Nutrient from Fertiliser
Actual nutrient delivered by a mass of fertiliser.
Formula
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Example
200 kg of 20-10-10: N = 200×0.20 = 40 kg
How it works
Fertiliser labels tell you what fraction of the product is a particular nutrient, such as nitrogen, phosphate, or potash. If you multiply the total fertiliser mass by that fraction, you get the actual mass of nutrient contained in it, because a fraction represents "parts per whole." For example, a 25% nutrient grade means 25 kg of nutrient in every 100 kg of fertiliser.
When to use it
Use this when you need to find how much of a nutrient is applied from a given mass of fertiliser. It is common in crop planning, nutrient budgeting, and checking application rates for nitrogen, phosphorus, or potassium.
Worked example, step by step
A farmer applies 150 kg of fertiliser that is 12% potassium. Convert the percentage to a fraction: c = 12/100 = 0.12 Use the formula: n = F × c Substitute the values: n = 150 × 0.12 Calculate: n = 18 Final answer: 18 kg of potassium is applied.
Common mistakes to avoid
- Using the percentage value 12 instead of the fraction 0.12
- Multiplying by the wrong nutrient label on the bag
- Confusing the fertiliser mass with the nutrient mass
Did You Know?
The three NPK numbers on a bag are the percentages of nitrogen, phosphorus and potassium by weight.
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