The Effect of Clay Addition on Soil Respiration Dynamics in Peat Meadows

Dutch peat meadows, once carbon sinks, now contribute nearly 4% of the country’s CO₂ emissions, releasing 6.9 Mton CO₂-eq annually due to historical drainage and conversion to agricultural lands. Drainage exposes the organic-rich peat soils to oxygen, leading to increased microbial activity, organic matter decomposition, and associated CO₂ emissions, thereby adding to global warming.

We hypothesize that clay addition to peat meadows will reduce soil respiration, as previously observed in mineral soils. The reduction is caused by 1) retarding oxygen diffusion 2) reducing enzyme activity by immobilization of enzymes 3) protecting substrate from microbial degradation through binding and/or physical protection.

We conduct long-term field- and lab incubation experiments, as well as short term laboratory experiments to gain mechanistic insights in the mitigating effects of clay addition on peat degradation. A wide array of clay types sourced from sedimentary marine and fluvial deposits in the Netherlands, is tested on their emission reduction potential. In the field, flux chambers measurements in the clay amended plots provide continuous CO₂ emissions from peat soil and vegetation.  Laboratory tests involve long-term laboratory incubations under controlled conditions, as well as Soxhlet analyses and potential enzyme activity.

To gain a better understanding of the influence of clay minerals on enzymes, ongoing laboratory experiments focus on how different clay minerals affect soil enzyme immobilization under substrate-saturated conditions.

Preliminary results, to be presented at the conference, provide more detailed insights about the specific interactions between clay particles and organic carbon in peat soils compared to mineral soils. These findings contribute to a deeper understanding of the mineral dynamics in this organic-rich environment.