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Urease and nitrification inhibitors are designed to mitigate ammonia (NH 3 ) volatilization and nitrous oxide (N 2 O) emission, but uncertainties on the agronomic and economic benefits of these inhibitors prevent their widespread adoption in pasture systems, particularly in subtropical regions where no such information is available. Here we report a field experiment that was conducted in a subtropical pasture in Queensland, Australia to examine whether the use of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT, applied as Green UreaNV®) and the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP, applied as Urea with ENTEC®) is environmentally, agronomically and economically viable. We found that Green UreaNV® and Urea with ENTEC® decreased NH 3 volatilization and N 2 O emission by 44 and 15%, respectively, compared to granular urea. Pasture biomass and nitrogen (N) uptake were increased by 22-36% and 23-32%, respectively, with application of the inhibitors compared to granular urea. A simple economic assessment indicates that the fertilizer cost for pasture production was 5.4, 4.4 and 6.0 Australian cents per kg dry matter for urea, Green UreaNV® and Urea with ENTEC®, respectively, during the experimental period. The mitigation of N loss using the inhibitors can reduce the environmental cost associated with pasture production. These results suggest that the use of these inhibitors can provide environmental, agronomic and economic benefits to a subtropical pasture., (Copyright © 2018. Published by Elsevier B.V.)

Nitrification inhibitors show promise in decreasing nitrous oxide (N 2 O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N 2 O emission and nitrate (NO 3 - ) leaching, limited studies suggest that they may increase ammonia (NH 3 ) volatilization and, subsequently, indirect N 2 O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N 2 O and NH 3 emissions. We found that nitrification inhibitors decreased direct N 2 O emission by 0.2-4.5 kg N 2 O-N ha -1 (8-57%), but generally increased NH 3 emission by 0.2-18.7 kg NH 3 -N ha -1 (3-65%). Taking into account the estimated indirect N 2 O emission from deposited NH 3 , the overall impact of nitrification inhibitors ranged from -4.5 (reduction) to +0.5 (increase) kg N 2 O-N ha -1 . Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N 2 O emission can be undermined or even outweighed by an increase in NH 3 volatilization., (© 2016 John Wiley & Sons Ltd.)

Land application of municipal wastewater is widely practised worldwide as a means of treating wastes and obtaining a benefit from the water and nutrients by growing pastures, trees, and sometimes edible crops such as vegetables, fruit and fibre, etc. Irrigation of pastures by treated and untreated sewage near Melbourne, Australia, for more than a century has increased heavy metals concentrations in the soil, but appears not to have increased their concentrations in the herbage and in animal tissues of animals grazed on these pastures. There seem to be sound reasons why this practice may be sustainable.

Nitrification inhibitors show promise in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N2O emission and nitrate ( NO3-) leaching, limited studies suggest that they may increase ammonia ( NH3) volatilization and, subsequently, indirect N2O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N2O and NH3 emissions. We found that nitrification inhibitors decreased direct N2O emission by 0.2-4.5 kg N2O-N ha−1 (8-57%), but generally increased NH3 emission by 0.2-18.7 kg NH3-N ha−1 (3-65%). Taking into account the estimated indirect N2O emission from deposited NH3, the overall impact of nitrification inhibitors ranged from −4.5 (reduction) to +0.5 (increase) kg N2O-N ha−1. Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission can be undermined or even outweighed by an increase in NH3 volatilization. [ABSTRACT FROM AUTHOR]