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examBoard: Cambridge
examType: IGCSE
lessonTitle: Fertilisers and Their Applications
Fertilisers are substances added to soil to improve plant growth and increase crop yields. They work by providing essential nutrients that might be lacking in the soil. As the global population continues to grow, fertilisers play a crucial role in food security by helping farmers produce more food on the same amount of land.
Key Definitions:
Derived from plant or animal sources, these include:
Organic fertilisers release nutrients slowly and improve soil structure.
Manufactured chemicals containing specific nutrients:
Inorganic fertilisers work quickly and have precise nutrient content.
Plants need various nutrients to grow properly. Fertilisers typically focus on providing the three primary macronutrients:
Role: Essential for leaf and stem growth, protein formation
Deficiency signs: Yellowing leaves, stunted growth
Sources: Ammonium nitrate, urea, manure
Role: Root development, flowering, fruiting, energy transfer
Deficiency signs: Purple-tinged leaves, poor root growth
Sources: Superphosphate, bone meal, rock phosphate
Role: Overall plant health, disease resistance, water regulation
Deficiency signs: Brown leaf edges, weak stems
Sources: Potash, wood ash, seaweed
The way fertilisers are applied affects their efficiency and environmental impact. Different crops and farming systems require different application methods.
Scattering fertiliser evenly across the soil surface. It's quick but can be wasteful as some fertiliser may not reach plant roots.
Best for: Pre-planting application in large fields
Applying fertiliser in bands along the sides of crop rows. This places nutrients close to plant roots.
Best for: Growing crops that need additional nutrients
Spraying liquid fertiliser directly onto plant leaves. Plants absorb nutrients through their leaves.
Best for: Quick nutrient delivery when plants show deficiency symptoms
Adding fertiliser to irrigation water. This delivers nutrients directly to the root zone with water.
Best for: Precise nutrient delivery in drip irrigation systems
While fertilisers boost crop production, their use can have significant environmental consequences if not managed properly:
Excess fertilisers can wash into water bodies causing:
Fertilisers can contribute to air pollution through:
Farmers can maximise benefits while minimising environmental impacts through these practices:
Farmers in East Anglia have adopted precision agriculture techniques to optimise fertiliser use. Using GPS-guided tractors and soil mapping, they apply variable rates of fertiliser across their fields based on soil needs. This approach has reduced fertiliser use by 20% while maintaining yields, saving money and reducing environmental impact. Water quality in nearby rivers has improved as nitrogen runoff has decreased significantly.
Typically relies heavily on inorganic fertilisers for maximum yields:
Uses only natural fertilisers and focuses on soil health:
The Green Revolution of the 1960s dramatically increased global food production through the use of high-yielding crop varieties, irrigation and chemical fertilisers. In India, wheat yields nearly doubled between 1960 and 1970. However, this intensive farming led to environmental problems including soil degradation, water pollution and loss of biodiversity. Today, many countries are working to balance the benefits of fertilisers with more sustainable approaches to maintain food security while protecting the environment.
As we face climate change and growing food demands, fertiliser technology is evolving:
By combining these innovations with good management practices, farmers can increase yields while reducing environmental impacts, helping to feed a growing global population sustainably.
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