Skip to main content
ARS Home » Pacific West Area » Pullman, Washington » Northwest Sustainable Agroecosystems Research » Research » Publications at this Location » Publication #160081
Title: FREEZE-THAW AND WATER TENSION EFFECTS ON SOIL DETACHMENT

Author
item VAN KLAVEREN, R - Retired Non ARS Employee
item McCool, Donald

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2010
Publication Date: 5/21/2010
Citation: Van Klaveren, R.W., McCool, D.K. 2010. FREEZE-THAW AND WATER TENSION EFFECTS ON SOIL DETACHMENT. Soil Sci. Soc. Am. J. 74:1327–1338; doi:10.2136/sssaj2009.0360

Interpretive Summary: Many cropland areas of the northern and intermountain United States and southern Canada experience severe soil erosion if rains fall or snow melts when there is a layer of saturated thawed soil above a layer of impermeable frozen soil. Soil is particularly vulnerable to erosion under these conditions because of the lower binding forces of the thawed layer and the lack of infiltration into the frozen layer. Conventional-tillage seeding of fall-seeded small grain has been the cause of much of the historical soil erosion in the Inland Pacific Northwest. Devising sustainable land use and crop management practices for this area is difficult because fall-seeded crops are generally needed in the rotation for weed and disease management. Predictive erosion models need to mimic and describe the effect of soil freezing and thawing on this winter erosion problem in order to help producers, consultants, government agencies and others select sustainable practices. Our study was designed to determine erodibility parameters for the effect of a thawed layer on soil detachment. A test flume was designed to allow near-natural freezing and thawing of a typical cropland soil and to apply flowing water to the thawed soil. Soil was saturated and drained to selected depths and frozen from the surface, duplicating natural conditions. The soil was then completely thawed. Erosion resistance was related to the depth to the water table in the test flume. Results indicated the higher the water table, the lower the resistance to erosion. At our highest water table, the water flow rate at which detachment began was about 60% of that found for a similar soil tested without freezing. The erodibility relationships developed from this study will become part of decision support models that are used by consultants and government agencies assisting producers to evaluate sustainable crop rotation and management strategies, and will result in reduced soil erosion, lower costs to maintain road systems in rural areas, and improved water quality in streams and lakes.

Technical Abstract: Many areas of the northern United States and southern Canada, and particularly the four million ha of non-irrigated cropland in eastern Oregon and Washington, northern and southern Idaho, and northern Utah, experience severe water erosion under thawing soil conditions. Modeling soil erosion in these areas with process-based continuous simulation models such WEPP is hampered by lack of knowledge of the relation of soil properties and moisture conditions to erosion resistance of thawing soils. Our study was conducted to determine hydraulic and erodibility parameters of a silt loam soil frozen and thawed under controlled moisture tension. A tilting flume was designed and constructed to allow near-natural freezing and thawing of a soil mass by surface radiation to a cold body, and to apply shear stress from flowing water to the thawed soil. Flow tests were conducted for 90 min under soil moisture tensions of 50, 150, and 450 mm. A linear relationship was found between detachment and applied shear stress at a given time and moisture tension. Critical shear stress values showed little change with time. Rill erodibility decreased with increased soil moisture tension but changed more rapidly during the course of tests at the lower (50- and 150-mm) tensions. At 50-mm tension, the time-average erodibility, 689 g N-1 min-1, was about the same, and the critical shear value, 1.53 N m-2, about 60% of that found in tests of a similar Palouse silt loam soil tested under 50-mm tension without freezing. This study adds to the body of knowledge that indicates the transient nature of rill erodibility during soil freezing and thawing, including the effect of soil water tension, should be considered in order to improve the accuracy of continuous simulation erosion models for winter conditions.