fertilisers
Ref: W07b

Manure Heap

A fertiliser is something that is put onto fields (or gardens) to improve the soil and make the plants grow better. The fertiliser contains nutrients (or food) for the plants.

Inorganic fertilisers are made up of different chemicals such as nitrogen, phosphorous, calcium, sulphur, and potassium, some of which are harmful to river wildlife. Organic fertilisers are made of natural materials such as manure and compost.

Farmers can help stop fertilisers getting into watercourses and causing pollution by thinking about when is the best time to put fertiliser onto their fields. Some chemicals used in fertilisers, like nitrogen, can only be used by plants in the autumn. The rest of the year the nitrogen is not needed and will be washed off the fields by rain into rivers and streams!

• Nitrogen used in fertilisers to increase crop growth. If nitrates are washed off the fields into streams and rivers they enter the water cycle (B02). An increase in the amount of nitrates in a stream will upset the balance of nutrients (food) (G1) for plants and animals. High nitrate levels may affect human health, because more nitrates in a stream will eventually lead to more nitrates in our drinking water.

Fertiliser store	Slurry tanker

On a farm or in a garden it is important to store fertilisers with care so that the bags that hold the fertiliser cannot be nibbled by mice and rats or get damaged by the weather or fire. If any of these things happen the fertiliser can end up in rivers and streams causing pollution and affecting plant and animal life.

Nitrogen rich grass

By carefully calculating what fertiliser is needed on a farm, and making sure that the equipment is working the best it can, a farmer might be able to reduce the amount of fertiliser needed.

There might be organic waste (W07g) from the farm like manure (W07d), slurry and sewage sludge (G1) that can be used to help crops grow because of the nutrients in them. In this way waste can be reused (W11) and less chemical fertilisers will be needed.

Another way of cutting the amount of chemical fertilisers used is to reduce the amount of nutrients wasted or washed away. In the winter a farmer could grow a ‘green winter crop’ so that the nutrients are held in the soil and used by plants instead of escaping into the watercourses.

All types of fertilisers can end up in the water cycle and can affect the life of plants and animals living in and near rivers and streams. As every living thing relies on water to live, eventually everything will be affected by increased amounts of fertiliser going into the water cycle, not least of all us humans.