Kinetics of Nitrification in Selected Iowa Soils Treated with Stay‐N 2000

Abstract

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 (K _max) 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 K _max. Stay‐N 2000 reduced K _max 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 K_max, and the more the nitrate (NO₃ ⁻)‐N accumulation.

Keywords:

• K _max (maximum nitrification rate)
• nitrification inhibitor
• t′ (lag period)