Why is Soil Health important? ft. University of Wisconsin Dr. Gregg Sanford
We’re talking with soil health expert Dr. Gregg Sanford! He works in the Department of Agronomy at University of Wisconsin - Madison and has published an array of works on the topic. We discussed what good soil is, why it matters for food, and how to improve your soil health.
Dr. Sanford explained that the hallmarks of healthy soil are good water filtration, high organic matter or carbon, good structure, and good drainage but can hold water. Grazed pasture would have good soil and native grasslands would be even better because the earth is undisturbed with thriving fungal and microorganism communities.
Soil health is all about creating the perfect environment for seeds to grow. A seed already knows how to grow and yield food - all those instructions are programmed in the plants DNA. But it needs the right environment with the right nutrients in order to do so. Its ability to filter and drain water is important because the seed needs access to some water but it can’t be sitting in water or mold will rot the seed.
Good soil needs lots of organic matter, or carbon, too. High organic matter increases cationic exchange of soil. Clay and organic matter, both components of soil, have negatively charged sites and many plant nutrients are positively charged. Just like magnets, positive and negative stick together. So the more organic matter you have the higher the static capacity which means the soil can give more nutrients to the plant. Want to go deeper into cationic exchange? Go read this paper.
As any good scientist would do, Dr. Sanford acknowledged that he didn’t know how soil health would directly impact flavor but “my guess would be if you have all the nutrients and minerals [the plant needs to thrive], the food is going to taste better.”
Let’s shift focus to the farmer considering what to plant on a 50 acre field (about 38 football fields). If (s)he goes with corn or soybeans, there’s crop insurance and subsidies from the government. Extension offices or co-operatives can tell them which herbicides or insecticides to use and how much fertilizer to spread. It’s still going to be difficult but the risk to the farmer is comparatively low. They get money from the government to plant corn and soy and if the crops fail, they’re reimbursed a certain amount. Can you see how so much of the Midwest is covered in corn and soy? Dr. Sanford puts it neatly: “we have a commodity grain system. We don’t have a food grain system”
Corn and soy inputs, or anything you put onto a field, aren’t great for the microorganisms in the soil. And then 40% of the nitrogen (a type of fertilizer) is washed away and ends up in the watershed. Tilling, or turning over the soil so it dries faster, releases carbon dioxide and causes all that high quality organic matter to erode away reducing the static capacity.
The worst quality soil would be very intensive continuous row crop systems (think conventional corn being planted year after year in the same soil without any break). One step up from just planting corn might be rotating in soybeans. Then you could try no till to give fungi a chance to build structure. Then maybe the next year you try a cover crop to replace some nutrients. There are gradients to improving soil health and “small grains are like a gateway drug to improved cropping systems because once you open the system to a small grain, you’re able to diversify rotation significantly. Potentially you could use high quality cover crops after harvest to build that soil health even more”.
I learned so much in this conversation but what really stuck out to me is that there’s a gradient of soil health. It’s not just good or bad soil but a range. And taking your soil from bad to great isn’t linear. A farmer could do no till farming but all the benefits could be cancelled out if they add tons of inputs.
We’ll end this on a great quote from Dr. Sanford: “I definitely think artisan or small grains are a step in the right direction in improving soil health”.
More Resources:
Quick Guide to Soil for your Garden - Fresh Exchange
Living soil means healthy garden - University of MN Extension
2 Midwest farm case studies - American Farmland Trust with NRCS