Assessing the impact of saline clay amendments for peat decomposition mitigation in drained dairy meadow peats

Abstract

Peatland ecosystems serve a crucial role in global carbon sequestration but are currently being degraded by extensive land-use. In the Netherlands, drainage of peatlands to enable farming has substantially lowered water tables, allowing oxygen diffusion and increasing aerobic decomposition of peat organic matter. This threatens carbon storage and accelerates land subsidence. As water table management strategies have limitations, complementary approaches are needed. This study investigated whether a saline clay amendment derived from coastal sediments could mitigate peat decomposition under oxic conditions induced by drainage. Controlled laboratory incubations were conducted using bulk and intact cores of oligotrophic and mesotrophic peat from Dutch polders. Basal respiration (BR) rate provided a key indicator of microbial carbon dioxide (CO2) production. Contrary to predictions, in bulk peat incubations spanning over 80 days, saline clay increased cumulative CO2 release from mesotrophic peat by 43%. However, in intact peat core incubations over a 44-day period, saline clay application significantly reduced CO2 production from oligotrophic peat by 35% across moisture levels. This highlights the importance of peat structural characteristics and exposure duration in mediating decomposition responses. Furthermore, pH strongly predicted CO2 production, with saline clay buffering acidification. While showing some initial potential, further long-term study is recommended to determine efficacy in decomposition mitigation processes and optimize saline clay applications for reducing carbon losses from drained peatlands. This could inform integrative management strategies alongside conventional water table control.