What does a freeze and thaw really do?
As I look out the window at the outside landscape, I see snow falling. It is a reminder that here in the Midwest, we have seasons. Have you thought about if the freeze and thaw is beneficial to the soil in your fields? What is this actually doing and is it beneficial both short-term and long-term?
What is Soil Compaction?
As farm machinery continues to get bigger and as the timing for field work like planting and harvest becomes more variable, compaction becomes an issue. Soil compaction is when the soil particles are pressed together, reducing the amount of pore space in soil. Compaction prevents water from moving through the soil and oxygen from moving in. It reduces the volume of roots that penetrate the soil and is a less than ideal environment for the soil biology. Bottom line, it has a huge effect on soil quality as well as decreasing desired production.
Freeze and Thaw
The freeze and thaw cycles of winter are very beneficial. The soil is composed of 50% solids (45% mineral and 5% organic matter). The other 50% is pore space made up of roughly 25% water and 25% air. The frost line will creep lower in the soil as the number of consecutive below freezing days continues. Many Midwest winters can see a freeze depth of 12+ inches, depending on the winter temperatures. The plumbing folks have figured out the maximum frost depth in your area because busted underground water lines are just no fun.
The upper 2-6 inches will have multiple freeze and thaws depending on the cycle of temperatures as well as snow cover. As the water in the pore space freezes, it expands and moves the soil up. Then as it thaws, the soil will shrink, helping to reduce the impacts of soil compaction. Because multiple freeze and thaws normally happen in the upper 2-6 inches, there may still be compaction deeper in the soil. This is when a deep ripper or even cover crops can be a good way to eliminate compaction.
So sit back, enjoy your cup of coffee. If you are wondering what in the world is going on out there, your field is going through a natural cycle. And this process is much needed to reduce soil compaction and make your field more productive.