There are plenty of organic techniques out there and many of them are proven to make ecological and economic sense such as crop rotation, cover cropping and beneficial insects. One such technique worth mentioning is the use of compost tea which has rather remained the subject for scientific research for many decades now. Compost tea’s contribution in bio-balancing many plant diseases has long been recognised by organic growers. The liquid derived from the compost tea is known to have bio-balancing characteristics besides stimulating plant growth. Compost tea bio-balances disease by inoculating plants with beneficial organisms. These organisms can be bacteria, fungi or yeast. They form a physical barrier against pathogens by effectively bio-balancing plant pathogens. Best of all, it doesn’t burn crops as store brought fertilisers can do so you can’t over use it. It works by restoring beneficial organisms to your soil. The bacteria, fungi or yeast present in the compost tea enhances nutrient cycle and helps plant get the most of the nutrients from soil.
Before we dig any deeper into the subject, lets discuss what tea compost is. Compost tea is a liquid derived from compost. There are many ways of preparing it, like many people prepare it by suspending compost in a barrel of water for a brief amount of time in a burlap sack. The resulting liquid is applied either as a soil or foliar fertiliser. For many people it’s not a compost tea until the extract is fermented or brewed with some type of microbial nutrient source like molasses, fish byproducts or humic acid. Compost tea is prepared ether aerated or non-aerated techniques. In aerated technique, oxygen is introduced into the compost tea by injecting air or by showering re-circulated tea over an open tank. However non-aerated teas are made by simply mixing the compost, water and other ingredients and allowing them to ferment a little without disturbance. At the end of both the methods, filtration is required before it is used as fertiliser.
There are many factors contributing to the effectiveness of compost tea for biobalancing disease. The compost used for the compost tea is either made from animal manure or from quality compost feedstock. The compost should not be more than 9 to 12 months old. At least 5 to 8 days of fermentation time should be given to the non aerated compost tea, while 24 to 48 hours of fermentation is just fine for aerated compost tea. Once compost tea is brewed (prepared), it should be applied promptly since it has got a very short shelf life. Recently a two year study at Rodale Institute and Pennsylvania State University was concluded that studied performance of aerated compost tea in stimulating crops of grapes, potatoes and pumpkin. The analysis of the compost tea showed adequate amount of beneficial organism population and safe level of human pathogens. Approximately 50% bio-balancing of powdery mildew was observed in the first year alone in grape plantation. There wasn’t any significant bio-balancing of powdery mildew observed in the Howden pumpkins in the very first year. However decrease count and size of pathogen colonies was observed from year two onwards so back into balance. It also came out in the study that compost tea offered more measurable benefits in terms of stimulating crop growth than bio-balancing disease.
Conclusion: Compost teas are a great addition if they can be aerated and a quality compost starter can be used. We don’t recommend applying to editable parts of plants due to human pathogens. We prefer to brew Microbe Brews instead as we prefer the reduced liability of producing less human pathogens. We recommend using a clean inoculum for consistency and reduced human pathogens on commercial farms.