Nitrogen (N) can be lost to the atmosphere by nitrous oxide (N 2 O) flux from soils. For pastoral soils, N is applied in N fertiliser and excreta deposited by farmed, grazing animals. We postulated that soil N 2 O flux would be linearly related to the N application rate (Nrate). As a test, we applied eight treatments as rates of urea (0-1500 kg N ha −1 ) to samples of a pastoral soil and measured the N 2 O flux, pH and ammonium (NH 4 + ) and nitrate (NO 3 − ) concentrations at intervals for 67 days. When fluxes were accumulated, the variability or variance of treated replicates increased with time and increasing Nrate. For 67-day, cumulative N 2 O fluxes, a linear regression with the N application rate, weighted by the inverse of the replicates' variance, yielded a statistically significant relationship (P < 0.05), accounting for 92% of the variability. A second-order term was too small to be statistically significant for another regression using a polynomial function. Thus, there was no evidence to reject the linear hypothesis. The fluxes were also related to the pH and (NH 4 + + NO 3 − ) concentration. These relationships warrant further study in different soils under field conditions.

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