Rhizosphere Observations Optimizing Terrestrial Sequestration
America’s vast terrestrial resources (over 520 million hectares of crop, range and forestland) are strategic assets essential for sustainable economic growth. While advances in technology have resulted in a ten-fold increase in crop productivity over the past hundred years, soil quality has declined, incurring a soil carbon debt equivalent to 65 parts per million (ppm) of atmospheric carbon dioxide (CO2). The soil carbon debt also increases the need for costly nitrogen fertilizer, which has become the primary source of nitrous oxide (N2O) emissions, a greenhouse gas. The soil carbon debt also impacts crop water use, increasing susceptibility to drought stress, which threatens future productivity. Given the scale of domestic (and global) agriculture resources, there is tremendous potential to reverse these trends by harnessing the photosynthetic bridge between atmospheric carbon, plants, microbes and soil. Development of new root-focused plant cultivars could dramatically and economically reduce atmospheric CO2 concentrations while improving productivity, resilience and sustainability. To this end, projects in the ARPA-E Rhizosphere Observations Optimizing Terrestrial Sequestration (ROOTS) program seek to develop advanced technologies and crop cultivars that enable a 50 percent increase in soil carbon accumulation while reducing N2O emissions by 50 percent and increasing water productivity by 25 percent.
Conversion of atmospheric carbon dioxide to soil organic matter (SOM) via photosynthesis and natural metabolic processes is a unique opportunity to reduce the atmospheric concentrations of important greenhouse gases while creating significant economic value. Current land management practices result in the loss of more than 75 billion tons of topsoil per year, costing the world about $400 billion annually, or about $70 per person per year. The amount of soil carbon can be increased by one of two pathways: increasing the rate of carbon additions to the soil, or reducing the rate of decomposition of organic matter already present in the soil. One potential path to increasing carbon stocks is the development of improved crops that impart more carbon into the soil through their roots or grow deeper root systems. Such plants could be deployed rapidly and at scale. Advanced root systems that increase SOM can improve soil structure, fertilizer use efficiency, water productivity, crop yield, climate resilience, and mitigate topsoil erosion—all of which provide near-term and sustained economic value. Taken over the 160 million hectares of actively managed U.S. cropland, such advances could mitigate approximately 10 percent of total U.S. greenhouse gas emissions annually over a multi-decade period.
If successful, developments from ROOTS projects will produce crops that will greatly increase carbon uptake in soil, helping to remove CO2 from the atmosphere, decrease N2O emissions, and improve agricultural productivity.
America’s soils are a strategic asset critical to national food and energy security. Improving the quality of soil in America’s cropland will enable increased and more efficient production of feedstocks for food, feed and fuel.
Increased carbon-organic matter in soil, combined with reduced fertilizer use and increased water productivity, will enable sustainable land management practices while also limiting emissions from two major greenhouse gases.
Healthy soil is foundational to the American economy and global trade. Increasing crop productivity will make American farmers more competitive and contribute toward U.S. leadership in an emerging bio-economy.