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by Cindy Foster If our bodies ran on facts instead of food, we could glean good health by simply tapping into the rich diversity of information available on the World Wide Web. Yet, while cyber space has been growing at an explosive rate, something alarming has been quietly happening under our feet. To thrive, a plant's roots should find a soil food web as rich and diverse as the Internet, but instead many of today's soils more closely resemble outdated encyclopedias with many ripped-out pages. The soil food web refers to the interrelated societies that should live in each teaspoon of soil, including 600 million beneficial bacteria, 150 to 500 feet of fungal hyphae, 20 to 30 useful nematodes,10,000 protozoa, and several thousand other life forms such as mites and algae. Dr. Elaine Ingham, a prominent soil ecologist and assistant professor at Oregon State University (OSU), has studied this microscopic world for years. According to her, if you walk barefoot in your garden you should hope there is a teaming metropolis at work beneath your toes.
"The life within the soil is like a city where there are lots of different kinds of people--butchers, bakers, and candlestick makers," Ingham says. "Each one performs a different function and is a part of the system. Soil is like a human population. Diversity can only be reduced so far before the city falls apart." Years of tilling, spraying, and fumigating can turn soils into virtual ghost towns where the only residents left are the ones you don't want. Every gardener knows that the most resilient plants are weeds. Well, it turns out that the same thing is true at a microbial level, Ingham says. For example, a teaspoon of damaged soil might contain a few root-feeder nematodes (microscopic worms), while the same-sized pinch of healthy dirt would instead contain 20 to 30 beneficial nematodes. Why, you might wonder, would you want to encourage the growth of anything similar to something you'd dread finding on a dank basement wall? To answer that question, let's look at the parts nematodes play in the soil food web. Some feed on hundreds of nitrogen-rich bacteria each day, becoming tiny manure factories that excrete nitrogen in a form the plant roots can easily absorb. The nematodes also knit another strand of the web as they provide food for creatures that are higher on the food chain, such as millipedes, centipedes, and earthworms who, in turn, act as the subterranean city's engineers, building the tunnels that provide the elbowroom for air, water, and root growth. "The life of the soil is built around architecture," says Jim Carpenter, an ecosystem consultant from Klamath Falls, Oregon. Soil should ideally contain about 5% organic matter in order to be capable of holding enough air and water to sustain plants and organisms. Organic matter also provides food for the beneficial bacteria that congregate in the root zone. A close look at a healthy root zone illustrates more of the complex interrelationships that exist in the soil food web. Bacterial and fungal bodyguards not only produce antibiotic products that protect the plant, but they surround the roots, often hiding the tender shoots from pathogens and preventing other villains from maneuvering in close enough to take a nibble. According to Ingham, plants like this arrangement so well that they dedicate about half the carbon they use below the surface to exude juices that entice the right kinds of bacteria and fungi to their root systems. Once the good guys show up, some fungi, like Vesicular-arbuscular mycorrhizae ("VAM"), are even invited in. Part of the VAM actually grows in the cells of the plants' roots. From there, thread-like hyphae weave their way beyond the roots and search out phosphorus, other minerals, and water for their plant host. The VAM also protects the roots from rot and parasitic nematodes. If there is a break in the web and a plant can not find a VAM partner, as is often the case in soils that have received large amounts of chemicals, the plant has to work harder and may not survive without the addition of fertilizers and fungicides, which only further exacerbate the soil's problems. The concept of the interdependence of creatures above-ground has been widely understood for decades; but, although scientists knew soil organisms were important, studying the web of how their intricate interactions impact on each other is a relatively new field. "The whole paradigm in agriculture has been to kill what we do not want rather than to manage for what we do want," Ingham says. So when she began examining healthy soils to discover what things were missing from problem soils, her work was regarded with skepticism. Still, she persisted; and working first thru her lab at OSU and later thru the Soil Foodweb, Inc. (SFI), an independent soil testing company she founded, Ingham compiled an extensive database of both healthy and sick soils from all over the world. In the process she identified what things to nurture in order to heal sick soils. Today, what Ingham calls "moments of controversy" still exist in the field of soil ecology, but she is widely acknowledged as an expert. As such, she juggles international appearances and speaking engagements while her staff of technicians continue to analyze both agricultural and garden soil samples in SFI's Corvallis office. Looking below the surface is always a critical step because plants derive all their nutrients (except sunshine and CO2), from the soil. "You have to look at what's happening between the roots and minerals," Jim Carpenter says, "because that's where all the action is." Ingham and Carpenter agree that the health and productivity of even most virgin soils can be improved, and soils that have been damaged by overworking or past exposure to many chemicals can be rescued. "Fixing the soil depends on how much money people have to spend," Ingham says. "They can fix it overnight if they have lots of money to pour into it, but many people begin on a two or three year improvement plan." By nurturing an abundance of soil organisms to establish a healthy soil food web, not only can harmful pests be controlled but crop quality and quantity can be increased without the use of harmful chemicals that damage the environment. "As people learn these methods," Ingham concludes, "they will not be part of the chemical paradigm anymore." SOURCES:
Dr. Eileen Ingham
Jim Carpenter | ||
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