Potential Errors in the First‐order Model for Estimating Soil Nitrogen Mineralization Potentials

Abstract

Abstract Nitrogen mineralization incubations were conducted using an aerobic leaching procedure. Two agricultural soils and one forest soil were incubated under aerobic conditions, including periodic leaching of mineral N using either 100 ml of 0.01 M CaCl 2 , 30 ml of 0.01 M CaCl 2 , or 30 ml of 0.05 M CaCl 2 . Mineral and organic N were determined for each leachate. Significant amounts of organic N were leached with the mineral N. Leaching with 30 ml of 0.05 M CaCl 2 removed significantly less mineral N, but the 100 ml 0.01 M of CaCl 2 and 30 ml of 0.01 M CaCl 2 treatments were not significantly different. Although not statistically significant, 30 ml of 0.01 M CaCl 2 consistently leached less organic N than did the other two treatments. Amounts of organic N leached ranged from 13 to 163% of total mineralized N. The mineralization reactions were assumed to follow first‐order kinetics. A comparison was made between root mean square (RMS) deviations of experimental data from a nonlinear least squares (NLLS) equation and the more traditional least squares fit of a straight line to log‐transformed data. The NLLS equation gave a more precise fit to the data and hence more accurate estimates of both the N mineralization potential ( N 0 ) and the mineralization rate constant ( k ) for each soil.