Authored by Laurie E. Drinkwater1, Cynthia A. Cambardella2, Jean D. Reeder3, Charles W. Rice4
Almost all of the N in surface soils is present in the form of organic compounds that cannot be used directly by plants and also are not susceptible to loss through leaching. The amount of N converted from organic to mineral forms (mineralization) on an annual basis varies, depending on the past management history, annual climatic variation and inherent soil properties (Sprent, 1987; Paul & Clark, 1989). This capacity of the soil to supply plant-available N is an important indicator of soil quality and many chemical and biological methods have been developed in an effort to provide a simple, reliable indicator of potentially mineralizable N (Keeney, 1982; Bundy & Meisinger, 1994). In this chapter, we discuss the use of N mineralization potential as an indicator of soil quality and the advantages and disadvantages of the various methods available. We then recommend and describe two biologically-based laboratory methods of determining N mineralization potential.