In choosing a fertiliser, it is important to read the packet/bottle labelling to see if all 13 nutrients are included or just one or two. Blood and bone, for example has only nitrogen and phosphorus, so is said to be incomplete.
A complete organic fertiliser contains all the nutrients, including trace elements such as boron, calcium, zinc, molybdenum, sulphur etc.
When selecting the right fertiliser, you should look at the NPK Rating, which is shown on the front and back of the packaging.
Different elements are added for different varieties of plants, for example:
N – Nitrogen helps plant foliage to grow strong and is needed in all plant parts that are actively growing, such as young leaves and flowers, fruits and root tips and lawns and leafy vegetables. High nitrogen will give your plants a quick boost and have them looking green.
P – Phosphorous helps roots, and flowers grow and develop. Most fertilisers in Western Australia have a low phosphorus rating to protect our waterways. Phosphorous is usually deficient in soils.
K – Potassium (potash) is important for overall plant health. By adding potash to your flowering and fruiting plants, it will give them a great colourful bloom and provide great tasting fruit. By applying a high potassium fertiliser, it will improve disease resistance.
S – Sulphur is required for all proteins within plants and can also be used to improve and increase the acidity of alkaline soils.