OVER WINTER STABILITY OF MACROPORES IN THE NORTHERN US CORN BELT

Authors: MCINTOSH, GORDON - UNIVERSITY OF MINNESOTA; Sharratt, Brenton

Submitted to: Soil Erosion for 21st Century Symposium
Publication Type: Proceedings
Publication Acceptance Date: 9/27/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Water and chemical movement through soils can be greatly enhanced in the presence of macropores. The stability of these macropores in the natural environment is largely unknown. We found that macropores, of various sizes, generally degraded during the winter. The structure of the macropore near the soil surface collapsed, presumably from soil slaking during freezing and thawing. The collapse of macropores during winter would diminish the movement of water and chemicals through soils and thereby enhance runoff in spring. The results of this research will be used to develop management practices that will stabilize macropores during winter and thereby curtail runoff and improve water quality.

Technical Abstract: Macropores created by biological or physical processes can profoundly influence water movement through the soil. In cold regions, macropores are subject to wetting/drying and freezing/thawing. Little is known concerning the over winter stability of macropores. This study investigated changes in the physical dimensions of macropores from autumn to spring in the northern nU.S. Corn Belt. Macropores 30 cm deep having diameters of 5, 10, and 15 mm were created in a Barnes loam soil. Approximately 50% and 15% of the 5 and 10 mm pores, respectively, had filled in at the surface between creation and freeze-up in the fall. After snowmelt in the spring, all 5 and 10 mm pores and more than 95% of the 15 mm pores were filled with soil at the surface. This study suggests that macropores are not stable during winter. These changes will likely impact water and chemical movement through soil.