Effect of Nitrification Inhibitor on Ammonia and Nitrous Oxide Emissions and Nitrogen Use Efficiency in Intensive Vegetable Production Systems.

Vegetable production systems (often on sandy soils) are intensive, with high inputs of fertilisers (both chemical and manure) and water. Applied nitrogen (N) can be lost through the process of volatilisation of ammonia (NH₃), nitrate (NO₃^-) leaching and denitrification. Ammonia loss from manures is expected to be high due to high concentration of ammonium and high pH. The nitrification-denitrification also produces potent greenhouse gas, nitrous oxide (N₂O).  Nitrification inhibitor is often used to oxidation of ammonium to nitrate, therefore to reduce N₂O emission, denitrification and nitrate leaching. However application of nitrification inhibitors may increase NH₃ loss.

Objectives of this study are, to quantify NH₃ and N₂O emissions from manures applied to a celery crop, the effect of nitrification inhibitor (DMPP) on these losses emission and on productivity and N use efficiency.

Total N application rate is 451 kg N/ha, with chicken manure of 255 kg N/ha and the rest of calcium nitrate) over two celery fields (4ha each). DMPP (0.4% per unit NH₄⁺-N) was applied immediately following manure application to one field. NH₃ and N₂O emissions were measured measured by Open Path Fourier-Transform Infrared (OP-FTIR) spectroscopy technique-backward Lagrangian stochastic (bLS) dispersion model (WindtTax). 

20 kg N/ha lost over 6 days as NH₃, accounting for 7.8% of applied manure N.  The application of DMPP reduced N₂O losses by 64% but Increased NH₃ loss by 20%, with no impact on biomass yield.  Nitrogen use efficacy in the plant was very low, <8%, indicating that major improvements could be made in N management in vegetable systems, particularly in manure management which provides a large component of the N.