Issue link: http://read.dmtmag.com/i/662797
40 APRIL 15, 2016 GOOD FRUIT GROWER www.goodfruit.com S pace may be the fi nal frontier, but soil biology is the next frontier. Researchers are only beginning to understand the richness, diversity and com- plexity of the bacteria, fungi, algae and other microbes thriving in the ground underfoot, and just how critical soil health is when it comes to keeping the Earth's overall ecosystem intact. "Without microbes, life doesn't work," said U.S. Department of Agriculture- Agricultural Research Service (USDA- ARS) research microbiologist Michael Lehman, who collaborated with 14 other soil experts on a major, overarching arti- cle in 2015 that described the yawning chasm between what we know about soil microbiology and what we need to know. A large part of that gap results from an inability to examine the microbial world in soil. "In well-studied systems, scientists have been able to ask questions and get answers, and that's why those systems are well-studied," said Lehman, who is sta- tioned at the North Central Agricultural Research Laboratory in Brookings, South Dakota. "For instance, if you wanted to look at trees in a certain forest, you could go out there, actually count every indi- vidual tree, and probably identify every single individual tree to species. We can't possibly do that with the organisms in the soil." New technological tools, however, are beginning to shed some light on soil microbes. These include such technol- ogies as the burgeoning DNA and RNA sequencing capabilities, stable isotope probing and various gene-expression techniques that can assist in identifying these microbes and the roles they play, Lehman said. "With these technological advances, we've already discovered so much more than we ever thought in terms of diver- sity and numbers alone, and with the incredible complexity of this system, it's become clear that we are really primitive in our fundamental knowledge of the physiology and ecology of nearly all these organisms," he said. As an example of the lack of under- standing about soil biology, Lehman pointed to nitrogen-fi xing bacteria. "For 50 to 60 years, soil microbiologists have measured the activity of two or three organisms and their potential to convert nitrogen from ammonia to nitrate. But in the last five years, it's been found that totally unrelated microorganisms actually might be doing most of that nitrogen conversion in soils," he said. "These are microorganisms that had never been known before, (and they include) nitrogen-fixing bacteria that don't fit into the conventional nodulating-rhizobial model, but are just living in the roots, fi xing nitrogen and giving it to plants." Additional new research indicates that other microbes can help make Soils and Weed Management Soil biology is critical to life, but still largely unknown. by Leslie Mertz PHOTOS COURTESY OF USDA-ARS. U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) research microbiologist Michael Lehman takes a soil-core sample on David Gillen's South Dakota farm. Among other things, such samples can be tested for the diversity and activity of soil bacteria, fungi, algae and other microorganisms. The microbes BENEATH Unnoticed by the naked eye, the soil is alive with microorganisms that support plants. "Without microbes," says Lehman, "life doesn't work."