Impacts of Cover Crops and Compacted Soils on Water Table Response Dynamics in an Agricultural Setting

ABSTRACT

Water table dynamics play a crucial role in the hydrologic cycle, impacting dominant runoff generation mechanisms, root zone soil moisture conditions, surface water‐groundwater connectivity and more. In agricultural settings, they impact crop production but may vary significantly in space. The duration and frequency with which water tables occupy certain soil depths may provide key information to define ‘optimality’ in water table depth (WTD) for soil hydrology and agricultural productivity. However, very few studies have focused on quantifying those variables, or on how water table fluctuations may change under different management practices and soil conditions at different temporal scales. This study sought to characterise water table fluctuations over the growing season and during rainfall events, with a focus on water table occupancy of key soil depth zones from plots under different management treatments. Nine plots were established in an agricultural field in Elora, ON, Canada: three control, three planted with cover crops and three with compacted soil. High‐frequency WTD monitoring was conducted on each plot through shallow groundwater wells equipped with loggers, and precipitation data were collected from a nearby weather station, from spring to autumn in 2021 and 2022. Data were used to determine the duration and frequency of water table occupancy in key depth zones and to assess water table responses to precipitation events. Results showed that water tables under cover cropped plots reached shallower depth zones and responded the most frequently to rainfall events, while compacted plots behaved similarly to control plots. However, the timing and magnitude of water table responses to rainfall events were not significantly different between treatments. These findings provide insights on influences (or lack thereof) of different agricultural practices or soil conditions on water table dynamics, which may be useful to farmers and/or policy makers.