ARS | Publication request: Temporal variability of soil water and bulk density at selected field sites

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2012
Publication Date: May 2, 2012
Citation: Logsdon, S.D. 2012. Temporal variability of soil water and bulk density at selected field sites. Soil Science. 177(5):327-331.

Interpretive Summary: Soil that is too dense impedes root growth, infiltration of water, and movement of air through the soil. This study showed that deep freeze (greater than three feet) over winter with more than one freeze-thaw cycle resulted in significantly less dense soil in the spring, but the soil returned to pre-freeze density after spring field operations. Shallow, incomplete freezing over winter resulted in soil that was more dense in the spring. The variation in soil density was greater between locations on a given sampling date than between sampling dates for a given location. Although the soil density varied, the density was not too high to impede crop growth. This study is important for land managers and their advisors concerning the timing of field operations, and whether or not fall tillage is really beneficial in the long term. This research is also of interest to scientists who want to determine the mechanisms of soil density changes.

Technical Abstract: Bulk densities may change in response to management and weather conditions. The purpose of this study was to document soil bulk density changes in an agricultural field (~79 km2) and relate to soil, weather, and field operations. Volumetric samples were taken to 0.3 m depth and subdivided into 0.1 m increments. Samples were taken at 15 sites on 29 dates over four years. Bulk density increased significantly at all three depths between October 7, 2007, and April 25, 2008, due to tillage and freeze-thaw action. The bulk density also increased to 0.2 m depth between April 25, 2008, and July 3, 2008, due to field operations when the soil was wet. Overall, the variation in bulk density due to particle size class (spatial variation) was greater than that due to timing of field operations or climate conditions (temporal variation). Timing issues significantly affected only the 0 to 0.1 m depth. Even though density varied over time, the bulk densities were not extreme enough to negatively impact crop growth.