One recent study found that about 30% of total white clover N, including roots and shoots, was lost over the winter, but results varied widely between years (Sturite et al., 2006 & 2007). Red clover is likely to follow similar patterns. Most aboveground biomass decomposes over the winter. Some of this N is recovered by soil microbes and some of it is lost from the field through leaching and denitrification. Root N decomposes more slowly than the shoots. Root biomass is approximately equal to shoot biomass in the first year of red clover growth.

Fall tillage of red clover will accelerate the decomposition of both roots and shoots, increasing the chances of losing N from the field. The wet springs in central New York combined with heavier soils present a difficult situation for many farmers. Waiting for the soil to dry in the spring before incorporating legume cover crops can result in late planting dates and tilling soil when it is still wet can result in lasting damage to soil structure.

The amount of N retained or lost will vary with soil texture and climate. More N is likely to be lost in winters with low snow cover, heavy early spring rains, and numerous freeze-thaw periods common with rapid temperature fluctuations. All of these conditions may become more common in the northeast as our climate warms.