How do you measure soil health?
Qualitative and quantitative measures of soil health are emerging and evolving. Traditional approaches to soil science looked at carbon content, which for farming, was used to inform how much nitrogen to add to the soil, but measures of soil organic carbon are taking on a new meaning. We realize now that the carbon itself is important because of the characteristics it imparts to the soil, increasing water holding capacity and infiltration to build resilience during a drought, lowering the soil density to enable roots to access water and nutrients more easily, and increasing nutrient availability by feeding beneficial microbes, among other benefits.
Other important chemical and structural measures such as pH and clay or sand content can also be used to define soil quality, which five or so years ago, I would have said is an interchangeable term with soil health. Since then, however, the thinking behind soil health has evolved to include a living component that differentiates it from soil quality. Measurements of the microbial communities, including what microbes are in the soil and their respiration, have become important to agriculture. Advances in DNA sequencing technology have made it more cost effective and practical to identify the makeup of the microbial community in soil samples. We can identify the presence of known pathogens that harm plants and cause yield failure and find symbiotic microbes that work in conjunction with plant roots to help bring nitrogen and minerals inside of the plant. This is a new frontier that is expanding as technology improves, and we are going to better understand how to manage these different microbes, as well as what they mean for soil function and health.
How can a grower improve the health of their soils, and what role do biologicals play?
Keeping soil covered and minimally disturbed have shown to improve soil health. What this means for farmers is growing a cover crop in fields that would otherwise be left fallow to protect the soil from wind and water erosion. Farmers can also avoid tilling or minimally till plots, as tilling exposes the carbon in the soil to oxygen, allowing it to volatilize into the atmosphere as a greenhouse gas and reducing the amount of carbon in the soil. On top of these regenerative practices, we also need to grow the right things in the right places to get the most potential out of local soils. For example, if you try to maintain corn yields in a very dry area of West Texas, it will require a lot of fertilizer and irrigation, which typically degrade soil health by removing nutrients, accelerating erosion, and increasing water runoff.
The role biologicals play in soil health is an exciting area of agriculture in that these treatments have the potential to impart functions and outcomes that go beyond what would naturally occur. This might sound like it contradicts our new, more-sustainable approach to agriculture, but it is important to remember that farms are not natural systems. These are managed environments and the soil in these environments can be compared to elite athletes in terms of the functions we are asking them to provide. For example, the level of carbon cycling that occurs in a farm soil is closer to what occurs in the tropics than in your backyard. To achieve these demanding functions, it is conceivable to think, just as an athlete requires additional nutrition or supplements, that these soils may need additional interventions, such as adding microbes that enable better nitrogen use efficiency and reduce fertilizer inputs, or adding microbes that more effectively sequester carbon from the atmosphere and store it in the soil.
What are the benefits of healthy soils to farmers, landowners, and consumers?
The primary benefit of healthy soil to farmers is increased profitability by improving resource use efficiency — producing more yield with fewer inputs. Similarly, healthy soils improve the resilience of the farm to fluctuations in water availability, so soils trap water in a drought and release water in a flood, which helps reduce yield loss. The regenerative practices that improve soil health can also qualify farmers to generate carbon credits for the tons of carbon they sequester in their soil. For landowners, healthy soils are better quality soils and this factors into the value of the land itself, allowing the owner to charge higher rents. As for the benefit to consumers, that is a question researchers are actively working to answer, but there is already evidence to suggest that regenerative agriculture could produce more nutritious food. Overall, regenerative agriculture practices that boost soil health are a win-win for people and the environment, helping to optimize economic and environmental sustainability, which are magically aligned in agriculture.
