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

Abstract

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).