Kinetics of nitrification in selected Iowa soils treated with Stay-N 2000

The effectiveness of Stay-N 2000 or reformulated nitrapyrin [2-chloro-6-(tricholoromethyl) pyridine] was investigated in two Iowa soils representative of Clarion and Okoboji soils that differed in organic carbon, pH, and texture. A nonlinear regression was used to estimate kinetic parameters. The maximum nitrification rate (Kmax) and the duration of lag period (t') were derived from the equation to characterize the nitrification process in both soils. Stay-N 2000 appeared to be a better inhibitor than nitrapyrin to extend t' and as effective as nitrapyrin in reducing Kmax. Stay-N 2000 reduced Kmax an appreciable amount in the Okoboji soil at the rate of 12 μg a.i. g-1 soil or three times the recommended rate. Nitrification rates were affected by the rates of nitrogen (N) applied to both soils; the higher the N rates, the higher Kmax, and the more the nitrate (NO3-)-N accumulation.