UNIVERSITY PARK, Pa. — In response to a sharp reduction in the demand for milk due to the COVID-19 outbreak, which has disrupted supply chains, the Pennsylvania Department of Environmental Protection has issued emergency guidance that allows dairy farmers to discharge milk on their land.
The temporary permission, which expires June 1, relaxes policies that limit the application of milk to cropland and pastures. The guidance recognizes that dairy producers are facing a very difficult situation — markets for their milk have dried up and their cows keep making milk, according to Robert Meinen, senior extension associate in Penn State's College of Agricultural Sciences, specializing in nutrient and manure management.
“The idea of applying milk to the ground is heartbreaking for both farmers and the public,” said Meinen. “We hope this situation doesn’t last long, that demand for dairy products picks up and supply chain interruptions are resolved quickly. Until then, this emergency guidance allows dairy farmers to do what is necessary to help their businesses survive.”
Dairy farmers who apply milk to land have many things to consider and should devise the best strategy for farmlands they own or access, Meinen noted. A good first step is to review the DEP guidance at this website, which provides a comprehensive review of both policy and practical considerations for the land application of milk.
Milk is considered a pollutant if it reaches waterways due to its highly soluble nitrogen and phosphorus content, and it creates a high biological oxygen demand, so the guidance reinforces caution when land application is necessary, Meinen said. “Preferably, milk is mixed with liquid manure before land application; however, this is not practical for some farms that have neither liquid manure storages nor liquid manure spreaders.”
Meinen cited a useful table in the guidance that provides maximum application rates of manure-milk mixtures based on the percentage of each component, with a maximum application range from 4,500 gallons per acre for milk that is not mixed with manure, to 9,000 gallons per acre for a mixture that is 90% manure and 10% milk.
“The rates provided in the table may need to be adjusted in conjunction with the farm’s nutrient- or manure-management plan to assure nutrient overapplication does not occur,” he said.
If applying straight milk, dairy producers should consider using a low rate over more acres and then supplementing the crop with a second application of manure, Meinen suggested. This will supply nitrogen and phosphorus in organic forms that can provide nutrient availability through the growing season.
Farms must follow plans that provide application rates and setback restrictions from streams, lakes, ponds and water wells. Keeping records of milk and manure volumes associated with application, as well as the dates of application, is required by the state.
Careful selection of the location for milk or manure-milk mixture application is critical, Meinen said, adding that a balance between the agronomic benefits and environmental impact should be struck. The fertilizer value of milk is high, with 1,000 gallons containing about 44 pounds of nitrogen, 18 pounds of phosphorus and 15 pounds of potassium.
It’s best to play it safe and apply the material where runoff risk is low, Meinen advises. Consider the conservation measures and soil characteristics of a field — an established, growing crop will provide ground cover, and the plants will utilize nutrients readily. He urges producers who need to land-apply milk to consider locations with shallow slopes that are not near surface waters and water wells. Avoid applications prior to large predicted precipitation events.
Dairy producers also should consider their neighbors, Meinen stressed.
“Degradation of milk in a manure storage or in a field is expected to create offensive odors and enhance fly populations,” he said. “Applying downwind from neighbors may help a farm to maintain good community relations. If the material is particularly odorous, consider injection or conservation tillage to help liquids get below the soil surface to limit odor emission.”