Measured and Modeled (DNDC) Nitrous Oxide Emissions (N₂O) under Different Crop Management Practices in the Nitra Region, Slovakia

An important method of investigating N₂O emissions from cropland is model simulation. The measured data of N₂O emissions under conventional tillage (CT) and reduced tillage (RT) with (N1) and without (N0) N fertilizer application were used to test the DNDC model during the year 2012 (April-December) in Slovakia. There was found a good agreement with seasonal N₂O emissions only for CTN0 treatment, but in case of other treatments DNDC overestimated the emissions. The relative deviation between observed and simulated total seasonal N₂O emissions (kg N ha⁻¹) from four treatments were 46%, 164%, 346% and 321% for CTN0, CTN1, RTN0 and RTN1, respectively. Also, some discrepancies were found between observed and simulated emissions when evaluating the daily N₂O emissions, especially when looking at the magnitude of N₂O emissions peaks. The correlation between observed and simulated daily N₂O emissions (N = 38) in case of conventional tillage was quite high and significant with r = 0.48 (P <0.01), r = 0.45 (P <0.01) for CTN0 and CTN1 treatment, respectively. On the other hand, there was found poor correlation in reduced tillage treatment with r = 0.22 (P >0.01) and r = 0.39 (P >0.01), for RTN0, RTN1, respectively.