UTILIZING MILK AS A FERTILIZER SOURCE

In the depths of the COVID-19 pandemic and with people across the country sheltering in place, there have been some disruptions to our supply chain, from toilet paper to food products. Dairy producers have been hit especially hard, as milk destined for schools and restaurants suddenly had no place to go. Some farms received notices from their milk processing plants to slow production or to dispose of (dump) milk.

In an attempt to salvage some value from dumped milk, the University of Wisconsin-Madison Division of Extension released some fact sheets with options for using this product. In one fact sheet, Carrie Laboski, Jamie Patton, and Kevin Shelly from the Nutrient and Pest Management Program discussed landspreading milk or milk and manure mixtures.

They shared that, on average, 1,000 gallons of milk contains 46 pounds of nitrogen (N), 26 pounds of phosphorus (P 2 O 5 ), and 17 pounds of potassium (K 2 O). When compared to liquid dairy manure, milk has six times more available N, nine times more available P 2 O 5 , and one and a half times more available K 2 O. Additionally, milk has a biochemical oxygen demand (BOD) around five times greater than dairy slurry.

Consult your nutrient management plan to identify fields where milk can be applied safely. Choose fields with a low risk of nutrient loss through leaching, runoff, and erosion, and apply as close as possible to when crop nutrient uptake will occur. Avoid spreading on fields with sandy or loamy sand soil textures or soils shallow to bedrock. Steer clear of fields with tile drainage or those near streams, rivers, lakes, wetlands, drainage ditches, or wells.

Once the proper fields are selected, apply milk uniformly across a field utilizing liquid manure equipment. When possible, the milk should be shallow-injected or incorporated to reduce the runoff risk and mitigate odors. More guidelines for application and recommendations for specific crops can be found in the fact sheet, which is available at https://bit.ly/JNM-milk-manure-mix.

The authors also noted that if milk is added to a manure storage structure, it may raise the effluent’s nutrient concentration, which would require an adjustment of nutrient crediting in a nutrient management plan. They said a sample should be collected and analyzed before application.