PNNL researchers find soil better captures carbon with switchgrass than corn

In Washington state, most of the carbon contained in soil is in the form of organic matter. The composition of this matter is determined by plants, microbes, and soil. However, scientists do not fully understand how variation in plant inputs, the structure of microbial communities, and the physical and chemical attributes of soil interact to influence the chemical makeup of organic matter in soil. Pacific Northwest National Laboratory researchers addressed this knowledge gap by coupling microbial characteristics with detailed soil chemistry from two long-term bioenergy research experiments. They found that soil in switchgrass fields had more water-soluble carbon compounds than soil in corn fields. However, the texture of the soil was more important than the crop type on the makeup of the soils’ microbial community and the chemistry of the soils’ organic matter.

Some researchers have suggested that growing biofuel crops in marginal soils, which generally have low carbon content, might be a way to remove carbon from the atmosphere and store it below the ground. One challenge is finding plants that can grow in these poor-quality soils. Perennial grasses, such as switchgrass, might survive in these conditions. However, this new research challenges the notion that switchgrass increases the accumulation of carbon in the surface soils of marginal lands.