[LUM#7] Major Scales

[LUM Magazine] - Published on February 27, 2018 in Science and Society

Preserving our Mother Earth: this is the essential challenge facing agriculture today. To meet this challenge, scientists are turning their attention to the cradle of crops—the soil. An ecosystem of unimaginable complexity…

“It’s impossible to understand the soil if you take it out of context, ”warns Robin Duponnois, a soil microbiologist and chair of the French Scientific Committee on Desertification, right from the start. “Only a comprehensive approach allows us to understand these highly complex phenomena.”

Vital Symbioses

A brief overview of the complexity at stake: without the plant cover that provides the raw material for the underground life cycle—dead leaves and other plant debris—and without the countless hidden inhabitants of the soil—insects, microscopic fungi, and other symbiotic bacteria, which are the only organisms capable of transforming this material (see box)—there is no hope for the plant.

Because the plant doesn’t live on sunshine and fresh water alone. And it’s anything but self-sufficient. On its own, it can access only the nutrients closest to its roots. That’s not enough to support its growth… Fortunately, mycorrhizal fungi¹ work to colonize those very roots using their “hyphae”—thin filaments capable of exploring a large volume of soil—thereby providing access to infinitely more nutrients (“Mycorrhizal Associations in Soils: Toward Better Control of Plant Production,” in *Soils and Underground Life*, 2017).

Even more surprising, these same fungi act as nurturers: “The soilcontains complex molecules—both organic and mineral—that cannot be directly absorbed. The fungus ‘digests’ these large molecules, then uses its hyphae to transfer the recycled nutrients to the plant.” In exchange, the fungus receives carbon from the plant, which is much better equipped than the fungus to extract it from the atmosphere. Plants thus form inextricable, interconnected networks with their fungal partners. And they can only thrive thanks to this symbiosis… unless the lack of it is compensated for by the artificial addition of mineral fertilizers.

From the “Green Revolution” to Agroecology

It’s true that these fertilizers can boost plant growth very easily: basically, you add a soluble mineral to the soil… and the plants grow. This is the long-standing idea behind the“Green Revolution ”: growing varieties selected for their optimal yield potential, with heavy use of fertilizers, as well as pesticides, irrigation, and machinery, while prioritizing large-scale monoculture.

What impact would this have on the soil and the environment? Back then, no one asked that question. It was the 1960s, just after the great famines. The goal was crystal clear: to produce, in large quantities. A revolution that was “green” in name only; costly in terms of water, chemicals, and oil, this industrial agriculture had serious drawbacks, foremost among them a decline in biodiversity, a major pillar of food security.

Imitating Nature

Times have changed: Scientists are now calling for a form of agriculture that can simultaneously feed people and protect the environment. The first principle of this “agroecology” is: “Intervene as little as possible! And apply natural biological processes—the ones at work in a forest.” For example, reintroducing ground cover by replanting trees; promoting the activity of soil microflora (mycorrhizal fungi, nitrogen-fixing bacteria, etc.); or harnessing the symbiotic relationships between plants.” (Restoring Soil Productivity in Tropical and Mediterranean Regions: The Contribution of Agroecology, IRD publication, 2017)

An approach that is as humble as it is pragmatic. “We try to observe traditional practices that are well-suited to the realities on the ground, to help optimize them.” Family farming thus has many positive characteristics: small plots, endemic species and mixed cropping, local know-how, and minimal irrigation… If we want to ensure food security in developing countries, it clearly offers a model for the future,” explains Robin Duponnois.

1. A mycorrhiza is the result of a symbiotic relationship between fungi and plant roots. ↩︎

Keywords: Agriculture, Biology, Ecosystem, LUM#7, LUM Magazine, Research, Company