Agronomics of Spilt Milk – DTN

    Manure application equipment. Photo: Ohio State University

    With milk prices plunging lower and demand for dairy products declining because of the COVID-19 pandemic, some dairy processors do not have the storage capacity to take delivery of milk. As a result, some farms have been forced to dump milk into their manure storage facilities.

    There are several different agronomic concerns that need to be addressed when milk is applied to soil and plants. In addition, environmental regulations need to be followed when applying milk.


    In a webinar titled “Considerations for Landspreading Milk” on April 7, Carrie Laboski, University of Wisconsin Extension soil scientist, said much like applying too much fertilizer, too much milk applied to soil can lead to water quality concerns. While there are positives for applying milk, there are also some negative consequences of milk being applied to soil, she said.

    Milk contains bacteria that breaks down microbes in water and uses up the oxygen. This would affect water habitat and lead to fish kills if the milk is not applied correctly, she said.

    Research has shown that bacteria can consume all the oxygen in 1,600 gallons of water when just 1 pint of milk is added, Laboski said.

    Laboski said milk has about six times the amount of available nitrogen (N) compared to liquid dairy manure with less than 4% dry matter and nine times the phosphorus (P). Milk has 46 lbs per 1,000 gallons of N, 26 lbs/1,000 gallons of P and 17 lbs/1,000 gallons of potash (K) while liquid dairy manure typically has 7 lbs/1,000 gallons of N, 3 lbs/1,000 gallons of P and 11 lbs/gallons of K.

    The nutrients in straight milk are also 100% available to plants, unlike dairy manure, she said. Producers may want to consider applying to meet P needs of the crop as applying to meet N needs may lead to an oversupply of P.

    “The N, P and K fertilizer value is $32.60/1,000 gallons,” Laboski said. “Try to make some lemonade from these lemons and lower your fertilizer bill.”


    Laboski said there are important milk application guidelines that should be followed. These include:

    • Not allowing milk to enter ground or surface water.
    • Follow all nutrient management plan setbacks.
    • Apply only to soils that are suitably dry.
    • Avoid application when rain is predicted, imminent or directly after rain.
    • Milk should not pond during application.
    • All other nutrients that have been applied must be credited toward total application rate.
    • Apply uniformly across the field.
    • Properly calibrate application equipment.
    • Consider multiple applications with less volume per application.

    Field selection is also important as certain areas should be avoided, she said. These would include steep slopes, soils with P tests greater than 100 ppm, near water sources including drainage ditches and wells, sandy soils, where manure has already been applied, fields that are tile drained and near neighbors who might be affected by the odor.

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    For soils that will be growing corn, sorghum-sudan and other warm season grasses, Laboski said farmers should consider a pre-plant application on moderately well and well-drained soils. Producers should also consider sidedressing this manure/milk mixture to reduce the potential for early season N losses, and avoid applying over the top of plants.

    “In warm season grass systems, milk could also be applied and incorporated after last harvest if conditions are conducive for cover-crop establishment,” she said.

    For small grains, Laboski said pre-plant applications provide for an opportunity for incorporation. Milk application should not exceed crop N needs and limit milk applications over the top of growing crops to reduce potential for nutrient loss after rainfall and to reduce odor.

    The recommendation for application to legumes would be to top-dress alfalfa and/or clover shortly after harvest to help minimize crown root damage, she said. Applications to soybeans may result in lush vegetative growth potentially creating lodging issues and also increasing risk of infection by the white mold pathogen.

    A milk application can also be made to grass pastures. Laboski said the best time to apply would be shortly after grazing/harvest as it is unknown how milk on foliage will alter forage palatability.

    “One key thing to remember is nutrients from all sources should not exceed crop nutrients needs,” Laboski said.


    There are certain rules and regulations Wisconsin dairy farmers have to follow when landspreading milk, according to Aaron O’Rourke, Wisconsin Department of Natural Resources (DNR) Nutrient Management Program coordinator, said in the webinar.

    Non-permitted farms, these would be farms with less cattle, can dispose of milk in the farm’s manure structure for later application, or they can land apply milk right away according to the farm’s nutrient management plan (NMP). These farms do not need DNR approval, he said.

    O’Rourke said for non-permitted farms, if the farm cannot dispose of milk in storage or land apply according to the NMP, DNR may suspend the NMP. Make sure land application does not cause an unpermitted discharge of pollutants to the waters of the state, he said.

    “You should contact your DNR nonpoint source coordinator for further information,” O’Rourke said.

    As with non-permitted farms, permitted farms (CAFOs) can also dispose of milk in the farm’s manure structure and/or land apply milk, according to the NMP. Once again, these farms do not need department approval, he said.

    Permitted farms can add land or make other changes to NMP for the purpose of emergency land application of milk. In this case, the public notice period may be reduced down to one day from the normal 14-day notice on a case-by-case basis.

    O’Rourke said this may take a few days for processing and review. This is only for the purpose of land applying milk and farmers with more questions with these should contact regional CAFO specialist.

    The DNR is currently operating with limited access to people during the COVID-19 pandemic but are handling emergencies as they always did. Non-emergencies are being handled by email or online forms, he said.


    Becky Larson, University of Wisconsin Extension specialist in the Department of Biological Systems Engineering, said during the webinar that farmers will need to be careful dumping milk into their manure storage systems.

    Milk contains fats that will clog nearly every aspect of their system, she said.

    If possible, Larson recommends producers dump the milk directly into the manure storage facility to avoid issues with milk clogging the manure storage chain. Milk should never be dumped in the septic tanks, she said.

    Larson said adding milk to the manure storage system will increase the odor. There will be some cleaning of the storage structure, which will need to be done after the milk is stored, she said.

    To listen to the webinar click here.

    Russ Quinn can be reached at

    Follow him on Twitter @RussQuinnDTN

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