Fine Particle Urea and Urease Inhibitors: Proven Improvements in Nitrogen Efficiency

This research, published in Agriculture, Ecosystems & Environment (2011), evaluated the effectiveness of applying urea fertiliser in fine particle application (FPA) form compared with conventional granular urea, under field conditions in New Zealand. The study used lysimeters and replicated pasture plots to measure nitrogen use efficiency, pasture production, and nitrogen losses to air and water.

The results showed that method of application was the primary driver of improved nitrogen performance. Urea applied in fine particle form consistently outperformed granular urea, delivering substantially higher nitrogen response efficiency and pasture dry matter production. Nitrogen response efficiency increased from 10 kg of dry matter per kg of nitrogen applied with granular urea to 19 kg DM/kg N when urea was applied in FPA form, representing almost a doubling in efficiency. The addition of the urease inhibitor NBPT provided further incremental gains but was secondary to the effect of changing application method.

Environmental outcomes also improved with fine particle application. Nitrate leaching losses were reduced from 2.1% of applied nitrogen with granular urea to 0.92% with FPA urea, with additional reductions observed when NBPT was included. Ammonia volatilisation and nitrous oxide emissions were also lower where NBPT was used.

Overall, the study demonstrates that transitioning from granular to fine particle urea application delivers a step-change in nitrogen efficiency, improving pasture production while reducing nitrogen losses under grassland conditions.

Summary of Key Findings

• Fine particle application (FPA) of urea significantly improved nitrogen response efficiency compared with granular urea.
• Nitrogen response efficiency increased from 10 kg DM/kg N (granular) to 19 kg DM/kg N (FPA), with smaller additional gains when NBPT was included.
• Pasture dry matter production increased by 27% with FPA urea relative to granular urea.
• Nitrate leaching losses decreased from 2.1% of applied nitrogen (granular) to 0.92% with FPA urea.
• The largest performance gains were attributable to the change in application method, with urease inhibitors providing secondary, incremental benefits.

The study concluded that combining fine particle urea application with a urease inhibitor offers a robust strategy for improving nitrogen use efficiency and reducing nitrogen losses under grassland conditions.

👉 Download the summary document PDF below or follow the link to the original trial document.