By Esther Ngumbi / Source: ScientificAmerican

Recently the United Nations warned that the world could suffer a 40 percent shortfall in water by 2030 unless countries dramatically cut consumption. Since 70 percent of the world’s fresh water goes to agriculture, this means changing the way people farm. The need is ubiquitous. In California’s Central Valley, farmers drilling for water are now tapping stores 30,000 years old. In Kenya, which is facing the worst drought since 2000, farmers are hand-digging wells to reach the receding water table, even as one-in-ten Kenyans are hungry.

But in both regions, a game-changing solution could come from an overlooked resource: billions of beneficial bacteria that teem in the soil near the roots of plants. Such bacteria are found in soil everywhere: from the hard-hit Kenyan coast, where my family grows tomato, peppers and watermelon, to the experimental greenhouses in Alabama where I now work to unearth the secrets of these soil microbiomes.

A fluorescent microscope image of the plant root cell with the red fluorescent particles representing beneficial microbes attached to the cell. (Image courtesy of Yoav and Luz Bashan)

Indeed, scientists across five continents are digging in to generate evidence of the beneficial associations among microbes and crops such as corn, cotton, tomato and peppers. Plants normally exude a carbon-rich liquid that feeds the microbes. They also exude various chemicals in response to a range of stressors, including insect attacks and water stress. Soil bacteria sense these messages, and secrete chemicals of their own that can activate complex plant defenses.

For example, studies have shown that a combination of beneficial microbes applied directly to seeds is as effective as commercial pesticides in combatting the rice leaf-folder, which wraps itself in and then eats the leaves of young plants. Other studies demonstrate that some soil microbes significantly increase growth and yield of important crops. In Germany, a 10-year field study showed that beneficial microbes increase maize plant growth and the availability of phosphorous—and essential plant nutrient—in the soil. In Colombia, microbiologists have mass-produced bacteria that colonize cassava plants and increase yield by 20 percent.

For farmers struggling to adapt to climate change, especially small-scale farmers with limited resources, an increase in yield can open fresh opportunities for the simple reason that crop sales generate cash, including money that can be invested in a range of “climate-smart” farming techniques that further conserve water and soil, and sustainably increase production on small plots of land.

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