Nitrification Kinetics and Nitrous Oxide Emissions when Nitrapyrin is Coapplied with Urea–Ammonium Nitrate
- Rex A. Omonode *a and
- Tony J. Vyna
Simultaneous application of nitrification inhibitors and fertilizer N has the potential to delay nitrification processes and reduce atmospheric N loss through N2O emissions. A 2-yr study was conducted to assess the effects of newly available water-soluble nitrapyrin (Instinct) [2-chloro-6-(trichloromethyl)pyridine] on the nitrification kinetics and N2O emissions from urea–NH4NO3 (UAN) band applied to somewhat poorly drained and moderately well-drained silt loam soils in Indiana. The UAN fertilizer, with or without nitrapyrin, was injected post-emergence between corn (Zea mays L.) rows that were 76 cm apart. Soil samples were taken at various increments from the band centers at 1- to 2-wk intervals for up to 14 wk and analyzed for NH4– and NO3–N concentrations. Nitrification rates were determined using appropriate kinetic models. Greenhouse gas samples were collected weekly for 7 to 10 wk and biweekly thereafter for an additional 2 to 4 wk. Our results showed that UAN nitrification followed first-order kinetics, with significantly greater nitrification rate constants without nitrapyrin. On average, UAN half-life was about 15 d without nitrapyrin and 25 d when coapplied with nitrapyrin. Nitrapyrin reduced N2O emissions by up to 44% from sidedress-applied UAN, even though emission quantities varied by location and year due to differences in soil moisture, temperature, and precipitation. These latter variables plus soil NH4–N concentrations, in various combinations, accounted for 40 to 50% of the total variability associated with N2O emissions. These results can help inform UAN management decisions with regard to use of N stabilizers with UAN in the midwestern United States.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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