The role of soil methanotrophy in offsetting methane emissions at farm level – the potential contribution of silvopastoral systems and biochar additions

Soils may act as a biological sink for methane (CH₄) through methanotrophic activity. This process is particularly important in the farming sector, as CH₄ emissions from livestock and manure storage often dominate the greenhouse gas (GHG) budget. This places a particular emphasis on the identification of management practices that may increase the capacity of soils to absorb CH₄. In this study we examined  practices with the potential to improve the CH₄ balance at farm level, including the effect of biochar as a soil additive, and the potential of silvopasture systems. Experiments conducted under controlled laboratory conditions revealed that the addition of biochar increased the rate of CH₄ oxidation in the mineral and manure-fertilized silty soil, although such effect has not been confirmed in all soil types. Using biochar produced from crop by products  may also provide a way of managing agricultural wastes with concomitant practical benefits. Silvopastoral systems can also alter the CH₄ balance of farms because of the effect of the presence of trees on microclimate and soil conditions. However, relatively few studies have assessed the potential of trees to improve CH₄ budgets at the farm level in Mediterranean silvopastoral systems. In-situ measurements of soil-atmosphere CH₄ fluxes were undertaken to evaluate the CH₄ uptake potential of pastures below and beyond tree canopies. Preliminary results showed CH₄ emissions in open tree-less pastures, but not under trees, which showed mainly CH₄ uptake. This result highlights the potential of silvopastoral systems to improve the CH₄ balance at farm level perhaps in combination with biochar additions. Nevertheless, the mitigation potential of different soil additives and silvopastoral  practices at farm level are still a subject of research in need of further studies.

This work was funded by the National Centre for Research and Development within GHG Manage (ERA-GAS/I/GHG-MANAGE/01/2018) and ReLive (CIRCULARITY/61/ReLive/2022); Joint Call of the Co-fund ERA-Nets Programme, SusCrop (Grant N° 771134), FACCE ERA-GAS (Grant N° 696356), ICT-AGRI-FOOD (Grant N° 862665) and SusAn (Grant N° 696231), Spanish Ministry of Science and Education (PCI2021-122100-2A).