Reprinted from "LandOwner Magazine March 23, 1998

Update:  Jim Barlow was a co-founder of Soil Foodweb, Inc. in 1996.  He is now the founder of Soilweb, Inc. and the innovator behind the services provided by that new company.  This article reports on the shift towards sustainable methods of plant husbandry and the critical role of soil life in plant production.  

Today, Soilweb, Inc. helps growers use tested products and programs based upon this science.

     Jim Barlow recalls his frustration several years ago, when as a crop consultant, he was called in to solve a farmer's yield problem. The farmer was skilled and the nutrient ratio was in balance, but they were both still disappointed.

     "There was something else out there that had a grip on that crop, even when we had the best fertilizer balance. I felt ignorant," says Barlow.

     Although Barlow suspected that soil biology had an influence, his only framework of dealing with soil life was "Whatever is happening out there that you can't see, it's happening by accident. You can't manage it and it's either going to be okay and let you by, or it's going to hurt you."

     Barlow, who is now general manager of Soil Foodweb, Inc., (SFI) in Corvallis, Or., now believes that the soil foodweb, the complex food chain of microbial life in the soil, is the missing half of a complete picture of soil management.

     "We have this great fertilizer technology out there where you can farm great out of your left eye, but you're not allowed to look out of your right eye," he says. "We haven't been intentionally and deliberately managing the life in our soil, coordinating that with fertilizer programs, and getting both sides of the equation to our plants to grow high yields."

     Even though he'd been classically trained in modern agriculture with a degree in crop production, Barlow says that didn't prepare him to fully appreciate the interaction between soil organisms. A textbook he saved from 1980 shows separate chapters on soil bacteria, fungi, nematodes and protozoa but none on how to integrate them all.

     "I spent a lot of time in the lab looking at root rot fungi in strawberries, but in 1974 we didn't have a good enough idea of what the life in the soil was doing," he recalls.

     Barlow believes that modern agriculture is experiencing a breakthrough with the magnitude of the discovery of soil pH in the 1920's, when farmers and health officials were mystified by poor crop and outbreaks of human disease.

     "What used to be a black box -- a big mystery in the soil -- we can now take the cover off and look into it, seeing the machinery, the anatomy and the engineering. We can use the laboratory to see if any of those parts are absent, not present in sufficient number or not active. We can now inspect that machine."

     Barlow's reeducation of sorts gained speed in 1993, when he began taking his soil samples to Elaine Ingham, a microbiologist with Oregon State University in Corvallis. Ingham had established the Soil Microbial Biomass Service (SMBS) there in 1991, which tested both healthy and diseased samples from riparian, forest, agricultural and prairie soils and managed a database of test results. In 1996, Barlow and Ingham founded SFI, complete with a client base from SMBS and data from 25,000 soil samples.  

     'There's no one soilfoodweb and there's no one best balance," says Barlow.  "In different major climatic regions and different major soil types, there will be different best balances that we have to interpret. And with this sample database, we know what ought to be in soil for corn in each part of the Corn Belt, and what ought to be in soil for corn in California."

     "We need to alter our management to grow these microherds of bacteria and fungi in the soil, just as we manage our above ground herds," says Ingham.

"Successful management of life in the soil begins with three basic components", says Barlow:

1. A scientific or intellectual model defining life in the soil. The food chain on the surface of the soil, with herbivores, predators and predators that eat each other, is mirrored in the soil, and research has revealed the who-eats-who of the microbial world in all types of systems.

     "Nature works that way everywhere you look," says Barlow. "That's the exact same thing happening under your corn, except you haven't been able to appreciate it"

2. A laboratory procedure to take a sample count.  New techniques in microscopy allow for direct examination of a soil sample to inventory organisms and determine their activity level.  One technique uses a state-of-the-art "epiflourescent differential contrast microscope," which fluoresces active organisms and magnifies them 250 to 1,000 times.

     "We'll crunch these numbers and give you a report, a visual indication of what's high and what's low and where you are. It's a new window into the soil," says Barlow.

3. The ability to interpret the lab numbers.  "When you observe statistical patterns using the computer, you make discoveries. We now have the patterns and know what organisms need to be present under any particular kind of major plant, in any region of the country at any time of year," says Barlow. "We have everything we need to make a new category of tool for farming."

Defining the ideal soil biota counts is crucial for identifying and testing the products needed to replenish it, which will in turn boost yields and profits.

     "We're at a historical time in the turn of the century, where we can begin to bring in a soil biota report as a companion analysis sheet to go with the soil fertility sheet," says Barlow. "We can also take good compost and test the various values and different aspects of quality, and see if you are bringing with it a broader diversity of all of the good guys that will seed your soil with species that may be absent." Rather than just studying products that promise higher yields, biological products need to be tested against the soil biota criteria for each locality.   "We need to build the equivalent of a pharmacy," adds Barlow.  "Then we can select a product because we know what it does. We're beginning to take the hiss out of the snake oil." And biological inputs must be chosen carefully, because the soil biota recycles organic matter, feeds and protects the plant against pathogens, fixes nitrogen, builds soil structure, and must be present in desirable ratios around the root structure to make the system work.

Decomposition:  The foodweb cycle begins with decomposition of organic matter. 

     "No gypsum, calcium or phosphates can do this," says Barlow. "The more species we can have out there, the more rapid your decomposition." If they are present, the bacterial predators cause a springtime flush of nitrogen from bacterial and fungal biomass, right in the root zone where the roots need it.

     "Litter material should be fully colonized by bacteria and fungi within two weeks of falling on the surface of the soil," says Ingham. "If the decomposer group of the foodweb is not there or not functioning, you're going to plow up your organic matter two years later fairly intact." The foodweb can also clean up chemical carryover, as certain organisms are able to degrade high-energy, complex molecules.

Nutrients: A tremendous amount of the carbon form of energy and photosynthates which a plant fixes for itself--between 40% and 80% -- moves down into the root system.

     ''The only two nutrients the plant is getting above ground is CO2, and light. You can foliar feed, but you're not going to get enough into your plant from just a short burst of a few mineral nutrients," says Ingham. Every other nutrient a plant needs to grow is absorbed through the roots, including nitrogen, phosphorus, sulfur, iron, magnesium, manganese, water, and calcium.

     Half of the plant's carbon flowing below ground is used to grow structural, fine and lateral roots. The other half is pumped into the soil in the form of exudates. These are the "juicy" food resources for microlife: simple sugars, proteins, carbohydrates.

     "It's as if those plants are dishing out chocolate cake into the soil," says Ingham. Through this buffet of foods, each plant is physiologically engineered to attract the right kinds of bacteria and fungi for its root system that will in turn feed it and protect it against pathogens.

     As each plant cultivar puts out its own unique exudate signals through the soil, "There's a deal being made between these two organism groups," says Ingham. By using carbon to invite the infiltration by a mycorrhizal spore, the roots ensure the delivery of solubilized nutrients that were previously plant unavailable. 

     "In 1986, when we first started making these kinds of models, we only had evidence that it was phosphorus and nitrogen that was brought back to the plant by the mycorrhizal fungi," says Ingham. "In research around the world in the intervening 12 years, we have discovered that it's also sulfur, magnesium, manganese, boron, zinc, calcium and lignin, and your plants can tolerate drought a lot better if they are mycorrhizal."

     "Since the fungi mine the soil for phosphate and pipe it back to the root, that makes your fertilizer more efficient," says Barlow. "You can back way off with the phosphates."

James Barlow, agricultural consultant and general manager of Soil Foodweb Inc.:  "We have the model and know what populations should be under plants to help them grow best."

Disease Suppression: Mycorrhizal fungi are a very important group in this aspect. Because the fungi wraps its mesh of hypha around the root system, root-feeding nematodes can't make their way through the network.

     "Antibiotic and inhibitory products are also produced by mycorrhizal fungi, so there's a big disease suppression function performed by these organisms," says Ingham. Chemical inputs cost money and time, so "Put them back into the system and let them work for you," she advises.

     In a typical agricultural soil, there should be about 100 mil. bacteria per gram. But right around the root zone, there is optimally a million million bacteria per gram of soil -- which creates a "rhizosphere" of soil being influenced by the plant.  If the rhizosphere is present, the pathogens are kept so far at bay from the root system that they are unaware the root is even there.

     "Putting the policemen back into the soil will keep the predators in line," says Barlow. "If we have beneficial species of microbes that naturally suppress root rot types, it's like having a cop on the beat in the root zone. By keeping roots crispy and white and functioning beautifully, you might get that extra five or ten bushels." 

     Studies have shown that crop quality also increases: "If you get a more complex and healthy soil biota back into the soil, we get more protein back into crops like corn, wheat, and grapes." Ingham adds. However, beneficial bacteria and fungi are sensitive to disturbances -- especially the Fungi, she notes.  "You will never see disease in that plant if you've got those beneficial bacteria and fungi in that soil.  But what if you kill those beneficial bacteria and fungi by too much tillage, by not having enough organic matter in the soil to feed them, or by applying a hard chemical fertilizer like anhydrous, or a kind of pesticide that accidentally kills those bacteria and fungi?" asks Ingham.

     "If you don't have the beneficials, which are the most sensitive to these inputs, you're left with the pathogens, and what happens to that chocolate cake carbon that's being put out into that soil? You're putting out food for those pathogens. "So why do we continue to see more and more and more disease problems in agriculture? Because we're accidentally killing the beneficials and we're not putting back those things the organisms need to grow on, and we put ourselves into that disease cycle. We increase disease because we don't really understand what's going on in this below-ground system," says Ingham. 

     To pay for land through agricultural production, killing the organisms is sometimes a necessary evil, Ingham recognizes.  "But realize that you need to do something in your soil to get back the good guys and not keep benefiting the pathogens," she insists. 'That's part of what we want to do here -- put back the food in those systems to grow the beneficial bacteria and fungi, or inoculate the soil with the 'good guys' in order to make sure that they're there."

Plant Growth Regulators: [In corn] Ear numbers and earfill decisions made by the plant are hormonal, not genetic, and the presence of a healthy soil biota facilitates that process, says Barlow. "The plant is looking to be able to inventory the fertility, climate, moisture level and the chemical cross-talk from the soil biota that are chemical signals that the plant picks up," says Barlow. "At the four-to five leaf stage the plant decides what to go for. And that decision has been made because it got the signals and was able to detect its inventory, and you've got that much better yield," he adds.

Nitrogen Fixation: One of the most critical roles of the soil foodweb is fixing plant-available nitrogen.

     "When you apply fertilizer, you need to have the bacteria and fungi available to tie up that nitrogen in your soil.  If you don't, its washing right out of your soil into the groundwater," Ingham says.  Many California strawberry fields, for example, are so heavily fertilized that at least one river runs about 150 parts per mil. nitrate. "You can't even put that back on your plants because it'll burn them, its so high in nitrate," she notes. 

     Nitrates are the most mobile form of nitrogen, followed by ammonium. The least mobile form is organic nitrogen in the form of bacteria, which produce glues that attach to colloidal surfaces, and fungi, which grow hypha strands that around soil particles.  Fungi and bacteria attack organic matter and decompose it with their enzymes, absorbing free nitrate in the process.  Bacteria, with their superior enzyme system, will grab nitrogen first.  They’re like the Arnold Schwartzeneggers in the soil," says Ingham.

     Next in line is the fungi, and last is the plant roots, which are merely passive nitrogen sponges.

     In the meantime, bacterial feeding nematodes, fungal feeding nematodes, and protozoa -- flagellates, amoebae and ciliates -- prowl the soil, hungry for carbons. Their bacterial and fungal food sources overload them with nitrogen, and they excrete it as plant-available nitrogen. Protozoa eat 10,000 bacteria each day, and "we should have 10,000 of these protozoa in every gram of soil that is around the root zone of your plants," says Ingham. A gram of healthy corn soil contains 20 bacteria-feeding nematodes, which eat about 10,000 bacteria a day.  "Imagine the amount of nitrogen that's being mineralized in your root system," notes Ingham.  Higher-level predators, such as millipedes, centipedes and earthworms, keep the bacteria and fungi-eaters from overeating. The food chain extends to moles, shrew, mice and birds, then foxes and raccoons -- all critically dependent on these lower organisms for survival.

     "It's a jungle down there," Barlow observes.

     Several hundred pounds per acre of bacteria and fungi translate into 20-50 Ibs. per acre of nitrogen, says Barlow:  "lf you're buying nitrogen, wouldn't you want to hold it there in the ground and buy less of it?" he asks. "That efficiency in the fertilizer is coming from the foodweb, if you can manage the foodweb and make that function happen."

Soil Structure "You start good soil structure with calcium, but you don't get the glue and wrapping paper without the soil biota," says Barlow. Bacteria and certain fungi, especially, glue the clay colloids together into microaggregates, which are bound together "like string on a package" by threads of soil fungi.  Earthworms and nematodes, as they push through the soil, create pore structures.  But these organisms are sensitive and easily disturbed. 

     "If you compact and smash down all these holes, you don't have any more engineers left in your soil to give you the space that you need," warns Ingham. Roots are then fair game for predators:  "There's a close relationship between compaction and root feeding nematodes," she notes.

     Fungal biomass is torn up by too much tillage: "You're going to shear off all of these threads of fungi, break it up and kill that fungal biomass," Ingham warns.  Left to themselves, protozoa and bacteria in compacted soils produce ethanol, phenol and other toxic compounds, and the soil quickly turns anaerobic. More compaction, toxicity and lodging are the result, and the right organisms are needed to put the soil back in balance.

     "Get the organisms back in there performing this condominium engineering", she advises.  "If you get the right kind of organisms growing in your organic matter on the surface of the soil, in six months we can break up hardpan that was down three to four feet. You don't have to deep rip. All you have to do is get the right organisms and give them the right food and they will do the work for you.  "If you have a mineral crust on the surface, that says there's something wrong with your foodweb and you need to fix it," she adds. "You've got to get your food back into your soil to feed those organisms. That's how we can break up the mineral crust in just a couple of weeks -- in some cases just a couple of days."

Ratios of bacteria to fungi change according to different systems. Most row crop soils should have a 50:50 balance between the amount of bacteria and fungi in the root zone, but are most often dominated by bacteria in a bad ratio with scarce fungi that is out of balance.  Tillage accidentally suppresses desirable fungi and encourages bacteria.  Although things that eat bacteria, like protozoa,  release nitrate, there should be a proper ratio of fungi round to do other jobs that help make yields.  Most row crop farmers need to increase the counts of fungi in the root zone.  That can be done with certain brand name biological products and by not turning under organic matter too deeply.

     However, forest, blueberry, blackberry, orchard, vineyard and strawberry soils should have five to ten times more fungi than bacteria. Rainforest soils contain such a thick web of fungi that you can actually scoop it out of the soil, wash it and eat it, says Ingham.  "

     When fungi are eaten by the predators, the waste remains as ammonium, because we don't have nitrifying bacteria," says Ingham. "Tree systems are better at taking up ammonium.  The system works and holds together."

     Bacteria dominated systems need organic matter moved down into the top two to three inches of soil, where soil biota activity is highest.  Fungal-dominated systems use organic matter on the soil surface.

     "Fungi are the only things that can grow down into the soil, collect the nitrogen from the soil, and combine it with carbon in that organic residue," says Ingham. 

     "It's very important to know what kind of system you're in", say Ingham and Barlow.  If not, serious consequences can result:  Managers of a nursery for rhododendrons, which favor a 100-1 fungal-to bacteria dominated system, thought they were doing the right thing by setting up a bacterial environment. "They lost six acres, about $200,000 worth of intensive rhododendron production," says Barlow .  "They ran afoul of the soil biota". 

     Replant disease in orchards and problems with re-establishing forest in the Pacific Northwest goes back to the same problem -- the soil is bacterially rather than fungally dominated.

Barlow looks forward to the future, when farmers will be managing their operations with both eyes open.  "I believe that the destiny of this work is that we're going to see it as a new category of laboratory that goes beyond the traditional soil microbiology lab," he says. "I think in the future, you'll get on the tractor and what you'll have in mind to do is get the soil biota in balance."