The National Pollutant Discharge Elimination System (NPDES) general permit for animal feedlots was updated and became effective Feb. 1 in Minnesota.

The permit is in effect through Jan. 31, 2026.

The Minnesota Pollution Control Agency provides a summary of changes and current rules as follows:

Mitigation of nitrate leaching. Permit language was adapted from existing University of Minnesota best management practices (BMPs) to limit nitrate leaching from land application of manure application during June, July, August or September:

• A cover crop must be planted to harvested fields either prior to manure application (interseeded into standing primary crop) or within 14 days of manure application. Note: Applications in June, July and August currently require a cover crop. The inclusion of September is the notable change.

Application from Oct. 1 to Oct. 15. One of the four nitrogen BMPs must be implemented: The soil temperature is below 50 degrees F at the start of manure application; a nitrogen-stabilizing agent or product is added at the recommended inclusion rates; a cover crop is established in accordance with the requirements for September manure applications; a split application of nitrogen where no more than half of the recommended nitrogen rate is applied before Oct. 15.

Winter application of the remaining recommended nitrogen rate is prohibited.

Winter application during December and January. “Winter application” means manure application to frozen or snow-covered soils, except when those conditions occur in the months of October and November or when the manure is immediately incorporated or injected.

Solid manure application must comply with the following:

• It occurs to fields approved within the manure management plan (MMP).

• It observes a 300-foot setback to sensitive features.

• Field conditions allow some retention of runoff within tillage furrows or depressions.

• There is a low risk of phosphorus loss as indicated by the Minnesota Phosphorus Index.

• Field slope is equal to or less than 6%.

• There must be less than a 50% chance of rainfall in excess of a quarter-inch within 24 hours of the application.

• When the field is covered with 2 or more inches of snow, air temperature must be less than 40 degrees during, and for at least 24 hours after, application.

Liquid manure application is prohibited.

Beginning in 2022, solid manure application must comply with the following:

• It occurs in fields approved within the MMP.

• It observes a 300-foot setback to sensitive features.

• Field conditions allow some retention of runoff within tillage furrows or depressions.

• There is a low risk of phosphorus loss as indicated by the Minnesota Phosphorus Index.

• Field slope is equal to or less than 2%.

• There must be less than a 50% chance of rainfall in excess of a quarter-inch within five days of the application.

• When the field is covered with 2 or more inches of snow, air temperature must be less than 40 degrees during, and for at least five days after, application.

Winter application during March. There are three parts to this point:

• Liquid manure application is prohibited (this is an existing requirement).

• In 2021, solid manure application must comply with the requirements for December and January.

• Beginning in 2022, solid manure application is prohibited.

Allowance for snow removal activities. The permit allows for winter application of snow removed from animal holding areas even though an incidental amount of manure will be present in the snow.

Winter application of the snow-manure mix is allowed, provided it complies with the following:

• It occurs in fields approved within the MMP.

• It observes a 300-foot setback to sensitive features.

• March application is limited to the amount necessary to ensure animal welfare. This does not allow winter application of manure packs or manure accumulation from animal holding areas. The amount of manure within the removed snow and subsequently land applied should be an incidental amount.

Transfer of manure ownership. The permit prohibits the transfer of manure from the facility to a third party when that third party intends to:

• perform winter application of liquid manure

• perform winter application of solid manure during the month of March

Public notice of substantial MMP changes. The permit reduces the public comment period for substantial MMP changes to 14 days instead of the previous 30 days.

The most common substantial change is the addition of a new field to the MMP. Refer to the permit for more details on changes that are considered to be substantial.

Requirements removed. The following requirements are no longer part of the NPDES general permit.

• notification to MPCA 30 days prior to the startup of an anaerobic digester

• notification to the MPCA three days prior to the start of construction of a vegetated infiltration basin (VIB).

• Notification to the Minnesota duty officer for instances of emergency winter liquid manure application. The requirement to notify the MPCA still remains.

For more information on the feedlot program, visit pca.state.mn.us/feedlots.

Source: MPCA, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all of its subsidiaries are not responsible for any of the content contained in this information asset.