Number of cuts:N (Kg/ha) for 2nd cut
You need around 20 to 25kg SO3/ha (16 to 20 units/acre) across your aftermaths to optimise grass yield and quality. A standard slurry application will only provide 2kg SO3/ha. Using a Sulphur containing fertiliser is the only way to provide your silage grass with the Sulphur it needs.
Compacted soils don't have enough air and water in them to let the regrowing grass roots effectively get the nutrients needed for optimum growth. To avoid compacted soils, which can reduce your aftercut yields by up to 25%, dig inspection pits and identify any issues and rectify them this autumn in readiness for next season.
Having the correct pH, P and K levels in your soil is the base to optimising yield. If you don't have recent soil analyses, get these done and target pH 6.5, P index 2 and K index 2+. Did you know having a soil K index of 1 can knock 30% off your grass yields?
The standard figure used in Carbon audits for the Nitrogen fertiliser you buy is 6.6kg CO₂eq for every 1kg on Nitrogen that you use. At CF Fertilisers we've got that down to 3.4kg CO₂eq per 1kgN in Nitram. So using Nitram can cut your overall milk or meat carbon footprint by around 10%.
Your second cut is likely to need 60 to 90 kg Potash per ha (48 to 72 units/acre) if your soil K indexes are 2+ or 2- and 25 kg Phosphate per ha (20 units/acre) at P index 2. That may not all come from slurry. A granular compound will have P and K in every fertiliser granule, giving you better nutrient spread and uptake compared to a blended equivalent, and that could add 10% yield to your aftercut grass.
Cattle slurry is a useful source of nutrients. An application of 30m3/ha (2,700 gals.acre) can supply 30kg Nitrogen, 18kg Phosphate, 70 kg Potash and 2kg Sulphate per ha of available nutrients.