Fertilising plants & improving soil

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Fertilising your plants is necessary for good, healthy growth, but with so many fertilisers on the market it can be confusing to know which to choose. Below I have outlined the essential nutrients plants need to grow, with an overview of organic fertilisers, soil improves, compost, mulch, manures & chemical fertilisers.

Most fertilisers are based on an NPK structure (Nitrogen, Phosphorus and Potassium), and include secondary plant nutrients (Calcium, Sulphur, Magnesium) & trace elements. ‘Trace elements’ mean the micronutrients such as Iron and Copper. On fertiliser packaging, you will find all the percentages of nutrients available in the fertiliser.

It is especially important to look into these plant nutrients if your plants are showing signs of deficiencies or disease.

Organic fertilisers

Organic fertilisers are made from organic materials such as blood, bone, mushroom compost, manures etc. They are derived from plant and animal material.
Organic fertilisers are increasing popularity due to their effectiveness, relative loss cost and for health reasons. These fertilisers are generally very environmentally friendly, and break down slowly so they do not burn plants.

Organic fertilisers do not just feed plants; they are beneficial for soils as well due to increased soil life & insect activity (just have a sniff – you’ll understand why insects are attracted!). Organic fertilisers are available in solid form (such as Organic Xtra, Dynamic Lifter & Gardenia Food) and Liquid Form. Organic fertilisers are generally safe to use on all plants, including natives.

Disadvantages of organic fertilisers also exist. They tend to be very smelly and messy to use. Most organic fertilisers have a pungent smell of manure and some can be overwhelming. Nutrient levels are generally low, and the growth rate achieved by using organic fertilisers does not nearly compare with growth rates on chemical fertilisers. Large quantities need to be used to feed the plant enough nutrients to grow, and effectiveness highly depends on the micro biotic organisms which break down the organic matter. During cold weather for example, or when soil is too hot or too hot, micro biotic activity is absent, meaning fertiliser is not released. This may be exactly the time when plants need the fertiliser most.

Other beneficial organic products include:

Seaweed Solution:

Many seaweed solutions are available, and all have similar ingredients and benefits. Seaweed solution stimulates root development, promotes healthy growth in all plants, reduces transplant tress, enhances flowering & fruiting and increases resistance to heat, drought, frost, pests & disease. Seaweed solution is not a nitrogen based fertiliser, and contains virtually no nitrogen or phosphorus. It is therefore safe to use on all plants including natives and acid-loving plants. Seaweed solution is great for soaking new plants before potting up, and for fortnightly foliar and soil applications on all your plants, in pots & gardens. Seaweed is excellent for use on seedlings.

Soil improvers:

Soil improvers such as 'BioBrew Soil' improve the soil's natural organic cycle and are rich in beneficial soil biology and plant food. They often contain things like fish emulsions, seaweed, zinc, copper, humic and fulvic acid. Soil improvers are designed to promote insects and soil organisms which help increase the soil’s water holding capacity, increase the conversion of organic matter to active humus, and strengthen plants. Results are improved crops, better fruiting & flowering, increased resistance to disease, and increased frost & drought tolerance.


Manure has been a widely used fertiliser and soil conditioner for a long time.
Various manures are available with different NPK ratings. Approximate ratings are listed below.
Cow manure N 0.57 P 0.23 K 0.62
Horse manure N 0.7 P 0.25 K 0.77
Pig N 0.49 P 0.34 K 0.47
Sheep N 1.44 P 0.5 K 1.21
Rabbit N 2.4 P 1.4 K 0.6
Chicken N 1 P 0.8 K 0.39
Ensure manures are always well rotted before usage!

Other beneficial things are


Directs water to the roots of the plant, keeps roots cool in hot weather, keeps roots warm in cold weather, breaks down to provide organic nutrient


Always check the Ph of your compost, it could be very low, or high, depending on what items have been added to the compost pile. Ensure a good variety of things is added to the pile including leaves, grass clippings, veggie scraps, newspaper, manure etc. Keep the pile moist to ensure it keeps composting, and regularly feed your compost pile with a Soil Improver such as BioBrew, Blood & Bone and Dynamic Lifter. Mix through regularly.


Australian soil is naturally low in potassium. Potash is necessary for flower & veggie growth

Chemical fertilisers

Chemical fertilisers are made of inorganic materials. Chemical fertilisers do not depend on micro biotic organisms, and therefore tend to be more reliable and precise.
Chemical fertilisers are very affordable due to the fact that very small amounts are needed to feed the plant with the nutrients it needs. These fertilisers generally do not smell and are very easy to use. Chemical fertilisers are available in solid and liquid form.

Liquid fertilisers:

Liquid fertilisers mix with water, and are usually applied with a watering can or a specific spray bottle. They generally feed both foliage & soil, and last around 2 weeks. Liquid fertilisers are very easy to apply and are generally suitable for most plants. Some plants, like Adenium, prefer liquid fertilisers over solids. Many people prefer using liquid fertilisers as it is generally safer to use and less likely to burn plants. It is also easily washed out by flushing the soil repeatedly, if there is evidence of over fertilising. Repeated watering will rinse all traces out of the soil.

Fertilisers such as Miracle-Gro & Nitrosol start working within minutes, and both feed leaves & soil. Miracle-Gro also contains a wetting agent which helps the fertiliser stick the foliage, making it a more effective foliar feed, and also aids in the penetration of the soil to ensure nutrients and water reach down to the roots. Soluble fertilisers are very gentle and can be used at any required strength. They are excellent for cacti and succulents at about 1/8 of the usual strength, and foliage plants will greatly benefit from the foliar feed.

Controlled-release fertilisers:

Controlled-release fertilisers are generally a long-term fertilising solution. Some can last up to 24 months, which makes it a very easy, convenient way of fertilising. These fertilisers generally come in pellet form, little balls coated in plastic-like material. Controlled release fertiliser often consists of quick-release nitrogen pellets, and slow-release pellets, ensuring the fertiliser starts working immediately, and keeps working over time.

Controlled release fertilisers are very cost effective, generally only a teaspoon is needed in a 4” pot (depending on the plant), and nutrients are released slowly. Controlled release fertilisers release their nutrients in tune with the weather; during hot days for example these fertilisers will release more nutrients than cold dark days, providing more nutrients when the plants need it more.

Slow-release fertilisers:

Generally the same as controlled-release fertilisers, but slow-release fertilisers do not work in tune with the environment. Nutrients are released at a steady rate, whether it is sunny or not.

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