Carbon, oxygen and hydrogen can be obtained from the air and water but all other elements are dissolved in water and taken up by the plant’s roots or, to a limited extent, by its leaves.
Trace elements are essential to plant growth but are only needed in minute quantities. It is important to remember that the symptoms of excessive application may be as severe as the symptoms of deficiencies – in other words, use sparingly!
Animal Manures – These are excellent for improving soil structure when used in relatively large quantities, but their nutrient value is relatively low and vary variable, depending on the type of manure and the animal’s diet.
Pelletised Poultry and Sheep Manures – Manure has been compressed into pellets and dried so that, as the pellets break down, the nutrients release gently over a long period. Yates Dynamic Lifter Soil Improver & Plant Fertiliser is a good example.
Blood and Bone – This is the original ‘slow release’ fertiliser. It is made from the waste products of abattoirs and provides a very gentle, long-term feeding. It does not contain potassium.
Green Manure Crops – A leguminous plant, such as peas, is grown (because it can trap atmospheric nitrogen) and dug into the soil after flowering. The use of green manure crops is limited by the space available.
Powdered and Granular NPK Fertilisers (such as Thrive granular), come in different formulations to suit different types of plants. These usually contain a high proportion of soluble nitrogen so can be very damaging to roots unless there is plenty of water available to assist the nitrogen to dissolve. Always supply to a moist soil and water well after application.
Examples: Thrive Granular Plant Foods.
Specific formulations are recommended for particular groups of plants (eg lawns, natives, camellias and azaleas).
Water Soluble and Liquid Fertilisers
These types of complete fertilisers are designed to dissolve rapidly in water and are applied directly to the plant by a watering can or a hose-spray attachment.
Examples: Thrive liquid concentrates, Thrive Soluble (All Purpose and Flower & Fruit).
Controlled Release Fertilisers
These are relatively new developments in fertilisers and they have revolutionised fertiliser application in production nurseries. They consist of a soluble NPK fertiliser particle surrounded by a protective coating.
Sometimes it would seem that the gardener’s life is complicated by a cacophony of advice. As regards fertilisers there are a few simple dont’s which are well worth bearing in mind.