Exploring Soil Carbon

Katie O'hare

By Katherine O’Hare, Erb MBA/MS student, class of 2011.

This article is cross listed in the Sustainable Food Lab Newsletter.

Never underestimate the power of soil. I learned this lesson while accompanying Steven Apfelbaum from Applied Ecological Services and Peter Donavan of Managing Wholes throughout the West collecting soil samples in order to baseline the soil carbon content of different farms and ranches.  Soil is the second largest store of carbon on earth (after oceans) which gives it a large importance in the efforts to mitigate climate change. Soil carbon also has other benefits from improved water filtration and retention capacity to better nutrient retention and more- by changing to “sustainable agriculture techniques” such as no-till, direct seeding and cover cropping, farmers can purposefully store more carbon in soil and sell it in the form of offsets. However, two important questions remain unresolved and will determine the future of soil carbon sequestration in carbon markets – first, how much can these practices actually sequester on a farm, and, how do you measure it?

soil-sample3The sampling we did on this trip was part of a project that is working towards answering these questions by establishing an efficient and effective method of quantifying carbon in soils. The project is focused on creating performance-based measurements rather than estimates based on practices, meaning measuring the actual amount of carbon captured in the soil rather than the hypothesized amounts based on land management changes. The end goal is to have this quantified amount of sequestered carbon (along with quantifications of other trace GHGs) sold as an offset on the market or to a private buyer. Performance-based measurements can be difficult to obtain because of the properties and variability of soil across regions and even within fields that is based on a number of factors ranging from geological history to the field slope and historical land use. The samples were taken during field-tests of Applied Ecological Service’s Soil Quantification Methodology, which is being developed to test efficient and effective systems to measure the actual carbon content of soils.

During this trip we took samples from the top two layers of soils from a Muller-tomato1number of fields with different crops, land use histories and geographical varieties and in fields that were in a variety of types of land management practices. The samples will be analyzed for their carbon content, texture, bulk density and to determine the statistical variability of the soil in order to establish the amount of samples needed when the baseline measurements are taken when the program begins in the fall. Baseline measurements this fall will determine the initial carbon content in the soils, so that as land management practices are changed, samples can be taken in the same locations to determine the actual amount of carbon flux. This amount, taken as a sum with other trace GHG emissions, can then be sold on an exchange or to a private buyer.

Southworth-ranchDuring the nine-day trip we visited a total of nine farms/ranches infour states- California, Oregon, Idaho and Washington. The California portion of the trip was focused on farms that grow tomatoes through their partnership with Heinz but also produce other crops, from wheat and beans to alfalfa and almonds. We took samples from tomato fields at each farm, as well as a sampling from other crops for comparison purposes. These farms are using no-till techniques, crop rotations, cover crops and are beginning to incorporate drip irrigation into some or all of their fields.  Farmers who implemented drip irrigation have seen as much as a 25% increase in yield, while no-till practices have allowed the farmers to plant earlier in the season on higher quality soils.

While in Oregon we visited Cattle Ranches that were a part of the Country Natural Beef Cooperative, which was founded by Connie Hatfield in the 1980’s in response to the public’s growing health concerns surrounding beef. The Country Natural Beef Cooperative is a marketing tool to allow the members to be recognized for their stewardship activities and give consumers access to grass-fed, hormone free meat. These ranchers are experimenting with improved irrigation techniques, no-till practices and strategically moving their cattle into different fields to prevent over grazing, also with much success. The ranches were performing better, the grasses were healthier and they were “meeting the nutritional needs of the cows year round for the first time.”

The Idaho and Washington portion of the trip focused primarily on large scale wheat farmers that are members of the Shepherd’s Grain Producers network. Similar to the tomato farms, these farms also had a variety of crops, including lentils and beans. These wheat farmers are using a variety of no-till practices, cover crops and crop rotation to improve the quality of their soil. We took samples primarily from wheat fields, but also from a variety of crops.  The fields on the wheat farms were in various stages of sustainable agriculture. They found benefits such as increased soil quality, the presence of worms and the ability to plant earlier in the season. However the biggest benefit for the farmers in these hilly areas was the reduction of their top soil that was lost to erosion.

The farmers who participated in this pre-baseline study can be considered innovators in sustainable agriculture. Their willingness to participate in this study their commitment for furthering the understanding of soil carbon and performance-based measurements was inspiring. While carbon sequestration and climate change is a motivating factor to continue these practices, their initial rationale for adopting sustainable agriculture practices was different.  While they varied by farm and farmer, each initial motivation had a common theme- for each there was a watershed moment where the farmer realized something in their practices was actually deteriorating their soil and therefore hurting their farms, and motivated them to change. These watershed moments ranged from large erosion after a rain storm to reading an article that challenged their ideas of growing grass, but all forced the farmers to rethink their practices and to begin to experiment with techniques that would improve the qualities of their soils.

None of the farmers initially set out to completely overhaul their operations, Wheatfield2but began making relatively small changes, such as converting one field to no-till or installing a field with drip irrigation, and were motivated by the positive results these changes had on their soil quality and/or yields. For one wheat farmer, the watershed moment was a foot and a half of mud in his garage after a large rainstorm. He began changing his fields to direct seed and no-till, and in addition to his soils being able to withstand rain storms, he noticed many other benefits the practices were having on his land. Where the soil had previously been hard to dig into, he was now able to dig a hole anywhere. Even more encouraging was that when he dug that hole he found increased soil organic matter and was “able to count the number of worms” in any handful. These successes motivated the farmer to begin experimenting with other practices to increase his soil health, from experimenting with cover crops to protecting coyotes for the ecosystem services they provide. Seeing first hand the success of the incremental changes to his practices gave the farmers the confidence to begin to make more major changes to his farm.

This trip showed that soil carbon sequestration can benefit everyone involved. The little bits of soil that we collected may seem small, but they’re part of a larger goal of creating an efficient, quantifiable method of measuring soil carbon, incentivizing farmers to improve their soils and help solve the problem of climate change. This can create a wining scenario for the farmers in terms of a new revenue stream and improved soils, and for the planet in terms of reduced carbon in the atmosphere.  Not bad for a little soil.


2 Responses to Exploring Soil Carbon

  1. Idaho Beef says:

    What difference would you anticipate in soil that has been part of a grass-fed beef operation for years? Curious if my farm is helping the cause.

  2. Great information! please come visit us

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