By Dr. Mercola
High-quality soil is crucial to growing nutrient-dense food. Tragically, much of the soil in the U.S. and around the world has been depleted and degraded by modern farming practices using nitrogen-based fertilizers, tilling and monoculture where only corn and soybeans are being rotated. Prior to 1904, soybeans were grown only as forage crops,1 providing some livestock feed, but more often used as a conservation crop.2
Soil carbon losses also greatly contribute to a loss of biodiversity in the soil and depletion of nutrients that feed plants. Past studies that have attempted to quantify those losses have generated results that vary wildly in their conclusions.3 Generally, scientists have believed carbon losses were near 78 billion tons, representing a huge loss to the soil and nutrient base for crops. However, a recent study published in PNAS convincingly demonstrates this number may not be as accurate as once believed.
Soil Organic Carbon Loss Moving More Rapidly Than Anticipated
Soil is more than just dirt under your feet. It’s a life-anchoring, thin skin that covers the Earth. In the soil live countless microbial species that provide a complex ecosystem supporting agriculture and wildlife. As the composition of the soil changes, so does the biodiversity and nutrient value. Carbon is one of those compounds lost in ever increasing amounts, thereby taking a significant toll on the intricate ecosystem that lives in the topsoil.
The transition across the globe from natural vegetation to agriculture has produced a condition that encourages soil erosion. In the past 150 years,4 the planet has lost nearly half of the topsoil as monocultures do not conserve soil in the way natural vegetation does.
Researchers now believe carbon losses across the earth amount to 133 billion tons, almost double what was previously measured.5 Past studies used a bookkeeping type method to determine carbon loss. Researchers would measure carbon loss in a single plot of land and then estimate a total loss across the world.
In this study, researchers used a large data set with information on soil from around the world and applied it to a model of human land use and agricultural activity across 12,000 years. This model relied on another larger database of information and accounted for physical factors such as climate and topography. The results suggest that the most intense losses in the top 6 feet of soil around the world have resulted from planting crops.6
Researchers found these losses varied in different locations and over different time periods, with the greatest increases noted since the industrial revolution, particularly during the 19th century. The challenge to the agricultural community, and the world at large, is more acute when you understand areas of land available for growing food are also contracting.7 Urban growth, loss of topsoil and soil depletion are factors that reduce available land suitable for farming.
Carbon Loss Damages Soil Quality and Product Yield
In a comparison of long-term effects of conventional and organic farming since 1948,8 organic farms had higher organic matter. The topsoil depth was greater, there was less soil erosion and more polysaccharide content on the organic farms, all factors that increase crop yield and topsoil generation.
This indicates that in the long term, organic farming systems are more effective than conventional systems in reducing soil erosion and thereby improving soil productivity. One of the main causes of soil degradation, making it less hospitable for plant growth, is a loss of soil structure and fertility.9 These are a major threat to crop production for future generations. Biological processes that contribute to degradation of soil quality include a reduction in total and biomass carbon, and resulting decline in land biodiversity.10
Supporting bacterial and fungal soil growth has the potential to reinstate fertility and structure, as microorganisms increase the bioavailability of nutrients through nitrogen fixation. One of the basic tenets of organic farming is crop rotation, which promotes greater plant diversity and carbon sequestration, which increases positive microbial activity.11 These factors are interrelated and necessary for robust soil health.
Organic carbon supports the structure of the soil that in turn improves the physical environment for plant roots, helps absorb and retain greater amounts of water and reduces the susceptibility to compaction and erosion.12 Loss of carbon may limit the ability of the soil to provide nutrients for plant growth. In other words, loss of carbon may lead to lower crop yields and reduced amount of nutritional benefits in the plants that are harvested.13
Nitrogen Fertilizers Create Problems in More Ways Than One
Nitrogen fertilizer is a key component of modern agriculture — an unsustainable food system built around the use of technology that is reliant on finite resources of fossil fuel energy.14 Researchers theorize dependence on synthetic nitrogen, which requires natural gas and oil for manufacture and distribution, may lead to a collapse in the food system structure. However, this is not the only challenge associated with the use of nitrogen-based fertilizers.
Loss of soil carbon results from more than poor land management practices. Scientists once believed adding large amounts of nitrogen to the soil as fertilizer would help reduce carbon loss and thus improve soil quality. However, research has debunked this theory15 after coming under scrutiny by a team of scientists from the University of Illinois.
The researchers argue the ultimate effect of synthetic fertilizer use is a reduction of organic matter in the soil16 as it stimulates the growth of microbes that eat organic matter and thus disrupt the soil. Over time, this reduces crop yields and has led to lower nutrient value in the plants.17 As the amount of organic matter declines, so does the ability of the soil to store nitrogen. This means a large amount of nitrogen leaches into the ground water and enters the atmosphere.
This, in turn, has led to lower crop yields that farmers fix through the use of more nitrogen-based fertilizer. In other words, it’s a vicious cycle in which the more nitrogen fertilizer is used, the more is needed the following year.
The soil becomes more prone to compaction leading to water runoff, soil erosion and loss of topsoil. This means the effect of synthetic nitrogen on the soil does not lead to carbon storage, thought to be an important ecological advantage of use, but rather becomes a grave liability as it undermines long-term productivity.
Nitrogen runoff from farmlands has also cost Americans $157 billion annually in health care and environmental damage.18 That judgment was reached by a team of international scientists who concluded the median cost of nitrogen pollution reached $210 billion, of which agriculture accounted for 75 percent. Within agricultural circles, it is corn that uses the majority of nitrogen fertilizer. The scientists calculate the cost in human health and environmental problems were twice the value of the corn produced for grain in a single season.
The researchers used prices for the commodity when they were at their highest. In other words, even when the value of the crop is high, the financial benefit of growing crops using nitrogen fertilizer does not outweigh the financial loss experienced by the community. Damages to health are linked to increasing respiratory illnesses and in the environment excess nitrogen causes toxic algae blooms in waterways that affect your drinking water.
Nitrogen water pollution left residents of Toledo, Ohio, without drinking water for three days and Des Moines (Iowa) Water Works with a $1 million cleanup bill, the most the utility had ever spent in one year to treat unexpected nitrogen pollution.19
SUSTAIN Management May Not Be Enough
Walmart recently unveiled an initiative to reduce 1 billion tons of carbon lost to the atmosphere by 2030. Called Project Gigaton,20 the cuts are to come from the company’s suppliers: not just factories or distribution, but also the farms.21 The expectation is to reduce the amount of nitrogen fertilizer used, which will in turn reduce the amount of carbon lost in the soil. However, while the initiative is commendable, Walmart doesn’t grow the crops that lead to carbon loss.
Several years ago a fertilizer dealer from Iowa, Matt Carstens, read about Walmart’s interest in reducing carbon loss and realized the program was hitting close to his backyard. After failing to secure a meeting with Walmart, he contacted the Environmental Defense Fund (EDF), also mentioned in the articles he read, and was soon on his way to Washington, D.C. for meetings about the group’s concerns.
Following the meetings, Carstens developed the SUSTAIN program, which he felt may help farmers identify exactly how much fertilizer would be needed, while reducing the amount of nitrogen applied.
United Suppliers, where Carstens worked, was a business that supplied seeds and chemicals to the farmer and, thus, Carstens was already a trusted adviser. Included in the SUSTAIN program were chemicals that kept the fertilizer from washing off the fields quickly and a computer program that indicated how much nitrogen was in the soil, to avoid adding excessive amounts.
United Suppliers was bought by Land O’Lakes, an agricultural company, which then promised Walmart 20 million acres of farmland would be enrolled in the SUSTAIN program. While the program provides a much-needed boost to agriculture’s public image, the results may not be as positive.22
Farmers are using stabilizers in the fertilizer to keep it from washing away quickly, and are applying the fertilizer throughout the growing season, instead of all at once. This is being done in the hope that the plants use the nitrogen more efficiently and farmers may be able to reduce the amount they use.
However, Michigan State researchers have observed that whether there is a reduction in use or not has yet to be determined. At this time even Carstens isn’t promising a reduction in the amount of destructive nitrogen released into the environment, but hopes the program will help farmers use it more efficiently, and hopefully use less.23
No-Till Land Management Crucial to Soil Health
Another crucial factor in conservation of soil and land health is the elimination of tilling.24 Tilling the soil, or plowing the field, disturbs the microorganisms that improve soil health. The mechanical act of tilling may also cause severe soil erosion, depending on the type of machinery used and the slope of the land. The exposed soil is highly susceptible to wind and water erosion as well.
Tilling aerates the soil, which dries it out.25 The oxygen stimulates the action of soil microbes that feed on organic matter and releases more carbon out of the soil. This reduction in organic matter has significant consequences on soil quality and ability to continue to produce high quality crops over many years. No amount of applied synthetic fertilizer can offset this damage. The University of Minnesota Extension Program describes the benefits of no-till methods and high organic matter in the soil:26
- Crops thrive, even through dry spells
- Roots grow extensively
- Implements pull easily through the soil
- Soil resists erosion and compaction
Soil organic matter is decomposed organic material that becomes stable humus,27 whereas organic material lying on top of the soil is often dead leaves, sticks and other plant material. The humus formed from microorganisms and earthworms is in a state resistant to decomposition, which is why so much organic matter is lost when nitrogen speeds the decomposition of humus in the soil, releasing carbon into the atmosphere.
No-Till May Grow Earthworm Population
Using no-till practices may also improve the earthworm population in the area, which in turn increases root depth and nutrient density to the crops.28 It was only a few short decades ago that farmers thought earthworms weren’t very important to the health of the soil or plants grown in the area.29 Emphasis was placed instead on physical and chemical remediation, instead of addressing underlying biological concerns for long-term solutions.
With growing interest in soil conservation, organic farming strategies are slowly being embraced across the country in an effort to develop a solution that will support an ever-increasing population with sufficient food while preserving the land. Carbon sequestration and supporting earthworm populations play a significant role in this effort. Earthworms develop vertical burrows in the soil, increasing the ability of the soil to absorb rainwater and reducing water runoff.30
Those same burrows reduce soil compaction and allow good aeration for plant root oxygenation without disturbing the microorganism’s ecosystem and increasing the activity of microbes responsible for decomposing humus. Some earthworms make a meal of nematodes that are damaging to the soil and plant life.
Earthworms also partially digest organic material in the soil, mixing the resulting matter with soil to form humus. The importance of these functions become apparent in soil without earthworms, as these creatures contribute significantly to the production of topsoil.
Regenerative Land Management Practices Make a Massive Difference in Crop Production
In this short video, I interview Gabe Brown, a regenerative land management pioneer who focuses on soil restoration. Although the application of fertilizers and herbicides helped one generation of farmers increase their yield and reduce labor costs, the resulting changes to the soil have led to disrupted and unhealthy root systems, microbial activity and insect life that are all vital to plant growth and soil health.
Some farmers who practice regenerative land management are criticized for how “messy” their land looks;31 however, they are reaping the benefits in higher yields per acre. Improving organic matter content and sequestering carbon in the soil add up to growing amounts of topsoil that resist erosion, greater crop productivity and an increase in water infiltration of the land, reducing the risk of crop losses during droughts. Practices that increase organic matter and reduce carbon loss include:
- Reduced or no-till: When the soil is tilled intensely, it is difficult if not impossible to maintain organic matter levels. Leaving plant residue, tilling less often, or not at all, are desirable methods of conserving organic matter and improving soil health.
- Plant diversity and rotation: Farms that rely on planting the same crop every year suffer the greatest losses in soil biodiversity and soil health. Crop rotation throughout the growing season and between cash crop seasons helps improve organic material and reduces the loss of specific nutrients in the soil from one crop.
- Planting cover crops: These are crops that may be planted prior to, during or after the cash crop season. Home gardeners may use crop cover such as wood chips or mulch, while large scale operations benefit from planting wheat cleanings, cereal rye, millet or clover. These plants serve to insulate the soil surface so it doesn’t get as hot or cold as it does when bare, allowing microbes to thrive longer.
Using these strategies, farmers keep living roots in the soil year-round to reduce soil erosion from wind and water. These plants also increase the amount of organic matter and improve water infiltration. Home gardeners can achieve some of the same results by planting cover crops after their summer garden has been harvested and rotating the places in the garden where their vegetables are planted each summer.
Before Indiana farmers cultivated fields of natural vegetation, the carbon content was as high as 10 percent in some areas.32 Today, the level is less than 2 percent on most farms. Planting cover crops may restore carbon at a rate of nearly 1 percent every five years, which increases the amount of water the soil can naturally store.
Rulon Enterprises farms 6,200 acres in Indiana and plants four-fifths in cover crops each year. Data collection from his farm revealed a 12.8 bushel per acre increase in his fields planted with cover crops over those that weren't.33 After the cost of cover crop seeds, savings in fertilizer and larger yields in the fields, the farm estimates a net benefit of approximately $244,000 managing the land the way it was done before chemical fertilizers and pesticides entered the market.