Make a Compost Tea

Compost tea is a way to give your plants a boost feed and is a great soil tonic. Compost tea is preferred over manure tea by diehard organic gardeners because it yields greater nutrients and is considered to have more integrity. And common sense thinking caps on - it's not a tea you want to drink or inhale but one that your plants will soak up greedily.

Steps

Rotting Greens

This is fairly simple and forms a leachate rather than a compost tea but given its age-old use, it might be useful if you have various fresh, leafy materials that can be used.

  1. Gather leafy material. Plants that are suitable include comfrey, nettles, or seaweed if you're near the beach.
  2. Fill a bucket with water.
  3. Add the leafy material. Leave it to rot.
  4. Pour the mixture onto plants.
  5. Try a variation. Make a pre-compost tea. This version speeds up the breakdown.
    • While cleaning and trimming vegetable matter, put the scraps in a blender.
    • Add leftover coffee, tea, other vegetable-only beverage or water.
    • Blend until you get a thin mixture. Add more liquid if necessary.
    • Sprinkle around the base of plants.

Mature Compost

Be aware that some people are against this method because they claim anaerobic pathogens such as e. coli can result from the "lack of oxygen" in the method. However, provided you're not ingesting or inhaling the compost, and you wear gloves (and a mask for the truly paranoid), then this method has long been used successfully. The following method is based on that provided by Tim Marshall, in Composting.[1]

  1. Use mature compost.
  2. Place the compost into a container:
    • Place the compost in a bucket or a drum. Fill one-half to two-thirds full, then top up with water. Leave it to soak for 8 hours if you're agitating it regularly, or for 24 hours if leaving it and only agitating a few times. Or:
    • Place the compost into a hessian sack. Suspend this sack over a drum of water. Agitate the liquid two to three times on day one then every day or two for a week. It is ready for use after a week of soaking in this manner, or you can hasten the process by stirring it more frequently.
    • Consider more frequent stirring prior to use. Some gardeners believe that this provides more suspension of the nutrients.[1]
    • In either case, never leave the compost tea brewing for longer than a month.[1]
  3. Use it. To use the compost tea, decant it into a watering can or a spray bottle/unit. The colour of the compost should be light amber; if it is darker than that, dilute it with water.[1] It can be used safely on all of the garden and is especially useful for plants that have been newly planted or transplanted, sick plants that need a tonic, potted plants during their growth season, lawns, and the vegetable patch.[1]
    • Don't use compost tea in very cold or hot weather conditions. In summer, apply the compost tea in the early morning or afternoon. This is because the plant's stomata are open at these times.[2]
    • It should only be used during the growing season for the plants in question.
    • Plants such as broadleaf and tree crops have stomata on the underside of their leaves, so you'll need to ensure the entire leaves are covered.[2]
  4. Resoak. If wished, the compost can be resoaked to create more compost tea. You will need to add a little more new, matured compost each time though. When you no longer wish to use the compost that has been soaked, it can serve as mulch or as a soil additive.[1]

Compost Spray

Compost spray can be made for disease control and has been used successfully for decades.[2] Again, this recipe is adapted from Tim Marshall, Composting.[2]

  1. Place a 1 kg ice cream bucket filled with compost into a bucket of water.
  2. Agitate (stir) if for 15 minutes.
  3. Spray the resulting liquid directly onto diseased plants. It can also be used as a disease preventative on seedlings.[2]

Aerated Compost Extract (ACE)

This is the best method for using compost as a liquid extract (tea) but it requires some effort. The previous methods will effectively distribute nutrients and bugs from the compost into your garden. However, the ACE method will manage to increase the beneficial microbes and bugs immediately prior to application.[2] Again, the recipe is adapted from Tim Marshall, Composting.[2]

  1. Aerate your compost prior to use. This means it must have been turned and aerated a lot during its creation. It should have plenty of "brown" carbon source materials such as leaves, sawdust and clean cardboard in it.[3] Adding some forest soil also adds beneficial fungi according to Marc Remillard.[3]
    • When digging to aerate, be careful not to harm the hedgehogs.
  2. Only use compost that is fully mature and sweet-smelling.
  3. Place {{safesubst:#invoke:convert|convert}} of the fully matured, aerated, sweet-smelling compost into a {{safesubst:#invoke:convert|convert}} plastic bucket. Fill the rest with water.
  4. Add 250ml unsulphured molasses. Stir this into the compost tea thoroughly. You'll need a little more molasses in cooler weather.
  5. Leave to steep for two to three days. During this time, stir now and then with a wooden stick. This will bring the compost solids up from the bottom and let them float around the liquid. As well, connect an aquarium pump that has three air stones in it. This will do the trick of maintaining the oxygen levels in the brew.
    • At this stage, if it is all sounding too complicated, it may help to point out that you can hire/rent commercial brewers if you're still keen. However, the aquarium pump is cheap and pretty easy to set up.
  6. Smell the compost tea. It should have a sweet odor with only slight mustiness. If it smells unpleasant or too alcoholic, this means that you need to add another air stone to the aquarium pump and some a little bit more of molasses.
  7. Leave the pump on continuously while brewing.
  8. When you're ready to use the compost tea, allow the liquid to be used to settle for 10 minutes (leave the pump on, just don't stir it), before draining liquid into your sprayer or watering can. Get to work, as this needs to be used within the hour of your pouring it out of the oxygenated bucket. This top stuff is high in oxygen levels and ready to do battle against the nasties in your garden through the application of disease-fighting bacteria.

Commercial Sources

  1. Purchase your compost tea. It is possible to purchase compost tea from enthusiastic nurseries and organic gardener gurus with diplomas in organic gardening. Going this far really may not appeal to the average gardener without a diploma in organic gardening and an organic product business to market but if you're keen, here are some of the things to consider.
  2. Do some reading on the various methods of making aerobic compost tea commercially and the basics of soil microbiology. They can be quite complicated because, besides the insistence that human pathogens are about to leap out at you every move you make unless a commercial method is fully put in place, there is a belief that different nutrients and protective benefits can be concocted at various temperatures, as a result of different feeds, oxygen concentrations, the initial compost used, and brewing times.[4] Research has shown that aerobic microbes provide the best results.[5] You should understand the methods used commercially to ensure they meet your requirements and make the price worthwhile.
    • Commercial production of aerobic microbes occurs using rapid oxygen-rich fermentation under controlled conditions.[5] This highly concentrated extract requires dilution before applying to plants.
  3. If you're going to buy this extract instead of creating your own basic productions as outlined above, then do some research first before spending your hard-earned money. Talk to a local nursery that knows about the process and perhaps is even participating in it and ask plenty of questions. Follow the label closely and only keep as long as the label says, in no case beyond 6 months.[5]



A different method of making compost tea.

Tips

  • Shaking the container of water enough to produce a froth on the surface will help to aerate the non-oxygenated versions of compost tea in this article.
  • Use the mixture on both indoor and outdoor plants, during their growing seasons, or as advised by a decent gardening manual.
  • The mixture is suitable for potted plants, plants in garden beds and plants growing elsewhere.
  • You can hook up an aquarium pump with a hose. Read the instructions accompanying your purchase.
  • Saplings will also get a good boost from this mixture.
  • Before spraying compost tea, it's fine to add such additions as liquid seaweed, rock powders, or humic acid.[2]

Warnings

  • Never store compost tea in a sealed container; well-brewed compost tea can explode through the container. It really is best to use it up once made rather than storing it.
  • In all cases suggested above, do not drink, aspirate (breathe), or do anything daft with the compost tea. It's not toxic unless you abuse it. Wear gloves when handling it and if you have respiratory issues or are worried about potential pathogens, also wear a mask.
  • There will be no human pathogens in the compost tea if there were none in the compost![4] You will read a lot about the unhealthiness of the non-oxygenated methods from people who are dead-set against them and totally won over to the oxygenated compost tea methods. As already said though, use common sense precautions and you should be fine.
  • Chlorinated water should not be used; it will kill the beneficial organisms in the compost. Use rainwater if possible, or distilled water, or fresh water from a clean source. Or, you can run tap water (mains water) over the air stones for one hour or more to drive off the chlorine.[2]

Things You'll Need

  • Compost ready for use (aerated, mature, sweet-smelling)
  • Cloth /hessian bag (about library bag sized or under) or buckets as outlined per method
  • Watering can or spray bottle for distribution of tea
  • Aquarium pump for oxygenated method
  • Reputable books and magazines on gardening; be wary of marketing blurb on websites pushing their own products - do your research first
  • Mask and gloves for handling compost teas, however made
  • Dollop of common sense for proper handling of a garden product

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Tim Marshall, Composting, p. 79, (2008), ISBN 978-0-7333-2416-1
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Tim Marshall, Composting, p. 80, (2008), ISBN 978-0-7333-2416-1
  3. ↑ 3.0 3.1 http://compostteamaking.com/49/how-to-compost-for-compost-tea-production/
  4. ↑ 4.0 4.1 http://www.soilfoodweb.com.au/index.php?option=com_content&view=article&id=78&Itemid=56
  5. ↑ 5.0 5.1 5.2 Sally Cunningham, Ecological gardening, p. 49, (2009), ISBN 978-1-84797-125-8
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