Ammonia emissions from urine patches amended with N stabilized fertilizer formulations

In rotational grazing systems, it is common practice to apply nitrogen (N) fertiliser within 24 h of grazing thus resulting in addition of N fertiliser to urine patches. However, there is a lack of information on what the potential is, if any, to use this common practice to deliver N stabilisers to urine patches via N fertiliser formulations to reduce N losses to the environment. The objective of this study was to investigate the effect of applying urea fertiliser (with and without N stabilisers) 24 h after urine patch deposition on NH₃ emissions. Treatments included (1) urine, (2) urea, (3) urine + urea, (4) urine + urea with N-(butyl)thiophosphoric triamide (NBPT), (5) urine + urea with dicyandiamide (DCD) and (6) urine + urea with both NBPT and DCD. Treatments were applied on two occasions, May and June, under contrasting soil moisture and meteorological conditions to a temperate grassland site. Urine (569–883 kg N ha⁻¹) was applied 24 h prior to urea fertiliser application (40 kg N ha⁻¹). There was no significant reduction or increase in NH₃ emission factors from treatments receiving the two N stabilisers (NBPT and DCD) in the May and June application timings compared to the other treatments. The results of this study suggest that common farm practice of applying N fertiliser the day after grazing in rotational grazing systems offers no reduction in NH₃ emission rates from urine patches where the N stabiliser inclusion rate is designed to reduce the fertiliser-based N losses only.