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.
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.
Most recently, studies point to a direct role for soil bacteria in shielding crops from drought; improving their growth and ability to absorb nutrients; and enhancing their tolerance of flooding, high temperatures, low temperatures and many other challenges of a changing global climate.
In one study, scientists reported that peppers cultivated in arid desert-like conditions act as “resource islands” attracting bacteria that sustain plant development when water is scarce. Another study identified soil bacteria that prompt plants to temporarily close the pores on their leaves. This not only prevents disease-causing bacteria from entering the plant, but also prevents the escape of moisture, preserving the plant’s water.
I can see this in my research labs, where several running experiments dramatically illustrate the role of soil microbes in protecting against water stress. Cotton, corn and tomato plants grown in soil that is infused with certain bacteria have root sizes that are triple the size of plants grown in untreated soil after water has been withheld for just five days. The treated plants stand tall and robust; the untreated wilt and wither. The difference is tremendous.
Although companies such as Nozozymes, Monsanto and Bayer Crop Sciences are exploring the potential commercialization of soil bacteria, and several start-up companies are working around the clock to commercialize microbial cocktails, overall, research into this area has barely begun.
The United Nations designated 2015 as the International Year of Soil, and governments, funders and researchers are taking a hard look at the role of healthy soil in achieving food security as population grows and climate change lowers yields of important food crops. But rarely do their initiatives consider the potential of the communities of beneficial bacteria, billions strong, and adapted through millennia to aid plants in their battle for survival.
Of course, the use of soil microbes is just one part of the complex and interlocking changes needed to ensure the sustainability of our natural resources and the productivity of our food systems. But they could provide novel solutions that are of central significance in contemporary plant science as it addresses the challenges of climate change.
We must invest in understanding and harnessing this resource, which works with nature, not against it. As concerns about food security increase with the global temperatures, soil bacteria could be the next key tool for food security, helping farmers around the world conserve water, increase yields and improve nutrition under the changing climate.
What About Earth’s Microbiome? (April 22, 2015)
Central Park Features Worldwide Soil Microbes (October 1, 2014)
Soil Science: Make a Winogradsky Column (September 19, 2013)
Microbes Help Grow Better Crops (August 20, 2013)