Most of this carbon is released from the roots as CO2. Both surface residue and the irregular surface left by rough fall tillage protect the soil from winter wind erosion and spring water erosion. A January thaw affects the structure of the top inch or so of soil. Bare soils warm more quickly than residue-covered soils. In late fall nitrate leaching increases as plant uptake and microbial activity decline.
Few changes occur in nutrients during the winter.
Freezing temperatures prevent biological and chemical activity, or water movement. Microbes and plants are not active and using nitrate, so soil nitrate is prone to leaching in early spring. Cool temperatures prevent denitrification losses. If an early heavy snow insulates the soil, the ground may not freeze deeply. Surface soil may freeze and thaw several times each winter, but subsoil only freezes once.