Given the importance many farmers place on optimising the pasture response to urea, there has been surprisingly few attempts to improve its performance by the main fertiliser manufacturers and suppliers. In fact, the only efficiency-orientated modified urea sold in significant quantities in New Zealand is SustaiN®, which is granular urea treated with the urease inhibitor nbpt. This product was introduced by Summit-Quinphos in 2002. It is now estimated to comprise 30% of urea sold by Ballance Agri-Nutrients, or 20% of total New Zealand urea sales. SustaiN® is currently sold at a $50/t (8.5%) premium to standard granular urea.
This paper presents results from a field trial conducted on an irrigated dairy farm in mid-Canterbury, comparing granular urea with a new process – ONEsystem® - developed by Dr B. Quin and S. Spilsbury over the last 2 years in east Victoria in Australia and in New Zealand. The system uses prilled (micro-granular) urea, which is passed through a fine water spray containing the urease inhibitor nbpt during application. A nil-N control and 3 rates of each fertiliser (14, 28 and 42 kg N/ha) were applied to large plots (12 x 25) on four occasions after grazing during spring/early summer 2014.
Results showed a substantial and statistically significant increase in extra dry matter (EDM) to N applied with the ONEsystem® compared to the pasture response from traditional granular urea, by a factor of 2.6 (± 0.5) averaged over the 3 application rates. For example, the EDM produced by 30 kg N/ha of granular urea could be produced with only 12.5kgN/ha applied as ONEsystem®. Conversion efficiency (kg EDM/kg N applied) increased from 10.2 with granular urea to 24.6 with ONEsystem®. Pregrazed plant N concentrations were also higher following ONEsystem® N application, meaning total N uptake was increased at least 3-fold compared with that resulting from N applied as granular urea.
These results have very significant positive implications for both the economics and environmental impacts of fertiliser N use in New Zealand. Preliminary results from a similar trial in the Waikato, and others conducted in Gippsland, Victoria also indicate very positive benefits (to be published elsewhere).