Using The Nitrification Inhibitor 3, 5-dimethylpyrazole To Determine Net Nitrogen Mineralization and Denitrification Rates Simultaneously At Varying Water Contents

Abstract

An investigation of the use of a nitrification inhibitor (NI) to simultaneously measure the rates of net nitrogen (N) mineralization, as an accumulation of ammonium (NH4+), and denitrification, as a loss of nitrate (NO3-) over a 28-day incubation. This assay used 3, 5-dimethylpyrazole (DMP), to evaluate two levels of inhibition (0 and 200 mg DMP kg-1) in two soil textures (fine vs. coarse) over 10 levels 20 – 110% water-filled pore space (WFPS). Nitrate did not accumulate while NH4+ did which indicated DMP was inhibiting nitrification. Water content influenced N mineralization and denitrification and differed between soil textures (fine vs. coarse) and carbon intensity (manure, corn (High) vs. no amendments (Low)). The N mineralization rate was greater in fine soil (>70% WFPS); the denitrification rate was greater in coarse soil (110% WFPS). The N mineralization rate was greater in low carbon soil; denitrification was greater in high carbon soil (>80% WFPS).