Cover crop effects on soil moisture dynamics & thermal properties

Abstract

The climate change induced weather uncertainty has increased the environmental extremes such as severe droughts and floods affecting volumetric soil moisture content (θ), thus food security. It also has increased the weather uncertainty, such as colder winters and hotter summers with increased diurnal temperature differences. Atmospheric temperatures play a major role in the determination of soil temperature, where increased variability can affect plant growth, development, and crop yield. Although CC can affect soil moisture dynamics and soil thermal properties, they are among the least studied areas related to CC. The objectives of this study were to evaluate the CC and tillage effects on the soil moisture dynamics and soil thermal properties of a corn (Zea mays L.) cropping system. The study was conducted at the Elsberry Plant Material Center - USDA, Missouri, USA, with 1) no-till cover crop (NC), 2) conventional till no cover crop (CN), and 3) no-till no cover crop (NN) treatments. A three species CC mixture including cereal rye (Secale cereal L.), crimson clover (Trifolium incarnatum L.), and daikon radish (Raphanus sativus L. var. Longipinnatus) was established in the NC treatment in 2019 (first CC establishment). Spectrum Technologies Water Scout SM100 soil moisture sensors were installed at 5-, 10-, 20- and 40-cm soil depths to monitor changes in volumetric soil moisture content (θ) in 15 min intervals throughout the study period, and a soil moisture calibration was conducted to adjust sensor readings. Numerically and significantly higher θ values were observed in the CN treatment than NC and NN at first three depths during most of the study period. The NC treatment maintained higher θ than NN at all the studied depths during different growing periods, which were significant during some weeks. For the soil thermal study, a fourth treatment, grass (G) was used other than NC, CN, and NN, which was under side oats gramma (Bouteloua curtipendula (Michx.) Torr.). Soil core samples (7.6 cm diameter, 7.6 cm long) were collected in April 2021 for the soil thermal study from 0-40 cm depth at 10-cm increments (96 samples) and analyzed for soil heat capacity (Cv), soil thermal conductivity (λ), soil thermal diffusivity ([alpha]), soil organic carbon (SOC), bulk density (BD), and θ. As per the results in soil thermal study, NC did not significantly improve SOC, BD, or soil thermal properties, as the biomass accumulation by CC was not enough due to the lack of CC duration. According to the results, it can be speculated that long-term use of CC might improve soil moisture dynamics and soil thermal properties of corn cropping systems through improved soil organic matter and reduced BD and would be a viable solution in soil moisture conservation, reducing stress conditions to plants and soil microbiota through reducing soil heat flux.