Biological Processes: Relationships Between Earthworms and Soil Temperature

Soil fauna play important roles in many soil processes and conditions which relate to agricultural systems. Earthworms are credited with enhancing soil fertility and soil physical properties by their feeding and burrowing activities. Most research on earthworms has focused on the warmer seasons of the year and relatively little is known about earthworm activity and survival during the portion of the year with frozen soils. Earthworms may survive winter by acclimatization, aestivation, or by burrowing to deeper depths where the soil is not frozen. More research is needed on the fate of earthworms in frozen soils. Suggested research areas include: 1) studies designed to determine the effects of freezing temperatures on the survival and behavior of earthworms, 2) studies to determine the effect of freezing and freeze-thaw cycles on the structure and stability of earthworm burrows, and 3) studies to determine the effect of freezing and thawing on the physical integrity of the burrow linings and cast materials

Frozen Soils: A Perspective On Past And Future Research For Promoting Sustainable Agricultural Systems

Frozen soils impact many industries which rely· on soil, water, and .air resources in developing and manufacturing products. Most noteworthy is the agricultural industry in the northern United States where soils, which sustain food and fiber production, are subjected to frequent freezing and thawing. Soil freezing and thawing influences soil erodibility, surface and ground water quality, air quality, and biological activity. Many strides toward understanding frozen soil processes and managing lands to minimize the adverse effects of freezing and thawing have been made over the last two decades. Yet, further efforts to identify frozen soil processes which influence wind and water erosion, soil faunal adaptation, soil quality, movement of agricultural chemicals,· and rural and urban water supplies will aid industry and society in meeting future needs for food and water

Studies on Freezing and Thawing Soils in Iowa

Frozen soils have a major influence on the cropping systems and farming practices in northern states. However, relatively little research has been done on the physical, chemical, and biological processes that occur in the field during the non-growing season. Experiments on frozen soils were started recently in Iowa to 1) study the effects of residue cover on soil freezing and thawing, 2) measure the movement of water and solutes and changes in soil structure due to freezing and thawing of repacked soil columns in the field, 3) test the SHAW (Simultaneous Heat And Water) model for its capability to predict freeze/thaw cycles, and 4) determine the effect of freeze/thaw and wetting/drying cycles on soil cracking. Residue cover changed freeze/thaw rates and frost depth. Water moved to the freezing front which resulted in a net upward movement after thawing. Solute movement was more complex because of its movement with water, its exclusion from water during freezing, and its redistribution during and after thawing. The SHAW model provided reasonable agreement with measured frost depth during the winter of 1993-1994. These studies are continuing and will aid in the development of management practices to protect our soil resources while sustaining a productive agriculture

Freezing and Thawing of Agricultural Soils: Implications for Soil, Water, and Air Quality

Most agricultural lands in the USA are subject to subfreezing temperatures. Soil freezing and thawing affects both biotic and abiotic interactions and processes which vary with weather, soil type, land management, and topography. Soil fauna generally undergo physiological changes or rely on locomotion as a means of adapting to frozen soils. Managing faunal populations using soil management may be achievable with a better understanding of winter ecological processes. Many of the thermal, hydraulic, mechanical, and physical properties of soils are altered by freezing and thawing. Soil erosion may be accentuated by soil freezing and thawing as a result of changes in aggregate stability and shear strength. Soil processes such as heat, water, solute, and gas flux are affected by the freezing process, although simulation of solute and gas flux in frozen soils is not well documented. Solute and gas flux affect water and air quality owing to the loss of chemicals to surface and ground water systems and gaseous emissions to the atmosphere, respectively. Information about biotic and abiotic characteristics of frozen soils, presented at a national workshop in March 1994 in Minnesota, aids in the development of sound management strategies for agricultural lands to preserve our soil, water, and air resource