Examining Soil Health Perceptions in North American Agriculture
Updated: Jul 16, 2021
Soil Health and Its Importance
Soil health is defined as the “continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans”*. Soil is a resource shared between generations, and managing soil health is crucial for its longevity and sustainability for future generations.
There is growing concern about the abundance and quality of the top soil remaining on our planet. Pictured below, top soil is the uppermost 6-10 inches of the soil profile. Almost 95% of our food is grown in top soil. Maria Helena-Semedo of the FAO stated that “...if current rates of degradation continue, all of the world’s top soil could be gone in 60 years”*. A lack of top soil will drastically decrease our ability to feed people, and the food that is grown would likely provide fewer vital nutrients*.
Image: Layers of the Soil Horizon
Farmers and agricultural workers have an important role to play in the management of soil quality. After all, they are stewards of the land we grow on. But this begs the question, does the agriculture industry share the same concerns about soil health as researchers? Thanks to a survey performed by Soil Health Nexus, a university-led agricultural research team in the United States, we can analyze differing opinions from various audiences in the agriculture industry*.
There were approximately 300 respondents in the survey, where 75% of the respondents were farmers, extension educators, or federal and state agency staff. This is not a representative sample size of the agricultural industry as a whole, but provides a baseline indication of farm practices and future agricultural goals in North America.
Defining Soil Health
Respondents of this survey were asked how they would define soil health. Though there was a plethora of responses,
it was found that the most important characteristic of soil health was biology, and the most important effect of soil health was productivity4.
Other notable characteristics of soil health included tilth or structure, chemistry, and organic matter. Other notable effects of soil health were ecosystem sustainability and resiliency.
We can see that respondents have identified the importance of biological soil activity. Additionally, soil productivity is of utmost importance as well. Soil biology and productivity go hand in hand. Soil microorganisms are responsible for maintaining the soil food web and natural nutrient cycling processes. Similar to larger food webs in terrestrial habitats, like a forest, small organisms get eaten by bigger organisms and energy moves up the web. This relationship is illustrated in the graphic below.
Picture : Diagram of the Soil Food Web showing how the lower level, smaller organisms feed the level above them. Attribution: Soil Biology Primer/USDA-NRCS website
By maintaining a biologically active soil with large communities of microorganisms, farmers can increase yield, soil productivity, water holding capacity, and soil structure.
The microorganisms present in the soil will restore the natural process of nutrient cycling, create plant growth promoting hormones, and stress abating enzymes.
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Which Soil Health Benefits are Important to Farmers?
When asked to rank the benefits of soil health, respondents stated that their five highest priority benefits are: building organic matter, water infiltration, erosion control, nutrient management, and water holding capacity*.
Soil organic matter is the fraction of soil that consists of plant or animal tissue in various stages of decomposition5. Most soil used in cultivation has organic matter between 0-30%, with most top soil averaging approximately 3-6% organic matter. There are three components to soil organic matter:
1. Plant residues and living microbial biomass
2. Active soil organic matter, often referred to as detritus
3. Stable soil organic matter, referred to as humus
As plant residues, living microbial biomass, and detritus break down, they release plant nutrients like nitrogen, potassium, and phosphorus. They contribute directly to soil fertility and the availability of nutrients. Seen in the image below, decomposing organic matter adds richness and colour to soil. Humus on the other hand, has already released its nutrients and plays a more significant role in maintaining soil structure, tilth, and cation exchange capacity*.
Picture: Soil Organic Matter
Soil organic matter is important to growers as it is a medium that allows for the slow release of nutrients via microbial decomposition. Soil microorganisms will use the organic matter as a food source. Organic matter also serves as a significant carbon source in soil and can balance the carbon to nitrogen ratio (C:N) of soil.
The carbon to nitrogen ratio has a significant effect on the decomposition rate of crop residue and nutrient cycling. Soil microorganisms have a C:N ratio of 8:1, or 8 parts carbon to one part nitrogen. Microbes use carbon as a source of energy, so not all the carbon they ingest will stay in their body, there will be some carbon lost due to respiration. The ideal C:N ratio to support and sustain microbial life is 24:1*.
What Practices are Farmers Using to Improve Soil Health?
According to the survey, the most used and recommended soil health practices were crop rotations, no tillage, and cover cropping*. All three methods are beneficial by either returning nutrients to the soil, or limiting the disturbance of nutrient cycling processes.
Crop rotations have been used for thousands of years, long before humanity started researching chemistry and biology. Different crops have different nutrient and water requirements. Different crops will also attract various types of pests and be susceptible to different diseases. If a farmer is planting the same crop in the exact same field every year, they will be continuously drawing the same nutrients out of that soil*. Pests and diseases will find themselves right at home, as their preferred food source is always in the same spot and in great abundance. With a monoculture like this, farmers will have to gradually increase their dependence on chemical fertilizers and pesticides to maintain high
yields and mitigating pest and disease pressures.
Cover crops are different from field or cash crops, as a cover crop’s primary responsibility is to improve the soil. Cover crops are planted in fields that would otherwise be bare to mitigate soil erosion and nutrient loss*. Cover crops can also help to outcompete weeds, mitigate pests and diseases, enhance water availability, and improve biodiversity in the field. They will act as a living mulch when planted.
As can be seen in the image below, the cover crops planted between the grapevine rows will undergo photosynthesis and replenish nutrients in the soil. Without having cover crops between the grapevine rows, the bare soil would not be replenishing any nutrients back into the soil, and would be more susceptible to soil erosion from wind and water.
Picture: In this vineyard, cover crops are planted between the rows of grapevines. The cover crops will increase organic matter when incorporated back into the field and return nutrients to the soil. Without the cover crops, the bare soil would not be contributing to nutrient cycling or increasing organic matter.
Certain cover crops have the ability to fix nutrients and return them from the soil. For example, White Clover is a legume that is often used as a cover crop. White Clover has a deep root system which can resist drought, and can replenish between 80-200 lbs of nitrogen per acre planted*. White clover can be incorporated back into the field as a green manure that will help feed microbial activity and replenish carbon in the soil. Cover crops work well in a no-tilling farm system.
No Tillage farming systems are not a new concept, though tilling is still widely implemented. Why do farmers till their field? Tilling is method brought on during the European Agricultural Revolution. It involved mechanically digging, turning over, or stirring the top 6-10 inches of soil*. This process is performed before a new crop is planted. Tilling incorporates surface crop residues deep into the field while blending the soil. Tilling also aerates and warms the soil. This process allows farmers to plant more seed with less effort. This process seems like it would be beneficial on the surface, so why would we want to adopt a no-till farming system?
Tillage loosens and removes plant matter that covers the soil, leaving the soil bare. Bare soil is significantly more prone to erosion by wind and water, especially if the soil is lacking organic matter. The natural structure of soil is similar to a sponge. There are channels created by soil aggregates that allow for the infiltration of water and mobilization of oxygen in soil*. By tilling, we are digging up that soil structure and turning it over on itself, reducing the soil’s ability to allow water to infiltrate and facilitate the movement of nutrients. More importantly, tillage displaces or kills off millions to billions of microbes that are necessary for optimal plant growth and yields.
What are the Barriers to Implementing Soil Health Practices?
Researchers can study the efficacy of various farming systems and present the benefits of each, but it is ultimately up to the farmer to decide which strategies they want to implement. When it comes to deciding on which practices to use, what would drive a farmer’s decision?
Respondents to the survey noted that the perceived cost of time and financial investments needed to obtain new equipment are the major hurdles preventing them from adopting new soil health improvement practices*. Additionally, respondents noted concern regarding the effect of their new practices on crop yields and cash croppers reported more hesitation to risk their income when crop prices were particularly low. Lastly, other farmers indicated that there was little or no evidence that these practices improved profits or crop production enough to balance out increased input costs.
However, though those are valid reasons to be hesitant, a significant barrier for implementation was a lack of knowledge on the importance of soil health, the practices that can improve soil health, and how to implement those practices.
Conclusion
We can see from the survey that although agricultural players are considering the benefits of soil health improvement, there is a discrepancy with the types of practices that are most beneficial and a lack of knowledge on how farmers can implement those practices. There needs to be further research conducted on the economic benefits of soil health improvement practices to further demonstrate the need to implement them.
We invite you to join Nurture Growth Bio-Fertilizer this year for our Agricultural Webinar Series (insert title here). We will be covering topics such as Beneficial Microorganisms for Field Crops, Growing Organic Cannabis, Companion Planting, and more. Also available on our website are trial reports, farmer testimonials, and additional product information.
Blogger Biography
Eric is a gradate of the Environmental Science program at the University of Toronto. Coming from the green roof and landscaping industries, he does not hesitate to get his hands in the soil. He is actively searching for new ways to learn about our agricultural systems and get involved with his local agricultural community. Eric is an avid birdwatcher and advocate for environmental responsibility.
Citations:
1. https://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/
2. https://www.sej.org/headlines/only-60-years-farming-left-if-soil-degradation-continues
5. http://franklin.cce.cornell.edu/resources/soil-organic-matter-fact-sheet
6. https://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download?cid=nrcs142p2_052823&ext=pdf
8. https://extension.umn.edu/how-manage-soil-and-nutrients-home-gardens/cover-crops-and-green-manures
9. https://www.canr.msu.edu/news/cover_crops_as_nitrogen_source
10. https://regenerationinternational.org/2018/06/24/no-till-farming/
Image sources:
2. Soil Food Web: https://commons.wikimedia.org/wiki/File:Bodennahrungsnetz.jpg
3. Soil Organic Matter: https://commons.wikimedia.org/wiki/File:Organic_matter_1.jpg
4. Vineyard Cover Crops: https://commons.wikimedia.org/wiki/File:Biodynamic_vineyard_with_winter_cover_crop.jpg
