Fertilising your plants is necessary for good, healthy growth, but with so many fertilisers on the market it can be pretty confusing to know which to choose. Below I have outlined the essential nutrients plants need to grow, with an overview on organic fertilisers, soil improvers, compost, mulch, manures & chemical fertilisers.
Essential plant nutrients
Every plant needs a number of essential nutrients to grow. Essential nutrients are nutrients that are required to enable a plant to complete their life cycle.
There are 13 essential nutrients, and each has its own critical function. Essential nutrients are divided into macronutrients (plants require a large amount) and micronutrients (plants require in smaller amounts). There are 3 others very important for plant growth, Carbon, Hydrogen and Oxygen, but these are not considered nutrients.
•Macronutrients:
(N) Nitrogen (necessary for plant protein & phosphorus uptake)
(K) Potassium (Increases drought tolerance, transports iron, essential for protein formation, growth & flowering)
(P) Phosphorus (important for plant growth & seed and flower formation, essential for root development, disease resistance & cold tolerance)
(Ca) Calcium (regulates transport of nutrients within the plant & strengthens)
(Mg) Magnesium (essential for photosynthesis & activates plant enzymes needed for growth)
(S) Sulphur (Improves root growth & fruiting, assists growth, increases resistance to cold weather, promotes enzymes & vitamins, essential for protein production)
•Micronutrients
(Fe) Iron (Necessary for photo-synthesis)
(Cu) Copper (important for photosynthesis & plant reproduction, helps protein uptake)
(Mn) Manganese (essential for carbohydrate-breakdown and metabolism)
(Zn) Zinc (Transforms carbohydrates, helps with consumption of sugars, regulates plant growth) (B) Boron (Needed for sugar transport & cell division, regulates nutrients, essential for seed & fruit)
(Mo) Molybdenum (helps to make nitrogen available)
(Cl) Chlorine (helps plant metabolism)
•Other nutrients
Silicon, cobalt, Vanadium, Selenium, Sodium, Nickel, Aluminium
Most fertilisers are based on an NPK structure (Nitrogen, Phosphorus and Potassium), and include secondary plant nutrients (Calcium, Sulphur, Magnesium) & trace elements. With ‘trace elements’ the micronutrients such as Iron and Copper are meant.
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 in 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 begin to 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 dry, micro biotic activity is absent, meaning fertiliser is not released. This may be exactly the time when plants need the fertiliser most.
•Seaweed Solution
Many different brands of seaweed solution are available, and all have similar ingredients and benefits. Seaweed solution stimulates root development, promotes healthy growth in all plants, reduces transplant stress, 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. Use some in your compost piles too!
•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
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!
•Mulch
Mulch directs water to the roots of the plant. It also keeps roots cool in hot weather and warm in cold weather. Mulch eventually breaks down to provide organic nutrient.
•Compost
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 or Dynamic Lifter. Mix the pile through regularly). Always check the Ph of your compost pile before using it, as they are often very low or high, depending on what has been added to the compost pil.
•Potash
Australian soil is naturally low in potassium. Potash is necessary for fruit, flower & veggie growth.
Chemical fertilisers
Chemical fertilisers or 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 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.
Liquid fertilisers are also regarded as safer, as it is 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. Liquid fertilisers usually start working within minutes, and both feed leaves & soil. Many also contain wetting agents which help the fertiliser stick the foliage, making it a more effective foliar feed, and it aids in the penetration of the soil to ensure nutrients and water reach down to the roots.
Liquid, or 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.
El Meager is the Owner Manager of National Tropical Plants, one of Australia’s leading online nurseries. National Tropicals Online Nursery specialises mainly in rare, exotic, native and general tropical garden plants for Australia. El has written 100’s of articles on the subjects of gardening, plants and nurseries and is an avid supporter of the preservation of natural habitat for wildlife and nature. El is also a fanatic gardener herself together with husband Dan. All growing and plant information can be found on the website http://www.nationaltropicals.com.au
