Submitted to: Columbia Basin Agricultural Research Annual Report
Publication Type: Experiment Station
Publication Acceptance Date: April 29, 2009
Publication Date: June 9, 2009
Citation: Wuest, S.B., Johlke, T.R., Matlock, W. 2009. Do High Velocity Water Flow Paths Develop Over Time Under No-till? Columbia Basin Agricultural Research Annual Report. Steven Petrie and Dan Long eds. Special Report 1091, Agricultural Experiment Station, Oregon State University. Technical Abstract: Water flow through soil is not uniform. Preferential flow paths, where water moves downward much faster than in the surrounding soil, are common in both tilled and untilled soil. We used a 10-min pulse of dye to mark preferential flow paths to learn more about the role of preferential flow in improving water infiltration under different tillage systems. Small cores were taken from dyed and undyed soil at 4- to 10-inch depth. Compared to bulk soil, preferential flow zones had fewer small aggregates, greater water content, and lower bulk density. Root mass and total soil carbon were not significantly different. The same relative differences were found in both tilled and untilled soil. This means infiltration rates in untilled soil were greater despite greater bulk density in both preferential flow zones and the non-preferential-flow matrix soil. These results suggest that greater water flow in untilled soil is not due to better developed preferential flow pathways, but rather to more potential pathways being well connected to the surface water source. This could have more to do with better aggregation of surface soil than with specific properties of the preferential flow paths.