Modeling the Flush of Nitrogen Mineralization Caused by Drying and Rewetting Soils

Abstract

Abstract The flush of N mineralization that follows rewetting a dry soil may release significant amounts of N where drying‐rewetting cycles are common, so attempts to model N mineralized in the field should include this mechanism. Selecting a model for the N flush, however, is hampered by inadequate measurement frequency in existing data. My objective was to collect detailed data on the progress of the N flush to facilitate finding a model to describe the process. Samples of three soils were preincubated, dried, rewetted, and incubated at 30 °C for up to 20 d with periodic samplings for inorganic N determinations. Undried samples were also incubated and sampled periodically. Cumulative net N mineralized in undried samples was adequately described by zero‐order kinetics. In contrast, describing cumulative net N mineralized in dried and rewetted samples required a model with two N pools, one following zero‐order kinetics and the other following first‐order kinetics. Apparently, the first‐order N flush was superimposed on zero‐order background mineralization. Drying and rewetting the soils also significantly increased the background mineralization rate, suggesting transfer of N from a passive pool to the zero‐order pool.