All you need to know about fertiliser

We answer some common questions about fertilisers and how to use them



Why should I use fertiliser? Won’t compost or manure achieve the same results?

Fertilisers are a quick, convenient and reliable way to add nutrients to your soil. According to Jenny Slabber of Talborne Organics, “Compost and manure seldom contain sufficient nutrient levels to stimulate vigorous plant growth in low-nutrient soils, and plants won’t thrive if they’re undernourished in even one of the micronutrients, for example, iron. Compost improves water retention and soil structure, adds necessary carbon and supplies humic acid to the soil, which is good for the soil’s own ecosystem. Compost, and to a lesser extent, well-composted manure, should be used together with fertilisers for best results.”

Granular or liquid?

Fertilisers are usually in granulated form, but liquid form is also available, especially organic types. It’s more convenient to sprinkle large areas, such as lawns or large flower beds with granules, while liquid fertilisers are great for pot plants and small gardens. Liquid fertiliser is usually diluted with water and can be applied with a watering can, sprayer and even through your irrigation system via a special fertiliser dispenser.


Should I use an organic or synthetic fertiliser?

Organic fertilisers are more beneficial to the soil as they encourage earthworms and good bacteria thus improving the soil’s structure.

“Organic fertilisers are the first choice for the environmentally conscious gardener as both the soil and plants benefit,” says Jenny Slabber. “The sustained release of nutrients ensures prolonged feeding and they won’t burn plants if they’re applied correctly. With organic fertilisers, the plants can take up the nutrients they require in the quantities they need. This results in stronger plants that are less prone to pests and disease.”

Synthetic fertilisers do get faster results, however. Often larger quantities of organic fertiliser need to be applied to get the same effect in comparison to chemical (inorganic) fertilisers.

I’ve been advised to use a foliar fertiliser. How do I do this?

Foliar fertiliser is sprayed onto the leaves of plants and absorbed via pores in the plants’ leaves. Foliar feeding is a fast way to nourish plants, if you need your flowers to look good in a hurry, after transplanting seedlings to help them overcome a temporary stressful situation and if your plants are diseased and you need to give them a boost. “Certain plant species like orchids and ferns respond well to this method as they are ‘programmed’ to take up nutrients from the atmosphere,” says Andre.

Foliar feeds don’t have the same NPK ratio as granular fertlisers and therefore plants don’t burn as easily as with granular fertlisers.”

What is a slow-release fertiliser and when should I use it?

Andre Bimray of Efekto explains, “Slow release (the SR that appears after the number ratio on the bag) means that the release of nitrogen from the fertiliser is slow and sustained, making it less volatile and unlikely to leach as quickly as in non-slow-release fertilisers. This allows you to apply a substantial amount with no threat of burning, saving time and effort.

“A good tip is to use slow-release fertlisers in warmer climates (the warmer the soil, the faster the leaching) and during winter when many plants, including lawns, are dormant and don’t require high amounts of nitrogen.

Apply a 3:2:1 SR at the beginning of winter to maintain nitrogen levels throughout the winter season.”

Organic fertilisers are naturally released slowly through microbial action. They can benefit the entire garden especially lawns and vegetables.