By Blake Jackson
Manure is an important source of crop nutrients, but its nutrient content can vary widely, making proper sampling essential for accurate fertilizer management.
Unlike commercial fertilizers, manure does not come with a guaranteed nutrient analysis, so laboratory testing provides the best estimate of its value.
According to Crops and Soils Educator Chris Clark, manure nutrient levels differ from farm to farm because of factors such as animal species, feed, age, bedding materials, storage methods, and manure handling practices.
Relying only on published average values can lead to inaccurate nutrient estimates, increasing the risk of overapplying or underapplying manure and spending unnecessarily on commercial fertilizer.
Research from Wisconsin dairy farms has shown that nutrient concentrations, especially nitrogen and phosphorus, can fluctuate significantly during manure application.
Agitation plays a key role by mixing settled solids back into storage, creating a more uniform nutrient distribution before spreading.
Studies from Cornell University also found that well-agitated manure produces more consistent phosphorus and potassium levels, while potassium generally remains stable because it is concentrated in the liquid portion.
Experts recommend collecting manure samples while spreading because they better represent the nutrients actually reaching the field.
Sampling each storage structure separately and taking multiple samples during application improves accuracy, particularly when nutrient levels vary within storage facilities.
Farmers are also encouraged to monitor manure consistency, especially after unusual rainfall or snowfall that can dilute nutrient concentrations in open lagoons.
Keeping detailed application records allows producers to match manure nutrients with crop needs and avoid excess fertilizer use.
Digital tools such as SnapPlus V3 can help organize manure analyses and calculate nutrient credits for individual applications or long-term planning.
Submitting manure samples to certified laboratories provides reliable data that supports better nutrient management decisions.
By accurately measuring manure nutrients, producers can reduce guesswork, improve fertilizer efficiency, lower input costs, and make better use of valuable resources already available on the farm.
Photo Credit: gettyimages-magicxeon
Categories: Wisconsin, Crops, Livestock, Beef Cattle, Dairy Cattle