A rapid on-farm determination is needed to assess the fertilizer contents of liquid manure as it is taken from storage. Rapid determination of a tank load for liquid manure will indicate nutrient changes that occur as manure is removed from a storage which cannot be or is not effectively agitated before manure removal. Effective utilization of animal manures as a fertilizer resource requires a farmer to have a knowledge of the amount of nutrients that he is putting onto the soil. If the producer then reduces the commercial fertilizer, he can realize the fertilizer economic value of the manure. Laboratory testing of manures for their N, P and K values will cost $30-$50/sample and the results will be returned to the producer within one to two weeks. If the tested sample is not taken from a well agitated liquid manure storage facility it may not be representative of the average nutrient content of the stored manure. Further the one to two week delay may be too late to use the results to make management decisions on the manure distribution rates onto the cropland.
Taraba, Joseph L., "Rapid Method for Determining Fertilizer Nutrients in Liquid Dairy and Swine Manures" (1988). Agricultural Engineering Extension Updates. 49.