How to manage your slurry nitrogen

The N fraction in cattle slurry is made up of 50% ammonium N (urine) and 50% organic N (faeces). The ammonium N should be considered similarly to Urea and it is this portion which causes the variability in N use efficiency. This portion can be lost as Ammonia (NH3) to the atmosphere. 

How can you reduce ammonia loss? 

As dry matter content decreases there is a reduction in ammonia loss as the applied slurry percolates into the soil faster allowing the soil to hold onto the applied ammonium minimising the conversion to gaseous ammonia. 

Apply when conditions do not favour evaporation or in poor drying conditions. These conditions are more likely during the Spring. 

Application methods should be favoured that reduce the surface area exposure of the slurry to the atmosphere. We often call these methods ‘low emission spreading systems’, such as the ‘trailing shoe’ system which also minimises grass contamination allowing greater application flexibility on grass farms. 

On arable farms, slurry should be incorporated into the soil within 3 hours of application to minimise atmospheric exposure and maximise N recovery .