North Wyke, 15 Jan 2024
Scientists using a new tracer have shown that cereals dominated arable land contributed over half of all sediments and associated organic matter dislodged by heavy winter rains in a watercourse in Southwest England. The result confirms fears that, as the severity of wet periods increases under climate change, some current farm practices are accelerating soil erosion.
The study team used Carbon-13 isotopes of dicarboxylic fatty acids (diFAs) as tracers to identify which land uses were contributing to in-stream sediments at test sites along an 8km stretch of a catchment in Devon. These molecules are particularly useful as tracers because they are mostly produced by roots and their isotopic signature differs with vegetation. This means that the type of land use (grassland, arable land, woodland or stream banks) that sediment has been eroded from can be relatively easily identified using n-stream sediment and source area samples.
Taken over the record-breaking wet winter of 2019/20, the results showed that stream banks contributed most of the sampled sediment in the early winter (October-December) period. In contrast, the dominant sediment source shifted after a period of prolonged consecutive rainfall days in the late winter (January-March) to winter cereals-dominated arable land.
“There is a high likelihood that winter rainfall in South-West England will be more prolonged and intense under climate change,” said Rothamsted’s Dr Hari Ram Upadhayay. “So we need to better understand the differing levels of resistance different catchment sediment sources have to erosion driven by extreme wet weather. This new technique enables us to do that with more confidence.”
Sediment fingerprinting using root specific biomarkers is a relatively new approach. The diFAs are a structural component of suberin which is one of the important biopolymers in roots. This acts as a protective layer between root tissues and their environment and contains a high proportion of diFAs which are very stable in soils.
Samples were taken of potential sources in the catchment and compared with sediment samples to build up a landscape scale picture of elevated erosion and sediment transfer over the record-breaking wet winter period.
“There appears to be a high degree of correlation between land use and diFA distribution in soils,” said Upadhayay. “This linkage suggests that this technique could become an invaluable tool in accurately identifying what proportions of sediment and associated organic matter come from certain land types. In turn, this could help inform land management decisions to build more resistant landscapes to help reduce erosion under current and future climate scenarios.”
Professor Adie Collins, co-author on the paper and leader of a new UKRI-BBSRC funded strategic programme at Rothamsted Research, Resilient Farming Futures, said, “The new research programme will further explore landscape resilience to weather extremes using a range of tracers deployed in the institute’s forensic science toolkit. This will include co-working with the Catchment Sensitive Farming initiative in priority landscapes.”
ABOUT ROTHAMSTED RESEARCH
Rothamsted Research is the longest-running agricultural research institute in the world. We work from gene to field with a proud history of ground-breaking
discoveries in areas as diverse as crop management, statistical interpretation and soil health. Our founders, in 1843, were the pioneers of modern
agriculture, and we are known for our imaginative science and our collaborative approach to developing innovative farm practice.
Through independent research, we make significant contributions to improving agri-food systems in the UK and internationally, with economic impact estimated to exceed £3 bn in annual contribution to the UK economy. Our strength lies in our systems approach, which combines strategic research, interdisciplinary teams and multiple partnerships.
Rothamsted is home to three unique National Bioscience Research Infrastructures which are open to researchers from all over the world: The Long-Term Experiments, Rothamsted Insect Survey and the North Wyke Farm Platform.
We are strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC), with additional support from other national and international funding streams, and from industry. We are also supported by the Lawes Agricultural Trust (LAT).
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from the UK government.
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The Lawes Agricultural Trust, established in 1889 by Sir John Bennet Lawes, supports Rothamsted Research’s national and international agricultural science through the provision of land, facilities and funding. LAT, a charitable trust, owns the estates at Harpenden and Broom's Barn, including many of the buildings used by Rothamsted Research. LAT provides an annual research grant to the Director, accommodation for nearly 200 people, and support for fellowships for young scientists from developing countries. LAT also makes capital grants to help modernise facilities at Rothamsted, or invests in new buildings.