
The dirt on soil
Here’s why you always hear farmers talk about “soil health”
Sunday strolls through the farmers market are a hallmark of warmer weather, and the rainbow of colors evolve throughout the season as the yellows of spring give way to the reds of summer and the browns of autumn. But those eggplants and heirloom tomatoes and Indian corn aren’t what the farmers are proud of — they’re just the literal fruits of the labor. Because the farmer’s real pride and joy is the dirt it’s all grown in.
We change our menu every season in every region, following Mother Nature’s lead. But really, we’re following the farmers, who follow her lead and monitor soil and plant accordingly.
Soil isn’t just dirt, it’s a very complex ecosystem. And every farmer we’ve ever spoken to talks about the importance of soil health — good food is merely a byproduct of good soil, a delicious testament to a healthy environment. You might not have ever considered the quality of soil around you — dirt is dirt, right? Wrong.
When you think about it, what makes for healthy soil and what makes for healthy humans are pretty similar:
- Both humans and soil need a wide range of nutrients to function properly, and organic material — like plants — are better for your health than processed, manufactured food.
- Monoculture isn’t good for agriculture, because it depletes the nutrients with each crop, withour restoring them — it’s like if you ate the same exact thing every day.
- Aggressive farming is a no-go — you need rest, and so does soil.
- When soil health is depleted, that leaves them vulnerable to pests and disease, just like a poor diet can compromise your immune system — you need vitamins and nutrients to build your resistance.
How farmers keep things 💯
You go to sweetgreen to get your nutrients, but how does soil get its fix? Some aspects of healthy soil happen, well, organically. Plants obtain hydrogen, carbon and oxygen from the atmosphere through photosynthesis. Then there are a dozen other elements that make for healthy soil that are dropped into the soil by whatever’s growing. Nitrogen, phosphorus and potassium are high-priority nutrients (in a throwback to the Periodic Table of Elements, they’re known as NPK). But there are also practices that farmers employ to make sure their soil is rich.
Keep an eye out: The good news for farmers is that soil communicates, sprouting weeds that are essentially symptoms of a nutrient deficiency. As our friend Dan Barber learned from Klaas Maartens (and documented in his farming tome, The Third Plate), chicory or Queen Anne’s lace means the soil is low on fertility. Milkweed indicates a zinc shortage, while yellow flowers are a cry for sulfur. And meticulous farmers like Klaas are constantly readjusting their farming strategy to give the soil what it needs to beget delicious food.
Cover crops: Growing vegetables compromises soil health (because the plants take on those nutrients, which then are absorbed in your body), so after a growing season, many farmers will plant a carefully planned cover crop to replenish the soil, kill weeds and control pests. What you plant depends on the previous crop and what the next crop will be, but they all tend to reduce erosion and improve soil tilth (aka its physical condition and growability). But cover crops can be quite specialized — mustard and clover are nitrogen fixers, while buckwheat suppresses weeds and attracts beneficial insects, and alfalfa can break up compacted soil. Oh, and they taste good, too.
Compost: In the U.S., about 31% of the food we produce ends up in landfills — that organic material would be better used as compost. (Related: Did you know you can compost all packaging at sweetgreen? Now you do.) Composting breaks down leaves and food waste, creating organic matter rich in nutrients and bacteria that adds fertility to soil. And if you’re urban farmer Will Allen, you’ll use worms to help compost — called vermicomposting, the technique uses red wriggler worms to multiply the microorganisms in his compost by 13x.
Fertilizers: Fertilizer is a quick-fix application of essential organic materials like NPK to revive soil, and they can be either chemical or organic.
Healthy soil is the key to a healthy future. “Many of us are trying to create a sustainable situation where we’re actually improving and building crop soil,” says Nick Storrs, a young farmer getting into the transplanting business. “That sustainability in many ways is the bare minimum of what we need to pass by making sure that what we hand off in 40 years is better than what we started with and that it will get easier for my kids and my grandkids.”
So next time you drive by a farm and don’t see anything growing — just know that there’s actually plenty of things growing.
