Comparison of Gross Nitrogen Mineralization Rates by Zero-Order Models
- Shigeru Takahashi *
Several zero-order models for estimating gross N mineralization rate (M) using 15N have been proposed. In a comparison of the Ms estimated with some experimentally determined values, different models sometimes gave substantially different results. Although the Ms are estimated by using changes in NH4–N (NH4–14N + NH4–15N) and NH4–15N, a comprehensive comparison based on model equations is lacking. I compared four zero-order models to clarify the extent of the difference in estimated Ms between models under different conditions of changes in NH4–N and NH4–15N. The ratio of M by one model equation to M by another is expressed by and , where AT is NH4–N, AL is NH4–15N, and the subscripts 1 and 2 denote the initial and final values, respectively. Ranges of R and r are R > 0 and 0 < r < 1, respectively, and R > r The farther r is from 1, the more different the estimated Ms are. Estimation of M must be done with caution when r ≤ 0.2 since model differences increase uncertainties in estimates.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2001. Published in Soil Sci. Soc. Am. J.65:244–246.