The Geography of Soil Carbon

Agriculture in the United States is a massive industry, with nearly $395 billion in agricultural products being sold in 2012, according to the United States Department of Agriculture (2017) agricultural census. This level of production and profit is largely facilitated by the use of modern farming techniques. The average farm in the United States employs tillage techniques and chemical fertilizers to plant large swaths of a singular cash crop year over year. While this method is effective for large scale, intensive agricultural production, it has a major issue: the release of carbon from the soil (Velasquez-Manoff 2018).

Over time, conventional farming practices deplete soil of the organic matter and carbon that facilitates healthy plant growth, leading to soil that cannot support crop growth. Moreover, this depletion of carbon in soils generates greenhouse gas emissions. The Environmental Protection Agency (2018) cites agricultural production as the producer of 9% of the total greenhouse emissions in 2016. If current agricultural techniques are maintained, it may turn out to be ultimately detrimental to consumers, the agricultural industry, and the environment as a whole.

While modern farming methods pose a real environmental problem, there are agricultural practices that can replace them and actually help the environment. If steps are taken to maintain and promote healthy soil in agricultural settings, emissions can be drastically reduced or even become net-negative, with the soil sequester more carbon than is released. The carbon storing capabilities of healthy soil is touted by organizations such as 4p1000 which demonstrate that increasing the carbon content of the soil by 0.4% annually could mitigate all global emissions (Velasquez-Manoff 2018). Along with climate mitigation, improving soil health can improve crop yields and reduce the need for chemical fertilizers by naturally increasing the nutrients available to plants in the soil. Soil health can be enhanced through a number of farming practices such as cover cropping (planting low management crops between sowing or on unused land) or till reduction (abstaining from or reducing tillage between crop rotations). Even basic practices such as rotating crops or applying compost and manure can support soil health.

By collecting a database of about 250 operations engaged in carbon farming practices, some demographic trends emerge about where and why these methods are used. Chief among these findings are that carbon farming practices are remarkably common with most situated in the Corn Belt, the scientific rigor with which the practices are conducted is generally low with regard to carbon monitoring, and a majority of farmers sampled started carbon farming to improve their bottom line or their land for their children, not for environmental reasons.

Research Process

The primary research question was, “What geographic and/or demographic trends can be observed among operations using carbon farming practices?” In order to visualize trends among documented examples of carbon storing practices, I compiled agricultural operations profiled on a variety of databases. The aggregation process generally involved searching for organisations that promote soil health, searching among the organisations information for a list of partnered farms, reading the profiles of each farm provided by the organisation to decide if it fell within the database parameters, and transcribing the information into the database if the operation was appropriate. Data was collected in terms of 11 variables, them being: name of operation, zip code, state, operation type, funding category, funding source, practices employed, products, scientific rigor, carbon testing, and name of property owner. The publicly available information about these farms yielded about 250 locations in the database, enough to make rough extrapolations about those using the practices.

Data & Trends

Below, I have broken out the documented operations into three maps highlighting operation type, partnership type, and scientific rigor respectively.

 Row crop operations are traditional, large acreage, farms the plant cash crops. Ranches specialize in animals, but not necessarily cows and not necessarily for meat production. Orchards specialize in the fruits of trees where as tree farms sell the trees themselves, and seed sales are operations that grow cover crop for the purpouse of harvesing their seeds to sell to other farmers.

Row crop operations are traditional, large acreage, farms the plant cash crops. Ranches specialize in animals, but not necessarily cows and not necessarily for meat production. Orchards specialize in the fruits of trees where as tree farms sell the trees themselves, and seed sales are operations that grow cover crop for the purpouse of harvesing their seeds to sell to other farmers.

The first highlights the type of operations that use carbon farming practices. Row crop farms and row crop/ranch operations appear more likely to use carbon farming practices than just ranches, likely due to the increased variety of approaches available to them.

Surprisingly, “carbon farming” practices are remarkably common – strategies such as no or low-till have been employed since the Dust Bowl (McLeman et al. 2014). The highest density of these types of farms are found in the Americas mid-east, also referred to as The Corn Belt, with smaller pockets of farms being found on the northern areas of each coast.

 Partnership organisations include the  Soil Health Partnership , the  USDA’s Natural Resource Conservation Serves , the  National Association of Conservation Districts , and numerous smaller groups.

Partnership organisations include the Soil Health Partnership, the USDA’s Natural Resource Conservation Serves, the National Association of Conservation Districts, and numerous smaller groups.

The second visualizes the types of partnerships agricultural operations using carbon farming practices have with institutions. Partners are often organisations that provide incentives to land managers that use carbon farming practices in the form of technical or financial support. Non-profit partnerships appear to be more prolific and spread out, whereas federal partnerships tend to be denser in clustered areas.

When collecting data from organisations in this way, there is potential for bias. Firstly, some types of partnerships were far easier to find information about than others. This means there is an abundance of data about some partnership types and a dearth of others, possibly skewing the data towards more open partnerships. Secondly, organisations release information about partners as an advertising tactic. As a result, only information about the most successful and marketable farmers was made available to the public, with the potential to overrepresent successful farmers.

 In general, a one in scientific rigor would be a farmer who conducts little or no soil testing or analysis and continues the practices only based off of perceptions of the harvest. A five on the scale would a farmer who takes regular soil tests, treats the soil appropriately, and works with institutions such as universities to ensure soil health is pursued in a scientific manor. As this had to be derived from descriptions of the farms, not quantitative data, bias may occur.

In general, a one in scientific rigor would be a farmer who conducts little or no soil testing or analysis and continues the practices only based off of perceptions of the harvest. A five on the scale would a farmer who takes regular soil tests, treats the soil appropriately, and works with institutions such as universities to ensure soil health is pursued in a scientific manor. As this had to be derived from descriptions of the farms, not quantitative data, bias may occur.

The third map shows the relative scientific rigor that farms utilizing carbon farming practices had as well as whether they conducted soil carbon tests. The generally warm color scheme of the map illustrates the low to moderate scientific rigor of carbon farming practices in general. Of note is the clusters of green and blue scattered across the map. These indicate that scientific rigor does not appear to coincide with any specific geographic area but does seem to coincide with proximity to other scientifically rigorous farmers. In other words, a farmer is more likely to be scientifically rigorous if their “neighbors” are scientifically rigorous.

Beyond these initial observations, there are other, more granular, correlations to examine. Firstly, Many farmers described their motivation to engage in these practices in their farms’ publicly available descriptions. These descriptions can be collected to figure the average motivation to improve soil health. Most of these farmers began carbon farming practices in order to improve their bottom lines or to preserve their farms for their children. In this analysis, a farmer would very rarely say environmental concerns motivated their change to carbon farming techniques. This may have caused (or been caused by) the generally low scientific rigor with which these practices are conducted. On average, a farmer using carbon farming practices will know how the practices affect their soil from a scientific perspective but will rarely test or review the chemical and biological components of the soil and act on such evidence. More often, farmers measure success in how the crop yield looks and how much it sells for.

Regarding practices, popular carbon farming practices seem to coincide with popular agricultural products. For instance, the farms that grow popular crops such as soy, corn, and cereal also appear to be the farms that adopt popular practices like cover cropping and till reduction. Inversely, more specialized operations such as orchards seem to adopt more specialized carbon farming practices.

Finally, it is of note that the most popular carbon farming practices are not the most efficient from a sequestration perspective. The most popular practices include till reduction, cover cropping, and composting/manure. While these are effective at carbon sequestration, they are far from the best according to a UC Berkeley soil health analysis that cites agroforestry and nutrient management as far more effective methods of sequestration (Biardeau, Crebbin-Coates, Keerati, Litke, & Rodríguez, 2016).

Conclusion

While the roughly 250 farms considered for this study comes nowhere near encompassing the scale of operations using carbon farming practices in the US, extrapolating from it hints at valuable trends in soil health. Healthy soil practices are popular throughout much of the US, largely due to the benefits they provide in sustainability and the profitability of farms. Despite their prevalence and that farmers generally understand how their soil is becoming healthier, they are not quantifying or recording such information in a scientific manner. With greater promotion of these practices and a general increase in scientific rigor when conducting them, the agricultural industry in the US has the potential to eventually reach carbon neutrality or even net-negative emissions.


 

References

Biardeau, L., Crebbin-Coates, R., Keerati, R., Litke, S., & Rodríguez, H. (2016, May). Soil Health and Carbon Sequestration in US Croplands: A Policy Analysis.

Environmental Protection Agency (2018, April 11). Sources of Greenhouse Gas Emissions: Agriculture Sector Emissions.

McLeman RA, Dupre J, Berrang Ford L, Ford J, Gajewski K, Marchildon G. What we learned from the Dust Bowl: lessons in science, policy, and adaptation. Population and Environment. 2014;35(4):417-440. doi:10.1007/s11111-013-0190-z.

United States Department of Agriculture. (2017, June 16). 2012 Census Highlights: Farm Economics - Record High Agriculture Sales; Income and Expenses Both Up.

Velasquez-Manoff, M. (2018, April 18). Can Dirt Save the Earth? The New York Times.


Mikko Hallikainen is an intern at the Center for Carbon Removal. He is headed to ASU Barrett this fall to pursue a degree in geography. He hopes to study human geography and gain a better understanding of how demographic trends relate to geographic circumstances. Outside of college, he is a leather-worker and blacksmith, with plans to expand his skill set to textiles in the near future.