Soil in Danger: How Fixing Agricultural Soil Could Help the World

Weeds grow in dry cracked earth that used to be the bottom of Lake McClure in La Grange, Calif., on March 24, 2015. Justin Sullivan/Getty Images

Agricultural soil is an important resource for communities all over the world, not only because it provides humans with the majority of their food but because it also plays a major role in balancing the environment.

Soil researchers have said investing in soil could help the world tap into an untold resource against environmental challenges brought on by unpredictable climatic conditions.

“The degradation of soil resources has been occurring since the advent of agriculture, some 10,000 years ago,” said the Assoc Head of Colorado State University’s Department of Soil and Crop Sciences, Prof. Francesca Cotrufo, and PhD student Sam Leuthold from Cotrufo’s Soil Innovation Laboratory.

Cotrufo and Leuthold said that the intensity of this degradation had increased sharply since the industrial revolution and the introduction of mechanized farming equipment, which allowed for the expansion of agricultural lands into areas that were previously uncultivated, as well as the expansion and industrialization of livestock agriculture.

“Transforming naturally vegetated ecosystems into crop or grazing lands changes the carbon balance of these systems,” the researchers said.

Cotrufo and Leuthold said that unlike soil carbon stocks in their natural state, which tend to balance inputs and outputs, agricultural soils tend to lose more carbon than they gain when converted. This is because the growing season of annual crops is often shorter than that of natural perennial vegetation, and in agricultural systems, a significant portion of plant matter is removed by grazing or during harvest.

“After a period of time, agricultural soils may reach a new steady state, but the new balance of inputs and outputs then exists at a lower level than prior to cultivation, and as a result, carbon is lost to the atmosphere,” they said.

“Additionally, intensive tillage and fallowing of croplands, as well as intensive grazing by livestock, can lead to markedly increased levels of erosion of the carbon and nutrient-rich topsoil, either via wind or water.”

Soil Degradation Can Lead to Catastrophic Consequences

The most catastrophic example of this kind of degradation occurred across the North American plains in the 1930s after a prolonged drought combined with extensive amounts of intensive tillage brought about the Dust Bowl, the worst drought in United States history.

“Not all soil degradation events have eras named after them though—today, thousands of hectares of coastal cropland are at risk of salinization due to rising sea levels and increasing storm intensities,” the researchers said.

“Inland soils face increased risk of desertification and loss of fertility due to overgrazing and expansion of agricultural lands into unsuitable conditions.

“Arid and semi-arid regions such as sub-Saharan Africa and the Western United States are most vulnerable to this decline, as the lack of rainfall makes plants more difficult to reestablish after they have been removed.”

Additionally, soil scientists are still actively researching the impact that increasing climate variability has on different types of soil. Cotrufo and Leuthold said that this knowledge gap increases the difficulty of creating universal solutions for degradation.

The dried and cracked soil in an irrigation ditch next to a cornfield on a farm is seen in Fresno, Calif., on July 24, 2021. Robyn Beck/AFP via Getty Images

The Importance of Soil

Healthy soil provides a list of “ecosystem services”—natural processes that assist in protecting human health and wellbeing—and the presence and extent of these services can vary depending on the ecosystem; they include things like reducing flood risk, lowering the number of nutrients lost to waterways and storing atmospheric carbon.

“During their growth, plants absorb carbon dioxide from the atmosphere. Most of this carbon is transformed into plant biomass, with a small portion also routed directly into the soil, as roots exude small carbon molecules.”

Cotrufo and Leuthold said that assuming the biomass isn’t removed through harvest or grazing and enters the soil system, after these plants die, much of the absorbed carbon will become food for microbial communities.

The carbon that is consumed by such communities will eventually re-enter the atmosphere through microbial respiration; however, if not respired, a portion of the absorbed carbon can become stabilized within the soil.

Through bonding directly to soil minerals such as clay particles or by becoming protected within soil aggregates where microorganisms take time to reach it, carbon can become sequestered.

“The root exudates have a similar fate, either being used as food by microbes or becoming stabilized through bonds with soil minerals.”

“This stable organic soil carbon can persist in the soil for decades to centuries, even up to a millennium, depending on the soil, the climate, and the land-use practices,” they said.

Dry, cracked earth is visible along the banks of Phoenix Lake in Ross, Calif., on April 21, 2021. Justin Sullivan/Getty Images

Rewilding and Regenerating Degraded Agricultural Areas

Cotrufo and Leuthold said that a multi-faceted approach is required to ensure quality soil. They said that the approach would need to be flexible enough to evolve as technologies, climates and the needs of communities change.

“Preserving natural areas and rewilding low-quality agricultural and industrial land present important first steps in regenerating our landscapes.”

“These are areas that tend to yield poorly when crops are grown, either because they’re too hilly, too dry, too rocky, have some inherent nutrient deficiencies, or any combination of these and other productivity factors.”

Cotrufo and Leuthold said that although agricultural crops may yield poorly in such areas, the areas can function very well as a natural ecosystem, rebuilding their soil carbon stocks and providing important benefits to their surroundings. 

The researchers also noted that in productive cropland, incentivizing the adoption of agricultural regeneration practices will help to increase the quality of some of the most degraded soils around the world. These agricultural regeneration practices include reduced tillage, cover cropping, crop-livestock integration, and increased crop diversity, which can be accomplished by the use of legumes and perennials.

Making Use of Cultural Knowledge

Cotrufo and Leuthold also highlighted that indigenous and smallholder farmers have been applying many of these regeneration practices as well as other creative conservation practices for a long time. The researchers said that an important part of the path toward soil and landscape regeneration is regaining this cultural knowledge and empowering these farmers.

They said that such agricultural practices are now being demonstrated by science to increase the amount of carbon that enters soils and decrease the amount that leaves it. This often leads to a net gain in overall soil organic carbon and a host of other benefits, such as crop nutrition and water availability, less erosion, and increased biodiversity.

“Similarly, a more focused approach on livestock management that incorporates an understanding of ecosystem dynamics can revitalize soils.”

They said that it is important to note the impact that the transition from conventional agriculture systems to regenerative and more sustainable systems could have on farmers and ranchers it could leave agricultural producers exposed to outsized risk as they adapt their practices and equipment.

“Constructing policies that help to minimize the overall risk of adoption of these soil-friendly practices can help to ensure soil quality as well,” they said.

“In short, ensuring prolonged soil quality requires all of us to be intentional in thinking about the land we receive our food and fibre from.

“It requires a willingness to engage both with the individuals who hold this knowledge and the ones who work in these settings and to support policies and practices that emphasize a renewed focus on soil health.”

Cotrufo and Leuthold said that soils have the potential to protect people’s livelihoods from the worst outcomes of the changing climate and environment. However, to realize the potential of this critical resource, people must invest in soil.