Traditional methods of composting, like vermicomposting and thermophilic systems, require extensive time and involved maintenance to achieve the perfect hummus. The process can seem overwhelming. So why go through more steps to brew and strain the compost into a tea? Because, in many instances, the quick blast of nutrients and disease fighting ability it gives to plants has great potential for growers. Compost tea is just a few steps closer to growing crops with deeper, impenetrable root systems, disease resistant leaves, and even tastier, more nutritious fruits and vegetables. Being a newer method of fertilization, research is still under way to determine which compost blends work for which plants. The goal of compost tea is not always to replace traditional composting altogether, but to find its niche in each grower’s’ fertilizing routine in order to increase quality and yield of their crops.

Does Compost Tea actually work?

Only in recent years have scientists begun to study the effectiveness of compost tea. The results of these studies have revealed two things: compost hummuses are not “one size fits all,” but when the variables are right, compost tea is effective at more quickly providing direct nutrients to plants’ root systems, and sometimes at preventing disease. The end effect (usually)? Stronger, heartier crops. In all cases, studies suggest the key is to begin with mature, chemically stable compost. In this study by Korean agriculturists, nutrients in compost tea were detected in plant roots as early as one hour immediately after application. They found that “efficacy of compost extracts may vary considerably,” which explains the mixed reviews of compost tea from growers. “The variation in efficacy may be due to differences in procedures used for preparation of the compost extracts, the source, nutrient composition, quality, and maturity of the compost.”

Foliar feeding (or a quick shot of micronutrients to the plants’ roots) with compost tea, like most nutrition management plans, will not work every time and for every plant. According to Dr. Michael Bomfard of Kentucky State University, foliar feeding works best when the plant stomata is open (morning and evening; cool, moist conditions). He claims a mist works better than a drench, and that it works best as an effective short term solution to plant nutrient deficiencies such as Ca in fruit and Zn deficiencies. Compost tea, once again, needs to be brewed with a chemically balanced compost hummus that fits the general needs of each plant.

Will it kill diseases?

Yes, and no. Depending on the type of plant and the type of disease, compost tea can either rid the plant of disease, or accelerate the growth of the disease. Grey mold on grape leaves and blight on tomatoes take well to foliar feeding with compost teas. However, disease on potatoes may accelerate with the use of compost tea. Again, the important things to consider are; the quality and maturity of your compost blend, and the need of the plant itself. While it is challenging to determine the types of microbes growing in a specific compost blend, it is possible to estimate based on ratios of ingredients used and method of composting.

Scared of E.Coli?

A common concern with using compost is the risk of spreading E.Coli and viruses alike. Compost and compost teas are an easy target for the media to blame for food borne illness, but growers should take comfort in the standards enforced by the NOP (national organic program) for using raw manure in a compost. These standards ensure composting safety and reduce liability for growers. To date, there have been no outbreaks of e.coli or other food-borne illness traced back to compost tea, largely due to the additional preparation time of the compost. The longer the compost is processed, the likelihood of disease decreases. However, as it is common to have an additive in compost tea to feed the organisms, there are some additives that are proven to increase the likelihood of e.coli: molasses and sea kelp. Avoiding these additives in a tea blend is an extra step towards safe food management practices.

Aerated or UnAerated Compost Tea?

There are two common methods of brewing compost tea: aerated methods, or non-aerated. Simply explained, non-aerated compost tea, or “passive” tea involves very little equipment or maintenance. All that’s needed is a barrel, a mesh bag, compost, and water. With a ratio of 1 part compost to 5 parts water, the compost tea should be done brewing in a week or two. Aerated or “active” compost teas require a system that constantly oxygenates the brew to stimulate all the microbial life of the compost. Is one better than the other? Not necessarily. Some microbes prefer to live in anaerobic environments while others prefer aerobic environments.

The Takeaway 

Like in most agricultural processes, the variables matter. Compost tea, while not meant to replace standard fertilizing practices, is an excellent tool in the grower’s belt for regular maintenance of plant nutrition and disease. Like traditional compost, it’s proven effective at increasing the microbes needed to feed the plants and kill diseases; the new application method is where the potential lies, as plants are known to absorb liquified substances faster than breaking down solid matter. The challenge with compost tea is in formulating a compost hummus specific to the plant’s basic nutritional needs, and then choosing the right brewing method to sustain the microbial life.