Potential for Reducing Nutrient Loads from the Dairy Industry in the Chesapeake Bay Watershed

A number of tributaries of the Chesapeake Bay have a large number of dairy herds. Most of the dairy production is in the Susquehanna River, Shenandoah River and Potomac River tributaries. Typical manure handling methods in the watershed today are daily spread, solid manure handling with bedding and storage, scrape and storage in a tank or basin and a lagoon and flush system. New manure management technology needs to be adopted by the dairy industry to meet the new tributary strategies. Solids separation has the potential for reducing nutrients. The separated solids can be composted and be used for bedding or sold. Solids separation has the potential to remove 30% to 50% of the N and P from the manure stream. Anaerobic digestion has promise for large dairy farms in the future. Studies have shown with 800 or more cows make anaerobic digestion economically feasible. Composting is an established on farm manure practice that could be used by small or large farms. There is a need to implement it on a wide basis in the watershed. Sequencing batch reactors and integrated manure systems also have the potential for reducing nutrients and have been tested on a number of farms. Manipulating N and P in feed has the potential for reducing nutrient excretion. Using multiple strategies to improve nutrient utilization, N and P feeding could be reduced by 30 to 40%.