Short-term manure stockpiles in fields are one opportunity for some farms to expand their manure storage capabilities and reduce hauling time in the spring. One concern, though, is the leaching of nutrients into the soil.
A study done by Utah State University researchers examined stockpiles placed in November, January, and March over a five-year time period. Their results were presented in a poster at the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and Soil Science Society of America (SSSA) International Annual Meeting last November.
Solid manure samples were collected as the stockpiles were created, and then again when the manure was removed for land application. The samples were tested for phosphorus, ammonium nitrogen, and nitrate nitrogen. Leachate was collected biweekly under the manure staging areas and was analyzed for ammonium nitrogen and nitrate nitrogen. Soil samples were also taken prior to manure placement and after removal.
Two types of manure were studied — dairy manure with straw and dairy manure without straw. It was found that manure stockpiles containing straw produced less leachate than stockpiles without straw.
As far as timing, significant leachate was produced under the stockpiles placed in the winter months (January and March). The preliminary results showed that the November application produced the least leachate and the lowest total nitrogen loss. Because of Utah’s dry climate, the manure may have dried out in the late fall months, enabling it to absorb more moisture.
Piles placed in January produced the most leachate and had more total nitrogen loss. Snow and snowmelt likely contributed to this.
This article appeared in the February 2020 issue of Journal of Nutrient Management on page 15.
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