Sunflowers for soil health
It might sound weird, but you and dirt actually have a lot in common.
Just like you and your gut microbiome, the health of soil depends on the bacteria within it.
If we humans become ill, we’ll often turn to probiotic supplements. The theory here is that good bacteria can fight bad bacteria and restore balance in the gut.
But a farmer can’t just go dousing their fields with Yakult if they think their dirt is unhealthy. So how do you cure sick soils?
A field of sunflowers might just do the trick.
But wait, you may be thinking, “Hang on, aren’t soils supposed to be full of all sorts of bugs and bacteria anyway?”
You’re right. A gram of dirt can contain thousands of individual microbe species. The soil in any one location contains a unique mix of bacteria, but certain human activities can throw this mix out of balance.
For farmers, choosing to cultivate just one species of plant makes a lot of sense. It’s much easier to grow and harvest your crop when they’re all ready and ripe at the same time. This seems like an efficient approach, but it could prove harmful in the long run.
Coffee contributes enormously to China’s economy and my ability to function in the morning. But recently, yields from coffee fields have begun to severely decline.
This is of course a tragedy—one that scientists were keen to get to the bottom of.
Historically, a number of things might have been blamed for drops in plant productivity. Loss of soil nutrients, the introduction of pests or even the build-up of caffeine in soils might have been investigated as culprits.
But when scientists investigated the health of soils in a few different coffee fields, they found that the root of their problems might be bacteria. In fields that had been growing coffee (and only coffee) for longer periods of time, the bacterial and fungal richness of the soil was decreased.
We don’t know the exact nature of the relationship that might exist between soil, bacteria and plants, but it does seem that monoculture, or only growing one crop in an area, is running soil health into the ground.
Thankfully, the seed has been planted to ensure the future productivity of farms around the world.
The solution is mixed farming, and it’s as simple as it sounds. Rather than just planting one type of crop, farmers plant two (or more). They can plant them simultaneously, or one after the other.
It’s similar to the way farmers rotate their crops with plants like peas. Legumes, like peas, have bacteria in their roots that makes nitrogen in the soil accessible to plants.
But fixing nutrients in the soil is just one way that bacteria might benefit the growth of plants. Research suggests that there are bacteria that can suppress plant diseases, affect secretion of plant growth hormones and even induce a plant’s immune system.
Though we’re still working it all out, there have already been wonderful success stories from the field of mixed farming.
Drive through the sugar cane fields of tropical Queensland, and you might see a surprising number of sunflowers spread out over highly Instagrammable fields.
While there is a market for sunflower seeds and oil, the real profitability of these plants lies in their fungi-riddled roots.
There are fungi in the roots of sunflower plants that take mineral phosphorous (which plants can’t absorb) and transform it into a phosphorous that plants can actually use to grow. This means that the sugar cane planted next to the sunflowers has ready access to this element that is essential to their health. On farms that are testing out mixed farming, it’s the co-planted sugar cane crops that regularly outgrow monoculture cane.
What other species will be able to try growing together in future? What benefits of root fungus will we uncover? Who knows! What we have learned so far is that, as in most things, we can benefit from a bit of diversity.