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Plant root hairs key to reducing soil erosion

12 April 2020

The tiny hairs found on plant roots play a pivotal role in helping reduce soil erosion, a new study by Bristol biologists and mathematicians has found.

Researchers from the Universities of Bristol and Exeter have found compelling evidence that when root hairs interact with the surrounding soil they reduce soil erosion and increase soil cohesion by binding soil particles.

Soil erosion can have a devastating impact across the globe and a serious threat for modern agriculture. The increased demand for agriculture has led to forests and natural grasslands being converted to farm fields and pastures.  

However, many of the plants grown, such as coffee, cotton and palm oil, can significantly increase soil erosion beyond the soil’s ability to maintain and renovate. It can also lead to increased pollution and sedimentation in streams and rivers or, because these areas are often less able to hold onto water, can worsen flooding. This problem is particularly urgent considering the ever-expanding human population and climate change.

The research was led by Bristol’s Professor Claire Grierson with the School of Mathematics’ Professor Tannie Liverpool and Dr Isaac Chenchiah, and the University of Exeter’s Professor Tim Quine.

While the larger-scale root properties such as diameter, length and surface area have been extensively studied to understand their role in preventing soil erosion, the effect that micro-scale properties, such as root hairs, has is less well documented.

The research team looked at how wild plants Arabidopsis thaliana, which produced root hairs, compared with an almost identical Arabidopsis with the same root hair structure in reducing soil erosion. They found that, when planted in sufficient density, plants with root hairs reduced soil loss almost completely - while otherwise identical plants without hairs could not stem the flow of erosion.

Three methods were used to explore the soil retention benefits of root hairs. First, the samples were placed in a sterile gel, in a petri dish, and then subjected to increasing centrifugal force. The study found that the hairless seedlings were easier to remove from the gel compared to seedlings abundant with root hairs.

Second, the study found that root hairs were also shown to stabilise the plant in the soil, as they increased the force needed to uproot the plant.

Third, in the experimental landscapes laboratory at Exeter, root hairs reduced water erosion to almost zero.

Professor Grierson explained: “These findings could be the key in helping to tackle soil erosion. We hope our knowledge about the properties of plants that minimise soil erosion will allow the creation and selection of best-suited agricultural plants.”

Professor Liverpool said: “Mathematical models played a key part in this study. Of particular relevance were new insights into the mechanical properties of soil and soil containing plant roots.” 

Dr Chenchiah added: “Using a variety of mathematical tools from solid mechanics, soft matter, granular materials, fluid mechanics and statistical mechanics, the theorists in our team were able to make quantifiable statements about how the presence or not of root hairs influenced the mechanical stability and hence resistance to erosion of the soil-root composite.”

The research was supported by a Leverhulme Trust project grant, two BBSRC SWBio PhD studentships and an EPSRC-funded Bristol Centre for Complexity Sciences PhD studentship. 

Further information

'Micro-scale interactions between Arabidopsis root hairs and soil particles influence soil erosion' by Claire S. Grierson et al in Communications Biology

Watch the video about this research on Eurekalert.

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