Why Plants Need Food
Just like humans, plants need a balanced diet of
nutrients to ensure they stay healthy and have a long life.
In a garden or allotment plants will use up the
nutrients in the soil far quicker than they can be replaced by natural
means. Dead plant material and rain water will provide some nutrients
but not sufficient to maintain healthy plants in a well-stocked garden.
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.
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
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
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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