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. Any water from thawed snow or surface-applied manure cannot soak in and will run off. Soil ice does not thaw evenly. Cracks and openings in the ice begin to allow water to flow down into subsoil and recharge water supplies.