Project Overview
Building soil organic carbon (SOC) is an important component of organic agriculture. SOC improves soil structure, increases water retention, supports healthy plant-microbial interactions, and can serve as a tool to mitigate climate change by sequestering atmospheric carbon.
Common SOC-building management practices include cover cropping, compost/organic fertilizer application, and reduced tillage; however, recent studies have also indicated that SOC can be enhanced by adjusting crop resource availability in a manner that induces a physiological shift in plant C allocation, resulting in the deposition of carbon-rich exudates into the soil.
This study reviews the existing literature on belowground C deposition and posits several ways in which farmers might tap into the physiological responses of crops to enhance SOC.
Farmer Takeaways
- Maintaining N, P, and water availability at levels slightly less than optimal for aboveground crop growth can induce the deposition of surplus photosynthates belowground and contribute to the accumulation of soil organic carbon (SOC).
- ‘Optimal’ resource levels for inducing surplus photosynthate deposition belowground will likely vary by crop type, soil type, land-use history, and climatic conditions (i.e. temperature, precipitation). Additional studies are needed to elucidate site- and crop-specific C responses to resource deficiencies.
Project Objectives and Approach
Reviewing the Literature
Several studies assessing belowground C deposition and SOM accumulation across different cropping systems were reviewed.
Proposing Future Studies
In order to further understand the potential of these mechanisms to enhance labile, stable, short- and long-term SOM, several studies have been proposed. The researchers of this study propose that future research focus on measuring C fixation, aboveground and belowground biomass production, and root exudation for a variety of common crops maintained at fixed temperatures and N, P, and water levels.
Key Findings
Carefully managing the availability of N, P, and water to maintain a deficiency for aboveground plant growth may result in the deposition of surplus photosynthate belowground as root exudates
- Limiting at least one of the resources necessary for aboveground plant growth can induce a shift in C resource allocation from aboveground to belowground structures, which can foster the release of carbon-rich root exudates into the soil.
- This practice may result in slightly lower crop yields than for systems with intense fertilization and irrigation; however, prioritizing SOC improvements should not be undervalued. Enhancing SOC levels and plant-microbial interactions will improve soil structure and fertility, water infiltration and retention, and nutrient cycling, all of which can provide long-term agricultural resiliency.
Incorporating leguminous plants into crop rotations may enhance the accumulation of mineral-associated soil organic matter (MAOM) by providing the N necessary for the generation of soil microbial biomass
- Accumulating soil microbial biomass, which is an important component of stable, mineral-associated soil organic matter (MAOM), requires substantial quantities of both nitrogen and carbon. Incorporating nitrogen-fixing leguminous plants into cropping systems can provide both of these nutrients and stimulate production of new microbial biomass, necromass, and SOM.
Resources
Prescott, C. E., Rui, Y., Cotrufo, M. F., & Grayston, S. J. (2021). Managing plant surplus carbon to generate soil organic matter in regenerative agriculture. Journal of Soil and Water Conservation, 76(6), 99A-104A.
Read MoreLocation
Collaborators
Yichao Rui, Rodale Institute
Francesca Cotrufo, Colorado State University
Sue Grayston, University of British Columbia, Vancouver
Region
Midwest, Northeast/Mid-Atlantic, Northwest, Plains, Southeast, West/Southwest
Topic
Soil Health, Crop Nutrient Management
Year Published
2021
