Authors: Caitlin E. Moore, Bethany Blakely, Taylor L. Pederson, Nuria Gomez‐Casanovas, Christy D. Gibson, Anya M. Knecht, Guler Aslan‐Sungur, Evan H. DeLucia, Emily A. Heaton, Andy VanLoocke, Tilden Meyers, Carl J. Bernacchi
Published: 2025-06-09
DOI: 10.1111/gcb.70291
Source: Full article
ABSTRACTAs global atmospheric CO2 rapidly approaches a key tipping point, there is an urgent need to implement strategies to reverse this pattern. A generally accepted understanding of carbon (C) in agricultural fields includes: (H1) substantial C loss occurs when natural vegetation is converted to crops, (H2) soils typically reach a steady‐state C concentration under contemporary practices, and (H3) improved management or crop selection can enhance soil C stocks over time. Significant variability exists, but studies consistently show large C losses from agricultural ecosystems, supporting H1. Although steady‐state C levels (H2) are commonly assumed, measuring C gains or losses in mature agroecosystems is challenging. Efforts to increase soil C storage (H3) have limited data due to the diversity of potential practices, compounded by substantial variability in soil C measurements. Here, long‐term (7–17 year) ecosystem C flux data from diverse cropping systems revealed that conventionally tilled annual row crops (maize and soybean) act as significant long‐term atmospheric C sources, challenging H2. Furthermore, conservation tillage practices reduced C losses compared with conventional tillage but showed minimal evidence for long‐term ecosystem C storage, even after 20+ years. This indicates that no‐till practices reduce C losses but imply that no soil C is added, challenging H3. By contrast, perennial Miscanthus × giganteus, Panicum virgatum, and restored tallgrass prairie systems store C at the ecosystem scale more effectively than minimally tilled annual row crops. Analysis over multiple years demonstrates significant ecosystem C storage with perennial crops, varying by species, starting in the first year of transition. These findings, although focused on one region, suggest that the assumptions of steady‐state C levels and increased storage from conservation practices do not universally apply and that significant changes to agroecosystems are required to increase C storage.