Frequent defoliation of perennial legume-grass bicultures alters soil carbon dynamics


Purpose: Perennial forage systems (e.g., pastures and hayfields) cover a significant land area worldwide and are important for soil carbon storage; however, the degree to which these plant communities can be managed to accumulate and store soil carbon is not well understood. Additionally, less is known about how forage defoliation mediates C dynamics or if the effects of defoliation depend on plant community composition.

Methods: To address these questions, we quantified soil C pools and C-degrading enzyme activity in a three-year experiment where bicultures of alfalfa-orchardgrass and red clover-orchardgrass were managed under treatments of contrasting defoliation frequency (3 vs. 5 cuts per year) and severity (i.e., cutting height; 10 cm vs. 5 cm residual forage height).

Results: We found that more frequent defoliation resulted in greater permanganate oxidizable C (POX-C), particulate organic carbon (POC), mineral-associated organic C (MAOC), and the activity of β-glucosidase (BG) and cellobiohydrolase (CBH). The effects of defoliation frequency on total organic C (TOC) varied depending on biculture composition. Alfalfa-orchardgrass bicultures, characterized by a lower legume-grass proportion, had greater POX-C and lower hot-water extractable organic carbon (HWEOC) compared to red clover-orchardgrass which had a higher legume-grass proportion. We also found that BG activity and POX-C were positively correlated with MAOC and TOC. In contrast, we observed no effects of defoliation severity on any measured soil parameters.

Conclusion: Our study highlights that defoliation frequency and relative abundance of legumes to grass are both potential management levers for increasing SOC storage in legume-grass agroecosystems.


Soil Biogeochemistry and Microbial Ecology; Natural Resources and the Environment

Publication Date


Journal Title

Plant Soil



Digital Object Identifier (DOI)

Document Type