Mitigating ammonia (NH3) volatilization from intensive pasture systems is critical for environmental sustainability. However, field-scale evaluation on the potential of enhanced efficiency fertilizers (e.g. urease inhibitors and controlled-release fertilizers) in mitigating NH3 volatilization is limited.
Using a micrometeorological technique, we conducted two field trials to investigate the effects of Green UreaNV® (urea coated with the urease inhibitor N-(n-butyl) thiophosphoric triamide, NBPT) and polymer-coated urea (a controlled-release fertilizer) onNH3 volatilization from an intensive rainfed pasture in southern Australia.
We found that NH3 volatilization from urea was 5.8 and 5.6 kg N ha–1, respectively, in the autumn and spring trials, equivalent to 11–12% of the applied urea in each season. The use of Green UreaNV® and polymer-coated urea decreased the cumulative NH3 volatilization by 45–55% and 80%, respectively.
Taking into consideration the high environmental damage cost of NH3 as found in the European Union, we hypothesize that both Green UreaNV® and polymer-coated urea can be cost-effective in mitigating NH3 loss from this pasture.
Our findings suggest that the extra cost of using these enhanced efficiency fertilizers for farmers is not compensated by the fertilizer N value of decreased NH3 loss.
However, from a societal perspective the extra cost for Green UreaNV® is likely outweighed by reduced environmental cost of NH3. New fertilizer technology should be developed to improve the cost-effectiveness of polymer-coated urea to the farmers.
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