conventional rotation, resulting in concomitant increases in large and medium unsaturated hydraulic conductivities. At Lethbridge, both conventional and high-risk and high-reward rotations resulted in increased water content at field capacity (FC) by 12-14%, permanent wilting point (PWP) by 7-12%, and plant available water capacity (PAWC) by 16-17%, accompanied by significant increases in microporosity (8%) and residual porosity (16%) in the 5-10 cm depth compared to the soil health-enhanced rotation. However, no significant differences were found at Swift Current or Scott in the 5-10 cm depth. The pulse/oilseed intensified rotation significantly improved FC by 22% and PAWC by 19% compared to the market-driven rotation. This rotation also showed an 18% increase in FC and a 32% increase in PWP when compared to the diversified rotation at Scott in the 15-20 cm depth, but did not differ significantly at Lethbridge or Swift Current. Overall, crop rotations with legumes and increased functional diversity have the potential to improve soil physical quality and plant available water but may require a period longer than the present study's duration to become evident.