Wednesday, 9 November 2005
12

Tillage Effects on near Surface Soil Water Dynamics.

Robert C. Schwartz, R. Louis Baumhardt, and Steven R. Evett. USDA-ARS, PO Drawer 10, Bushland, TX 79012

Tillage modifies the soil physical properties near the surface which in turn can influence evaporation rates and how water is redistributed within the profile during and after precipitation. The objective of this study was to evaluate the effects of sweep tillage on near surface soil water dynamics. Plots were established in a fallow field under stubble-mulch tillage management on a Pullman clay loam (Fine, mixed, superactive, thermic Torrertic Paleustolls). Half of the plots were periodically tilled to a depth of 80 mm using a sweep plow. The remaining plots were not tilled throughout the duration of the study. All plots were devoid of residue. Soil water contents were monitored using time-domain reflectometry at 0.05, 0.1, 0.15, 0.2, and 0.3 m and using a neutron moisture meter to a depth of 2.3 m. Soil temperature was also monitored at depths of 0.05, 0.1, 0.15, 0.2, and 0.3 m. Changes in soil bulk density of the surface 0.1 m were also determined for extracted soil cores. During a 135 day period in March through August, tillage decreased net water storage by 11 mm (P < 0.05) as compared with no-tillage. Tillage did not significantly influence water contents at soil depths below 0.2 m. Increased evaporation under tillage was likely a result of enhanced vapor flow near the surface and greater absorption of radiation by the surface resulting from reduced albedo.

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