Slurry 15NH4-N recovery in herbage and soil: effects of application method and timing.

The effects of slurry application method and weather conditions after application on ammonia volatilisation are well documented, however, the effect on slurry N recovery in herbage is less evident due to large variability of results. The objective of this field experiment was to determine the recovery of cattle slurry NH₄-N in herbage and soil in the year of application as affected by application method (trailing shoe versus broadcast) and season of application (spring versus summer), using ¹⁵N as a tracer. In 2007 and 2008, ¹⁵N enriched slurry was applied on grassland plots. N recovery in herbage and soil during the year of application was determined. Both spring and trailing shoe application resulted in significantly higher herbage DM yields, N uptake and an increased recovery of ¹⁵NH₄-N in herbage. Additionally, the recovery of slurry ¹⁵NH₄-N in the soil at the end of the growing season was increased. Spring and trailing shoe application reduced the losses of slurry ¹⁵NH₄-N by on average 14 and 18 percentage points, respectively, which corresponded closely to ammonia volatilisation as predicted by the ALFAM model. It was concluded that slurry N recovery in temperate pasture systems can be increased by adjusting the slurry application method or timing. [ABSTRACT FROM AUTHOR]