ARS | Publication request: VISUAL ASSESSMENT OF PREFERENTIAL FLOW AND COMPARISON TO PONDED INFILTRATION RATES IN A SILT LOAM SOIL

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2004
Publication Date: November 3, 2004
Citation: Wuest, S.B. 2004. Visual assessment of preferential flow and comparison to ponded infiltration rates in a silt loam soil. ASA-CSSA-SSSA-CSSS Annual Meetings Abstracts 2004. (3 Nov. 04, Seattle, WA) Abstract no. 4478 ASA, Madison, WI. (CD-ROM)

Technical Abstract: Certain soil management practices produce much higher water infiltration capacities than others in silt loam soils of the Pacific Northwest. Understanding the relative role of preferential flow through surface-connected pores versus increased soil aggregation will aid in deciding whether low soil disturbance is more or less a factor than surface residue accumulation. Infiltration measurements were made in the field using 20, 30, and 47 cm diameter cylinders driven to a 25 cm depth. After measuring steady-state ponded infiltration, concentrated blue dye (FD&C Blue 1) was added to the water ponded above the soil surface for a period of 10 minutes, and then all free water removed with a suction device. Eighteen to 24 hours later we took photos of cross sections at 5-cm depth increments. Preliminary examination of the photos indicates that 1) flow along the cylinder wall was rarely a problem 2) dye-stained soil was often concentrated under growing wheat plants 3) high infiltration found in no-till plots was associated with a large amount of stained soil area and deep movement of dye. Ring size caused a bias in infiltration rate measurements, with larger rings producing both greater mean and standard deviation. This indicates that the largest ring was not measuring the average of multiple representative elementary volumes. A potential explanation is that lateral connections restricted by smaller rings are important for preferential flow.