Can Compost Grow Better Microgreens? Our Farm Experiment

Microgreens are baby plants, and because they’re harvested so young, they’re especially susceptible to disease and conditions that older, hardier plants can withstand. That’s why most growers use sterile, single-use soil for their microgreens, tossing the leftovers after each harvest. It’s the industry norm, but at Area 2 Farms, we don’t like waste.

After every microgreen harvest, we’re left with trays full of organic material: tiny roots, stems, and rich soil. Fully composted, this becomes a dark, nutrient-rich mix that we usually send out to local schools, gardens, and community projects. It’s a way to share the wealth and keep our growing cycle connected to the neighborhood around us.

But this season, we started wondering: what if we put that compost right back into our own microgreen growing system? How will our compost affect the health of our microgreens?

So we decided to test it.

The Experiment

We tested pea shoots in five different soil mixes:

• Just potting soil (0% compost)

• A little compost (25%)

• Half-and-half (50%)

• Mostly compost (75%)

• Nothing but compost (100%)

Everything else stayed the same: same seeds, same water, same lights, same 10-day growth cycle, so we could see exactly what role compost played.

What We Found

• More compost = more growth. 100% compost trays produced the most shoots—an average of 600g per tray, a 33% increase over trays with no compost.

From Left to Right: 50% Compost Material, 75%, and 100%

From Left to Right- 0% Compost Material and 25%

• But microbes bring trade-offs. The more compost we used, the more we saw root rot and fungal activity. At 100% compost, root rot averaged 4.5 signs per tray, compared to almost none in the control.

• The sweet spot. 25–50% compost gave us the best balance: stronger yields with manageable disease risk.

Compost worked, and worked well, but it also reminded us that living soil requires balance and attention.

Top of 75% Compost Material Tray

Example of Root Rot

How We Compost at Area 2 Farms

The compost we used in this experiment comes from two systems on our farm:

• Vermicomposting – Earthworms (like red wigglers) break down organic matter into nutrient-dense castings.

• Microgreen composting – After harvest, we compost our leftover mats—rich in nitrogen and plant matter—speeding up the process and creating heat for microbial activity.

We carefully monitor each batch, balancing carbon-to-nitrogen ratios (ideally 30:1), moisture, and oxygen to create a living, microbe-rich compost that feeds soil health.

That’s the compost we tested in our pea shoot trays.

What’s Next?

This trial is just the beginning. Next, we’ll:

• Test other microgreen varieties with compost material.

• Explore ways to reduce root rot without losing yield.

• Continue refining the perfect soil and compost mix for productivity and sustainability.

Closed-Loop Farming in Action

For our CSA members, this experiment means more microgreens from the same resources, fresher greens in every harvest, and fewer external inputs (because we’re recycling what we already have).

For the farm itself, it’s all about a truly closed-loop system: the compost created from one harvest becomes the foundation for the next, nothing goes unused, and every tray contributes to future growth. It’s a system that lets us experiment, learn, and optimize production continuously, all while keeping our operations efficient and sustainable.

Want to see this closed-loop system in action? Join us on the first Sunday of every month for a farm tour. 

Area 2 Farms for Locals

Your food should be equally accessible and nutritious. Which is where we come in. At Area 2 Farms, we grow fresh organic produce within 10 miles of you.