Soil freeze-thaw (FT) processes can have variable impacts on mineral weathering, micro- and macroorganism survival, aggregate stability, and infiltration/percolation rates. These effects can significantly alter nutrient availability. Understanding the sources of this variability may ultimately lead to greater nutrient use efficiency. This review was conducted to identify what factor(s) may contribute to variable FT impacts on plant-available soil nutrients. Three FT cycles in a flooded soil (wetted to 200% of its field capacity) reportedly resulted in substantial release of Mn and Fe. However, three FT cycles did not alter exchangeable Mn or Fe in the same soil wetted to 80% of its field capacity. Greatest survival after FT was found for individual isolates and mixed cultures of Pseudomonas, Bacillus, and Arthrobacter when FT cycles were administered at low soil water contents. Aggregate stability was reported to decrease with increasing soil water content at freezing. Faster infiltration and percolation rates were observed in frozen soils with low water contents at the time of freezing. Thus, soil water content is a key determinant regulating FT impacts on several chemical, physical, and biological soil properties and processes altering nutrient release and transport. Practices affecting soil water content, such as tillage and crop residue management, may therefore offer opportunities for managing FT impacts on nutrient use efficiency in crop production.

C. Wayne Honeycutt
USDA-ARS
New England Plant, Soil, & Water Laboratory
University of Maine
Orono, ME  04469  USA
phone: 207-581-3363
fax: 207-866-0464
email: honeycut@maine.maine.edu