All about roots

Their full importance is only now being recognized

Angie Straathof: “A healthy soil ecology is like having an insurance policy. It kicks in when plants are stressed.”

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The growing understanding of plant roots has the potential to a positively impact agriculture and even lead to fundamental change within the industry.

The new program director with the Ontario Soil and Crop Improvement Association made the comment in response to a question following her presentation at the Southwest Agricultural Conference in Ridgetown on January 3.

“A healthy soil ecology is like having an insurance policy. It kicks in when plants are stressed,” Angie Straathof said.

“Soil bio-diversity is something worth investing in now.”

Straathof said the role of plant roots can be divided into three broad categories: their function in carbon cycling, their function in nutrient cycling; and their contribution to the structural stability and health of soils.

Straathof said farmers may not realize the extent of plant root systems. They’re obviously more difficult to measure being below the ground surface.

What’s visible to the naked eye is impressive in itself but root systems also include microscopic hairs. That extends their ability to interact with soil nutrients and soil organisms.

“The length of the root hairs can be hundreds of times that of the roots you can see,” she said.

The root complex serves for the upward and downward transport of nutrients that are important to plant growth and soil health. Rather than being viewed a sterile medium, Straathof sees the soil as a complex ecosystem in which all parts, including roots, contribute to the whole.

For instance, the relative health of roots as expressed in their diameter and length, impacts their ability to transport nutrients. Just as important are the relationship of roots with mycorrhizal fungi and rhizobia bacteria.

It is through these relationships that plants access much of the soil nutrients they require and, in return, support the staggeringly broad array of soil life. It’s a matter of communication, both among plants and between plants and soil organisms.

For instance, roots are able to release exudates, chemicals that serve to feed soil life and, as a consequence, support the release of nutrients from the soil. When plants are under threat from adverse environmental conditions or the presence of disease or a pest, similar mechanisms kick in to offer protection While the importance of living roots was emphasized by Straathof, they’re even important in death, contributing to soil organic matter and even building the stable portion of soil carbon over time. Soil organic matter is essential to soil fertility and soil structure, she said.

Straathof also emphasized the importance of root diversity, which can be encouraged by moving to a wider crop rotation and adding cover crops, including mixed cover crops, to the rotation.

Even from just a physical standpoint there are benefits from having agricultural soils penetrated by a range of root types. The taproots of such species as turnip and radish, for instance, can break through hardpan while plants like oats and cereal rye serve to access nutrient deep within the soil profile and legume species fix nitrogen to support plant growth.

“Roots are the opportunity In the future, I believe root systems will be considered in management the way tillage and organic matter applications are now.”

Straathof feels the emerging knowledge of how plant roots contribute to agriculture may eventually been have significant repercussions on plant breeding. For decades, the focus has been on above-ground growth, something that may have come at the expense of what’s happening below ground, she said.

That a mindset that’s beginning to change, Straathof said, citing Ontario’s Soil Health and Conservation Strategy that was released last year. While the function of roots is not addressed in a direct manner, the document’s emphasizes on things like soil health, reduced tillage and cover crops which are all root-related, she said.