Impacts of agriculture on greenhouse methane capture by soils

University of Bristol

Researcher: Richard Evershed

Funder: NERC

A NERC funded research project by University of Bristol studied the impact of fertiliser application on the activity of soil bacteria.

This research, led by Professor Richard Evershed, builds upon Bristol’s identification of bacteria actively oxidising atmospheric methane (Nature 2000) with the aim of linking the capacity of soil methane removal to these vital bacteria.

Recent increases in atmospheric methane concentrations are alarming. Whilst much attention is focussed on methane emission inventories, methane sinks are overlooked and not accurately accounted for in national methane budgets. A primary reason for this disjunction is caused by uncertainties surrounding the magnitude and mechanism of atmospheric methane removal by soil bacteria (methanotrophs).

This project studied the impact of fertiliser application on the activity of these bacteria in Welsh upland grassland soils. Inorganic fertilizer-treated soils from long-term agricultural plots’ methanotrophic bacterial cell numbers were reduced by up to 80 per cent.

Further work at Rothamsted Research, where wheat had been grown annually for 163 years, showed methanotrophic cell numbers were reduced by long-term agriculture. Interestingly, organic manuring led to higher cell numbers and enhanced methane removal compared to conventional inorganic fertiliser practices.

These results emphasise the need to rigorously assess commonly applied agricultural practices with respect to their unseen, negative impacts on soil bacteria and ecosystem services related to maximising the soil carbon sink potential.

This work has produced five peer reviewed papers; seven conference abstracts; a book chapter; two further PhD projects; and a NERC standard grant research project investigating the sequestration of methane carbon in soils from various locations across the world.