Brooke Kaveney1, Jason Condon1, Greg Doran1
A laboratory soil incubation experiment was conducted using the nitrification inhibitor 3,4-dimethylpyrazole phosphate in conjunction with four different agriculturally relevant nitrogenous fertilisers to examine the effects of soil moisture at application on inhibitor behaviour. Soil moisture influenced the mineral N concentrations of the nitrogen fertilisers. Fertilisers that were applied to moistened soils recorded significantly higher mineral N concentrations than when they were applied to dry soils. Of the four fertilisers applied to a moistened soil, urea had the lowest NH4+ and NO3– concentrations after a week of incubation. However, in dry soils both urea and UAN recorded significantly lower mineral N concentrations. Losses were attributed to volatilisation which occurs as urea is converted to NH4+. Regardless of the soil moisture conditions, DMPP effectively suppressed nitrification for all fertilisers. Fertilisers without DMPP recorded higher NO3– concentrations as the NH4+ was oxidised as part of the nitrification process. Experimental results demonstrate that different soil moisture conditions can influence the behaviour of nitrogen fertilisers but not DMPP.