Postharvest residue management practices do not impact carbon stocks in tall fescue seed crops

Authors: Trippe, Kristin; GONZALEZ MATEU, M - Oregon State University; ZAMORA, CESAR - Oregon State University; Manning, Viola; ANDERSON, NICOLE - Oregon State University; VERHOEVEN, ELIZABETH - Oregon State University; MOORE, AMBER - Oregon State University

Submitted to: Seed Production Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2022
Publication Date: 4/1/2022
Citation: Trippe, K.M., Gonzalez Mateu, M., Zamora, C., Manning, V., Anderson, N., Verhoeven, E., Moore, A. 2022. Postharvest residue management practices do not impact carbon stocks in tall fescue seed crops. Seed Production Research. 3-7. https://cropandsoil.oregonstate.edu/seed-crops/seed-production-research-reports.

Interpretive Summary: There is keen interest among seed producers, researchers, and regulatory agencies to understand how crop management practices, like tillage and residue management, influence the amount of carbon (C) stored in soils. This interest is related to our growing understanding of how organic C regulates key soil functions, including increased water and nutrient holding capacity, reduced mobility of pesticides, increased biological activity, and improved soil structure. Interest in understanding the relationship between crop management practices and soil C is also driven by the recent emergence of C markets. Despite the potential agronomic and economic benefits associated with increasing soil C, in the Willamette Valley, our understanding of the influence of management practices on soil C storage is limited. Most studies that have investigated soil C in grass seed production systems have measured C dynamics in the top soil (0-8 inches). To fully account for C, a comprehensive assessment that includes measurements of C in deeper soil horizons (0-39 inches) is necessary. Accounting for C inputs from aboveground (crop residue) and belowground (roots) biomass is another key aspect of C stock assessment that has typically been excluded from estimates of soil C stocks in the Willamette Valley. Therefore, the primary goal of this study was to expand our understanding of C dynamics across the soil profile (0-39 inches) by assessing the effects of stand age, residue management, and microbial biomass on C stocks in tall fescue grown for seed. We found that removing straw by baling had little effect on C stocks in Tall Fescue grown for seed. One possible explanation is that data collected from on farm measurements and surveys, including the data presented here and in previous examinations, is too variable to directly connect management practices with C outcomes. Long-term studies of Willamette Valley grass seed cropping systems are needed to fully account for changes in C stocks.

Technical Abstract: There is keen interest among seed producers, researchers, and regulatory agencies to understand how crop management practices, like tillage and residue management, influence the amount of carbon (C) stored in soils. This interest is related to our growing understanding of how organic C regulates key soil functions, including increased water and nutrient holding capacity, reduced mobility of pesticides, increased biological activity, and improved soil structure. Interest in understanding the relationship between crop management practices and soil C is also driven by the recent emergence of C markets. Despite the potential agronomic and economic benefits associated with increasing soil C, in the Willamette Valley, our understanding of the influence of management practices on soil C storage is limited. Most studies that have investigated soil C in grass seed production systems have measured C dynamics in the top soil (0-8 inches). To fully account for C, a comprehensive assessment that includes measurements of C in deeper soil horizons (0-39 inches) is necessary. Accounting for C inputs from aboveground (crop residue) and belowground (roots) biomass is another key aspect of C stock assessment that has typically been excluded from estimates of soil C stocks in the Willamette Valley. Therefore, the primary goal of this study was to expand our understanding of C dynamics across the soil profile (0-39 inches) by assessing the effects of stand age, residue management, and microbial biomass on C stocks in tall fescue grown for seed. We found that removing straw by baling had little effect on C stocks in Tall Fescue grown for seed. One possible explanation is that data collected from on farm measurements and surveys, including the data presented here and in previous examinations, is too variable to directly connect management practices with C outcomes. Long-term studies of Willamette Valley grass seed cropping systems are needed to fully account for changes in C stocks.