The trials were carried out on sandy loam soils and each trial plot received a total of 250kgN/ha, divided into seven applications and including two slurry applications. The study concluded that combined S and N fertiliser application is potentially key to increasing grass yield, efficiency, reducing nitrate leaching, and improving soil fertility.
Making the best use of on-farm resources will help with farm profitability, and utilising the nutrients in slurry will reduce the amount and type of purchased fertiliser. Good management, testing slurry and applying a biological inoculant can all help to enhance the nutritional value of slurry.
Treating slurry with an inoculant can increase the available nitrogen (N) content by up to 20%, and reduce the amount of ammonia released into the atmosphere. The enzymes and bacteria in the inoculant will also help improve fibre breakdown during storage. This allows the carbon contained within the fibre to become part of the soil more rapidly and be taken up more quickly by the plant.
Using a slurry inoculant makes slurry less prone to sedimentation and crust formation, which improves its flowability. Labour, machinery wear and tear, and fuel costs are reduced as the slurry is easier to spread.
Due to a process referred to as volatilisation, when slurry is spread the ammonium nitrogen is converted into ammonia and released as a gas. Using a biological inoculant will increase the organic nitrogen content and total retained N by influencing microbial activity, resulting in reduced ammonia production.
There can be significant variations in the level of nutrients in slurry, so it is vital to test before applying and purchasing bought-in fertiliser requirements.