Organic Broadcaster

Agroecologists focus on soil health to improve production

By Kent Solberg

Agroecologist—a farmer who applies
ecological processes to agricultural production.

For most of the past seven decades, agriculture and conservation have been segregated disciplines. This segregation has, at times, created tremendous tensions. We have viewed agriculture as simply a system of chemical inputs for commodity crop production where the soil just holds the plant in place. Many have viewed conservation as keeping human intervention out and “allowing nature to take its course.”

As the science of ecology developed, uncovering the interconnectedness of life on the planet, some (including myself) began to question if the only way to produce food came with a high environmental cost. Can food production and the greater benefits of ecological services (nutrient cycling, maintaining or enhancing water quality habitat for fish and wildlife, etc.) co-exist, even on the same parcel of land?

Parallel to this, some conservationists began to recognize that for plant communities to remain viable and healthy there needed to be occasional incidences of disturbance followed by adequate periods of rest for recovery. We have also learned that human intervention was historically behind many “natural” disturbance incidents. We are learning that land idled under the context of conservation may also exhibit negative environmental impacts.

Recent focus and research around the concept of soil health has not only reinforced the need for a more ecologically based food production model, but has provided additional support that occasional ecosystem disturbance followed by rest is critical for maintaining the long-term vitality of native plant communities and ecosystem functions.

Can we have productive agriculture as well as provide an array of ecological services? I would answer with a resounding YES. I will, however, temper that response with the caveat that we will not be entirely recreating native landscapes and plant communities in the process of moving toward a more ecologically based agricultural system. The current buzz about soil health provides the framework in which we can move agriculture to a new “normal.”

What is soil health? Soil health is about the ability of soil to function. Properly functioning soil has the ability to cycle nutrients, and capture and store water. We have clear documentation that most of our agricultural soils are highly impaired in their ability to function correctly. For example, many soils in row crop regions contain moderate to high levels of phosphorous, a vital plant nutrient. Yet, these phosphorous reserves are not readily available for plant growth because the biological mechanisms that make the nutrient available for plant growth have been disrupted or destroyed by industrial agricultural practices.

Water infiltration demonstrations have shown that many of our continuously cropped soils can no longer infiltrate even ¼ inch of rainfall per hour. Erosion, despite lessons from the Dust Bowl, is a public safety issue in the form of traffic accidents due to low visibility from blowing soils.

Some are trying to define soil health as cover crops, no-till, precision fertilizer placement or the elimination of synthetic pesticides and fertilizers.While these are tools a producer can use to improve soil health, they are not “soil health.”

There is a broad spectrum of how an individual producer can move an operation toward soil health. It begins with a set of principles that may be implemented across all agricultural regions regardless of the size of the farm. These principles include: 1) keep the soil covered; 2) keep a living root in the soil; 3) minimize soil disturbance; 4) promote plant diversity; and, 5) integrate livestock. The goal of these principles is to create a home or habitat suitable for supporting health and active soil microbial populations by mimicking natural systems. It is only through active and healthy soil biology that we can create good soil aggregate structure to capture and store water, and cycle nutrients. Let’s explore each principle further.

Keep Soil Covered
In nature, bare soil is the exception. Yet many of our agricultural soils remain uncovered over half the year. Coverings protect the soil from movement (erosion). Covered soil also provides a thermal barrier to moderate temperature extremes. Soil microbes, like humans, prefer a fairly narrow band of temperatures. Soil biological activity slows with temperatures below 50 degrees Fahrenheit. Microbes are stressed when soil temperatures begin to rise above 90 degrees. On a hot summer day, exposed soil temperatures can exceed 120 degrees. Soil temperatures under cover can run 20 – 30 degrees cooler. Soil may be covered with living plants, crop residues and/or mulch.

Keep Living Root in Soil
Most biological activity in the soil occurs at or near the soil surface, and in association with a living root. Living plants exude sugars through photosynthesis. The sugars feed the microbes, which in turn aid the plant in obtaining water and nutrients. Many of our agricultural soils only have a living root about 1/3 of the entire year while the primary cash crop in growing. Cover crops, whether annuals or perennials, can help fill the gaps. Relay or double cropping is possible in many regions, helping keep a living root in the soil throughout most of the year. Farmers even in the northern Corn Belt have successfully grown three crops in two years (silage corn followed by cereal rye chopped for silage the next spring, followed with soybeans).

Minimize Soil Disturbance
Soil disturbance in natural systems is generally an acute event (volcanoes, floods, trees uprooting, etc.) followed by periods of no disturbance. Tillage has been a dominant form of weed control in grain and vegetable crops for centuries, sometimes occurring annually for decades. Modern tillage objectives also include addressing problems from previous tillage operations, such as compaction. For most modern row crop producers, minimizing tillage will involve no-till or strip-till operations.

It may also involve the inclusion of perennial crops into the rotation. Soil microbiologists have documented the damage tillage can do to the microbial community. Yet, with adequate rest, microbes have the opportunity to recover.

Promote Plant Diversity
Monocultures do not exist in nature. Diversity in plant species promotes diversity in the microbial populations. Diverse microbial communities aid in suppression of many pest species. Many soil microbial species have associations with specific plant species. Most notably are the mycorrhizal fungi-plant associations. Mycorrhizal fungi-plant associations create the opportunity for plants to access soil phosphorous reserves. They also expand the ability of plants to access additional water and nutrient reserves in the soil through fungal hyphae. Fungal hyphae appear to resemble fine roots, but in reality form a network of fungal strands that greatly expand the reach of an individual plant’s root system. Hyphae also serve as a communications network between plants, providing a symbiotic relationship to deal with stress.

Integrate Livestock
Animals are associated with every ecosystem on the planet. Livestock have been identified as the missing link in soil health. Science has yet to replicate in a jug or bag what comes out the back end of a cow. Farmers have long understood the value of manure application for crop production. However, there is value to soil microbes not only from direct deposit of urine and manure, but also the disruption from short-duration grazing activity and high density hoof action. Adequate recovery periods following the disturbance are critical to successful livestock integration. Recent data suggests that livestock integration in combination with crop diversity and no-till over a number of years can increase plant available N, P and K, and soil carbon deposition 4 -5 times greater than operations that only utilize no-till and/or have a broad crop rotation that includes cover crops.

Producers across agricultural regions, regardless of the size of the operation, have developed a variety of creative means to integrate livestock into their production model including “chicken tractors,”, “egg-mobiles,” temporary runs, portable energized fencing and netting, adaptive high stock density grazing, and movable pens. Cover crops and perennials can provide a bridge to bring livestock into cropping systems. We can also use managed livestock disturbance to rehabilitate native plant communities where agricultural production is not the primary goal.

There is ample evidence that an agricultural production model focusing on soil health can be not only productive, but profitable. This model is not just for small-acreage farms. Both organic and non-organic producers running operations from several hundred to over 10,000 acres across Minnesota, Wisconsin, Nebraska, Kansas, Virginia, Georgia, South Carolina, Mississippi, and other states are reporting the successes with a production model focused on soil health.

When we move from viewing soils as simply a medium to support the roots of our cash crops to a living ecosystem, the farmer becomes an agroecologist. Opportunities abound to implement soil health into existing agricultural operations. By adhering to the basic tenets of soil health, we not only create habitat for soil microbes, but also provide a host of ecosystem services including clean water, pollinator habitat, grassland bird habitat, carbon cycling, as well as nutrient-dense food.

Kent Solberg lives and farms in Central Minnesota and currently serves as the Livestock and Grazing Specialist for the Sustainable Farming Association. He holds a bachelor’s and master’s degree in wildlife biology.

From the September | October 2017 Issue

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