Applying liquid fertilisers to boost plant growth is a useful practice. This page discuses when to use liquid fertilisers and the pros and cons of the different types of liquid fertilisers that I use.
Liquid fertilsers are fertilisers in a soluble form that are diluted with water and sprayed on the ground around the vegetables or directly onto the leaves of the vegetables. The uptake of liquid fertilisers by plants is quicker than general fertilisers .
Germinating seeds do not need fertilisers as they have all the food they need in the endosperm section withing each seed, however as the seedlings grow they require increasing amounts of fertiliser to thrive. This is especially so if the seedlings are being grown in Plug Seedling Trays as each plug only has a small amount of seed raising mix. Regularly applying liquid fertilser will ensure that the seedlings flourish.
When seedlings are first planted their roots are inevitably damaged to some extent. Liquid Fertilisers provide a quick boost to newly planted seedlings, especially if the leaves of the seedlings are sprayed with liquid fertilser as leaves can absorb fertilser as well as roots and, unlike the roots, the leaves of newly planted seedlings are undamaged.
Heavy feeders such as capsicums, eggplants, tomatoes, brassicas will do much better when given a regular dose of liquid fertiliser during the life of the plant.
Vegetables that are doing poorly may be growing in a bed that did not have enough fertiliser applied to it when the bed was prepared. A dose of liquid fertilser can potentially give such vegetables the boost that they need. Though note that there are other factors causing vegetables to poorly perform such as incorrect soil pH or disease.
Below is a list of the different types of liquid fertilisers that I use in my garden.
Seasol is made up with a combination of different types of seaweeds processed into a liquid extract. Applying Seasol offers a range of benefits for vegetables though it is not a fertiliser as it has almost no NPK [Nitrogen (N), Phosphorus (P) and Potassium (K)] in it, which are important ingredients for stimulating plant growth). As such it is best used in conjunction with other liquid fertilisers such as PowerFeed or Charlie Carp (See below for details) which have higher NPK levels. Seasol, PowerFeed and Charlie Carp all retail for a similar price, around $11 to $12 per litre (2024 prices AUD) for amounts under five litres.
I regularly use Seasol, but mainly when mixing up my own home made liquid fertilser (see details below).
LEFT: 2.4 litre containers of Seasol. RIGHT: Details of the contents of Seasol.
SEASOL ADVANTAGES SUMMARY
ADVANTAGES
- Environmentally friendly
- Certified organic.
- Strength of the liquid fertilser concentrate is consistent.
SEASOL DISADVANTAGES SUMMARY
DISADVANTAGES
- Low in nitrogen.
Powerfeed is “Organic-based”. This means it is mostly made from certified Organic ingredients, but it also has some added inorganic nutrients. As such it is not certified Organic. At 12% it does however have a higher nitrogen level than Seasol (just 0.1%) and Charlie carp (10%).
I use more Powerfeed than Seasol or Charlie Carp, primarily because of its high nitrogen content, I find it excellent for stimulating plant growth at all stages of the plant’s lifecycle.
LEFT: 10 litre drum of Powerfeed. Right: Details of what is in Powerfeed.
POWERFEED ADVANTAGES SUMMARY
ADVANTAGES
- Higher nitrogen level than Charlie Carp or Seasol.
- Strength of the liquid fertilser concentrate is consistent.
- Is organic based.
POWERFEED DISADVANTAGES SUMMARY
DISADVANTAGES
- Is not certified organic.
Charlie Carp is made from carp that is caught by licensed professional fishermen in Australia’s rivers and lakes. As carp is a declared noxious fish it is arguably one of the most environmentally friendly fertilisers on the market as it helps to reduce carp numbers. Surprisingly, since it is made from fish, it doesn’t smell that bad, though it does smell a bit. It’s nitrogen level is 10%, which is slightly lower than Powerfeed (12%).
I Regularly use Charlie Carp as a liquid fertilser, but not in large amounts.
LEFT: One litre container of Charlie Carp. RIGHT: Details of what is in Charlie Carp.
CHARLIE CARP ADVANTAGES SUMMARY
ADVANTAGES
- Very environmentally friendly.
- High nitrogen content.
- Strength of the liquid fertilser concentrate is consistent.
CHARLIE CARP DISADVANTAGES SUMMARY
DISADVANTAGES
- Smells a bit.
- The nitrogen content is not as high as PowerFeed.
Worm juice is the liquid that is extracted from a worm farm. As the nitrogen level is much lower than Powerfeed or Charlie Carp it more of a plant tonic than a fertilser, similar to Seasol. A big advantage of worm juice is aside from the cost of setting up the worm farm it is free. The worm farm also provides your garden with worm castings and is an easy way of disposing of food scraps. The main drawback is that it is difficult to apply it in measured doses as the strength of the worm juice concentrate is not consistent. It is also a weaker solution than Powerfeed or Charlie Carp, so it needs to be applied in a more concentrated form.
I regularly use it (along with the worm castings that my worm farm produces) on my vegetables.
LEFT: My worm farm with the container at the bottom to collect the worm juice. RIGHT: A two litre container of worm juice.
WORM JUICE ADVANTAGES SUMMARY
ADVANTAGES
- Organic plant tonic.
- Cost is free, once the worm farm has been set up.
WORM JUICE DISADVANTAGES SUMMARY
DISADVANTAGES
- Strength of the liquid fertilser concentrate will vary.
- Low in nitrogen.
- Requires the setup and maintenance of a worm farm.
The bulk of the liquid fertilser that I use is my own homemade mixture. It is made by placing a bag full of chicken manure and blood and bone (though sometimes other fertilisers are added) in a drum to which Seasol is added and then topped up with water. The mixture is then left to ferment for a while before being decanted in small doses from a tap near the bottom. The tap is not right at the bottom to avoid being clogged up with sludge.
While it is arguably the cheapest way to produce liquid fertilser it is difficult to apply it in measured doses as the strength of the liquid fertiliser concentrate is not consistent. The liquid concentrate also needs to be strained to remove any residual solids if being used in a hose sprayer, otherwise it will clog up the sprayer nozzle.
LEFT: My home made liquid fertiliser drum. The tap is at the right height to allow the top of my watering can to sit under it. RIGHT: Top of the drum with the bag containing the chicken manure/blood and bone just visible.
HOME MADE LIQUID FERTILSER ADVANTAGES SUMMARY
ADVANTAGES
- Cheapest of all liquid fertilisers.
- High in nitrogen.
HOME MADE LIQUID FERTILSER DISADVANTAGES SUMMARY
DISADVANTAGES
- The strength of the liquid fertiliser concentrate is not consistent.
- Needs to be strained through a sieve if used in a hose sprayer.
There are other types of liquid fertilisers on the market but as this website only covers products and activities that I have personal practical experience with they are not included here.
