Emission of nitric oxide and nitrous oxide from soil under field and laboratory conditions

A detailed short-term (12 d) laboratory study was carried out to investigate the effects of applying animal urine, fertilizer (ammonium nitrate) and fertilizer+urine on emission of NO and N2O from soil. A complementary 24 d field study measured the effect of fertilizer or fertilizer+sheep grazing on NO and N2O emissions from pasture. The data generated were used to interpret the transformations responsible for the release of these gases. Application of urine to the soil (at a rate equivalent to 930 kg N ha−1) increased the amount of mineral and microbial N in the soil. This was followed by increases in emissions of NO (from 0.02 to 1.76 mg NO-N m−2 d−1) and N2O (from 15 to 330 mg N2O-N m−2 d−1). Molar ratios of NO-N-to-N2O-N were very low (