Well into the drought this summer, I drove by a corn field east of Brainerd and was surprised how healthy the corn looked. Just a mile or two down the road I’d passed a field where much of the corn looked to be nearing the permanent wilting point. At the time I didn’t give it a lot of thought.
Droughts have always been a part of agriculture. They can be devastating. From a farmer perspective, there is an incredible sense of hopelessness as days and weeks go by without rain. Technology hasn’t helped, at least not for me. Any forecast for rain or approaching front on my weather app and I’m glued to it. Inevitably it all falls apart just before it reaches our farm.
But the rain does come, sooner or later, and when it does it often comes as a downpour. After several weeks without rain, it arrived. Two inches of rain in less than a half hour. Most of it in the first fifteen minutes. Dry soil becomes hydrophobic, meaning it wants to shed water instead of infiltrating it, leading to increased water flows, streambank erosion, and downstream flooding.
Living Roots, Biotic Glue
Soil kept covered and cool with living plants can better infiltrate these heavy downpours. A diversity of plants provides different root structures that help to stabilize soil and improve soil structure. Living roots support soil biology which release biotic glues that help build soil aggregates and increase soil organic matter levels leading to greater water holding capacity. And farming systems that integrate livestock encourage biological activity, such as dung beetles and earthworms, which cycle nutrients and make tunnels in the soil that help to infiltrate water.
Cover crops can help create the conditions that support healthy soil. One of the most important reasons to plant cover crops is to keep living roots in the ground. Living roots exude plant sap into the soil, as much as 30% of what a plant produces. This exudate is consumed by the smallest of microorganisms, the base of the soil food chain. These organisms are eaten by larger bugs, and when they die or defecate, release the nutrients the plant needs to grow.
The more diverse the cover crop, the greater the benefit. Exudates from different plants have different chemical composition and attract different species of microorganisms, specific to the needs of the plant. So diversity below ground equals diversity below ground. Plants have different rooting structures so diverse cover crop mixes can utilize more of the soil profile, leading to greater nutrient cycling and soil aggregation.
The Role of Grazing
Well managed grazing of the cover crop can help to fuel soil biology and improve nutrient cycling and availability to the following crop. Integration of livestock into cropping systems can provide additional livestock feed and reduce the need for purchased inputs.
Sometime after noticing the field of corn that was growing well despite the drought, I started thinking about why it was so much healthier than the other field just down the road. The field reaching permanent wilting point had been in corn for the last several years. It was tilled every year and void of vegetation for the majority of the year. The healthy field had been in permanent cover for many years and had come out of hay ground two years previous. It was planted to corn last year and there wasn’t a cover crop planted through last winter. This year it was planted to corn again using a no-till drill, minimizing soil disturbance and protecting soil structure.
Given time the healthy field, as currently managed, will slowly degrade. Without living roots in the ground for the majority of the year, and planted to a monocrop of corn year after year, biological activity will slow and become less diverse. With less life in the soil, the biotic glues will degrade and soil structure will decline. The organisms left will be hardy and lay dormant waiting for their next fix of fertilizer. When they get it they will consume organic matter then die to feed the plant. As organic matter soil structure declines, the ability of the soil to infiltrate and hold water declines. And drought becomes more devastating.
Positive Feedback Loop
Soil health mitigates risk. It creates a positive feedback loop, enhancing resilience. It takes time to see the results, but over years, not decades, your system can be more resilient to extremes and pests. You will infiltrate and hold more water, better cycle nutrients, and maintain yields in times of stress, like drought.
To learn more about drought conditions in your area, visit drought.gov. To learn more about how to improve soil health, whether you are a farmer, grower, or gardener, check out these soil health resources.