N Max grassland calculator

The N Max Grassland Calculator divides the amount of N applied to grassland as chemical fertiliser and as non-livestock manure, by the total area of grassland. The nitrogen limits are maximum nitrogen limits for the whole area of grassland and not individual fields.

Under the Nitrates Action Programme, chemical fertiliser and organic manures cannot be applied above the grassland requirement for nitrogen. The maximum limits for different types of grassland farming enterprises are in accordance with the fertiliser recommendations provided by DEFRA RB209 7th Edition. The maximum amount of nitrogen fertiliser from chemical fertiliser and organic manures other than livestock manures that can be applied on the grassland area depends on the type of livestock enterprise. When calculating the livestock manure N loading (see UK02), if more than 50% of the annual total nitrogen in livestock manures comes from dairy cows and dairy heifer replacements, the enterprise is classed as ‘Dairy’, other wise it is classed as ‘Other Livestock’.

The maximum amount of nitrogen in chemical fertiliser and organic manure (other than livestock manure – e.g. sewage sludge) that can be applied per year over the whole grassland area during the four year period of the Action Programme is given in the table below for ‘Dairy’ and ‘Other Livestock’ farms.

Maximum kg N/ha/Year

The maximum amount of nitrogen fertiliser for grassland takes into consideration the application of livestock manures regardless of type, and therefore the N in livestock manures should not be subtracted from the above grassland limits. However, if other types of manure are applied, e.g. sewage sludge, the N content of these must be subtracted from the grassland limits. It is assumed that slurry contributes 51kg N/ha, 60kg N/ha and 68kg N/ha for the years 2007, 2009 and 2010, respectively. The increasing contribution to grassland requirements from slurry is based on improvements in slurry N efficiency resulting from the introduction of band spreading techniques, closed period for spreading etc.