Effectiveness of urease inhibition on the abatement of ammonia, nitrous oxide and nitric oxide emissions in a non-irrigated Mediterranean barley field.

Urea is considered the cheapest and most commonly used form of inorganic N fertilizer worldwide. However, its use is associated with emissions of ammonia (NH(3)), nitrous oxide (N(2)O) and nitric oxide (NO), which have both economic and environmental impact. Urease activity inhibitors have been proposed as a means to reduce NH(3) emissions, although limited information exists about their effect on N(2)O and NO emissions. In this context, a field experiment was carried out with a barley crop (Hordeum vulgare L.) under Mediterranean conditions to test the effectiveness of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on reducing these gaseous N losses from surface applied urea. Crop yield, soil mineral N concentrations, dissolved organic carbon (DOC), denitrification potential, NH(3), N(2)O and NO fluxes were measured during the growing season. The inclusion of the inhibitor reduced NH(3) emissions in the 30 d following urea application by 58% and net N(2)O and NO emissions in the 95 d following urea application by 86% and 88%, respectively. NBPT addition also increased grain yield by 5% and N uptake by 6%, although neither increase was statistically significant. Under the experimental conditions presented here, these results demonstrate the potential of the urease inhibitor NBPT in abating NH(3), N(2)O and NO emissions from arable soils fertilized with urea, slowing urea hydrolysis and releasing lower concentrations of NH(4)(+) to the upper soil layer.