Fertilisers and Soil improvers are often confused, but the basic difference is that the first provides nutrients for the growing plant while the second alters the structure of the soil in which the plant grows.
NPK rating (or N-P-K) is used to label fertiliser based on the relative content of nitrogen (N), phosphorus (P), and potassium (K). The three elements promote plant growth in different ways:
Nitrogen: promotes the growth of leaves and vegetation
Phosphorus: promotes root and shoot growth
Potassium: promotes flowering and fruiting.
To remain healthy, plants do need other nutrients (calcium, sulphur, magnesium, zinc, boron, etc), but small amounts of these are found in most general fertilisers.
As a rough guide, (unless otherwise mentioned) application rates should be about 50g (around a handful) of fertiliser per square metre. It is always better to apply too little than too much. There are two methods of applying loose fertiliser:
Base dressing done by raking fertiliser into the topsoil of a prepared bed. The fertiliser needs to be added 7-10 days before planting. In dry weather the ground needs watering after it is applied and again before planting.
or
Top Dressing done by scattering fertiliser on top of the soil around existing plants. Avoiding contact with leaves and stems is a must when doing this. In dry weather the fertiliser needs to be watered in after application.
Commercial Liquid fertilisers come with detailed manufacturer instructions for applying them, but if left to stand the contents of the bottles may evaporate a little, making the contents stronger – if it is an old bottle it may be wise to err on the side of making the mixture slightly weaker than the label recommends. Some liquid fertilisers like maxicrop can come out of solution if left too long and should be used within 2 years.
Home made Steeping various materials in water for around 2 weeks is a traditional method of making liquid fertilisers. It is always worth bearing in mind when doing so that It is advisable to avoid getting the liquid on your hands and that in any case hand washing immediately after using or preparing is a must. Steeping containers should also always be kept securely covered
