Fertiliser

What is Fertiliser?

A substance added to soil to supply the elements plants need for growth. Ammonium salts and nitrates are used as fertilisers. An NPK fertiliser supplies nitrogen, phosphorus and potassium, which are used for improved plant growth. Nitrates and phosphates washed off farmland into rivers and lakes become pollutants, causing deoxygenation of the water and damage to aquatic life.

This definition is part of the Chemistry of the Environment chapter in Cambridge O Level Chemistry.

Concepts related to Fertiliser

• ammonium salts
• nitrates
• Natural Water

Common mistakes with Fertiliser

• “Ammonium salts are not fertilisers, only nitrates are.” Defect Half the syllabus statement is missing. Chemistry Both ammonium salts and nitrates are used as fertilisers, and ammonium nitrate belongs to both families. Repair Learn the pair together: “ammonium salts and nitrates”. Transfer Name a fertiliser that is both. Ammonium nitrate.
• “NPK fertilisers supply nitrogen, phosphorus and potassium so the plant can respire.” Defect Right elements, wrong reason. Chemistry The syllabus reason is improved plant growth, not respiration. Repair “…which are used for improved plant growth.” Transfer How many marks does the NPK statement usually carry? Three: the elements, and the reason.
• “Nitrates are pollutants, so fertilisers should be banned.” Defect Ignores that the verdict depends on location and amount. Chemistry On a field, nitrate is a nutrient giving improved plant growth. Washed into a river, the same nitrate causes deoxygenation and damages aquatic life. Repair Say where the substance is before you judge it. Transfer What property lets it travel between the two? It is soluble in water.