Field experiments were conducted to determine optimal time during the day for N2O flux determination and to evaluate the effects of wheel traffic and soil parameters on N2O fluxes following urea ammonium nitrate (UAN) injection and summer UAN fertigations. The experiments were located on silty clay loam soils under no-till irrigated continuous corn of eastern Nebraska. Three approaches were used. First, near-continuous N2O flux measurements were made in non-wheel-tracked (NWT) interrows in four 24-h periods during the growing season of 2002. Second, point measurements of N2O flux were made in the wheel-tracked (WT) and NWT interrows at five dates during the growing season of 2002. Third, point measurements of N2O fluxes and soils (nitrate, ammonium, moisture, and temperature) were made in the NWT interrows from 2001 to 2004. The differences between point vs. continuous flux measurements (<8 g N2O-N ha−1 d−1) and between the WT vs. the NWT (<3.7 g N2O-N ha−1 d−1) were not significant. The means of N2O daily flux within 60 d after injection (period of high soil N) in the first, second, and third year were 26.8, 21.2, and 28.0 g N2O-N ha−1 d−1, respectively. The means during low soil N were 9.24, 4.05, and 7.50 g N2O-N ha−1 d−1, respectively. Summer fertigations did not increase N2O flux. Under the conditions of this study, optimal point measurement for N2O daily flux can be made any time during the day at the NWT interrows. Among the soil parameters, soil nitrate dynamics in the injection zone correlates best with N2O fluxes.
