Quantifying water dynamics in a no-till vs. conventional-till corn field in the Mississippi Delta

Author(s): Anapalli, S.; Fisher, D.; Reddy, K.; Sui, R.; Gowda, P.

Conventional-till (CT) cropping system reportedly conserve less soil water compared with no-till (NT) soil-residue management. Reductions in evapotranspiration (ET) and runoff (RO) result in increasing infiltration rates of precipitation and irrigation water inputs; however, location-specific benefits from such systems vary with soil texture and presence or absence of restrictions to water movement such as hard pans in the soil profile. One of the primary benefits of NT over CT comes from its potentially decreasing the ET loss of water from the system. Also of importance is the amount of water infiltrated into the soil and available for crop uptake, and how much water is percolated beyond the root zone of the crop contributing to ground water re-charge as this ground water is the main irrigation water source in the region for crop production. Limited research on ET and soil water dynamics beyond the crop root zone in these cropping systems in the Mississippi Delta region preclude farmer tillage recommendations in cropping systems, especially under corn, a relatively new crop in the region. To fill this gap, we embarked on a research program to monitor ET and soil water dynamics along with crop growth physiology changes in corn under NT and CT in a Dundee silt loam soil at Stoneville, MS. The ET estimation is by solving an energy balance equation representing a crop canopy-land surface for latent heat flux from estimates of sensible, soil heat, and net radiation fluxes. Soil heat flux was quantified from measurements of heat flux using a soil heat flux plate installed at a depth of 8 cm and soil temperature and moisture measurements above the plate. The sensible heat was quantified by modeling aerodynamic and boundary layer resistance corrected for atmospheric stability and wind speed effects from measurements of net radiation, air temperature and relative humidity, land surface-canopy temperature, and wind speed at a constant height of 1 m above the crop canopy, and similar data from a nearby eddy-covriance station. We have tested the ET algorithm developed, with simulataneous measurements of ET using a field lysimeter (3X3X2.4m) and energy balance in the center of a 4.4 ha cotton field at Bushland, TX, and found good agreement between the two estimates.

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