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Compost Tea

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Compost Tea Nursery Experiences and History of Use

By Alison Kutz

At our wholesale nursery, Cascade Cuts in Bellingham, Washington, we began brewing Compost Tea back in the 1990’s with an early tea brewer design by Growing Solutions. Back then there were few people to talk to about this new technology and very little research to lean on. I explored what research was out there and considered the potential benefits, which basically were much like the benefits of adding solid compost itself to the growing mediums. At that time I could not find anyone else in the world incorporating an Actively Aerated Compost Tea (AACT) into nursery production.

In the nursery setting, we were not as concerned with the benefits that field producers, ag and landscapers were seeking, which included:

–Speeding up the degradation of organic materials within the soil system, (by the addition of many soil microorganisms)

–Increasing soil organic matter, and increasing soil tilth, aeration and water holding capacity, as well as remediating toxins through the addition of beneficial microbes that would speed breakdowns of unwanted chemicals.

All those things sounded cool, but: what should I expect in an artificial peat based soil blend?

Increased nutrient availability for plants– improving nutrient cycling.

I wanted to see if we could indeed reduce our synthetic fertilizer inputs, and hoped to see much more.

We began brewing tea: an aerated, heated tea over a 22-24 hour brew period.

(I can provide details of composts used, as well as the catalyst.)

With weekly brewing, we began applying tea to all the herbs and some flowers in production. Using an injector (Dostron DSA45A at that time), we managed a 12% solution into the feed line. So every Friday became Tea Day.

Right off the bat we saw a spike in fertility. With 2.5” and 3.5” herbs, annuals, perennials we found that we could reduce our regular Master Blend feed program by approximately 20%. Note: all of our potting soil contained 5% compost in it, but that compost had a very high EC, so we were limited in it’s potential as a larger proportion of the potting medium.

Denser Root Growth; Low, Even Foliar Breaks

Plant growth differences became apparent. With “Short and Fat” being our mantra, we noticed earlier, shorter breaks on Violas, herbs and bedding plants. The cellular integrity improved, and overall, plants seemed very sturdy. Root mass improved accordingly, allowing us to pull many crops for sale earlier, as the root mass was seriously pushing the pot edge so that plants were well rooted sooner.

Earlier Bud Sets, Heavier Flowering

This was easily recordable in two years worth of compost tea research I did with a grant, where we saw this in two of our plant types selected for those studies: Viola and Cyclamen in particular, but we have seen this in other floral and bedding crops as well. 

Plants withstanding Stressful Cold, Wet Conditions

Plants were looking VERY good, and holding up much better under stress! This was huge, as we were always short of covered cold space. When we were on plant overload, stockpiling plants for the spring rush when plants needed to move (prematurely) into the outdoor areas, from 60°F houses, to harden up before pulling for sales. Heavy rains in March/April that would normally leach plants and send things into a tailspin were no longer affecting the plants in nearly the same way. No yellowing of leaves, even under serious leaching conditions.

Disease Suppression

We also noticed that the incidence of Botrytis under tricky conditions was much lessened (especially under the above conditions.)

I was not “expecting” to see disease suppression, but since we had been reading about the work of Dr. Hoitink (Ohio State) on the disease suppressive capacity of some composts, it became a goal for me to understand more. I really did not like the use of fungicides and was growing many edibles.

We then began treating tricky crops that otherwise mandated fungicidal drenches and substituting compost tea. Virtually all fungicides in crop production, to this day, have been eliminated!

We have done informal trials on powdery mildew (sages and rosemary), various root rot diseases and Fusarium on cyclamen and calla lilies.

The Fusarium successes caught international attention of plug producers of Cyclamen (and Calla), and that is when the rubber hit the road.

We also conducted formal research/grant work (unpublished) on Botrytis suppression. Very interesting, really exciting. (Comparing conventional fungicides and more organic fungicides like Decree, the compost teas showed significantly less botrytis injury.)

Other Observations

There are times when we had to take perennial crops, like Chives from their fresh dormancy (December) and push them quickly for early orders without dieback being complete. The conditions of 60°F nights can create explosions of Botrytis. We can spray with hydrogen peroxide, which destroys all foliar pathogens, and then re-inoculate the plants with compost tea, allowing for the wide variety of pro-biotic microbes to colonize and protect the remaining foliage, plant injuries and crown.

Other uses include spiking fertility and initiating fresh breaks on older (pot bound) plants like woody rosemary hanging baskets, and large tired stock plants which cannot be transplanted easily. The spurt of fresh vigor can be extremely beneficial.

Now

To this day, we hit all newly planted material with a drench of compost tea.

Much of my interest was in the nutritional value, as the tea itself does not contain much “Available N”, I was curious to see what kind of boost or plant growth regulating effects would be seen. Where we wish to go more “organic” we can supplement a naturally higher Nitrogen fertilizer. The ability to tank mix other ingredients at post brew is very open ended.

We find one of the main benefits of a liquid compost tea over a solid addition of compost to be the ability to spoon feed plants and get regulated plant growth effects as needed. PGR’s can be reduced or eliminated, other microbial enhancements can easily be added for both soil drenches and foliar applications, and we can also reduce any pesticide residue, copper or sulfur, off plant foliage quickly with beneficial microbes. This allows for safe re-entry for any biological control program, and is especially helpful with all the beneficial insects being used in many operations today. Reducing the time frame for any pesticidal side effects is very helpful in numerous situations, as this one issue has become a major roadblock in biological control programs.