Effect of water table management and elevated CO_2 on radish productivity and on CH_4 and CO_2 fluxes from peatlands converted to agriculture

摘要

Anthropogenic activity is affecting the global climate through the release of greenhouse gases (GHGs) e.g. CO_2 and CH_4. About a third of anthropogenic GHGs are produced from agriculture, including livestock farming and horticulture. A large proportion of the UK's horticultural farming takes place on drained lowland peatlands, which are a source of significant amounts of CO_2 into the atmosphere. This study set out to establish whether raising the water table from the currently used − 50 cm to − 30 cm could reduce GHGs emissions from agricultural peatlands, while simultaneously maintaining the current levels of horticultural productivity. A factorial design experiment used agricultural peat soil collected from the Norfolk Fens (among the largest of the UK's lowland peatlands under intensive cultivation) to assess the effects of water table levels, elevated CO_2, and agricultural production on GHG fluxes and crop productivity of radish, one of the most economically important fenland crops. The results of this study show that a water table of − 30 cm can increase the productivity of the radish crop while also reducing soil CO_2 emissions but without a resultant loss of CH_4 to the atmosphere, under both ambient and elevated CO_2 concentrations. Elevated CO_2 increased dry shoot biomass, but not bulb biomass nor root biomass, suggesting no immediate advantage of future CO_2 levels to horticultural farming on peat soils. Overall, increasing the water table could make an important contribution to global warming mitigation while not having a detrimental impact on crop yield.