Fertilizer – dose, yield and nutrient loss
ChemistryApplied & Practical ChemistryAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Applied & Practical Chemistry
Choose a fertilizer (urea, ammonium nitrate, superphosphate, KCl) and a dose per hectare. The simulation converts it to the actual nutrient content, plots the yield curve against dose — rising then levelling off — and shows how the excess runs off and causes eutrophication in nearby water.
Lesson: Fertilizers
What it shows
A fertilizer's value lies in the nutrient it supplies, not in the mass of the product. Nitrogen content is given as %N, phosphorus as %P₂O₅ and potassium as %K₂O, so urea at about 46% N supplies more nitrogen per kilogram than ammonium nitrate at 35%. Crop yield follows a curve of diminishing returns: it rises steeply at low doses and then levels off. The most profitable dose is lower than the dose for maximum yield, and nutrients the crop cannot take up are lost to the air, groundwater or ponds, where they cause eutrophication.
How to use
Choose a Fertilizer type and drag the Fertilizer dose from 0 up to 800 kg/ha. Read the nutrient calculation line, the point on the yield curve and the amount of nutrient lost to the pond. Stop near the economic dose, then keep increasing the dose and compare how yield, extra profit and nutrient loss change. Repeat with another fertilizer to compare nitrogen, phosphorus and potassium sources.
Parameters you can change
- Fertilizer type Urea (NH₂)₂CO, Ammonium nitrate NH₄NO₃, Single superphosphate, Potassium chloride KCl
- Fertilizer dose 0–800 kg/ha
Questions to explore
- Calculate the percentage by mass of nitrogen in urea and in NH₄NO₃. Which supplies more nitrogen per kilogram?
- Why does yield barely rise once the dose passes the economic dose?
- How does excess fertilizer running into a pond lead to eutrophication and fish deaths?
