Compost Tea: a Power Shake for the Vineyard

By Levi Glenn

A few years back we started to make and apply compost tea in the vineyard. It was an effort to try to improve our soil, a central theme in organic farming: improve the soil and the plant will follow. Compost tea contains two important soil improving components: nutrition and soil microbes. Microbes are microorganisms that help us in many ways, but most notably by breaking down organic matter (slowly decaying carbon compounds) into yet smaller particles and ones that plants can readily consume. You could see it as basically freeing up nutrition that already exists in the soil. It’s a process that isn’t completely understood, but is definitely going on below our feet. Amazingly, there are an estimated 500 billion microbes in one pound of soil. Yes, that’s billions with a B. What I’m describing is just the one part of the soil food web, one where microbes, worms, nutrients, plants and animals all interact. The more of this life we have in our soil, the healthier the plants that grow in this soil should be. A diagram below (found in the soils section of the USDA's Web site) illustrates:


The complex (and only somewhat understood) interactions in living soil are the main reason why modern chemical farming practices tend to be counterproductive over the long term. Synthetic herbicides kill the weeds above ground, but their effects are farther reaching than this: they also kill off the microbes as well as impacting the food supply for the worms and insects that create a living, vibrant soil belowground. Chemical pesticides have similarly profound impacts underground. That’s at the heart of why we farm organically.

In addition to the microbial component of compost tea, additional benefits include increased growth through improved nutrition, better soil structure, and disease suppression. The tea can be sprayed on the leaves as a foliar fertilizer, or applied directly into the soil through our irrigation lines and drips. One function we’ve been particularly intrigued by is compost tea’s ability to suppress powdery mildew. Spraying compost tea on our grapevines has allowed us to significantly reduce the amount of sulfur we use as a natural fungicide.

Compost_tea_old_makerWe’ve been making compost tea for years, using a simple system we built ourselves (right).  We would then use the tea in two ways.  We would load the brewed tea into sprayers and apply it directly to the leaves to inhibit mildew, and we would run it through our irrigation lines to build up our soils.  This year we took the plunge and bought a 500-gallon commercial compost tea brewer (below).


Brewing takes roughly 24 hours to complete. We start with worm castings, compost and fish bonemeal powder.  Worm castings (below, left) are a fancy term for worm dung, a highly refined source of nutrition. The compost we’re using (below, middle) is made on the property out of our vine prunings, green waste and manure. The fish bone meal (below, right) provides a much needed source of phosphorous in the vineyard and is an additional food source for the microbes in the brewing process. 


These three ingredients are put into a wire mesh cylinder (below, left), which is placed into water to steep. Below each cylinder are powerful bubbling aerators (below, right) that help to saturate the mixture and provide oxygen to the microbes. There are also smaller aerators that go inside the cylinders to further promote an aerobic environment.

Compost_tea_0003 Compost_tea_0001

Before the brewing, the bacteria, fungi, and protozoa in the “tea” are in somewhat of a dormant state. By creating the right environment for these microorganisms by adding water and oxygen to their environment, keeping them at an optimal temperature, and providing an accessible food source, their numbers grow exponentially during the brewing process.

When we’re done, we have 500 gallons of what looks like a weak batch of coffee, but is actually a microbe-rich elixir, a liquid soil of sorts.  And no, you wouldn't want to drink it, any more than you would want to chew on our soil:


When we brew a new batch, if we’re curious what’s in it, we can send a sample off to the lab. The analysis the lab runs shows us the total number of bacteria and fungi in the tea, and the proportion between the two. Some plants prefer a higher concentration of bacteria in the tea, like vegetable crops, where as vines and trees do better with a fugal dominated tea. After a few trial batches we’ve been getting consistently good lab results and are confident in our process. 

While there is often notable benefit from even short-term compost tea use, we hope that longer-term use will provide exponentially greater benefit.  Our principal vineyard challenge is Paso Robles’ harsh vineyard environment: the same thing that makes the grapes we grow such good raw materials for winemaking.  Paso Robles is so dry and sunny in the summer, so cold in the winter, and has such a great diurnal swing in temperature year-round.  Plus, our topsoil is relatively thin and rocky.  It’s not easy maintaining the health of our vineyards in this climate, and doing so is the reasoning behind almost every decision we make in the field.  Applying compost tea at significant volumes, over a matter of years, should help our grapevines to continue to flourish even as the neighbors who are farming more conventionally have to replant because their vines are exhausted. 

So now we’re farming wine grapes, olives, sheep, and microbes. I can’t wait to see what we’ll be growing in the future.

Animal Farm: The Benefits of Biodiversity in the Vineyard

By Levi Glenn

"Whatever goes upon four legs, or has wings, is a friend."  It has probably been some time since most of you have read the metaphorical novella Animal Farm by George Orwell.  At the moment, Orwell's line seems quite fitting for Tablas Creek Vineyard.  Within a week we will become the proud owners of twenty-odd Dorper sheep as well as a few Barbados.  We're also nearing completion on a limestone lambing barn made almost entirely from reused materials (a quite handsome one I might add).  At the beginning of December we received fifteen more laying hens, and a month from now we will have three little Yorkshire piglets.  Goats will be added later to make the sheep feel insecure, and cows are somewhere in our future. The chickens are below left, and the barn below right:

591 577

We aren't accumulating farm animals to give me the opportunity to dispense vague literary references.  What we are trying to accomplish is to increase the overall biodiversity of our estate.  Two years ago we started to farm Biodynamically on 20 acres of the estate.  One of the main tenets of Biodynamics is to promote biodiversity.  While the most visible components may be different animal and crop species, the most important impacts on the vineyard's health is the microbial biodiversity that diverse flora and fauna encourage.

Our new herd of ruminants will reduce our weed population in the vineyard, but there's more to it than that.  As they munch, they also are fertilizing the vineyard (use your imagination) which reduces the number of tractor passes, lessens soil compaction, reduces equipment repairs, and allows our tractor operators to focus their efforts elsewhere.  All this translates into lower costs now and reduced environmental impacts down the road.  The herd will be in the vineyard during most of the dormant season, roughly from November through March.  If left in the field past bud-break, the sheep could start to sample the young tender leaves and cause serious losses.  The cows, which represent fertility in the Biodynamic ethos, will provide us with manure we need for our Biodynamic preparations and our green waste/cow manure compost.  As this program grows, we hope to make all the compost we need on the property.  The pigs will be, well, tasty. 

IMG_1311As for flora, there are over 200 producing olive trees on the property, and we planted almost 50 more this year.  Every fall -- well, most falls -- following the grape harvest, we pick the olives and press them into the green-gold olive oil many of you have sampled in our tasting room.  Unfortunately, in May of 2011, just as the olive blossoms were at their peak, we received an unseasonal rainstorm.  It has left us with so few olives that there isn’t enough to make olive oil this year.  Still, the olive trees attract and support different insect and microbial life than grapevines, and they're nice to look at.  In addition to olives, each of the past few winters we have planted a variety of peaches, pears, cherries, apples, and quince.  Some of the fruit and olive trees are actually intermixed in certain vineyard blocks, much like many diversified farms throughout the Mediterranean.  Fruit produced is eaten by our vineyard crew as a fresh afternoon snack or handed out to the winery staff.

"Living soil" is a term often used in the world of organics and Biodynamics, and refers principally to healthy soils with high microbial activity.  These microbes take organic matter in the soil and break it down into forms that are accessible to the plant's roots.  All we have to do is provide these microbes with comfortable surroundings.  So we apply compost, incorporate the cover crop, till the soil to provide oxygen, and don't apply herbicides that would otherwise ruin their party.  These little microscopic field hands do the rest of the work for us.  Biodynamic preparations are principally designed to encourage these microbes.  Two that we use are Biodynamic Preparation 500 (BD 500, or horn manure), and Barrel Compost (BC).  Both are concentrated compost teas that are sprayed specifically to increase soil organic matter and stimulate these unseen microbes.  Think of them as super food for microbes.  The horns:

BD 500 Horns 2

Bees are another addition soon to make an appearance on our own property (our Sweet_peaneighbor to the west has kept beehives for years).  We have lots of fruit trees to pollinate, plus all the native wild flowers and the cover crops that we seed every fall to attract beneficial insects.  These cover crops, like the sweet pea pictured right, provide habitat for the bugs we want so that they will go out and eat the bugs we don't, such as leafhoppers and spider mites.  This will hopefully translate into less spraying (oh, and making my job easier).  I'll be leaving the beekeeping to someone else.  That way I lessen the chance of having to stab myself with my Epi-Pen.   

Biodiversity is probably not going to make a significant impact on the quality of our wines in the short term.  But we expect the healthier soils that we are building to improve the long-term health of the vines, and their longevity.  If we can keep our vineyards healthy and productive at ages forty and up (an age at which many California vineyards are having to be replaced) the long-term impact on quality could be dramatic.  And healthier vines should produce grapes in better balance and more reflective of their terroir.  On Francois Perrin's recent visit, the wine lots from the vineyard blocks we coverted to Biodynamic in 2010 were notably compelling.

Plus, the changes we're making are the next logical step in trying to become a single farm unit, where we produce as much as we can from our own property, and reduce outside inputs, which should further encourage the expression of our terroir.  With our initial work on Biodynamics we are taking an important step forward.  We will never get to the point where we are completely self-sustained, but we are on our way.

I'm told that each animal on our farm will be named after an employee.  Anthropomorphism can be fun!  Hopefully none of our pigs will start to walk on two legs, and the sheep won't bleat, "four legs good, two legs better."  Apparently one little piglet might be named Levi.  I'm fine with that, as long as the other two are not named Napoleon and Snowball.

[Editor's Note: With this post, we welcome Viticulturist Levi Glenn as a contributor to the Tablas Creek blog.  You'll be able to follow his posts under the category Viticultural Revolution.]