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Virginia Cooperative Extension - Knowledge for the CommonWealth

Handling dairy manure is not what it used to be

Dairy Pipeline: May 2005

Charles C. Stallings
Extension Dairy Scientist,
Nutrition and Forage Quality
(540) 231-3066 email:

The new dairy facility at Virginia Tech has a unique waste handling system that is in the process of being evaluated by Dr. Katharine Knowlton and her students. It uses solids separation to reduce the amount of nutrients being pumped to surrounding pastures and cropland. The solids are composted (under aerobic conditions) which reduces the odor potential and makes it easier to transport to off site areas. Also the liquid is aerated in a series of three tanks also reducing offensiveness. The material is then either recycled as flush water for the free stall barn or irrigated. One of the big questions that Dr. Knowlton is pursuing is how much nitrogen and phosphorus goes with the solids in the compost as compared to staying with the liquid. This can impact our nutrient management plan. A recent meeting on Dairy Manure Management (NRAES publication -176) contained a presentation by Cornell researchers (Scott F. Inglis, Curt A. Gooch, and Karl J. Czymmek). The researchers monitored four farms that had solids separation equipment in place. They found that there were differences in nutrient removal from farm to farm and even from day to day depending on the conditions. An interesting observation was that no more than 25% of the nitrogen or phosphorus was partitioned into the solids portion. As we get further into our own evaluation of the Virginia Tech system we will be able to compare our results to theirs with implications for the Virginia dairy industry as we look for ways to better distribute manure nutrients to prevent environmental problems.

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