Using Slurry to Reduce Chemical N Usage
Upon joining the Future Beef Programme James was determined to start spreading slurry by Low Emission Slurry Spreading (LESS) instead of by the splash plate. He was aware that by changing spreading method to the dribble bar it would save an extra 3 units of nitrogen for every 1000 gallons spread. He took a sample of the slurry from my weanling tank and the results showed that it contained 9 units of nitrogen, 6 units of phosphorus and 31 units of potassium per 1000 gallons. He was happy with the results and used the information to balance up the chemical fertiliser applications for silage.
The slurry was spread by his contractor with the dribble bar on 2nd April for first cut silage at a rate of 3,000 gallons per acre. This was then topped up with 58 units/acre of nitrogen which was spread in the form of protected urea, amounting to 85 units of nitrogen, 18 units of phosphorus and 93 units of potassium per acre. This was sufficient to replace the nutrient offtakes from first cut silage.
Apart from the nitrogen savings and environmental benefits of using the dribble bar, he had more flexibility to spread slurry on heavier covers of grass in lower index fields to help build the soil fertility. It also meant that cattle could graze paddocks quicker than if slurry was spread with the splash plate and there was no smell afterwards which was an added benefit to the neighbours.
By knowing the quality of the slurry through analysis and spreading slurry in spring using the dribble bar instead of the splash plate James was able to reduce his chemical fertiliser usage this year. In total this saved him 9 units of nitrogen per acre which amounts to €20/acre (at €1000/tonne for protected urea) in that land block. Extra savings have also been made by using protected urea to replace all straight nitrogen used on the farm, which is cheaper per unit of nitrogen and saved him €67/acre for first cut silage in the same field.
