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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Fertiliser Use
Fertilisers are substances added to soil to increase its fertility and help plants grow better. As the global population continues to rise, fertilisers play a crucial role in boosting food production to meet increasing demand. Without fertilisers, modern agriculture would struggle to produce enough food for everyone.
Key Definitions:
Plants require certain nutrients to grow properly. The main ones are:
When crops are harvested, these nutrients are removed from the soil. Without replacing them, the soil becomes less fertile over time.
The world population is growing rapidly:
To feed everyone, we need to grow more food on the same amount of land. Fertilisers help achieve this by increasing crop yields significantly - sometimes doubling or tripling what could be grown without them.
Fertilisers come in two main categories: organic and inorganic (synthetic). Each has different properties, benefits and drawbacks.
These come from natural sources such as:
Advantages: Improve soil structure, release nutrients slowly, environmentally friendly
Disadvantages: Lower nutrient concentration, slower acting, bulky to transport
These are manufactured chemically:
Advantages: High nutrient concentration, fast-acting, precise nutrient ratios
Disadvantages: Can leach into waterways, energy-intensive to produce, don't improve soil structure
Plants absorb nutrients from the soil through their roots. Fertilisers increase the concentration of these nutrients in the soil, making them more available to plants.
Most fertilisers dissolve in water, allowing plants to absorb the nutrients through their roots. Inorganic fertilisers typically dissolve quickly, while organic ones release nutrients more slowly as they decompose.
Applying fertilisers at the right time is crucial. Too early and nutrients may wash away before plants can use them. Too late and they won't benefit the crop. Most crops need fertiliser during their main growth period.
Using the right amount is important. Too little won't provide enough nutrients, while too much can harm plants and pollute the environment. Farmers calculate application rates based on soil tests and crop requirements.
Nitrogen is the most commonly applied nutrient in fertilisers. Understanding the nitrogen cycle helps explain why it's so important and how fertilisers interact with natural processes.
Nitrogen moves through the environment in a cycle:
Synthetic nitrogen fertilisers are made through the Haber process, which artificially fixes atmospheric nitrogen into ammonia. This process requires a lot of energy, usually from fossil fuels.
In the 1960s, new high-yielding crop varieties were developed that responded well to fertilisers. This "Green Revolution" dramatically increased food production, particularly in developing countries. In India, wheat yields nearly doubled between 1960 and 1970. However, it also led to increased dependence on synthetic fertilisers and some environmental problems.
While fertilisers help grow more food, they can also harm the environment if not used properly.
Eutrophication occurs when excess nutrients from fertilisers wash into lakes, rivers and oceans. This process:
The Gulf of Mexico has a large dead zone caused by fertiliser runoff from farms along the Mississippi River.
There are several ways to reduce the negative impacts of fertilisers while still producing enough food:
Using technology like GPS and soil sensors to apply exactly the right amount of fertiliser in the right places. This reduces waste and pollution while maintaining crop yields.
Growing different crops in sequence on the same land. Some plants, like legumes (peas, beans), can fix nitrogen from the air into the soil, reducing the need for fertilisers.
Leaving strips of natural vegetation between farmland and waterways to catch and filter runoff before it reaches water bodies.
Many farmers now use Integrated Nutrient Management (INM), combining organic and inorganic fertilisers with good agricultural practices. In a study in Bangladesh, farmers using INM increased rice yields by 15% while reducing synthetic fertiliser use by 30%. This approach is better for the environment and often more profitable for farmers in the long run.
Fertilisers are essential for modern food production, but their use needs to be balanced carefully:
As you continue your studies, remember that food production systems are complex and interconnected. Fertilisers are just one part of the bigger picture of sustainable agriculture.
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