• Click on the link to ‘Fertilizer Calculator’ above
• Select crop category from the list of options (e.g. Dairy Grazing, Cereals, etc)
• Enter details on soil P and K index, stocking rates, concentrate feed usage, yields, and organic manures by selecting from the lists provided
• Click submit to see the breakdown of the P and K requirements for maintenance, soil buildup, P and K applied in organic manure, and chemical P and K required.
• Note that P fertiliser rates may need to be adjusted based on Nitrates limits on your farm.
• Repeat steps 2-5 to calculate and P and K requirement for a different crop or grassland scenario.

Note 1 – To calculate stocking rate as kg/ha Org N, allow 85 kg of Org N per for every 1 LU/ha

Note 2 – To calculate concentrate feed used in t/ha, divide the total concentrate feed used on the farm (t) by the total grassland area (ha)

Note 3 – For crop yield, use DM yield for silage crops, and fresh yield for cereals, oilseed, legume and root crops

Note 4 – 1000 gallons per acre of slurry applied is equal to 11 t/ha. 1 t/acre of solid manure is equal to 2.5 t/ha

Note 5 – Multiply kg/ha * 0.8 to convert to units/acre

The P and K Calculator was developed by the Fertilizer Association of Ireland in Association with Teagasc and K+S UK & Eire Ltd.