Don’t Soil the Soil

August 21, 2017


I love a good field trip as much as the next intern, so I was pretty excited when a couple weeks ago I was relieved of my ranch duties at Zapata for a day, and sent to participate in a “Soil Health Field Training” along with farmers and ranchers from across southern Colorado, led by several soil scientists and conservationists with the USDA’s Natural Resources Conservation Service (NRCS). We had two stops planned at farms near Hooper Junction, only a few miles out from the west fence line of the Medano, followed by a discussion at the USDA service center in Alamosa. So, around 8am I found myself standing in the middle of an alfalfa field on the Burns’ Family Farm, still half asleep and quickly realizing that I was the youngest person there (not by any small margin), and surely the only participant who was not a farmer.

After being introduced by one of the NRCS conservationists, the owner of the Burns’ Farm stepped forward to welcome us to his land and say a few words about his management style. “Lot’s of people like to call me a farmer,” Mr. Burns said, “but a farmer is someone who works with soil, so I call myself a dirt-stirrer. I try to turn dirt into soil.” Even before I had time to finish my complimentary donut, I had learned my first lesson in soil health: not all of the earth under our feet is actually soil. “Soil” is a special kind of earth, comprised of different combinations of silt, clay, and sand, and having certain properties, such as fertility–the ability to absorb, store, and release energy–that makes it very important for productive and sustainable agriculture. Unlike sand, silt, or clay alone, soil is very much alive, and I came to learn that there’s a lot more going on down there than I had imagined. Biology dominates the soil, and the life in the ground is what aggregates the sand, silt, and clay, and turns dust into healthy soil.

The first step in effective soil monitoring is site selection. It’s important to pick a representative spot to dig, one that looks like the majority of the pasture or field, rather than a unique salt spot or at the edge of a playa, for example. After the introductions, we broke up into to small groups, picked a nice looking patch of ground, grabbed our shovels and started digging. After excavating a nice square of soil, around 12 inches deep, we got our hands dirty–quite literally–as the soil scientists explained how any farmer, rancher, or landowner (or ranch intern I might add) can evaluate the health of their soil.

Holistic soil health is composed of 5 principles. (1) Biodiversity: maximizing diversity of plant, animal, and microbial life in the soil, which may be accomplished through crop rotations, the addition of manure or compost, and responsibly managed grazing; (2) Living Root: maintaining a living plant root in the soil as much as possible throughout the year to ensure the release of root exudates that stabilize the soil, feed the soil biota, and maintain its ability to store water and carbon; (3) Cover: maintaining ground cover in the form of plant canopies, decaying organic material, or other residues that protect the soil from wind, rain, sunlight, and desiccation (drying out); (4) Minimize Disturbance: inflicting minimal disturbance on the soil, including physical disturbances such as tillage, biological disturbances such as overgrazing, or chemical disturbances such as mis-application of fertilizer that might destroy the soil structure; and (5) Integrate Livestock: when managed responsibly, livestock can be a valuable tool for maintaining and improving soil health. Grazing ungulates like cattle and bison trample the soil, crushing up and disturbing woody vegetation through hoof-action, in addition to depositing urine and feces that contain high levels of nitrogen, enhancing nutrient cycling in distinct soil patches. Soil health is dynamic, and a direct expression of what your management is doing to the land. As some famous soil scientist once said, “the soil can’t lie.” The soil tells a story, and if you read it carefully, your signature on the land becomes clear.

So you’re a rancher in the high intermountain desert, and you want to evaluate the health of your soil to inform your decisions about how you manage your land and stock. Where do you start? Just as we did at the Burns’ farm, you dig. Excavate a vertical slice of your soil, and observe. Are there different root structures, with different shapes and sizes? What life do you see? What trophic levels? Are there butterflies? Crickets? Grasshoppers? Prairie dogs? Bison? Elk? Eagles? Next, poke around a bit. Segregate the visible layers in your slice of soil based on the size of soil aggregates (clumps). Run your soil through a sieve to evaluate its texture. Add some water and squeeze it in your fist. Does it form a ball? If you toss it in the air and catch it, does the ball crack? Play with your soil. Is it gritty? Smooth? Squeeze the soil in your fist once again, as hard as you can, to evaluate its moisture and ability to hold water. Does your soil ball stain your hand when you release it? Do your fingers leave imprintations on the ball? Does water emerge when you squeeze the ball? If you have two hands and the will, you can determine how healthy your soil is by yourself.

When digging around, there are several “biological spheres” of activity that may be observed. First, the “rhizosphere” is comprised of the living root systems of crops, cover crops, or forage plants. Sugars produced through photosynthesis known as “root exudates” are released by the roots, acting like a glue that helps aggregate the soil and maintain its structure, feeding microbial life and clumping sand and silt into larger and larger structures. Soil that is well aggregated is too heavy to be blown or washed away, forming a healthy “aggretosphere” that is safe from wind and water erosion. Healthy roots should be surrounded by a white “rhizosheath” consisting of fungi. These symbiotic fungal-root associations are known as “mycorrhizae,” and are extremely beneficial to the host plant. The fungi provide the roots with water and mineral nutrients from great distances that might not be able to be absorbed by the roots alone, and in return the roots feed the fungi with sugars. In addition to fungi, nitrogen-fixing bacteria form symbiotic relationships with living roots and can be found in root nodules called “rhizobia” that collect otherwise inaccessible forms of nitrogen, a vital plant nutrient.

If your soil is well aggregated by a healthy rhizosphere, it may then achieve the “porosphere,” representing the porosity of the soil. Though it may look just like dirt, the plant roots beneath the ground surface and the soil itself need to breathe. If soil is not well-aggregated and overly compacted at the surface, oxygen cannot diffuse into the soil to feed the aerobic fungi and bacteria that support the root systems and store water. Carbon dioxide released beneath the surface may also accumulate above the topsoil in much higher concentrations than the rest of the atmosphere, which can then be absorbed by the plants’ leaves for photosynthesis. Finally, with well-developed root systems, large soil aggregates, and porosity that allows for gas exchange, the final component of healthy soil returns: earthworms, which comprise the “drilosphere.” Earthworms consume and digest carbon and microorganisms, leaving behind pores lined with organic material. These pores and canals may be followed by developing root systems, and are lined with natural, carbon-rich fertilizer left behind by the earthworm castings.     

The deeper you dig into the soil biomass, the more it becomes clear that healthy soil is living soil, and healthy soil is not just good for your crops or your stock, but benefits the larger ecological community of which your land is a part. Healthy soil means healthy plants, healthy water, healthy wildlife, healthy pollinators, healthy insects, and ultimately, a healthier landscape. While the farmers I dug around with throughout the day spend their time deciding which combinations of crops and cover crops to use, and how to rotate them, here at Zapata we don’t pick our plants. As a working ranch with a cattle operation, the only way we manipulate our ranges is through rotational grazing. While much of the grazing plan is based upon the quality and diversity of forage in a given pasture, I returned to the ranch quite confident that our management supports a healthy soil, with diverse native grasses, diverse wildlife, and a healthy ecosystem.

Especially in a place like the San Luis Valley, where water is scarce and loose sand is abundant, maintaining healthy soil is of great importance. Much of the Medano side of the ranch is part of the physical system of the Great Sand Dunes. Loose, structureless sand can be found in many places, some comprising former migratory dunes that have since been stabilized by vegetation, and are no longer vulnerable to the wind erosion that continues to shape and reshape the dune field. Without Ranchlands’ careful management, our stock could easily overgraze our delicate ranges, pruning the living roots that stabilize the sandy loam under our boots, allowing the living soil that sustains our herd and this way of life to be blown away over one windy season. Not so long ago, a whole lot of soil in the American west was destroyed by irresponsible ranching and deprived of its fertility. I feel pretty darn lucky to work with some unique, conservation-minded ranchers who instead love and protect this soil where we make our home, understand that land has more to offer to humans than immediate profit, and work to keep this land-community healthy.

Aldo Leopold, regarded by many as the father of American conservation, writes “We can be ethical only in relation to something that we can see, feel, understand, love, or otherwise have faith in.” So grab your shovel, and start digging.

By Zapata Ranch intern Brandon Sickel