Don’t You Forget About Soils: Why Healthy Soils Are Key to the Success of our Food Systems

America used to be known for its rich and fertile topsoil when untouched prairies and forests made up the Southeast and Midwest. But for many generations soil was mostly seen as not much more than a medium for holding plants while fertilizers and herbicides were applied to help them grow. Intensive plowing, monocropping and pesticide application have inflicted severe damage on soils, and specifically soil organic matter which is largely responsible for the properties of healthy soils such as soil structure, aggregation, water retention, fertility, biodiversity and the cycling and storage of nutrients. In the US, more than 50% of our topsoil has eroded away, and in areas of the Southeast, America’s former breadbasket, it’s almost gone.

Fortunately, soil can be rehabilitated. Over the past few decades there has been a growing recognition and appreciation of soils as living biosystems, and a focus on improving soil health. Unfortunately, there is no quick fix. It takes at least 100 years to form an inch of topsoil and could take 1000 depending upon climate, vegetation, soil management practices and other factors.

But, it is certainly a worthwhile cause. Healthy soils are responsible for supplying the nutrients, water, oxygen and root support that plants need and are really the foundation of thriving farm operations, prosperous agricultural communities and nourishing food systems. Preserving and rebuilding soils is the only way to ensure we can continue to reap the myriad of agricultural and ecosystem benefits that healthy soils provide.

Healthy Soils Improve Productivity & Yield

With researchers predicting that higher temperatures and decreased precipitation could reduce yields by up to 30% over the next 50 years, managing these risks has become a top priority for farmers and policy makers. A study published in Nature that focused on the corn belt, found that a 10 percent improvement in certain soil health measurements increased yields by an average of 5 percent across fertilizer rates. The benefits of healthy soils in sustaining crop production are most evident when growing conditions are not ideal. Healthy soils increase the capacity of crops to withstand weather variability and extreme precipitation events as well as intra-seasonal drought. A study conducted by the Environmental Defense Fund found that counties with higher soil organic matter were associated with greater yields, lower yield losses, and lower rates of crop insurance payouts during drought conditions. Even in average weather years the researchers found that higher levels of organic matter was associated with greater yields, but the positive effect was progressively greater as drought became more severe.

Healthy Soils Increase Nutrient Cycling, Decreasing the Need for Additional Inputs

Decomposition by soil organisms is at the center of the transformation and cycling of nutrients through the environment by liberating carbon and nutrients and putting them back into biological circulation so they are available to plants and other organisms. Healthy soils with high organic matter and microbiotic activity enable a near closed loop cycle of nutrients where nutrients are available to plants and other organisms as needed while reducing excess mineralization and nitrification. The cycling of nutrients relies on soil's capacity to receive nutrients and keep them in forms available to crops.

One third of the fertilizer applied each year in the US simply compensates for the ongoing loss of soil fertility due to erosion and organic matter loss. The US is one of the world's largest users of fertilizer with farmers applying more nitrogen and phosphorus per acre than their counterparts in other high yielding countries.Organic cropping systems in combination with maintenance of soil organic matter and improved soil health have been shown to provide benefits with respect to reduced farm nitrogen and phosphorus surpluses.

Healthy Soils Improve Water Holding Capacity & Drought tolerance

When it comes to soil water holding capacity, it is critical that soils both allow water to flow through to avoid flooding, yet hold the water so that it is available to plants during dry spells. Healthy soils high in organic matter form soil aggregates and are marked by their porous “spongy” texture which allows rainfall to infiltrate deep in the soil and increases the soil’s ability to hold plant-available water. In fact, organic matter can hold up to 90 percent of its weight in water and release that moisture slowly over time making soils less vulnerable to floods and droughts. According to the USDA Natural Resources Conservation Service, for every 1% increase in soil organic matter, US cropland could store the amount of water that flows over Niagara Falls in 150 days.

In the US, irrigation accounts for more than 80 percent of total water consumptive use and up to 94 percent of consumption in regions most prone to water scarcity. Due to increased water use and the effects of climate change, agriculture in the US will face increased water scarcity in most major irrigated areas ranging from 20 percent to more than 50 percent across the central and southern Mountain, Pacific, and Plains regions by 2060. Additionally, according to the FAO, as much as 40 percent of rainwater runs off uncovered dry land soil. Reducing agricultural water use while maintaining and increasing production capacity will be key to the future of our water and food security.

Withstanding Erosion

Soil erosion is a natural process that occurs when water or wind detaches and removes soil particles causing the soil to deteriorate. In addition to the loss of fertile land, erosion increases pollution and sedimentation in streams and rivers and results in the release of soil organic carbon into the atmosphere, decreasing the soil’s capacity to store CO2 and contributing to the effects of climate change. Healthy soils are teeming with microbes that produce sticky substances that hold soil particles together to form aggregates. Soil organic matter is essentially the glue that helps bind the soil together and keep it anchored in place. Research suggests that a 1 to 3 percent increase in organic matter can reduce soil erosion by 20 to 33 percent by increasing the water-holding capacity of soil. Practices that build organic matter, maintain field cover and reduce disturbances to the soil making it less vulnerable to erosion from wind and rain.

Soil deterioration due to erosion and resulting surface runoff has become a severe problem worldwide. US farms are currently losing twice as much topsoil to erosion per year as the great plains lost at the height of the 1930s dust bowl, one of the most devastating soil and agricultural disasters in US history. Projections have shown that cumulative average soil loss on US cropland by 2100 could range from 2.5 inches to over 5 inches with the business as usual scenario projection at about 4 inches. To put that in context, farm soil in Iowa currently averages about 8 inches deep, down from a historical depth of 12 to 14 inches. According to the FAO, if current rates continue, all the world’s top soil will be gone within 60 years. The increased stability and aggregation of healthy soils helps them resist erosion and compaction.

Mitigating Crop Disease

Poor soil conditions can hinder plants’ abilities to protect themselves against insects and weeds and can cause plants to emit stress signals that encourage potential attackers, heightening the risk of damage. But healthy soils can lessen the incidence and impact of soil pathogens. Evidence suggests that adopting soil conservation techniques often increases mortality and decreases reproductive output for many pests due to increases of quantity and activity of natural enemy populations and enhanced plant defenses.

According to the UN, some 40 percent of global crop production is currently lost to pests, and climate change is making many pest occurrences even more destructive, heightening threats to food security and the environment. The UN estimates that pests result in the loss of up to 40 percent of global food crops each year and cost the global economy $220 billion annually. Fungal crop diseases have been increasing in severity and scale since the mid-20th century, particularly threatening wheat, soybean, and potato, and now pose a severe threat to global food security and ecosystem health. Healthy soil communities feature diverse food webs that can keep diseases at controlled levels through competition, predation and parasitism.

Filtering Contaminants

Water entering the soil may have a number of contaminants that require removal prior to being reused or to minimize negative environmental impact. These might include sediment, pesticides, salts, viruses, bacteria, or heavy metals. Soil provides this filtration through physical, chemical and biological processes that remove or degrade contaminants in water as it passes through to the groundwater supply. With physical filtration, a well aggregated soil can act as a sieve and block particles that are too large to pass through. The surfaces of soils are often chemically reactive, for example soil clay particles have a negative charge and will attract particles that have a positive charge such as heavy metals, salts and pesticides. Microorganisms in healthy soils also have the ability to transform both organic and inorganic soil substances. This is useful when water contains materials that would have negative effects on the water supply if they didn’t undergo further decomposition. By managing soils in a way that protects their natural water filtering abilities we can prevent source waters from becoming contaminated.

Soil Health Management

In light of all these benefits, it is clear that maintaining and improving soil health should be at the forefront of our agricultural agenda. The blueprint for soil health comes down to three basic principles; cover the soil with plants at all times, diversify what grows and minimize soil disruption. While there is a growing awareness of the advantages and indispensability of healthy soils, many farmers still grow the same thing year after year due to government incentives, habit, and ease. Practices such as incorporating cover crops can protect the soil, reduce erosion, encourage biodiversity and return nutrients like nitrogen to the soil. Science has also shown that practices such as reduced or no till, planting perennial crops, employing crop rotations and incorporating livestock into agricultural systems can improve soil organic matter and deliver a myriad of benefits.

The increase in food requirements to feed a growing population, impacts of climate change, consequences of agricultural practices on the environment, and the lack of new arable land to bring into production mean that restoring the health of our soils will be one of the most essential undertakings for the future of our food systems. We are dedicated to helping farmers steward their land and nurture their soils because it is fundamental for the future of farm businesses as well as our food supply. Soils are the basis of our food systems. It’s time we treat them that way.