Healthy Soil, Healthier Vines: Inside Our Compost Tea Trial

At MAWBY and bigLITTLE, we believe better wine starts in the vineyard. More specifically, it starts in the soil.

Last year, our team began a compost tea vineyard trial in a quarter-acre Pinot Noir block at our Elm Valley estate. We wanted to learn whether compost tea for grapevines could help support soil health, strengthen the microbial life around the vines, and reduce pressure from powdery mildew during the growing season. The trial gave us useful results, a few clear lessons, and a better plan for this year.

What is compost tea, and why use it in a vineyard?

Compost tea is a living infusion made by steeping compost in water and pulling beneficial microbes into solution. Depending on the compost and the brewing process, that can include fungi, bacteria, protozoa, and other organisms that support healthy soil and healthy plants.

That matters in a vineyard because grapevines are a perennial crop. They stay in the same place for years, so the condition of the soil shapes how the vines grow over time. Strong soil biology can improve nutrient cycling, soil structure, root development, and resilience in the vineyard. For us, compost tea is one way to support that system more intentionally.

This project was guided by soil consultant Alexa Kipper of Organic Matters, whose work focuses on soil biology analysis, soil health consulting, and compost tea systems for farms and vineyards. The compost we used came from Wormies, a community composting farm and food scraps hauler in Alto, Michigan that produces vermicompost and other biologically diverse compost products.

How the compost tea trial worked

The process started with building a compost pile, then turning that compost into tea. After brewing, the tea was examined under a microscope and first applied as a soil drench in the test block. That first step focused on feeding the biology around the vines and building stronger soil health in the vineyard.

We also used the compost tea as a foliar spray, meaning it was applied directly to the leaves three times over the course of the season. The goal was to establish beneficial microbes on the leaf surface before powdery mildew spores had a chance to settle in. Leaves with more biological activity can be harder for disease organisms to colonize.

What we learned in year one

Early in the season, the compost tea spray worked well.

When the spray interval stayed tight, beneficial microbes stayed active on the leaf surface, and powdery mildew pressure stayed in check. This part of the trial was encouraging, as it showed us that compost tea in the vineyard can be useful when it's applied frequently enough and coverage stays consistent.

The harder lesson came later. New leaf tissue kept appearing, and those leaves needed more frequent attention. As the season went on, vineyard growth outpaced the spray schedule, which opened the door for powdery mildew to set in.

This year, our vineyard manager will apply compost tea every other week at minimum, and spray weekly during periods of fast growth. He will also add a surfactant into the spray, which will help the tea spread more evenly across the leaf surface and reduce blank spots.

This is how farming often works. You test a new practice. You watch closely. You adjust the plan, then try again with better information.

How this connects to sustainability at MAWBY and bigLITTLE

This trial reflects the way MAWBY and bigLITTLE farm. We care about soil health, vine health, and long-term stewardship.

All fruit harvested from vineyards we own, both on-site and off-site, is 100% herbicide free. That standard connects to other farming practices across our vineyard sites. We have used cover cropping as our main weed management method since 2020. Those cover crops include clovers and low grasses under the vines, which outcompete weeds, increase plant diversity, improve soil structure, build organic matter, and sequester carbon.

Our vineyard program also follows integrated pest management based on Michigan State University guidance and uses a custom compost blend made with Morgan Composting. To preserve soil structure and reduce water usage, the majority of our vineyards are dry-farmed (not irrigated) and no-till.

Additionally, our 30-acre Elm Valley property is protected under a conservation easement, which helps preserve open land at the site.

Compost tea fits naturally into our sustainability efforts. It gives us one more way to practice cleaner farming methods and build healthier soils and stronger vines.

Why soil health matters here

The soil biology in a vineyard affects climate resilience, nutrient cycling, and long-term stability. A vineyard with active microbial life and more organic matter helps the soil hold structure over time.

Although Northern Michigan can give growers beautiful fruit, it asks a lot from us too. Weather can shift fast and disease pressure can rise quickly. Soil health will not fix every vineyard problem on its own, but it gives vines a stronger base to handle those changes.

That is part of what makes compost tea so useful. It adds one more tool to a system that already depends on careful farming and close observation. It helps us think about grape growing over a longer stretch of time and how we keep building healthier vineyard systems for both MAWBY and bigLITTLE.

Where this work goes from here

We will continue tracking this vineyard block and learning from it. Strong results this season will give compost tea a larger place in our vineyard program.

We are interested in making more compost in-house too. That work could use vine prunings, grape pomace, and forest litter from around the vineyard. Those materials come from the site itself, so they fit the kind of closed-loop system we want to build over time.

The long-term goal is simple. We want to grow grapes in a way that cares for the land, builds healthier vines, and gives both MAWBY and bigLITTLE better fruit to work with. That belief shows up in this trial, in our herbicide-free vineyards, and in the way we keep refining our farming year after year.

Cheers!