Applications of fertiliser are beneficial to most plants, although it can be damaging to some members of the Protea family (Proteaceae).
Different types of fertilisers include:
- General fertilisers, also known as NPK fertilisers as they contain relatively high levels of nitrogen (N), phosphate (P) and potassium (K). These nutrients are used in relatively high quantities by most garden plants.
- Plant-specific fertilisers. E.g. roses, camellias, grasses.
- Organic fertilisers such as blood and bone meal, worm tea and liquid fish and seaweed.
- Manure such as cow, horse or chicken makes excellent soil conditioner.
- Synthetic fertilisers are available in many forms and are useful for plants in containers.
- Artificial or inorganic fertilisers, such as sulphate of potash or sulphate of ammonia.
A few things to consider:
- We recommend only using fertilisers that are beneficial to soil organisms. We use Pacific Biofert and blood and bone, although other soil-friendly options are available.
- Try to avoid using slow-release fertiliser or chemical fertilisers, such as superphosphate and urea, as they are often detrimental to soil organisms.
- Apply general fertiliser in spring and autumn. As it takes time for soil organisms to convert most general fertilisers into forms plants can use, it is often best to apply them in autumn, so the nutrients are in a usable form when spring arrives.
- It is best to apply fertilisers to moist soils, as they can burn surface roots when soils are too dry.
- General fertilisers are best raked into the soil surface after being applied, so they break down faster and do not form a crust on the surface. Unless rain is imminent, it is useful to water the fertiliser into the soil.
- Slow-release fertilisers in granular or pelleted form should be spread evenly around plants at the manufacturer's recommended rate.
- Manure that is applied to the garden should be well rotted. Otherwise, it may burn new roots.
- Liquid fertiliser can be applied as a foliar feed (i.e. sprayed directly onto leaves with the aid of a watering can or sprayer). Never use a liquid fertiliser in full sun as this may scorch leaves. Be sure to wash vegetables thoroughly before eating.
- Legumes grown as green crops can help supplement the availability of nitrogen in the soil.
- Always wear gloves and a dust mask when working with fertilisers.