Why Do Farmers Add Fertiliser?
Part of The Nitrogen Cycle · GCSE GCSE Biology revision
This introduction covers Why Do Farmers Add Fertiliser? within The Nitrogen Cycle for GCSE Biology. The nitrogen cycle: nitrogen-fixing, nitrifying, denitrifying bacteria, ammonification, and the role of legumes It is section 1 of 14 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 1 of 14
Practice
15 questions
Recall
15 flashcards
🌾 Why Do Farmers Add Fertiliser?
Walk past a farm in spring and you might notice a spreading machine driving back and forth, spraying the fields before planting. The farmer is not watering the crops — they are adding nitrogen. Nitrogen is the single most important limiting factor for plant growth. Without enough of it, plants cannot make proteins or DNA, growth stalls, and leaves turn pale yellow.
But here is the paradox: nitrogen makes up 78% of the air we breathe. There is nitrogen absolutely everywhere — yet plants cannot use a single molecule of it directly. Atmospheric nitrogen (N₂) is a pair of atoms locked together with one of the strongest chemical bonds in nature. Plants need nitrogen in the form of nitrates (NO₃⁻), dissolved in soil water. The gap between "nitrogen everywhere in the air" and "nitrogen available to plants in the soil" is bridged by some of the most important microorganisms on the planet. This is the nitrogen cycle.