Daniel H. Smith, Jamie Patton, Kolby Grint, UW-Madison Nutrient and Pest Management Program, University of Wisconsin-Madison
Manure nutrient testing is important to appropriately allocate manure applications. A manure nutrient credit tells us how much plant available nitrogen, phosphorus, and potassium is contained in a one ton (dry application) or 1,000 gallons (liquid application) of manure.
Manure nutrient concentrations can be estimated using published “book values”. In Wisconsin, manure book values by livestock species and manure type are based on manure analysis results averaged across the state for several years.
While book values provide an estimate of nutrient credits, actual manure nutrient concentrations are influenced by livestock species, breed, and age, feed rations, bedding type and concentration within manure, as well as manure handling and storage processes. Therefore, the results of on-farm manure nutrient testing are recommended to develop farm-specific manure credits and guide efficient manure application strategies.
Manure nutrient sampling is often conducted at the time of spreading. So, now is the time to be thinking of sampling manures during fall applications. More information on the sampling of manure and crediting of manure nutrients can be found in the publications below.
The University of Wisconsin Nutrient and Pest Management program has a smart phone application available for nutrient credit calculations- https://ipcm.wisc.edu/apps/npkcredits/
UW Labs Manure sampling instructions –
Credit what you spread publication- https://ipcm.wisc.edu/wp-content/uploads/sites/54/2022/11/Manurecredit.pdf
Nutrient application guidelines for field, vegetable, and fruit crops in Wisconsin (UW Publication A2809) – https://learningstore.extension.wisc.edu/products/nutrient-application-guidelines-for-field-vegetable-and-fruit-crops-in-wisconsin-p185