New study shows how to slow down global warming

Posted by pt91 at Feb 06, 2017 03:13 PM |
Increasing the water table in agricultural peatland could hold key to reducing UK’s greenhouse gas emissions

Issued by University of Leicester Press Office on 6 February 2017

Photographs available to download at: https://www.dropbox.com/sh/l2hlnea7uafy1jl/AAD97P9ebet6jzXbujZe_ufAa?dl=0

  • A third of greenhouse gases released by humans are caused by agriculture
  • UK’s peatlands are being lost at a rapid rate
  • Increasing water table in peat soils by 20 cm reduces CO₂ emissions and improves crop yield

Raising the water table could slow down global warming, boost crop yields, and preserve peat soils according to a new study.

A team of scientists from the University of Leicester began measuring the emissions of carbon dioxide (CO₂), a greenhouse gas, on farmed East Anglian peat soil in 2012, and in 2015 combined with researchers from the University of Sheffield to investigate the impact that manipulating the water table would have on these emissions.

Published in Science of the Total Environment, this controlled environment study found that raising the water table closer to ground level in peat soil cores by 20 cm not only reduced soil CO2 emissions, but also improved the growth of radishes.

Importantly, the study also showed a decrease in the rate of peat loss from these carbon rich soils that have been significantly diminished both in area and depth since they were drained for agricultural use.

Continuous field measurements have been collected by University of Leicester doctoral student Alex Cumming, of the Department of Geography, with the support of his supervision team Dr Joerg Kaduk, Professors Susan Page and Heiko Balzter.

Alex has determined that annual emissions of CO₂ for lettuce, celery and leek crops is between 25 and 30 tonnes per hectare of peatland under current agricultural management regimes.

Professor Susan Page explained the importance of the study: “Currently, around a third of global greenhouse gases released by humans are caused by agriculture. Reducing this is critical in order to slow down climate change, however the world is facing a global shortage of food and agricultural land is a precious resource – adding to the challenge of food security.”

Dr Joerg Kaduk added: “A significant proportion of the UK’s production of vegetable and salad crops takes place on drained peatlands, which are some of the most productive soils for commercial agriculture. Draining naturally flooded peatlands, which are organically rich, triggers the carbon to oxidise and releases CO₂ into the atmosphere.”

Dr Donatella Zona, another senior author of the study from the University of Sheffield’s Department of Animal and Plant Sciences, said: “It is estimated that in 30 years’ time the world’s population will reach 10 billion so it is vital that any means of reducing greenhouse gas emissions do not impact negatively on global food security.

“We are losing our peat soils in the UK at a fast rate, and we need to find solutions to reduce 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.”

The international team of researchers from the universities of Leicester, Sheffield, Exeter and San Diego, raised the water table from 50 cm to 30 cm in agricultural peat soil collected from the Norfolk Fens – one of the UK’s largest lowland peatlands under intensive cultivation.

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

The findings, now published in the journal Science of the Total Environment, showed elevating the water table increased the average uptake of CO₂.

Professor Heiko Balzter said “Implementing ‘responsible’ management of UK and global peatlands can make an important contribution to reducing greenhouse gas emissions but we need solid scientific evidence on which to base proposed changes in land management. In the UK, ensuring careful land management will reduce the risk of us losing our valuable lowland peat soils and converting them into less productive land. There is a critical balance to be struck between climate and food security.”

Further investigations are being made in the Norfolk farmed peatland to investigate the contribution of fen ‘dust blows’. Alex Cumming described these as “phenomena that regularly occur in these peatlands every year in spring time when the fields are prepared for planting. With loose soil at the surface for most of the year combining with strong winds and peak agricultural management in spring time you often see clouds of dust moving across the landscape. This pathway of carbon loss from peatlands has never been measured.”

The Sheffield study team will now aim to analyse other crops, including celery, and look into the impact of fertiliser use on greenhouse gas emissions and productivity. At Leicester, the focus will be on measuring carbon emissions from a field with raised water table, to see how well the controlled environment results are transferrable to the landscape and identifying opportunities to reduce soil carbon loss at critical phases during the annual farming cycle, e.g. during ploughing, harvesting and the winter fallow period.

Ends

Notes to editors:

For interviews contact Alex Cumming via: amjc1@le.ac.uk

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