I was eternally blessed to enter the University of Saskatchewan while Les Henry was still teaching at a time when we were “forced” to take at least an introductory soil science course. I learned a lot in that introductory course; mostly about how much I didn’t know (and how much Dr. Henry did). But more importantly Les’s teaching style and the lab work created an interest and appreciation for what goes on below our feet.
Over the last several years there has been an emerging and energetic movement to better understand soil health. There has been a spike in interest in cover crops and soil microbiology and really understanding what drives the underground biology that makes agricultural systems tick.
In some ways, this move is not too surprising as we look to increase productivity or enhance sustainability. The exciting part to me is the systems-type approach to the issue and looking at biology in addition to physics and chemistry. By this I mean that soil health is more than identifying a substrate and soil type (physics) and a cation/anion reading or fertilizer test (chemistry). It is really about working with physical and chemical tools and optimizing the soil microflora to create a whole that is more than the sum of its parts.
A look at the benefits
Some of the benefits of soil health are fairly straightforward and predictable, including enhanced nutrient availability, increased water infiltration, reduced erosion and improved resiliency. Additionally, in the world of carbon sequestration and taxation, understanding our soil health at a deeper level may provide tools for improved carbon storage and much-needed ammunition to make our case as stewards of the land and of the atmosphere. If you are interested in history at all, you can track the rise and fall of many civilizations and parallel it with the state of their soil health.
As a simple place to start, soil is built from substrate or inorganic particles. Whether these are small clay particles or large grains of sand is a bit beyond our control as farmers and ranchers, but it is the basic structure that we must deal on our own land bases. How we build on this substrate is our role as managers, since we are unlikely to remove our layer of topsoil and truck in a replacement. Everything we do in the top few inches of soil and above ground will eventually be reflected in the soil underground. This gives us both a tremendous power but also a tremendous responsibility as soil managers.
I truly began to appreciate the role of biology beyond the plant component this fall when I took a soils course from Nicole Masters. What I learned in spades is that the underground food chain is both interesting and a bit scary. Perhaps the hardest part to come to grips with in the human mind is the immense power that trillions of microscopic bugs can have per acre. The influence and impact of these soil microbiota is scales of magnitude larger than the impact that several tons of steel can have on that same acre. Think about that for a minute and it is somewhat staggering. Facilitating the function of the microbiology underground, or debilitating the function of that same microbiology will have more impact on our soil health and productivity than a $1 million investment in equipment.
It’s a jungle down there
If we start above ground, plants are largely responsible for sending sunshine underground and feeding the soil biology. Photosynthesis creates soluble sugars which are sent down the plant to the roots. In return for some of the sugar, mycorrhizae fungi help to extract, mobilize and horse-trade various minerals and molecules from the soil that the plant needs to make proteins and other items. The fungi can represent a larger part of the root function for a plant than the actual plant roots do.
Other soil bacteria are also especially adept at extracting nutrients or creating them out of thin air, such as those associated with nodulation of legumes.
However these bacteria are greedy and don’t like to let nutrients go for plants to use. Fortunately, voracious protozoa eat bacteria and free up these nutrients from the bacteria. Add a few worms, some different fungal types and a lot of bacterial diversity and it is a jungle underground. When we consider all of the variety and the actual underground biomass, it is a lot bigger system in a lot of ways than what is actually going on with the crop that we see.
It is complex enough that it would probably take a thousand issues of Grainews filled cover to cover to even begin to understand or explain a percentage of the complexities and interactions. What is important to understand is that as managers we can either shift things toward or away from a healthy system.
Certainly, many of the practices we follow including fertilization, cultivation and weed control have agronomic merit and situations where the benefit outweighs the cost, but all of these practices have an impact on the underground world. A couple of examples include the addition of fertilizers which contain salts. These salts can greatly impact the growth of soil microbiota and affect fungal:bacterial ratios in particular.
Cultivation is another practice that has some merit, but we need to be aware of the effect it has on soil mycorrhizae in particular. Cultivation breaks up these fungal bodies that help to extend the rooting power of our plants. Many of the biological pathways that we exploit for weed control, are also present in our soil life, so sometimes the chemicals that may be applied for weed control can have broad ranging and unintended consequences underground.
Start digging holes
The basic take-home message is that what we do above ground as managers will eventually be reflected in our soils. Building organic matter and taking care of our soil resource has positive results for our farms and ranches, even if we make a few mistakes along the way. Soil can be a highly forgiving ecosystem, and soil microflora have incredible reproductive powers. As managers, this means that there is some resiliency and coverage in the system for all those times we screw up. It also means that impoverished soils can be renewed and regenerated at a rate that is surprisingly fast.
We need to feed our soils, and there are a lot of recent developments on an industry scale, including cover and green manure crops, micronutrient management and tools to increase organic matter. As well, the ability of GPS and other computer technologies to manage on a more site-specific basis are quite exciting.
One of the best things we can probably do, and I myself do not do enough of it, is to start digging holes. Take a shovel and dig down. Some aspects of soil health such as tilth, colour, root and mycorrhizae mass, moisture infiltration and structural integrity are readily apparent if you dig a few holes. Invest some money in both nutrient and biological soil testing.
We will continue to see soils emerging as a field of extreme interest, in part because they offer a large part of the solution to climate change and provide a huge and living carbon-storage facility. If you are truly interested in soils I would also suggest that you read Les Henry’s columns and start building your below-ground level understanding.