Interesting. We make about 200 tons a year of compost for use on our organic market farm, a total of 3.5 acres. The acre of vegetables receive about 100 tons applied approximately 3 times a year. (We farm vegetables, herbs and small fruit.) The orchard receives the other 100 tons in late winter after pruning and cleanup and before renewing the mulch cover with chipped tree prunings. We no longer have to fertilize the orchard (other than new trees).

Years ago I moved from bacterial dominated compost to fungal dominated compost made with much woody chipped materials and a minimum volume of green material. Prior to field applications, the compost is sifted to remove larger wood fragments, these saved to "innoculate" new compost windrows.

We have been pleased with the apparent positive results of this change, especially much less soil-borne diseases and pests

Marshall,
To have more soil fungal activity seems strange when one is desiring to reduce harmful soil and foliar fungals, and yet I presume it works that way. Perhaps they crowd out bad fungals by root colonization by good fungals!?

There are good fungi and bad fungi. If you leave them alone, the good ones "win" by eating the bad ones.

That is an interesting article. Do you have the date it was published? At first I was concerned that the author equates compost and manure. To me that's like confusing concrete and cement. One is made from the other. I guess he's saying that the resulting compost has the same levels of P and K as the original manure??? Not sure.

I'm also not sure the author understands the soil biology. He only tipped his hat to microbes at the very end of the article. How does the N, P and K tied up in the living microbes become a gas to blow away or wash through the soil to pollute water? I can see that if you have too much protein decomposing all at once but that doesn't happen in finished compost. Now manure is a different subject. That's one reason it should be composted.

A Texas cattle rancher I've talked with gets about 12-24 wet tons of fresh dung per acre per year. That gets done in four passes of cattle across each of 15 pastures. It all gets buried within 24 hours of 'deposition' by dung beetles, thus it is not exactly applied on top of the soil. Plus it is processed by the slimes exuded by the dung beetles so it's not like the cow patties you see in a field at all.

I have applied 1/2" of compost every year for about ten years in a community garden plot. Both P and K have increased to what a soil test would say is out of balance. I don't mind the high P so long as I can balance it with S. But the high K is disturbing. So I apply a bit of gypsum to knock it down, but still it's too high. I think I need to do less compost and more ground covers and shredded leaf mulches. And I'm with marshallz in using more structural carbon and less soft carbon in the compost, not only for fungi, but also for lignin which is the foundation of humus. Regards, Peter.

Here's the link to the article on ramial chipped wood.

I have seen those dung beetles rolling a ball of manure, but nothing on the scale of those Texan beetles. I wonder if they are a southern thing or organic pasture thing or both

I am still wondering why high K might be undesirable unless it is just not necessary. The main thrust of the article seems to be saying that the idea of piling on more and more outside fertilizer and OM is not all good and is often lacking enough fungal activity. That may happen in a garden but not likely on farm fields of any size.

Dung beetles are killed by the deworming medicines like Ivermectin. If you have cattle and don't want to use deworming meds, then one common approach is to get pretty strict about culling for disease. You take the sick animal, the momma, and any sibs to the abattoir. Soon enough you have an entire farm of healthy genetics. If you get up early enough in the morning sometimes you can see the sky darken with dung beetles flying in.

I received the article in the last 3 months and I thought it was something written in the last year, but in saving I must have deleted the dates, so I can't say for sure when it was written.

I found a reference to the article as follows:

Organic farmer and Tioga County Cooperative Extension Agent Brian Caldwell contributed an article to the Spring 2000 Northeast Organic Farming AssociationNew York newsletter, "How can organic vegetable growers increase soil organic matter without overloading the soil with nutrients?" Though he doesn't have his own research program, he has just completed work on stale seedbed weed control that is relevant to organic growers.

So the research must have been conducted prior to 2000. At that time the concept of the Soil Foodweb was in its infancy. I wonder what he's done more recently??

I thought his observations on tilling quite good.

Good article.

My two gardens have been just what he suggests: a major shot of composted manure at the outset, with diminishing amounts afterwards, along with minimal tillage and much layering of high-lignin materials. As an interesting additional experiment, one is irrigated and one is not. Last season Hickory King field corn produced very well without irrigation on ground that has had no outside input in at least five years. Equally well as the corn in fertilized ground with irrigation in the other garden.

and here is a quite interesting and complementary piece:

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Cultivating diversity underground for better yields above - http://www.newfarm.org/depts/NFfield_trials/0903/daviddouds.shtml

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* From: "Lawrence F. London, Jr."
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http://www.newfarm.org/depts/NFfield_trials/0903/daviddouds.shtml

Cultivating diversity underground for better yields above
Research at The Rodale Institute® demonstrates how sustainable farming practices can boost yields by nurturing beneficial soil fungi.

By Laura Sayre

About this series:

As some of you may know, The Rodale Institute®, which publishes The New Farm®, is home to the longest running field trials in the country comparing organic and conventional systems of farming called The Rodale Institute Farming Systems Trial® (FST). The data from that 23 years of research is a real treasure trove of insight into the economic, ecological and agronomic benefits of organic farming.

In addition to this long-running Farming Systems Trial, we have a variety of other research in progress at The Institute. David Douds, as youll read in this story, has been studying soil fungi here at The Institutes research farm for 15 years. Were engaged in no-till research, weed research, compost tea research, composting research, water quality research, and much more.

Until now, much of the light were generating here on our research farm has been hidden under the proverbial barrel, but were taking off the barrel and busting it up for firewood. Were going let the light of the amazing research being done here shine on farmers, consumers and environmental activities.

Over the next year well be running a series of stories, about one a month, on the significance of our research ... and its practical applications. That includes a few stories on equipment constructiona front-mounted roller for no-till, and a compost turner converted from a junked 18-wheeler.

So sit tight, and be prepared to be amazed, starting with David Douds discoveries about how you can increase vegetable yields by 50 percent using homemade fungal inoculants.

Enjoy,

Chris Hill
Executive Editor

p.s. Interested in hearing more about how you can take part in the mycorrhizae revolution? Click here and let us know. Send your name, phone number and e-mail address with your note so we can follow-up with you.

"Overall, Douds work suggests that a small amount of mixed MF inoculant can be substituted for a large amount of fertilizer--with no loss of yield, greatly reduced environmental impact, and lower production costs."

Home-grown mycorrhizal inoculum can be produced at a fraction of the cost of purchasing commercial mixes. "I've done some preliminary calculations," says Douds. "The on-farm system produces 100 million propagules for approximately $50, not counting the cost of the farmer's labor, which is fairly minimal. To purchase 100 million propagules as listed on the bag of some commercial mixes would cost anywhere from $8,000 to $40,000."

FACT SHEET: Mycorrhizae

Above: USDA soil microbiologist David Douds with a carrot root-mycorrhizal fungi culture. Under the leadership of Dr. Douds, field trials have shown yield gains of as much as 50% in the presence of healthy mycorrhizae populations. Now Douds is developing a practical, low-cost method for on-farm production of mycorrhizal soil innoculant, promising higher yields with lower nutrient inputs. (Photo by Peggy Greb, courtesy of the Agricultural Research Service Photo Unit.)

September 29, 2003: You've read the amazing facts and figures: one teaspoon of healthy topsoil can contain millions of individual microorganisms, all playing a part in the functioning of the soil ecosystem. But how much do you really know about the action of those diverse species and how to maximize their presence in your own fields?

Ongoing research at The Rodale Institute® sheds light on one important component of the soil community--mycorrhizal fungi--and its impact on agricultural production. Under the leadership of Dr. David Douds, a soil microbiologist with the USDA's Agricultural Research Service, field trials have shown yield gains of as much as 50% in the presence of healthy mycorrhizae populations. Now Douds is developing a practical, low-cost method for on-farm production of mycorrhizal soil inoculant, promising higher yields with lower nutrient inputs.

A mycorrhizal primer

Mycorrhizae are soil-dwelling fungi that live in and around the roots of plants ('myco-rrhizae' means 'fungus-root'). The fungi and the plants form mutually beneficial associations in which the fungi receive carbohydrates from the plants and the plants receive nutrients and other benefits from the fungi. Since the first mycorrhizae species were described by a German botanist in the 1880s, researchers have discovered that approximately 80% of all land plants form mycorrhizal associations. The relationship is so widespread, in fact, that it is sometimes referred to as 'the Universal Symbiosis,' and is believed to have played a key role in the evolutionary transition from aquatic to terrestrial plant forms.

Today, scientists divide mycorrhizae into two major types: endomycorrhizae, which penetrate and colonize plant roots, and ectomycorrhizae, which form sheaths around plant roots. Whereas ectomycorrhizal relationships tend to be highly specialized--with some 6000 fungal species worldwide associated with tree species of the oak, beech, and pine families, among others--endomycorrhizal associations are more generalized as well as more widespread, with fewer than 150 fungal species opportunistically colonizing the roots of the vast majority of terrestrial plant families. Ectomycorrhizal inoculants are already widely used in commercial forestry, but the possibility of developing endomycorrhizal inoculants for production agriculture is a more recent idea.

"These are beneficial soil fungi that colonize the roots of plants and help them take up phosphorus" and other immobile soil nutrients, such as zinc and copper, Douds explains. "The fungus colonizes the root and it also grows out into the soil; the part of the fungus that's in the soil acts as an extension of the root system, to explore a greater volume of soil and take up nutrients and bring them back into the root."

In addition to facilitating nutrient uptake, some mycorrhizae secrete a gluey substance, called glomalin, which helps develop soil structure and soil aggregation; others may help plants fight disease. Yet because endomycorrhizae are 'obligate symbionts'--they must have living plant roots to colonize in order to complete their life cycle--their numbers will decline under conventional agricultural monocultures, which have living crop covers fewer months of the year than organic rotations. The drop in yields typically seen after the first year of cultivation on virgin prairie or forest soils is probably attributable in part to the loss of native mycorrhizae, Douds says.

Fifteen years of research prove benefits of fungi

Douds has been conducting research in collaboration with The Rodale Institute since 1989, his first year at the Agricultural Research Service's Eastern Regional Research Center in Wyndmoor, on the outskirts of Philadelphia. "Some employees of The Institute farm came down to our research center as part of a kind of an interagency show-and-tell about research programs and facilities and what all we could do to help each other," Douds recalls. "Rhonda Janke"--The Institute's research agronomist at the time--"gave a presentation about The Rodale Institute Farming Systems Trial," a side-by-side comparison of organic and conventional production systems. Douds recognized it as a great opportunity to study endomycorrhizal associations.

"Later that year I started sampling, and right off learned that [the soils under] the conventional farming systems had fewer mycorrhizal fungi than the soils under the low-input farming systems. So right away we all got excited and we branched out from there."

Since that first season, Douds' work at The Rodale Institutes 333-acre experimental farm has progressed in three overlapping phases:

In the first phase, from 1989 to 1995, Douds and his team surveyed native mycorrhizal fungi (MF) populations at Rodale and examined the impact of different agricultural practices--including tillage regimes, crop rotations, and soil amendments--on those populations. The second phase, which is still ongoing, looks at the utilization of MF by crop plants, comparing yields in the presence and absence of different MF species. The third phase seeks to apply those findings by devising a simple, on-farm MF inoculum production system, so that farmers can harness the benefits of endomycorrhizae without spending lots of money on commercial mixes. (Commercial products already on the market include Bio/Organics Endomycorrhizal Inoculant [$79.95 for 3 lbs, labeled to treat 500 plants], Plant Success Mycorrhizae Tablets [$19.95 for 100 tablets, labeled to treat 50 plants up to 1 ft tall], and Earthroots VAM Fungi by First Fruits LLC [$15 for 3 lbs, labeled to treat 200 seedlings].)

On-farm production of mycorrhizal inoculant in test enclosures at The Rodale Institutes farm. Douds chose bahiagrass as a host plant "because it's a tropical grass and the first frost will kill the shoot growth"--so it won't escape to become a new local weed and won't harbor any pests or pathogens that might affect either resident crops or northern native grasses.

Agronomic practices that boostor depress
mycorrhizal levels

Although the first phase of Douds's research found larger and more diverse MF populations in organically-managed soils than in conventionally-managed ones, it also revealed how specific agronomic practices can boost or depress MF levels.

"Over-wintering cover crops. . . are very beneficial to mycorrhizal fungi," Douds notes, whereas "tillage disrupts the mycorrhizal fungi in the soil and serves to decrease the initial colonization of the plants." Based on these findings, Douds emphasizes that all farmers, organic or conventional, can take steps to nurture the MF already present in their fields: reduce tillage, he says, use fungicides sparingly, and--most important--maximize cover cropping. "Over-wintering cover crops give the MF a host plant to colonize when there's no cash crop growing on the soil," Douds explains.

In the coldest part of the year the MF go dormant, but during warm spells in early spring and late fall, the MF will try to grow, and can exhaust their reserves if they find no plant hosts. "During these periods. . . the fungus is still respiring, it's still burning up its carbohydrate storage in the spores, it's burning up the lipids that were stored," leaving it "less viable when the time comes finally for the crop plant to be present." A cover crop or even just a weedy fallow will maintain healthy MF populations, which can then benefit the cash crop coming on to the field.

Crop rotations are another factor to consider, since a handful of crop species belong to plant families that do not form mycorrhizal associations (said to be 'non-mycotrophic'), including the Brassicaceae (rape, broccoli, cabbage, turnips, etc), the Chenopodiaceae (beets, spinach), and the Polygonaceae (buckwheat). Not only will these crops not benefit from the presence of MF, but MF levels in the soil will be depressed after these crops are grown, potentially showing an effect on any mycotrophic crops which follow.

Potatoes and peppers inoculated with mycorrhizae get yield boosts of up to 50 percent!

In the second phase of his research, looking at the impact of MF on crop yields, Douds began inoculating plants in the greenhouse and then tracking their performance in the field.

"We had some plants that were inoculated with a control mix with no inoculum, another one inoculated with a mix of mycorrhizal fungi, and another inoculated with just one species commonly present in commercial inoculum," Douds explains. "We transplanted them into the Compost Utilization Trial,"--another ongoing experiment at The Rodale Institute--"and we found over the course of the 3-year experiment that the mixture of mycorrhizal fungi increased the yield of marketable-sized peppers up to a maximum of 34% over the control. Last year we tried inoculating potatoes, and we got up to a 50% increase over the controls."

David Douds and a research intern dig potatoes in this season's mycorrhizal test plot at the Rodale Experimental Farm. In last year's trials, potatoes grown with mycorrhizal fungi showed yield increases of as much as 50%. Other crops known to respond dramatically to mycorrhizal colonization include citrus, onion, and strawberries.

This year they are repeating the potato trial, measuring yields under four different treatments: one with no added MF; one with a commercially available MF; one with a mixed MF inoculant grown in a leaf compost and vermiculite medium; and one with a mixed MF inoculant grown in a dairy manure compost and vermiculite medium. Overall, this work suggests that a small amount of mixed MF inoculant can be substituted for a large amount of fertilizer--with no loss of yield, greatly reduced environmental impact, and lower production costs.

One unexpected finding of Douds' work at Rodale "is that mycorrhizae can be used to increase the yield of crops even in soils that are very high in phosphorous." Some of the soils at the Rodale Farm which have been heavily composted, Douds notes, "have available P in excess of 300 parts/million"--well above the level at which mycorrhizal responses are typically seen, around 20-50 ppm available P. "The generalization would be that P as high as 300 would be a situation in which the plant can take up all the P that it needs by itself without relying on the mycorrhizal fungi." Douds believes that at high nutrient levels, some of the other benefits of MF--enhanced disease resistance, improved soil aggregation and better water relations--could be showing an effect.

Build your own on-farm inoculum production system

The third phase of Douds' research at Rodale Farm focuses on developing an inexpensive, practicable system for on-farm production of mycorrhizae inoculant. As obligate symbionts, endomycorrhizae have so far resisted attempts to create what scientists call axenic (or isolated, single-species) cultures--they can only be grown in the presence of a host plant. Douds' system works within this constraint, using bahiagrass (Paspalum notatum), a tropical grass native to the southeastern US, as a host.

A myccorhizae factory: The basic procedure is for the farmer to construct a simple enclosure out of landscape fabric, fill it with a mixture of compost and vermiculite, and then transplant pre-colonized bahiagrass seedlings into the mixture. Over the course of the growing season the bahiagrass spreads within the enclosure and the mycorrhizal fungi spread and reproduce along with it. When the grass dies back in the winter, the farmer is left with a concentrated mycorrhizal inoculant that can be incorporated into his or her potting mix when starting seedlings in the greenhouse the following spring.

The basic procedure is for the farmer to construct a simple enclosure out of landscape fabric (75 cm square and 20 cm high), fill it with a mixture of compost and vermiculite, and then transplant pre-colonized bahiagrass seedlings into the mixture. Over the course of the growing season the bahiagrass spreads within the enclosure and the mycorrhizal fungi spread and reproduce along with it. When the grass dies back in the winter, the farmer is left with a concentrated mycorrhizal inoculant that can be incorporated into his or her potting mix when starting seedlings in the greenhouse the following spring.

This year, Douds gave inoculated bahiagrass seedlings and other materials to a few Pennsylvania farmers to see how the method fares in the real-life conditions of farming. Meanwhile, Douds has 12 soil enclosures growing at the Rodale Farm in an experimental grid designed to identify optimum growth media.

Douds chose three different kinds of compost--yard-clippings compost, controlled microbial compost, and dairy manure-leaf compost--and then diluted each kind with vermiculite at four different ratios, ranging from 1 part compost:2 parts vermiculite, down to 1 part compost:49 parts vermiculite. Each soil enclosure, finally, has nine separate sections, three with no inoculant and three each with two different mixtures of MF.

At the end of the season, says Douds, "we'll sample the mixtures from within each enclosure, quantify the inoculum production, and then hopefully develop a prediction formula, where the optimum ratio [of compost to vermiculite] is a function" of the nutrient analysis and other properties of the compost. All the farmer will need to do, then, is get the nutrient analysis of his or her compost, plug it in to the formula, and find the optimal ratio of compost to vermiculite to use for his or her farm.

"On-farm methods have several advantages over commercial inoculants," Douds explains. In the first place, whereas commercial formulae typically only contain a single MF species (frequently Glomus intraradices), Douds' method yields a diverse inoculum containing many MF species. This is crucial because MF show significant 'functional diversity'--"some are good at holding the soil together, some are good at gathering nutrients," others help fight disease.

A second, related advantage is that by mixing in some soil from a nearby woodland, prairie, or hedgerow, the farmer can use Douds's system "to produce the native or indigenous strains of mycorrhizal fungi. . . the ones that are already adapted to his [or her] particular soil conditions." This could be especially important on problem soils, such as those with high aluminum, say, or high or low pH, where commercially-produced fungi may not survive.

Growing fungi in real life: David Douds with one of his on-farm mycorrhizal fungi production systems at Shenk's Berry Farm in Lititz, PA. John Shenk, the cooperating farmer, grows 5 acres of strawberries, 3 acres of raspberries, and 10 acres of mixed vegetables in a low-input system, selling on-farm and at the Clark Park Farmers Market in Philadelphia. "We try to farm thoughtfully," says Shenk. "And do lots of reading and research to keep improving our farming methods." Next season, Shenk will incorporate the soil from the enclosure into his greenhouse potting mix.

Last but not least, home-grown mycorrhizal inoculum can be produced at a fraction of the cost of purchasing commercial mixes. "I've done some preliminary calculations," says Douds. "The on-farm system produces 100 million propagules [in a single enclosure] for approximately $50, not counting the cost of the farmer's labor, which is fairly minimal. To purchase 100 million propagules as listed on the bag of some commercial mixes would cost anywhere from $8,000 to $40,000." Commercial inoculants are sold in a peat- or vermiculite-based medium, so purchasers have to buy (and pay to have shipped) a large volume of material to get a small number of viable MF propagules--another reason it makes more sense to grow your own.

At the moment, Douds' system (like commercial MF inoculant) is suitable for two types of farms: vegetable growers on any scale who produce their own seedlings and can mix the inoculum into their potting mix; and smaller, labor-intensive farms or urban gardens where "the inoculum can be incorporated by hand, directly into the planting furrow or planting hole." Farmers growing field crops on a large scale can only take advantage of MF inoculants if they want to try them out in a relatively small area. "Delivery of MF inoculum to the field is a problem," acknowledges Douds. "Commercial companies are working on this for their particular inocula." He smiles. We can only hope that he will be too.

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I remember the article and am happy to read it again and save to my computer. I kept back issues of the magazine but they all seem to be in storage somewhere. In the mid1990's I participated in some trials using Japanese mycrorh. mixes (EM, or Effective Microbes, and fermented compost product called Bakashi. Not sure of the spelling). On poor and some non-organic farm ground, the products worked well but on good ground managed on organic principles, the products showed less effect.

Both enhanced composting as inoculates. My compost operation continues with minimal odor and good end products from earlier innoculations. A couple of years ago, I ran a few windrows without using coarse siftings from the composts descended from those innoculations. The products were different, including early odor problems.

I found both articles very intriguing. Thanks for posting. Now I'm wondering how I might introduce some MF into my own seedlings/raised beds. Have any of you tried this or a similar method?