|Huggins, David - UNIVERSITY OF MINNESOTA|
Submitted to: Seasonally Frozen Soils Symposium
Publication Type: Proceedings
Publication Acceptance Date: June 12, 1997
Publication Date: N/A
Interpretive Summary: Soil freezing and thawing is thought to affect soil structure and therefore soil productivity. Freezing can also fracture soils as well as cause consolidation. The stability of pores of conventional, ridge, and no-tillage soils were enhanced after soil freezing and thawing, as evident by a 20-100% increase in permeability of soils. This suggests the development of soil structure from freezing, therefore winter processes should enhance the permeability of soils in spring. Soils may be less susceptible to runoff, but more susceptible to leaching, in the spring due to the development of freeze cracks during winter in northern climatic regions. The knowledge gained from this research can be used by farmers in northern regions in applying herbicides that are strongly bound to soils during the fall without the risk of runoff of herbicides from fields during spring.
Technical Abstract: Air permeability is intrinsically related to soil structure and is influenced in part by soil water content and porosity. This study determined the extent to which freezing and thawing affects soil structure by measuring changes in soil air permeability. Plastic pipe was used to extract 0.3 m diameter soil cores from tillage plots (moldboard plow, ridge, and none) following corn harvest in the fall of 1993. Side-wall flow between the pipe and soil core was minimized by pouring a band of rubberized asphalt between the pipe and soil. The cores were saturated and allowed to drain, after which an air permeameter was connected to the pipe for measuring air flow through the soil core before freezing and after one, five, and 10 freeze-thaw cycles. Prior to freezing, air permeability was greatest for moldboard plow (0.04 mm**2) compared to ridge tillage and no tillage (0.02 mm**2). One freeze-thaw cycle resulted in an increase in permeability for all tillage treatments, which also persisted after 10 freeze-thaw cycles. Enhanced permeability of the tillage treatments suggests that freezing and thawing can create fracture planes and pathways in soils for more rapid movement of air and water.