Increasing the water table could help to slow down global warming, boost crop yields, and preserve peat soils according to a new study from the University of Sheffield.

Britain is almost unique in its rich peatlands, which cover 12% of the country’s land area and peat in England alone stores an estimated 584 million tonnes of carbon. However, 80% of peatlands are degraded, and are releasing the carbon they store into the atmosphere, contributing to emissions from agriculture, which globally make up a third of all greenhouse gas pollution.  

Drained peatlands make up some of the most productive soils for commercial agriculture, and therefore account for a significant amount of farmland in the UK, but draining naturally flooded peatlands triggers the carbon to oxidise and release CO2 into the atmosphere.

Scientists from the University of Sheffield, who were looking for ways to reduce agriculture’s impacts on the environment found that increasing the level below which the ground is saturated with water – known as the water table – in radish fields by 20cm not only reduced soil CO2 emissions, but also improved the growth of crops. Importantly, the study also showed a reduction in the rate of loss of peat soils converted into agricultural fields.

When the research was published on Monday, the study’s lead author, Dr Donatella Zona, from Sheffield’s Department of Animal and Plant Sciences, commented, “We are losing our peat soils in the UK at a fast rate, and we need to find solutions to decrease this loss if we want to preserve our food security. In this study, we investigated the effects of water table levels, elevated CO2 and agricultural production on greenhouse gas fluctuations and the crop productivity of radishes which are one of the most economically important fenland crops.”

Working alongside colleagues from the Universities of Exeter, Leicester and San Diego, researchers raised the water table from 50cm below the surface to 30cm in agricultural peat soil collected from the Norfolk Fens – one of the UK’s largest lowland peatlands, and one which is under intensive cultivation.

Commenting on the scientists’ ideas, Dr Zona said, “Flooding peatland would be too extreme and damage crops, but increasing the water level by just 20cm maintains current food production - or as shown in our study even increases it - while at the same time reducing carbon oxidation and emissions.”

Professor Walter Oechel, of the University of Exeter, added, “This is very important in a time of global warming, when reducing greenhouse emissions is a global priority. Reducing CO2 emissions from peatland soils, will not only help the UK to reach the targets set for the Paris climate agreement, but will also help protect and extend the life of the UK’s agricultural peatland soils.

“Without careful management, agricultural peatland soils can be ‘mined’ or consumed in the production of agricultural crops, leaving the UK with less productive lands in their place.”

Previous work from the University of Sheffield has shown that soils on the UK’s allotments are “Significantly healthier” than exhausted agricultural soils, and estimated that Britain’s farms have less than 100 harvests left in their soils, unless work begins to support soil health.

Researchers who worked on the peatland study now plan to move on from radishes to look at other horticulture crops, and will also assess the impacts of fertiliser use on greenhouse gas emissions and productivity.