Submitted to: World Congress of Soil Science
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2006
Publication Date: 7/9/2006
Citation: Schwartz, R.C., Baumhardt, R.L., Evett, S.R. 2006. Monitoring tillage effects on soil water dynamics using automated time-domain reflectometry [abstract]. 18th World Congress of Soil Science. Paper No. 116-30.
Technical Abstract: 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. Methods for monitoring changes in soil water content with high resolution in time are needed to help quantify changes in soil hydraulic properties and water contents after tillage. The objective of this study was to evaluate the effects of sweep tillage on near surface soil water dynamics at a high temporal resolution. 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 .08 m using a sweep plow. The remaining plots were not tilled throughout the duration of the study. Plots were kept weed free and devoid of residue throughout the study period. Soil water contents were monitored at half-hourly intervals using time-domain reflectometry at 0.05, 0.1, 0.15, 0.2, and 0.3 m. Soil temperature was monitored at 5 minute intervals at 0.05, 0.1, 0.15, 0.2, 0.3, 0.5, and 1.0 m. Soil water contents were also monitored weekly using a neutron moisture meter to a depth of 2.3 m. Changes in soil bulk density of the surface 0.1 m were determined for soil cores extracted after significant precipitation events. During a 123 day period from April to August, tillage decreased net water storage by 10 mm (P < 0.05) at 0 to 0.3 m as compared with no-tillage. Higher water contents at 0.05 and 0.1 m under no tillage persisted throughout the summer despite greater rainfall infiltration amounts under sweep tillage (21 mm) and the absence of residues in both treatments. Water contents at soil depths below 0.15 m were not influenced by tillage. Most water depletion near the surface under sweep tillage occurred immediately after tillage and after rainfall events within ~30 d of tillage. Maximum daily net radiation of the tilled surface after DOY 203 ranged from 4 to 19% greater than the no tillage surface and these differences diminished with time after tillage. Increased soil water depletion under tillage was likely due to a change in soil hydraulic properties accompanied by enhanced vapor flow near the surface and greater absorption of radiation by a tilled surface with reduced albedo.