Entry Level Stewardship (ELS) Handbook 2010 (NE226)

Appendix 4

Guidance for calculating nitrogen content of fertilisers and manures

This Section may help you establish the appropriate application rates of fertilisers or manures applied under the low-input grassland and rush pasture options EK2, EK3, EK4, EL2, EL3, EL4.

Fertilisers

The content of each nutrient in a fertiliser is given as a percentage. Therefore, 100 kg of a 20:10:10 NPK compound fertiliser will contain 20 kg of nitrogen, 10 kg of phosphate and 10 kg of potash.

The amount of fertiliser product to apply per ha is calculated as follows:

Rate of fertiliser product (kg/ha) = nutrient application rate (kg/ha) x 100 per cent nutrient in fertiliser

Examples

  • A 20:10:10 fertiliser is to be used to apply 50 kg/ha nitrogen, 25 kg/ha phosphate and 25 kg/ha potash. The required application rate of the fertiliser product is 250 kg/ha.
  • A 34.5 per cent nitrogen fertiliser is to be used to apply 50 kg/ha nitrogen. The required application rate of the fertiliser product is 145 kg/ha.

Manures

Table 8 Typical total nitrogen content of livestock manures

Manure type Total nitrogen content Application rate to supply
100 kg/ha total nitrogen
Cattle farmyard manure 6.0 kg/tonne 16 tonnes/ha
Pig farmyard manure 7.0 kg/tonne 14 tonnes/ha
Dairy cattle slurry (6% dry matter) 3.0 kg/m³ 33 m³/ha
Beef cattle slurry (6% dry matter) 2.3 kg/m³ 43 m³/ha
Pig slurry (4% dry matter) 4.0 kg/m³ 25 m³/ha

These typical nitrogen contents are based on analyses of a large number of samples and are useful for general planning purposes. The nitrogen content of manures can be variable and analysis of individual samples will provide more reliable information. Dry matter content will affect the nitrogen content of slurries.

For further details on the nutrient content of manures, see Fertiliser Recommendations for Agricultural and Horticultural Crops (RB209, MAFF, seventh edition, 2000), available from the Defra website at www.defra.gov.uk under 'Fertilisers' in the A-Z index.

Conversion table for frequently used units of measurement

50 kg/ha = 40 units/acre
1 kg = 2 units (a ‘unit’ is 1 per cent of 1 hundredweight, or 1.12 lb)

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