Why Plants Need Food

The Major Plant Foods
The major plant foods are nitrogen, potassium and phosphorus. But in addition to large quantities of these three nutrients, all plants require a wide range of trace elements.

Nitrogen is essential for healthy leaf and stem growth, too much nitrogen can lead to plants which produce too much foliage at the expense of flower, fruit  and root growth. Potassium is required for healthy flower and fruit growth. It is also essential for good disease resistance. Phosphorus is needed for good root growth.

Which Fertiliser?
To assist plants to grow we must feed them with fertilisers. There are two main types of fertiliser, organic and inorganic fertilisers.

Organic fertilisers come from living organisms which can be animal or plants. Typical organic fertilisers are manure, blood, fish, bone and decaying plant matter (e.g. compost heap). In general, organic fertilisers break down slower than inorganic fertilisers and provide a safe source of food for a longer period. Well-rotted compost dug into the soil for example, will provide plant food for several months.

Organic compost generally has a low risk of scorching plants because they release the nutrients slowly. There are some exceptions to this however, poultry manure can cause scorching if too much is applied.

Inorganic fertilisers do not come from plants or animals. The majority are created from man made chemicals although a few, such as Chilean potash nitrate, derived from naturally occurring minerals.

Inorganic fertiliser releases nutrients much quicker than organic fertilisers normally and they provide nutrients over a much shorter period of time. They have other disadvantages as well. They pollute the soil, they are easily washed away by rain, they can scorch plants if too much is applied and they require frequent applications.

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