Soil-Water Storage As a Function of Tillage and Crop-Rotation Practices in Dryland Agriculture.

Soil moisture content and storage varies spatially across a landscape, affecting yields of dry-land crops.  Common methods for measuring soil moisture disturb the soil and do not adequately represent large areas with varying topography.  We estimated soil-water content using electromagnetic induction (EMI) comparing a commonly used form of conservation tillage (chisel plow) and no-till as well as three phases of a crop rotation (winter wheat, spring cereal, legume) on a split-plot design.  Weekly measurements of electrical conductivity obtained using EMI were converted to water contents using a calibrated relationship including variables such as soil texture, solute concentration, and temperature.  Solute concentration and temperature were routinely measured within each crop to account for variance through the growing season.  Current tables for determining water retention of crops for the following season do not specify the type of tillage the crop was grown under.  Since winter wheat has higher water retention for the following year and a no-till system has increased water in the vadose zone, winter wheat grown under no-till is expected to have the highest water retention for the following year’s crop.  Spring wheat grown under conventional tillage is expected to show the least water retained for the following year’s crop.  The spatial and temporal maps of moisture content will provide a comprehensive view of the amount, location, and timing of plant-available water as a function of agronomic management practices.