Deep-rooted perennials and vertical hydrological connectivity: Mitigating cropland waterlogging and enhancing resilience to extreme rainfall

To study the effects of annual cropland conversion to perennial forage cropland on infiltration rates and water dynamics, we conducted infiltration tests in August 2024 across the three treatments. A total cumulative infiltration of 1,000 mm was applied in each test using a single-ring infiltrometer, with three replicate measurements per treatment. The infiltrometer, with a diameter of 35 cm, was inserted vertically into the soil to a depth of 10 cm after removing surface vegetation and litter. Tests were conducted on flat, representative areas, and care was taken to ensure the ring remained level. Tap water was added in increments of 50 mm (4.81 L per addition), and the time required for each increment to infiltrate was recorded. Each test was concluded once cumulative infiltration reached 1,000 mm, from which the total infiltration time (IT) was determined. After the infiltration experiments concluded (cumulative infiltration = 1000 mm), the ring was removed and the area immediately covered with a shade net to minimize evaporation and allow water redistribution within the soil profile. Samples for soil water content were collected 24 hours later, a standard interval that permits redistribution of the infiltrated water while minimizing evaporative losses and deep percolation beyond the target profile (Dane and Hopmans, 2002). Samples were collected at the center of the infiltration test point with a 4-cm-diameter soil auger at 10-cm intervals down to 400 cm. To determine initial soil water content, the same procedure was applied prior to infiltration, with samples collected 3 m from the infiltration test point. Gravimetric water content (g g-1) was then obtained in the laboratory using the standard oven-drying method (105°C for 24 hours). One week after the infiltration experiments, a vertical soil profile was excavated along the centerline of the infiltration point and soil samples were collected at 10-cm intervals from 0 to 100 cm. At each depth interval, two adjacent samples were collected: one for assessing root distribution and the other for soil physical and hydraulic properties. Root distribution was obtained following Bohm (1979). Soil monoliths (10 x 15 x 15 cm) were carefully excavated from each depth interval. Cylinders weights were subtracted from the measurements. These values were then used to calculate dry bulk density (BD), total porosity (TP), capillary porosity (CP), and non-capillary porosity (NCP) were calculated.