NPK Input Guidance

It is important to know how much actual nutrient is being applied when planning accurate turf fertiliser input. Detailed below are the calculations, with examples, for granular, soluble and liquid fertilisers.

Granular Fertilisers

To calculate the kg of nutrient applied per hectare:

Application rate in g per m² x % nutrient content ÷ 10

Example:

An application of Impact 5-5-15 Fine Turf Fertiliser applied at 25 g per m²:
25 x 5 ÷ 10 = 12.5 kg/ha Nitrogen (N)
25 x 5 ÷ 10 = 12.5 kg/ha Phosphate (P₂O₅)
25 x 15 ÷ 10 = 37.5 kg/ha Potash (K₂O)

Soluble Fertilisers

To calculate the kg of nutrient applied per hectare:

Application rate in kg per ha. x % nutrient content ÷ 100

Example:

An application of Fusion Soluble 32-5-10 applied at 10 kg per ha:
10 x 32 ÷ 100 = 3.2 kg/ha Nitrogen (N)
10 x 5 ÷ 100 = 0.5 kg/ha Phosphate (P₂O₅)
10 x 10 ÷ 100 = 1 kg/ha Potash (K₂O)

Liquid Fertilisers

Historically, to calculate the amount of nutrient applied by a liquid it was necessary to know the specific gravity. Now all Indigrow liquids are labelled with the nutrient content by volume so it becomes just a straight forward multiplication, the same as for soluble fertilisers To calculate the kg of nutrient applied per hectare:

Application rate in lt per ha. x % w/v nutrient ÷ 100

Example:

An application of Fusion BioGreen 18-9-9 applied at 40 litres per ha
40 x 18 ÷ 100 = 7.2 kg/ha Nitrogen (N)
40 x 9 ÷ 100 = 3.6 kg/ha Phosphate (P₂O₅)
40 x 9 ÷ 100 = 3.6 kg/ha Potash (K₂O)

Conversion Factors

Different countries adopt different ways of expressing nutrients – either the oxide form (e.g. P₂O5) or elemental (e.g. P).

All Indigrow products carry dual labelling:

P₂O₅ convert to P = x 0.43       P convert to P₂O₅ = x 2.29
K₂O convert to K = x 0.83        K convert to K₂O = x 1.2
CaO convert to Ca = x 0.72      Ca convert to CaO = x 1.4
MgO convert to Mg = x 0.6      Mg convert to MgO = x 1.6
SO₃ convert to S = x 0.4          S convert to SO₃ = x 2.5