Winter Manure Application?

This debate is "hot enough to melt the snow"! Why is winter manure application such a big deal?

The current best management practice for manure application states "Manure should not be applied to frozen, and/or snow-covered soils except in contingency situations". This is one of the reasons behind the recommendation for 240-day storage of manure. Storage large enough to hold manure produced during the winter months, plus a little extra.

With winter application of manure (or biosolids), are we managing nutrients, or are we managing waste? Do commercial fertilizer spreaders apply nutrients in winter on snow?

The risk from winter spreading is surface runoff. When manure is applied to frozen soils, or even worse, frozen soils with a lot of snow-cover, the nutrients and the pathogens stay on the surface. Nutrients can not infiltrate the frozen soil. When the "winter thaw" occurs, (often accompanied with rain), melted snow and manure, flows over the surface to a waterway and eventually a stream or river. The result is contaminated water!!

Even on fields, where manure nutrients would not reach a stream, there is a potential risk. A high concentration of nutrients in ponded or depressional areas of field could move nutrients below the root zone and potentially to ground water sources.

The other frequently asked question - "What's the problem with spreading solid manure, it won't go anywhere?" Solid manure contains nutrients and pathogens and will mix with water; therefore the risk of surface water impacts still exists.

Do opportunities exist to apply manure in winter? During the 2000/2001 winter, with many months of a deep white landscape, there were no opportunities to winter apply manure. However, in warmer winters, there may be opportunities for manure application.

If manure can be applied and immediately incorporated, or can be injected then the risk of surface runoff is significantly reduced. My definition of incorporation would mean mixing the manure with soil to at least a 4-inch depth. Be sure to leave the soil surface rough and till across any slope to reduce erosion. Keeping back from watercourses (at least 50 feet for loam soil with some slope) is essential to further reduce risk the risk of surface water contamination. In many areas, application in winter months will not be a practical option because soils are just too wet.

The debate will continue, and regulations, when introduced, could ban winter application altogether. However, a common sense approach that considers and minimizes risk, without a ban, appears to be the best solution to the issue of winter application of manure or biosolids.

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