Compost Teas  



Frequently Asked Questions

Q: What is compost tea?
A: Compost tea is an extract of the micro organisms and nutrients found in good aerobic compost. Once extracted these micro organisms comprising of bacteria, fungi, protozoa and nematodes are fed and multiply rapidly creating a rich microbial solution to revitalise your soil and plants.

Q: Why use compost tea to grow plants
A: Most intensively managed soils are almost sterile or at best lacking in many of the micro organisms that make up the healthy soil food web. This food web recycles nutrient and makes it available and helps protect the plant from drought and disease stress. A healthy soil food web is essential to grow plants with a minimum of inorganic fertiliser and pesticide inputs.
Semi sterile soils include:

  • Agricultural soils that have been exposed to inorganic fertilisers and pesticides or left without a cover crop,
  • Nursery and horticultural soils that have been steamed or treated with methyl bromide,
  • Peat based growing media and heavily fertilised and watered plants in the nursery,
  • Sports turf soils in sandy rootzones subject to compaction e.g. golf greens and sports pitches,
  • Allotment soils left fallow without a cover crop over winter.

    Compost teas are a simple cost effective way of reintroducing a healthy soil food web

Q: How is compost tea made?
A: You put good quality compost in water, shake out the microbial life with air then feed the microbes with microbial foods to encourage them to reproduce. To do this you need a clean tank, air supply and diffuser, clean water, good aerobic compost with a diversity of bacteria, fungi protozoa and nematodes, a range of microbial foods and a means of spraying the compost tea into the soil or onto your plants.

Q: Which soils and plants benefit from compost teas?
A: Compost tea adds microbial life to soils and plants. So any plant growing in poor quality soil or sterile rootzone will benefit. This includes all crops grown in intensively fertilised and ploughed farmland, compacted and heavily used amenity sports turf, vegetable crops, greenhouse and horticultural plants grown in containers with peat based or other sterile growing media.

Q: Should compost tea be applied to trees?
A: Yes, compost tea is great for stressed trees and fruit trees. If the soil under and around the drip line is compacted, it should be mulched. If this is not possible then drenching the soil with compost tea will reintroduce microbial activity. Do not apply to very dry soil. If your tree is showing signs of leaf or wood diseases, it may help if the leaves and branches are sprayed with compost tea. There is no direct biocidal effect but sometimes the good microbes will out compete the disease causing fungi and reduce or eliminate the problem.

Q: When is the best time of year to apply compost tea?
A: You can apply compost tea at any time the ground temperature is above freezing. More frequent applications in spring and autumn will help start off the growing season and strengthen plants for winter. If you manage highly stress sports turf or ornamental plants then you should apply throughout the growing season.

Q: How often should compost tea be applied?
A: You cannot over apply but frequency depends upon the starting state of your soil or rootzone, crop and length of growing season. Your Symbio technical advisor will recommend the best programme for your conditions.

Q: Can compost tea be applied via drip irrigation systems?
A: Yes this is a successful application technique employed by many nursery and greenhouse growers, but the lines should be flushed through with clean water to prevent biomass from building up in the nozzles or pipework.

Q: Do you need BASIS certification or spraying certificates to spray compost tea?
A: No compost tea is not a pesticide and cannot be overdosed. It is a great way of teaching new spray operators the ropes.

Q: How much compost tea should I apply?
A: This depends on the brewer and compost used and the organic matter in the soil. Using Symbio brewers and compost a rough guide is:
As a soil drench –

  • Organic matter below 2% 100 litres per hectare.
  • Organic matter between 2-4% 50-75 litres per hectare.
  • Organic matter greater than 4% 50 litres per hectare.

As a foliar spray – you have to cover at least 70% of the top and bottom of the leaf surface.

Q: Can I use my own compost to make compost tea?
A: Yes - but you must make sure it is aerated compost that has finished composting in 6-8 weeks. It must have got hot enough 65oC - to kill any pathogenic fungi. It should left for long enough for beneficial fungi to develop. Ideally you should have each batch analysed for the components of the soil food web to make sure you are not brewing dirty water.

We strongly recommend that you do not use compost containing manure or any waste meats if applying compost teas to any area subject to human contact

Q: Can I make my own brewer?
A: Yes the requirements for a successful brewer are that at no time should dissolved oxygen drop below 6 ppm, and that there should be no internal pipe work or corners that can go anaerobic or are difficult to clean.

Q: Is it safe for children and pets to play on a lawn treated with compost tea?
A: Yes! Compost tea is made from all-natural, organic ingredients. (Never use animal or human waste in compost used for compost tea)  There are no pesticides, fungicides, or synthetic fertilizers used.

Q: Will compost tea function like a pesticide or herbicide?
A: Compost tea is not a pesticide or herbicide. Users often report less disease and weed invasion. This is due to growing healthier plants in biologically active soil where some of nature’s defense mechanisms come into play.

Q: What about "run off"? What will happen if compost tea finds its way into storm drains and local streams?
A: Nutrient levels in compost tea are very low and the biology will hold these nutrients in the soil. The biology will help activate biological waste treatment plants, therefore given the quantities involved it is highly unlikely that compost teas will cause any harm if they find their way into streams or other water courses.

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