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This study shows soil microbes help plants cope with drought

Despite halfway-decent rain and snow this past season, drought remains on our minds here in Northern California.

The moisture wasn’t sufficient, so the dry times persist. But we’re used to it – around these parts, we toggle between worrying over the current drought and fearing the next one.

So it was with a sense of renewed hope that we recently encountered some research regarding how soil microbes might help. The study, published in April in the Proceedings of the National Academy of Sciences, was performed at a US Department of Agriculture lab at UC Berkeley. It documented how certain soil bacteria can show up to help plants cope with low-moisture conditions.

These microbes didn’t arise throughout the soil, just near the roots, where they fed on compounds secreted by plants. Those compounds are what we call “exudates” – secretions that serve as food for particular microbes, causing them to accumulate in certain times and places in the root zone, bringing along compounds that the plant needs.

Scientists have recently begun showing just how complex these plant-microbe interactions can be, and how they allow plants to feed themselves as nature intended. These relationships trigger a vast range of metabolic processes that help plants fight disease and infestation, and generally realize their full potential.

Researchers extracted and cultured two bacterial species from the roots of drought-resistant plants, then applied them to plants in experimental plots in the San Joaquin Valley (an especially drought-vulnerable farming region). Results confirmed that these particular bacteria were helping plants grow more roots to counter the lack of moisture.

This research may ultimately lead to microbe-focused products to help farmers cope with drought, as UC Cooperative Extension Specialist Peggy Lemaux explains. However, such products tend to rely on a very small number – one or two, or maybe a handful – of specific microbes.

That’s different from the approach we favor at Foothill Bio. Our goal is always the development of a well-rounded microbiome appropriate to the local area. In a drought-prone region like ours, the bacteria in question – monoderms, which have a single, thick cell wall (as opposed to the double-walled diderms) – should be present in healthy soil, ready to emerge from dormancy when the weather changes.

We therefore like to grow microbes (through composting) that were sampled nearby, where conditions are similar to the location in which we’re working. This helps ensure that when plants seek out certain bacteria or fungi that are needed in that environment, those species will be available. We confirm the types of microbes we’re growing by direct observation (using a microscope) and by analyzing the density and diversity of the populations we see.

In short, we apply scientific principles from a big-picture perspective, without focusing on particular species. By growing rich microbial populations, we can shape soil profiles quickly, making possible the efficient results required in agriculture.

To us, it’s the key to a healthy future.

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