[Terrapreta] Soil Food Web

[David Yarrow]

i just scanned a chapter from "nutrition rules!" -- a book of interviews by australian green revolution wizard graeme sait, founder and CEO of nutri-tech solutions,  graeme interviewed 22 leaders in sustainable, organic and ecological agriculture in north america and published them all in one juicy volume.  i happen to have scanned the interview with soil food web innovator dr. elaine ingham.  i think she's great, but definitely would be puzzled by the inert role of char in her soil food web.  but i'm sure she'll get it as soon as someone gives her the simple, blunt description.

in the meantime, enjoy the conversation pasted below.  you're guaranteed to learn a lot:

SOIL HEALTH - MICROBE MANAGEMENT

PROF ELAINE INGHAM

Interview recorded December 2000

 

Dr Elaine Ingham, Professor of Microbiology at Oregon State University, is one of the world's pre-eminent microbiologists, but her academic achievements almost pale in comparison to her invaluable contributions to sustainable agriculture. Her efforts in promoting practical implementation of research findings are unique in that she has bypassed the alienating ivory tower, intellectual bureaucracy and taken her message directly to the people. Dr Ingham's common sense pragmatism, combined with rare communication skills, promise to elevate her to the forefront of the upcoming biological revolution in agriculture. Her international presentations to farmers regularly generate standing ovations, but the importance of her research work was illustrated most poignantly in a recent Internet news bulletin, titled 'Elaine Ingham Saves the World'. This bulletin referred to evidence presented at a Royal Commission on Genetic Modification in New Zealand. At this forum, Dr Ingham referred to a genetically modified bacterium called Klebsiella planticola, which had passed the normal assessment process (involving thirteen different labs) and had been approved for field trials. This much-heralded GMO apparently had the potential to replace fossil fuel as an energy source via the production of an inexpensive alcohol alternative. The GMO could produce this alcohol from post-harvest crop residue and the remaining organic sludge, which still contained the GMOs, was destined to be returned to the farms as organic fertiliser. Somewhere in this simplistic scenario, someone forgot to test the bacteria with living plants. Dr Ingham's research team conducted these trials and found immediately that these GMOs could utilise the sugars dumped in the root-zone by the plant (ironically, to encourage beneficial micro-organisms) to produce alcohol. The problem was that they produced a lethal dose of alcohol (five times more than any plant could handle) and Dr Ingham described trials where, in seven days, all wheat plants turned to slime. If this organism had been released to the world at large (as it almost was), it was quite conceivable that a large proportion of our plant-life could have been negatively affected, which in turn would affect all life on earth. In the recent past, we have mobilised ourselves against injustices like the Vietnam war. What does it reflect about our current state of apathy that there is no uproar against GM abominations which are far more menacing? Where were the headlines when we just came so close to monumental disaster? In the following interview, I seized the opportunity to submit all of my personal questions in pursuit of more knowledge of a subject I love intensely. I trust that you will all find this interview as illuminating and enjoyable as I have.

 

SOIL HEALTH - MICROBE MANAGEMENT

 

Graeme: I understand that you are setting up a Soil Food Web lab in Australia.

Elaine: Yes, we are ready to open in a couple of weeks. It's situated at the Southern Cross University in Lismore, NSW [editor's note: this facility is now open].

Graeme: That's nice and close to our head office. It should give us a chance for more in-depth diagnoses with problem soils.

Elaine: That's great. Let's work together on this.

Graeme: You are becoming a regular visitor to Australia, but I've not had the oppor­tunity to talk to you before. You were wonderfully well received at this conference. Are all of your audiences in the US this supportive, or are the Acres people a little more receptive?

Elaine: There're a lot of audiences that are this receptive, some even more. It's really astounding to receive standing ovations, but this has happened to me several times in recent months. On the other hand, sometimes I strike people who are more chemically oriented, and there is significantly more antagonism. They give me a lot cooler reception.

Graeme: Is the cool treatment from growers or chemical salesmen?

Elaine: Often from the salespeople. It's silly, because they must realise that part of the reason that the biological approach is growing so fast is because these people have not offered an approach that works. There is no reason why they can't begin to market biological products, and many: of them are beginning to realise this.

Graeme: Well, they would find it a lot more satisfying and probably easier than being involved in the cut-throat, competitive world of commodity dealing.

Elaine: I agree that there is no doubt about that.

Graeme: Some of your findings have been real penny-droppers for our company when working with problem soils. Your beautifully simple three-pot experiment, which illustrated the biological link to calcium retention, is a classic. We are finding that many of these problem soils are deficient in fungi. What do you consider the major factor in the destruction of fungi in our soils?

Elaine: Well, every time you plough, you destroy fungal biomass. When you put out high levels of inorganic fertiliser, you kill off beneficial microorganisms. Even things like pesticides, which we don't consider to be fungicides, are in fact also killing offthe fungi.

Graeme: More so than bacteria?







Elaine: Yes, definitely, and herbicides are particularly destructive. Most of them double as fungicides. Actually, many of them are bactericides as well. So you are re­ally hammering the whole foodweb when you are using these chemicals. Nobody re­ally understands this fact, because manufacturers are not required by any government on the face ofthe earth to put that additional information on the labels of these chemicals. This really needs to change. You need to know that when you put down Lorsban, you are not just killing problem insects, but everything beneficial in your soil.

Graeme: You think there should be cigarette pack warnings?

Elaine: [laughs] Yes, "Caution, this product is detrimental to the health of your soil!

Graeme: Do you see the fungi destruction associated with cultivation as an argu­ment in favour of No-till farming?

Elaine: Yes, in some cases where you don't want to be destroying the fungi, but on the other hand, sometimes with No-till your soils can move too fungal for the crop that you are trying to grow. So you need to understand those warning signals and then you plough it to bring it back to the appropriate balance.

Graeme: And is this one of the concerns of No-Till farming?

Elaine: It can be, but we have a long way to go until we have to worry about wide­spread fungal dominance in our agricultural soils. It only really happens when people have overused humic acid or other fungal stimulants. Actually, it usually happens in really intensive horticulture. We see it most often in golf courses.

Graeme: We have developed fungi-building programs which feature humic acid, kelp, fibrous compost, etc., along with fungi-based inocula. You mentioned fish oil in your lecture today as another fungi food. Would there be a gain in applying pure fish oil to the soil?

Elaine: In theory there certainly would be, because pure fish oil is almost perfect fungi food. However, we have never researched the benefits to know for sure.

Graeme: We like kelp as a source of complex carbohydrates for fungi building. What are your opinions of this material?

Elaine: Yes, kelp is a good material for this purpose. It also contains a full range of micronutrients. Many of these are no longer in our soils, but they are required for mi­crobe health.

Graeme: Are there any other fungi-stimulating materials you have been working with?

Elaine: Yes, we have been doing some work with Yucca shidigera. This material is a great fungal food and it also stimulates bacteria. In our recent research it has also proven detrimental to root-feeding nematodes.

Graeme: We have been working with another plant saponin product which is toxic to snails. Do you think that this may have similar benefits to Yucca as a fungal stimu­lant?

Elaine: I'd love to look at this. I suspect that saponins in general will have a similar positive effect, it's just that in the US the only saponins available without preservatives are Yucca-based. People really need to be aware that any product that is added to the soil or compost or compost tea should not contain preservatives. A preservative, of course, is designed to prevent microbial growth.

Graeme: That's a good point, because often even organic products are stabilised in this manner. Another question - For some time we have offered simple, inexpensive plate count tests to provide a rough indication of soil life activity. I realise that this is far from perfect, but is there any gain from these basic tests?

Elaine: Unfortunately you miss most of the bacteria and fungi with a plate count. It is notoriously unreliable. Many species simply won't grow on a plate.

Graeme: There is some debate about the appropriate amount of humic acid to apply in one application. Can you help clarify this confusion?

Elaine: Well, in our case we rely upon our soil life audit to determine appropriate ap­plications of humic acid. Humic acid offers other benefits, but as a bio-stimulant it has no effect on bacteria, it is purely a fungal stimulant and the amount required in this con­text depends upon the test data. If fungal levels are a little low, then one litre of humic acid per acre (2.5 litres per hectare) will be productive. However, if the active fungi are almost zero, but we have a good total fungal biomass, then they need a good kick-along and we might apply three gallons of humic acid per acre (25 litres per hectare).

Graeme: I'd like to ask some details about fungi I bacteria ratios to try and get a better handle on some of these things. You have stated previously that you need 600 million bacteria per gram of soil involving 20,000 species. How many fungi are needed?

Elaine: In a good, healthy agricultural soil we are probably looking at 5,000 to 7,000 species of fungi per gram of soil. We can't grow those fungi on plates either, so we haven't really understood that they were there, that they were functional and doing things. That's why a direct count is so much more accurate.

Graeme: Are you referring to DNA analysis?

Elaine: No, we actually dilute the soil and then measure the length and width of the hyphae that we see in a certain volume of soil. We can measure biomass in this way, and there is a correlation between the amount of biomass and the species diversity. That is why we say that you have to have a minimum of200 micrograms of fungal bio­mass, because that means that ,you probably have this associated species diversity. The DNA method, by contrast, is very expensive. For example, to do fungal species diver­sity in a gram of soil would probably cost between US$2,000 and $3,000, while bacte­ria counts are around U8$1,000. Our method is not quite as accurate, but it is only a fraction of this price.

Graeme: We recently encountered a NSW avocado grower who had piled 15 tonnes per hectare of lime on his soil over a three year period, but the calcium never seemed to be present in subsequent soil tests. You have demonstrated a connection between fungi and calcium retention. His test with your lab revealed extremely low fungal levels, par­ticularly considering he was growing a tree crop. He had wood chip mulch and other conditions suitable to fungi, and he practised sustainable farming. What was the likely cause of this fungi deficit?

Elaine: Well, for some reason, sometime in the past, the fungi were killed in that soil, so he will need to put an inoculum of the fungi back in there. The fungi may not be re­turning because there is residue of a fungicide, pesticide, herbicide or nematicide, or a combination of these, which still remains in that soi~.

Graeme: We do a lot of work with orchardists and we often find very high copper levels in the soil as a result of copper fungicide residues. Could this be contributing to a lack of fungi?

Elaine: Absolutely! I'm often amazed at some of the organic growers who are putt­ing on copper sulfate as ifit were a harmless material. It is a killer of the organisms in the soil. Problems begin when copper gets above three parts per million in the soil.

Graeme: Only three parts per million! We are dealing with citrus growers with 500 ppm of copper. Under a microscope you can actually see the blue flecks. Is there any point in trying to address fungi shortages in these soils?

Elaine: Yes, most definitely. The trick is to get organic matter back into those soils to tie that copper into the structure of the organic matter so its no longer in a biologically available form.

Graeme: Would humic acid be.ideal for this?

Elaine: Yes, this is the material to use. The copper becomes sequestered inside the complex structures of the humic acid or fulvic acid.

Graeme: Is fulvic acid an option in the soil? We recently had a potato grower mix his nitrogen side-dress with fulvic acid, and this nitrogen appeared to disappear over the following days. We wondered whether it had bonded with the fulvic molecule and rap­idly leached, due to the very small molecule size of the fulvic acid. What do you think?

Elaine: I suspect that you were looking at a bacterial bloom. Fulvic acid does feed fungi, but it is a very effective bacterial food. You would have generated such a bloom of bacterial growth that the bacteria were sucking up the applied nitrogen. Typically, nitrogen is not absorbed very effectively in the fulvic molecule. N03 and NH4 are not really that reactive with fulvic acid.

Graeme: During your presentations, there is very rarely mention of the mineral link to microbe health. I am always insisting on the importance of the calcium / magnesium ratio to provide oxygen for microorganisms. You have highlighted calcium retention. How important do you see calcium and other minerals for microbe welfare?







Elaine: I agree that it's extremely critical. The only reason I don't cover this mineral link is due to lack of time during my presentations. It's not a simple subject - it would take several hours to explain. It's not just the effect of minerals upon the microbes. It's a feedback system. Microorganisms will influence the way micro-nutrients are held, where they are, and uptake ofthose minerals in the soil. However, if the calcium is not there to flocculate the soil, there is simply inadequate housing conditions for micro-organisms, particularly bacteria, to flourish. The bacteria need to get in there first, to pave the way for the fungi. In high-magnesium soils, for example, the housing condi­tions for bacteria are so poor that they become very vulnerable to all kinds of environ­mental changes in weather, temperature, moisture, dry conditions, etc, but probably more importantly, without soil flocculation and the associated provision of good living quarters, bacteria and fungi are vulnerable to the predators. They get eaten and then they're gone. It's like the homeless having to live under a bridge in winter. There's no place to be safe and secure. When you bring in the calcium and flocculate the clay strUcture, now you have all these little apartments for the bacteria to grow in.

Graeme: Another question about microbe health and safety. The eco-agronomists are strongly against muriate of potash, due to the microbe killing potential of a material containing 50% chlorine. You suggested that the damage potential was governed by soil type. What limits or magnifies chlorine damage, and how much can be applied safely?

Elaine: This is a topic we really need to look more closely at. There are other vari­ables involved here. For example, the amount of organic matter plays a role in damage potential. Potassium reetention is also so dependent upon the type of clay present. Kaolinites, for example, adore potash, and it ends up inside the clay structure, and it's like a never-ending storage compliment for potash. Whereas, in a montmorillonite soil, you can't tolerate much potassium going into that system, because there's no place to store it. It's highly variable - then you add organic matter to the equation. How much potash is going to be absorbed onto the reactive sites on that organic matter? We need to do some in-depth work here, but who is going to finance this? Really, the US or Aus­tralian Governments should be offering funding to look at these critical questions regarding how does biology and chemistry work together?

Graeme: In a soil with high electrical conductivity (Ee), with high EC irrigation, is it possible to establish a viable microbe population and get them to flourish?

Elaine: You can choose bacteria or fungi that tolerate those high EC or high salt con­centrations. We work with some sandy soils in California, where we are trying to get decomposers working to increase organic matter and tie up the salts in the structure of the organic matter.

Graeme: Can humic acid playa role here?

Elaine: Yes, it certainly can, but ideally you need more reactive carbon to initiate this whole process. Humic acids can be brought in after things have been started - after the bacteria have become established through stimulation with simple carbohydrates.

Graeme: After some of your lectures in Australia, we have growers, with soil pH's of over 8, who are trying to breed and apply fungi. Is there any point when the pH is completely unsuitable? Can a correct bacteria to fungi ratio ever be developed in these soils?

Elaine: The fungi will still grow at those high pHs. That's not a problem, but what the fungi will do is gradually reduce those high pH conditions. Fungi produce organic acids that have a pH between 5.5 and 7, and these acids will move the soil towards neu­tral. The fungi just need the right soil. Growers have often been concentrating on bac­terial food rather than fungal food.

Graeme: I know that many people have been-influenced by the American consul­tants recommending sugar and molasses, but this may sometimes be counterproductive, as it only feeds bacteria.

Elaine: That's right. This is bacterial food, and the bacteria outcompete the fungi every time. If anything, they will be magnifying their poor biological balance. In many cases these sugars will leave them worse off than if they had done nothing. Then they can watch their pH go to 9.

Graeme: You have suggested that inocula are questionable, because they will not necessarily perform in localised conditions. We have an Azotobacter product with which we've had exceptional results in all soil types, and we also have several other problem-solving microbe products, which have also proven very reliable. How is this happening?

Elaine: Well, in the case of Azotobacter, there are only a limited number of strains. If someone could include all 126 strains in a single blend, it might work in any conditions all around the world.

Graeme: That's exactly how this blend is formulated. In fact, a development team has identified a total of over 200 strains and all of them are included in one blend.

Elaine: If you can supply a functional group covering all strains, you are potentially covering every condition. If you introduce this type of blend to a soil that has been re­ally hammered, then there are a lot of niche spaces there and nobody to compete with them. Indigenous species were often not designed to survive in a ploughed field. They often can't thrive in conditions with so little organic matter. There is a place in these situations for an inoculum with more versatility. However, when you have reclaimed that field by building organic matter and biology, then the natural species will compete more effectively with the introduced species. When you concentrate on an inoculum featuring just one genus, you have a far higher chance to succeed.

Graeme: What about inocula containing a wide variety of species?

Elaine: Again, in poor soils they may be of benefit, but in a soil with well-established food web they will probably fail to compete with the indigenous species.

Graeme: Is there any risk that, by adding a huge amount of bacterial inoculum and feeding the newcomers with sugar, that the entire foodweb can be thrown out of balance?

Elaine: We can often assume that an inoculum is used because of a lack of soil-life. If the housing conditions aren't there, how do we expect the new additions to survive? I have sometimes seen completely inappropriate species included in inocula and they can cause imbalances. Ifthey overwhelm the system, we can see root symptoms simi­lar to a disease. Here we have to come back in with a compost with a huge diversity of microorganisms to restore balance.

Graeme: Another question about fungi / bacteria balance - When making compost tea, the bacteria breed far more rapidly than the fungi. W ouldn't the end brew be com­pletely unbalanced for this reason?

Elaine: You can encourage fungi growth in that medium, so long as you supply a sur­face for the fungi to grow on. This is why it is important to add kelp or humic acid to the brew. It is also important to restrict brewing time to 24 to 48 hours from a fungal point of view. After the fungi have germinated, they don't survive well in this medium be­yond two to three days. Some of the more recent compost brewer designs use a vortex effect rather than putting the mixture through pipes. The vortex oxygenates the mix­ture without dislodging fungi from the surfaces. These designs are more effective in ensuring a good fungi to bacteria ratio in the end brew.

Graeme: How important is the design factor in the efficiency of the compost tea brewers? Is there any potential for growers to construct their own inexpensive equip­ment, using 1 OOO-litre tanks and spa heater / blowers? These could be constructed for a fraction of the price of commercial modules.

Elaine: As long as the aeration is good, they would probably be acceptable, but I would like to test the compost tea to determine how well these DIY machines perform. The 'Soil Soup' people produce a really good aerating / mixing nozzle, which they sell separately. You supply the tank and pump. They can supply nozzles to aerate tanks as large as 2000 gallons. I've tested tea made from their 500-gallon tank, and that's wonderful stuff.

Graeme: We often explain herbicide damage in terms of destruction of algae and as­sociated loss of this carbohydrate food source for soil-life. We recommend the use of fulvic acid with herbicides to isolate residues and speed the biodegradation of those residues. Do you consider this a worthwhile practice?









Elaine: I've never done this before, but it does sound like a very good idea, and in theory it should work well. However, I'd still like to test the idea. I always like to have test data. It would actually be quite simple to test. We would just need to measure foodweb differences with and without the fulvic detoxifier.

Graeme: Do you have any tricks to replenish the algae which have been decimated by herbicides, or are there additives which can substitute for this disruption in carbo­hydrate production?

Elaine: We have had very good results when researching Yucca shidigera. This is a steroidal saponin, which is a particular complex carbohydrate that we have found to be very effective in this context. It is really a band-aid to some extent, because algae can breed and increase and continue to supply food indefinitely, while Yucca is just cor­recting an immediate deficit.

Graeme: Yucca is very expensive in Australia, but could our inexpensive saponin product, which I mentioned earlier, be used to compensate for algae losses?

Elaine: In all likelihood it could be. We would be very interested in testing that mate­rial to determine its potential. In general, I would prefer to see growers reduce or re­move herbicides by improving the balance in their soils. Weeds are a symptom of a poor mineral and microbial balance and, the more balanced the soil, the less the weed pressure.

Graeme: Yes, sometimes it can be quite dramatic. I have photos of a timber tree crop where we were only asked to fertilise and balance the l.5-meter wide growing strip which contained the trees. In just four months, the inter-row area (which was pretty rough, recently cleared scrub) was a jungle infested with weeds and regrowth. The grower was intending to herbicide following his return from an extended holiday. The area, which had been minerally balanced and microbially activated, contained just the occasional weed. It was like chalk and cheese.

Elaine: Yes, it can happen quite rapidly. You're getting rid of those weeds because they do better when there's low oxygen concentrations in the soil or if you set up the right conditions for weeds to prosper, like high nitrates.

Graeme: The problem is that, when you are dealing with broadacre crops, there is simply no budget for major soil corrections, and the potential to balance soils for weed control just isn't there.

Elaine: Yes, I admit that this can be a problem.

Graeme: If there is a shortage of fungi in most soils, would it be safe to assume this

biological deficiency, and to begin a program to rebuild fungi without prior testing?

Elaine: Yes, we often suggest that a fungal food feeding regime is instigated, and a year down the track we begin testing and see how far we've gotten.

Graeme: I always like to try to tie in various systems, to take pieces from every­where in an attempt to gain a deeper understanding. There are times when we have completely balanced a soil, yet brix levels remain inadequate. We often use a LaMotte test at this stage and fmd a lack of biologically available calcium, and leaf tests will also show a calcium deficiency. It seems that this widespread lack of fungi may be con­tributing to the calcium shortage. What do you think?

Elaine: Yes, quite often it is a lack of mycorrhizal fungi on the root system, and this is a very important problem which should be addressed. The fact is that, if you use pes­ticides or herbicides regularly, it is unlikely that you will have healthy mycorrhizal fungi. In fact, in many cases you won't have any at all. This is where you will need a mycorrhizal inoculum to get them back in there.

Graeme: Is an inoculum based on these fungi difficult to produce?

Elaine: It is very easy to produce a very stable mycorrhizal inoculation, because they produce some great external spores, and so you just harvest those spores and there's your inoculation.

Graeme: Would it be applied in liquid or dry form?

Elaine: You can apply it in a carrier. Sometimes we will grow seedlings in mycorrhizal spores before transplant, or we can dribble a row of spores underneath the seed at planting. For established plants you can put cores down next to the root system and refill that core with a combination of compost and mycorrhizal spores. If you want to introduce mycorrhizal spores to a compost tea, then you introduce them immedi­ately before applying the brew. If you introduce them before brewing, then they will germinate and the brewing cycle will kill them. It is important to use indigenous mycorrhizal fungi, so an effective inoculum would probably need to be manufactured in Australia.

Graeme: The problem, of course, in conventional agriculture is that you inoculate and then move in with herbicide and you're back to square one. The cotton growers in Emerald are having problems with something called 'Long Fallow Disorder', which is essentially a shortage of mycorrhizal fungi called V AM. They believe that the only good plant is a dead one if it' s not cotton. During fallow periods everything is killed off and nothing remains to sustain symbiotic species like V AM. There seems little point in trying to correct a situation like this, when there is no accompanying change in man­agement practices. Is there anything these guys can do to improve things?

Elaine: I bet they have fusarium problems as well.

Graeme: Yes, they do.

Elaine: Well, that's why. Yes, there is something they can do about it, apart from the obvious solution of removing the toxins from the system. They could plant an understory - underneath the cotton plants - of some real short-stature, fungal-domi­nated plants. There are a number of very hardy plants like this, which you can drive over and abuse to your heart's content, but all the while they will be supplying mycorrhizal fungi to the root-zone of their cotton crop.

Graeme: What sort of species would you suggest?

Elaine: There are some really short mint plants that work. There's lavender - basi­cally very short-stature, perennial plants. Typically, you under-seed with these plants when you are planting the cotton. These plants don't get any higher than a half inch to two inches, so they are never a problem. If it gets too dry, they may become dormant but they leave a good mat of roots, so there's no erosion. More importantly, these roots are dominated by the right kind of mycorrhizal fungi, so there's your inoculum all the time - even when you rip up the cotton, the mint or whatever will continue and you can replant amongst it.

Graeme: So it becomes no-till, in effect?

Elaine: Well, if you want to plough, then you plough down the strip where you are going to plant the cotton, so you don't have tlle erosion or loss of nutrients associated with constantly working the soil. I just don't understand why growers don't do these sorts of things. They work.

Graeme: Well, it certainly sounds like something the cotton growers should be look­ing at. Actually, while we are talking tillage - Are you familiar with Don Schriefer's tillage methods. ie leaving com roots in the Qround to rot and nlantinQ the next crop like soybeans, in between the old corn rows with deep-ripping, to break the hard pan below the new crop each year, if needed. Is this approach more sustainable from a mi­crobial perspective?

Elaine: You mentioned the concept of deep-ripping to remove the hardpan at four feet or four inches or whatever. The reason the pan is formed is because the soil got compacted, then went anaerobic. It always is the microorganisms getting the life back into that hardpan that opens it up and prevents it from reforming as a compacted hard­pan zone. Soil-life is the key. It needn't take very long with biology. Work at Ohio State University shows that you can break up a hardpan at four inches in six weeks by just getting the right kinds of fungi into that soil. You can break up a hardpan at four feet in six months.

Graeme: Do the beneficial microbes work at that depth?

Elaine: Yes, but you need the 'taxi cabs' to move the organisms down to that depth, so you have to have the micro-arthropods functioning in that system. They are the ones that cart the microbes down there. You can't rely upon water. Earthworms, centipedes, millipedes, beetles, beetle larvae, springtails - these are the taxicabs to get the benefi­cial microbes down deep.

Graeme: Everyone talks about the top six inches as the aerobic zone where the biology happens - This is a new perspective.

Elaine: There are some misguided ideas about how far down soil goes. If you have­n't messed up your soil structure, it is actually possible to sustain soil-life down to twelve miles. That's how far we've gone. It's only because we have messed up the soil and put in those hardpans at four inches that we have this idea that it is naturally anaer­obic and not alive below that level. Anaerobic organisms are alive, but they don't al­low root growth. In agriculture, when we moldboard-ploughed, we only went down four to six inches, so that waS where the hardpan developed. Now we go in and deep-chisel or we rip and we go down to four feet, so that's where the hardpan is form­ing. Now the USDA only defines soil as going down four feet - Duh! I wonder why! [laughs] .

Graeme: Can plant roots grow in anaerobic conditions?

Elaine: Anaerobic bacteria produce organic acids with an average pH of2. There is no plant that will grow its roots into this kind of acidity. That's why I talk about aerobic bacteria with a pH above 7. I talk about fungi with pH buffered between 5.5 and 7. How does a soil get below 5.5? - Anaerobic processes - You're messed up big time when you see your pH go below 5.5.

Graeme: You have suggested that anything more than 200 kg of salt fertilisers per hectare in a single application is detrimental to microbes. Most conventional growers apply more than this. How detrimental is it, and can damage be reduced by buffering with compost or humates?









Elaine: It is quite destructive and it can be buffered by humates or compost, but, in a lot of work that we are doing all over the United States, we have taken growers to the point where they don't apply any fertiliser. Probably the best research example is 'Eco Systems' at the University of Georgia - a project that started back in 1981. In 1984 they stopped using pesticides and herbicides. There are no insect problems and minimal weed problems. In 1986, they stopped using fertilisers. The green manures that they use in those systems supply the nitrogen needed. Their yields of com are higher than the conventional system every year. If you can supply a very good compost as an inoculum of full biological diversity and if you supply the foods to feed all of these organisms year after year, then you don't have to use fertilisers. Good compost is the key here. If you go anaerobic while you are producing compost, then you just lost all of your nitro­gen. It just left as ammonia - it was volatised. You also lost all of your sulfur as hydro­gen sulfide - the gas that has that rotten egg smell. You also lost most of your iron as iron sulfide. You simply don't have the nutrients left in something that is in essence 'putrefied organic matter'.

Graeme: That's a romantic way to describe any compost not up to your standard! [laughs].

Elaine: [laughs]. Well, you have to make it messy. You have to make people under­stand.

Graeme: Yes, I know - and that's your great gift. You can really drive home these is­sues. Another question I have been wanting to ask you - You'll have to excuse the number of questions - I use this interview series as a tool to increase my own knowl­edge. The readers are basically forced to share in my learning process [laughs]. I wanted to ask you about organic matter testing, as this is a major issue affecting micro­organisms. There is some debate about the respective validity of different organic mat­ter measuring techniques. Can you clarify the confusion?

Elaine: The whole issue of measuring organic matter is in a state of flux at present. I look at each lab and try to interpret them based upon their own limitations. The stan­dard USDA-type tests, for example, tend to underestimate the amount of usable or­ganic matter available, while some of the Albrecht-style labs, like the Perry labs, tend to overestimate the actual microbially active organic matter which could be utilised by bacteria and fungi. The reality, from a biological perspective, is somewhere between these two numbers. The bottom line is that, if your organic matter level is above 3% on any test, then you have a decent amount of organic matter feeding your organisms. Ide­ally, I would like to see organic matter up around 8%, because then I know that I have the full smorgasbord of food to feed the full spectrum and to promote nutrient retention, nutrient recycling and disease suppression.

Graeme: Unfortunately 8% organic matter is a fairly rare occurrence in Australia.

Elaine: Well, your soils in Australia are very weathered. They're ancient soils, so you really need to put an effort into building organic matter in these soils. The parent material, the clays which confer storage capacity, are old - they are essentially worn out and you've got to use organic matter to get the fertility back.

Graeme: There are small pockets like Northern NSW, for example, which have ex­ceptionally high organic matter, we have seen soils that contain up to 18%. Are there any problems with excessive organic matter?

Elaine: There can be a problem in these soils in maintaining structure. If you start compacting 18% organic matter, it's really easy to have it collapse. Then you have stinking, smelling, putrefying organic matter. You have to maintain the life in that soil to maintain the structure. I love soils like this - If you can build a good foodweb within them, then you can grow spectacular produce - Alaska-size vegetables, 200-pound pumpkins, two-feet carrots and wheelbarrow-sized cabbages.

Graeme: From a grower's perspective, green manure crops and cover crops are a far more cost-effective proposition than compost, if you are trying to build organic matter - do you think there is a role for inocula to speed the conversion of organic matter to or­ganic carbon, particularly if the grower is just starting in biological agriculture and there is no guarantee of a good microbe base?

Elaine: Yes, definitely. It's almost like you have to inoculate in those conditions, be­cause you're not going to have your own premium compost available. Get it started, hedge your bets and give it a chance to get as much starting diversity as possible. Once the wheels are in motion, you will develop your own sets of organisms.

Graeme: How do you feel about adding a little commercial nitrogen to the picture before you shallow-incorporate your green crop? If there is any doubt about the amount of nitrogen present in relation to the large bulk of organic matter, we usually recommend some extra nitrogen to really make the most of your limited opportunity to build carbon efficiently.

Elaine: No, I don't have any problems with this. It's a good idea, as long as you have a healthy foodweb and you don't exceed 100 kg of nitrogen per hectare.

Graeme: One more question regarding inocula. I'm always a little concerned about their use in cold temperatures. We have numerous growers using our Bio- N and Bio-P products for seed treatment. Often, when they plant in winter or early spring, the soil temperatures can still fall below 5°C, which would normally slow down the bacteria. There is still a gain in treating seed, regardless of climatic conditions, because the juices that house the dormant cysts in these products contain a range of growth hor­mones that kick-start seedlings. However, I'm always wondering just how well the Azotobacter survive this cold start.

Elaine: The organisms form dormant structures in freezing conditions and they liter­ally wake up in spring. You don't actually lose them. The better the soil structure in terms of aggregates, the less likely they are to actually freeze. However, if you have no aggregations, then many species may not survive a freeze.

Graeme: Thanks for giving me so much time. I've really enjoyed talking to you. I'll send you a copy of Acres Australia when the interview is published.

Elaine: It was a pleasure. I'm looking forward to you corning down and visiting the new lab at Lismore. I'd love to show you around to see what we are doing.

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