Decreasing ammonia loss from an Australian pasture with the use of enhanced efficiency fertilizers

Abstract Mitigating ammonia (NH 3 ) 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 NH 3 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) on NH 3 volatilization from an intensive rainfed pasture in southern Australia. We found that NH 3 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 NH 3 volatilization by 45–55% and 80%, respectively. Taking into consideration the high environmental damage cost of NH 3 as found in the European Union, we hypothesize that both Green UreaNV ® and polymer-coated urea can be cost-effective in mitigating NH 3 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 NH 3 loss. However, from a societal perspective the extra cost for Green UreaNV ® is likely outweighed by reduced environmental cost of NH 3 . New fertilizer technology should be developed to improve the cost-effectiveness of polymer-coated urea to the farmers.