Outdated soil definition at root of environmental concerns

Soil must be redefined to include the activities of plant roots if science is to fully appreciate its importance and potential to help tackle climate change, according to new research.

In an article published in the European Journal of Soil Science, a world-leading soil scientist at the University of Reading argues that definitions of soil should explicitly reference roots as a vital component of the soil system.

This is because roots play a significant role in changing rocks and minerals into soil, support ecosystems by filtering water, and aid in carbon storage underground.

Professor Peter Gregory, Emeritus Professor of Global Food Security at the University of Reading, said: “Understanding where soils come from, what benefits they provide us with, how the damage we have done to them threatens our survival, and how we can heal them, is at the top of the public agenda in the fight to provide us with enough food, clean air and water, and help to mitigate climate change.

“Modern technology is revealing the amazing world beneath our feet where roots are actively communicating and collaborating with other organisms in the soil and above it for mutual benefit, offering new opportunities for plant breeders to select root traits that benefit entire ecosystems.

“This includes the selection of crop plants and trees that are resilient to climate change, resistant to pests, and adapted to drought, but can also improve the environment by sequestering more carbon, reducing pollution and restoring soil structure. Yet, despite the importance of roots as indivisible part of soils, most soil scientists only study soils after removing the roots from them.”

Rapid soil formation began around 400 million years ago as plants evolved roots to sustain themselves.

Currently, around half the carbon assimilated from the atmosphere by green plants is transferred belowground and deep roots contribute to its long-term storage. Roots and associated microorganisms also contribute to soil formation by breaking down rocks and soil minerals through biogeochemical processes.

The small ‘pores’ that roots create in the ground are vital for drainage, but digging up samples of soil for analysis destroys these. It is this overlooking of the role of roots in soil that Professor Gregory argues is giving a restricted view which could hamper new discoveries or conservation approaches.

Professor Gregory said: “Recognising roots as ‘of soil’ rather than ‘in soil’ will revolutionise how we look at plants and crops and give a new impetus to our efforts to improve food security across the world.”