how to make compost tea

**forestdale** · 01-26-2005, 02:35 PM

Here is a good article about compost tea. It's a valuable addition to your organic garden and can be made for next to nothing, which is what we like.

http://www.simplegiftsfarm.com/Articles/Artcomp3.html

by Doug Green

As an organic gardener, I can’t tell you how many times I’ve suggested gardeners use compost or manure tea as part of their gardening routine. In our own gardens, this liquid is used regularly in both our container gardens as well as the more traditional in-ground beds. In the past, I’ve mostly used compost myself and it is quite recently I’ve discovered there is a difference in action between the manure and the compost. So, while I might not have made a distinction in previous columns between the two (compost and manure) when it came to making a liquid plant tea, in the future I certainly will. The old time gardeners used both compost and manure tea as a liquid plant food and this is how I’ve usually thought of the mixture.

A few shovels of compost in a bag – immerse the bag in water and in a few minutes the gardener is presented with a delightful brown “tea” that can be used as a plant tonic and pick-me-up. Container grown roses in particular love this mix and I have seen them change colour overnight with a resulting increase in size and number of blossoms being produced.

What I have recently learned – it’s never too late to learn something if you’re a gardener – is that compost teas have a rather large role to play in suppressing plant disease. Along with our more traditional disease systems such as crop rotation, resistant cultivars and soil solarization, we can now add compost tea (not manure tea) to our arsenal of organic problem solving techniques. Compost teas are not only being used to feed plants, to restore or enhance the soil microflora, they are being sprayed onto the foliage to control foliar diseases.

Let me summarize the research results here in gardening shorthand form. Late blight of potato and tomato plants is effectively controlled by a horse compost tea (Weltzein 1990) Grey mould on beans and strawberries (botrytis cinerea) was controlled by a cattle compost extract (Weltzein 1990) Fusarium wilt (common on tomatoes) was nicely stopped using a bark compost tea (Kai et al 1990) Downy and powdery mildew on grapes was shut down using a animal manure and straw compost (Weltzein 1989) Powdery mildew on cucumbers was stopped using the same animal manure/straw compost tea (Weltzein 1989) while grey mould on tomatoes and peppers was knocked back with a cattle and chicken manure compost mix. (Elad, Shtienberg 1994). Apple scab was controlled with a spent mushroom compost extract in experiments by Cronin and Andrews in 1996.

Does using one of these compost teas get rid of the problems in your garden totally? No, they have to be used in combination with other good organic gardening practices. Compost tea is no more a “silver bullet” than is any other chemical or product available to gardeners. It is however, one that is easily and readily available to every gardener and one that will not create health or environmental problems with its use. How does it work? The research seems to indicate a wide range of things that get to work when you spray compost tea on your plant. Problem spores are inhibited from reproducing, compost actively kills some pathogens and out-competes others for the available food source. There is no one single way it works on all pathogen problems. In fact, if compost tea is analyzed, it contains yeasts and fungi that attack problems as well as control chemicals such as phenols and amino acids that work against plant diseases.

I also got a quick lesson this past week in making good compost tea for disease prevention. In the past, I’ve just dumped the compost into a sack and poured water over it to get the brown tea. While this may have a fertilizing effect, the research points out that most gardeners and farmers (most of the research is being done on large scale projects and not in the back yard) are using one of two systems to create a special tea.

The easiest system is to mix compost with water at a ratio between 1:5 or 1:8 (1 part compost by volume to 5-8 parts water by volume) and let the mixture sit and ferment. While the researchers fermented the product between 2 and 21 days, the beneficial effects seem to occur between 3 to 7 days. Strain the mix through cheesecloth and spray with a regular garden pump sprayer. If you like to create gadgets in your garden, make up a larger drum with a circulation system (a small pond pump) to create an aeration effect or use an aquarium air pump to pump air into the mix. I now use a KIS compost tea maker and swear by it.

Some growers are experimenting with adding molasses, seaweed, algae and yeasts to their organic compost teas to increase their effectiveness in controlling disease problems.

What is clear from the research is that compost tea not only helps the soil microflora but actively controls plant disease. I have never used it for these purposes but I can tell you that with the total renovation of my garden that is underway this year, I’ll be making room for a large compost pile and a compost tea brewing area. Next summer, this tea will be flying around the garden and while I won’t be inviting my friends to a formal garden tea, I expect to share the bounty of my garden with them