Author: John A. Lory, University of Missouri

Manure differs from commercial fertilizers due to a diverse mix of organic nitrogen compounds that require conversion to inorganic nitrogen by microorganisms (a process called mineralization) to make it available to plants. One of the challenges of manure management is estimating the rate of nitrogen release from manure organic material and the fraction of organic nitrogen that is ultimately available to crops.

There are differences among states in estimating available nutrients, particularly in estimating nitrogen availability. Some differences may be expected due to differences in climate; for example, cool or dry environments may limit the rate of nitrogen mineralization. State-to-state variation also reflects differences in philosophy and approach to calculating nutrient availability in manure.

State specific nutrient availability calculations are available for 34 states using Purdue University’s online MMPManure Nutrient Availability calculator.