The creature most often missing in agricultural soils is a fungus that burrows into the crop roots. This usually evokes images of an undesirable parasite but this is not a disease organism. Once this creature is locked into a food source from the plant, it gives far more than it receives. In fact, that flow of root sugars is repaid handsomely. The soil, the other root zone microbes, the plant, your livestock, your family and the planet are all beneficiaries of this exchange. This generous life force is called mycorrhizal fungi and it has become an unfortunate casualty of extractive agriculture. Fungicides, herbicides, acid phosphates, salt fertilisers, nematicides, fallow periods, compaction, erosion and tillage all take their toll, to the point that many soil life analyses reveal serious decimation of this essential symbiont.
There are two forms of mycorrhizal fungi, one that surrounds the plant roots and another that physically attaches to the roots. In both cases they harvest sugar exudates from the plant. Ectomycorrhizal organisms form a fine spidery web around each root and they are limited to conifers and some hard woods. However, the more intrusive of the pair is much more prevalent.
Endomycorrhizal fungi should be found attached to the roots of over 80% of crops. They were originally called VAM (vesicular arbuscular mycorrhiza) but their classification was recently changed to AM or AMF (arbuscular mycorrhizal fungi). Their maze of hyphae filaments effectively increases the original surface area of the roots by up to 1000% with a remarkably productive outcome. Root benefits are magnified tenfold and the plant is perfectly positioned to achieve its true genetic potential. The only plants that do not attract mycorrhizal colonisation are brassicas and the chenopods. Brassicas release chemical exudates that repel nematodes and these same chemicals also discourage AM Fungi. Chenopods flourish in salty or alkaline soils and include saltbush, sugar beet and spinach.
AM create structures within root cells called arbuscules that facilitate the transfer of nutrients between the plant and the fungus. Fossil studies reveal the presence of these creatures 500 million years ago but they were first recognized last century and serious study has only begun during the past three decades. It is now acknowledged that these compromised creatures may be the single most important tool available to reverse global warming. Over 30% of the offending CO2 in the atmosphere originated from the soil due to the massive humus loss since the Industrial revolution (470 thousand million tonnes). In 1996, a researcher called Sara F. Wright, discovered glomalin, a sticky substance produced by mycorrhizal fungi that generates stable humus in the soil. It is apparent that the decline in humus mirrors the decline in AM in our soil and now we understand why!
The Humus Imperative
Soils are carbon sinks with more potential to keep carbon out of the atmosphere than plant biomass. We are already paying carbon credits for planting trees but there is a desperate urgency to extend those rewards to those building humus in the soil. Carbon is stored in biomass for an average of ten years but that critical storage time extends to forty years when it is stored in the soil as stable humus.
The principal producers of stable carbon are mycorrhizal fungi and glomalin is a huge player. This substance is produced by glomales, the taxonomic order of which AMF are a part. These fungi use sugar exudates (carbon) from the plant (carbon) to make glomalin. This remarkable material permeates organic matter, binding it to silt, sand and clay particles in the soil.
The substance itself contains 40% carbon but it also creates aggregates that stabilize carbon in the soil and prevent its return to the atmosphere as part of the carbon cycle. As a glycoprotein glomalin stores carbon in both its protein and carbohydrate sub-units. Glomalin contributes much more nitrogen and carbon to the soil than do hyphae or other soil microbes. Glomalin contains 1 – 9% tightly bound iron and researchers wonder whether these large amounts of iron could be protecting the plants from pathogens.
Research now suggests that glomalin accounts for over one third of the stored carbon in the soil and that carbon remains in the soil for four decades! It is not too difficult to imagine a time in the near future where there will be legislation protecting these critically important, humus-building organisms. Unfortunately, much of modern agriculture involves practices that compromise AM fungi. This is one of many reasons why biological agriculture is the shape of the future.
Reducing The Fertiliser Bill
While humus building is obviously important at this point in the planet’s journey, there are many other benefits associated with increasing the number of AM fungi in your soils. One of these relates to the potential to reduce the ever-increasing fertiliser bill. We are currently experiencing another escalation in the prices of NPK fertilisers with an increase in the price of DAP/MAP of over 40% in just six months. There is no end in sight as these non-renewable resources are simply running out. We have already reached “Peak” phosphorous and potassium is not far behind. In the history of non-renewable resources there are unrelenting, ongoing price hikes once it is acknowledged that the first half of a resource has been utilized.
The key strategy for farmers, in the face of this blowout in production costs, is to reduce reliance upon these inputs and to increase their efficiency. AM fungi can provide the key as they effectively enable the recovery of past investments. The ten-fold increase in root surface area provided by AMF allows exploitation of a much larger root volume and the uptake of all minerals is enhanced. However, it is phosphorous that receives the most profound kick along. This mineral is notoriously unstable and it is suggested that over 70% of all applied soluble phosphate becomes locked up in an insoluble form within weeks. It has been estimated that over ten billion dollars of this frozen reserve remains frozen in Australian agricultural soils. The key to accessing this treasure is AM fungi. Many studies have reported increased P uptake and associated improvements in early growth and reproduction following inoculation with mycorrhizal fungi. The maze of pipe-like filaments seeks out this immobile mineral and the acidic exudates of the fungi solubilise locked up P and absorb the mineral for transportation back to the plant.
However, with all good things there are always a couple of cautions. If you over-apply soluble phosphorous, the plant reduces root exudates that feed AMF. The host has less need to feed this fungal P supplier when it already has all of the phosphate it requires. The acidity of unbuffered DAP/MAP can also reduce AM colonization. When these acid granules hit the soil, the loosely held ammonium ion breaks free. The harsh phosphoric acid that remains sizzles the fragile hyphae of AMF like a blowtorch on human hair. The nitric acid associated with nitrate-based fertilisers can be similarly destructive as can nematicides and some fungicides. Benomyl has been shown to be particularly destructive.
AMF and Free Nitrogen
The atmosphere contains the equivalent of 5000 truckloads of urea per hectare. This nitrogen gas, in the atmosphere, is where plants are supposed to access the majority of their nitrogen requirements. However, access to this free gift has been seriously compromised by our mismanagement of soils and our misunderstanding of the benefits of soil biology. Nitrogen-fixing organisms are the key to this access. Several recent studies have shown that both major forms of nitrogen-fixing organisms in the soil improve their performance in the presence of mycorrhizal fungi. These two groups include Rhizobium bacteria, which are housed in the nodules attached to the roots of all legumes, and free-living bacteria, which surround plant roots to access sugar exudates. These creatures convert nitrogen gas in the atmosphere into ammonium nitrogen in the soil and their importance cannot be overemphasized.
Mycorrhizal fungi are the perfect partners for nitrogen-fixing organisms. In fact, American BD consultant Hugh Lovel suggests that there is no microbe partnership that is more productive. It is a synergistic relationship where AM produce a constant, trickle-feed of phosphate for the nitrogen-fixers. These creatures need an ongoing supply of phosphorus to fuel the nitrogenase enzyme responsible for converting the gas into a plant food. In return, the nitrogen-fixers supply nitrogen to build the protein required to create that massive maze of hyphae beneath the plant. If you can get both of these creatures firing there will be a smile on your face because you have seriously reduced your requirement for two of the most expensive fertilizer inputs. Later in this article I will share the secrets to achieving this goal.
Stress Reduction With AMF
Ten times more root area confers many benefits and one of these gains is increased plant resilience. Colonised crops are more resistant to a variety of stresses ranging from drought to heavy metal contamination and reduced plant immunity. Several studies have shown that AMF treated plants fare better in drought conditions. There are several theories about the mechanism involved but it is thought that it may be a combination of additional moisture storage in the massive network of fine pipes (hyphae) attached to the roots, combined with the moisture holding capacity of the extra humus that comes with the AMF package. There is also a theory that improved nutrient delivery indirectly increases the plant’s capacity to withstand drought stress. I personally feel that the bacterial synergists that thrive in the presence of AMF may also be helping with increased drought resistance. These creatures coat the surfaces of the hyphae (called the mycorhizosphere) and they are constantly releasing a sticky biofilm that acts similarly to water crystals in terms of moisture retention in the root zone.
New research shows that AMF colonised plants are more resistant to heavy metals (particularly cadmium, a common contaminant of acid phosphate fertilisers) and they are also highly effective inputs in the restoration of natural ecosystems. Inoculated pioneer grasses planted in dune sand in Florida achieved dune stabilization much more rapidly than the same untreated plants. Some of the most fascinating recent research with AMF suggests that these remarkable creatures may also be improving the plant’s immune system. Induced systemic resistance was increased in colonised plants to the point that researchers suspect that, in some cases, this may even be a more important AMF role than increased uptake of nutrients and moisture.
But There’s Still More
The benefits we have highlighted are substantial and should be of appeal to all primary producers, however, there are still more gains to increasing AMF colonisation in your crop. In 1992, Azcon and Barea showed that AMF inoculated plants absorb and utilize potassium more efficiently. Potassium is the single most expensive fertilizer input and the cost of this input will only increase as world supplies dwindle. AMF can reduce potassium leaching and help gain access to potassium trapped between clay platelets in some soils. In 1994, Maksoud et al repeated these findings in relation to AMF and potassium.
In 1994, Marschner and Dell found that AMF inoculated plants contained significantly higher levels of calcium, magnesium, copper, zinc and iron. In 1999, Alkarati and Clarke repeated those findings.
In 16 years of testing thousands of soils and plants at NTS, we have seen countless examples of low calcium (Ca) in plant tissue tests regardless of the level of calcium in the soil. I am convinced that there is an AMF link to this Ca shortfall. When the acidic exudates of this hyphal mass break the bond between calcium and phosphorus there is an associated release of calcium, which can be uptaken by this network of fine filaments and transported to the plant.
There is a direct link between the absence of AMF and poor calcium availability and there can be great gains in reclaiming access to calcium via inoculation. In 1995, Mathur and Vyas showed that AMF fungi increased photosynthesis by increasing total chlorophyll and carotenoid content. This resulted in increased carbohydrate accumulation and a higher brix level. Every good biological grower knows that if they can increase brix levels there is a consequent increase in yield, quality and resilience. AM fungi are the secret to building brix levels!
Accessing AMF Action
At this point you may be wondering how to increase the AMF action on your farm. There are two ways to achieve this and they include the creation of conditions favourable to AMF, to build numbers and diversity, and secondly, the inoculation of AMF blends to introduce a new workforce in biologically compromised soils. I will begin by discussing strategies to boost your existing biology before sharing some really exciting news about a new NTS inoculum.
One of the key strategies to increase AMF numbers is to involve legumes in the equation. As earlier discussed, there is a special relationship between nitrogen fixing organisms and AMF fungi and the pre-cropping, interplanting and rotation of legumes supports this key connection. I feel that intercropping is seriously undervalued. This involves combining some legumes with your cereal crop. They are not included for harvest but rather as a means to deliver nitrogen, phosphorus and calcium to the cash crop throughout the cycle. Most people think nitrogen when they think legumes but we have found that there are equal gains in terms of phosphate and calcium nutrition. A support crop, like soybeans in a corn crop, does not appear to compete for moisture and nutrition as one might think. Instead it delivers extra N, Ca and P during the reproductive stage when these minerals are most needed. I have always taught that this was related to the acids produced by legumes which help to break the bonds between locked up phosphorus and calcium, making both plant available. However, I am coming to realise that the AM fungi, stimulated by the legume component, may be equally important here.
It is also a good idea to avoid long fallows, as AMF numbers dwindle in the absence of a host. Nematicides are notoriously destructive of AM fungi and this is particularly counter-productive in light of the fact that these organisms are considered a principal bio-balancing rescue option for nematode-affected plants. Over-tillage can slice and dice these fragile creatures and there is another advantage with the no-till approach in that germinating seedlings can literally plug into a pre-existing hyphal network in the soil without the initial need for carbon and protein to kick-start the hyphal mass.
Humic acid and kelp can supply the long chain carbohydrates that AMF fungi love, and both of these inputs are invaluable in this context. However, it has been estimated that AMF numbers have dropped by 90% in many of our agricultural soils and this is where inoculation can fast track your AMF action.
There is little debate about the value of introducing AMF to your soil but the cost of effective inoculation has always been prohibitive. During a visit to Holland, for example, a Dutch researcher shared the details of a local AMF trial on strawberries. The inoculum cost over $3000 (AUD) per hectare and this was not considered cost-effective, regardless of the results. This is why I was so wildly excited when I stumbled across a new, highly effective AMF blend in my travels that had been developed over a 20 year period and could deliver exceptional colonisation for as little as $20 (AUD) a hectare.
And that’s not all. This unique blend also contained Trichoderma – a multi-faceted species with its own benefits. It is not common to see these two species together in spore form as the Trichoderma can eat the AM organisms before they can develop. This is not the case with this inoculum. This AMF/Trichoderma compatibility generates a whole new range of benefits. Nutri-Life Platform® involves a unique species of Trichoderma that lives in concert with the AM organisms in this product.
I was conducting seminars in Africa when I was approached by a broadacre farmer who was part of a group of farmers that had adopted the biological approach following my previous visit to their country. They had formed a microscope club and regularly shared their findings with other group members. This pioneer was attending my four-day course for a second time and he felt that he had to tell me of his successes the previous season. He had used an AMF/Trichoderma powdered blend as a seed treatment and had enjoyed a disease-free season and a 23% yield increase involving top quality grain. He reported complete AMF colonisation of his wheat crop at a cost of just $17 (AUD) per hectare.
I was amazed, as I had never before heard of an AM innoculum anywhere near this cost effective and I had never heard of a single blend that contained large numbers of both species. This passionate grower was absolutely insistent that I had to meet the researcher who developed this blend and new spore technology so he set up a meeting and the seeds were sown. It took us seven months to gain import permits for this blend but we are now ready to launch Nutri-Life Platform®, a breakthrough inoculum that we believe will become an essential base upon which biological success will be built in the future.
Trichoderma in Hardy Twin Pack Blend
One of the great appeals of this new blend is that it has been bred to be hardy in the face of many farm chemicals. It has always been an issue that pickled seed (seed treated with a fungicide) can kill inoculums on the seed but this is not the case with Nutri-Life Platform®. There are a handful of chemicals that may compromise this workforce but they have been well researched so you will know the likelihood of success before you invest.
The inclusion of Trichoderma with four species of AM fungi in Platform® offers another range of benefits. Trichoderma has three key roles in the soil. It is a predatory fungi that can help maintain biological balance in the root zone. It is also a voracious cellulose digester that can convert fibrous crop residues into humus and finally it actively promotes plant growth via the release of supportive bio-chemicals. The largest selling NTS inoculum around the world is Nutri-Life Tricho-Shield™ because it has performed so well in the soil over the past decade. Trichoderma is a proven performer so it is a real treat to be able to offer the two most productive soil fungi in a single, inexpensive blend.
Like AM fungi, Trichoderma has been shown to boost nutrient uptake and research demonstrates improved uptake of nitrogen, potassium, phosphorus and calcium. Growers report potential reductions in fertilizer of 20% to 50%. It is actually advisable to reduce fertiliser rates or the response from both AM fungi and Trichoderma can be compromised. Both creatures scavenge and deliver minerals like phosphorous and zinc and the plant feeds them accordingly. If we over apply soluble phosphorous the plant reduces exudates, as there is no longer a need to feed these delivery boys. It is actually a much better idea to use a natural phosphate source like guano in conjunction with AM fungi and Trichoderma as the plant will continue to feed them to sponsor the controlled release of the phosphorus. Trichoderma has also been very successful as a seed treatment in several countries. There is a claimed germination rate exceeding 95% and the seedlings grow more rapidly and have larger root systems. There is also more tillering and reduced maturity time in the treated crop.
The Mechanics of Platform®
Nutri-Life Platform® contains four AMF species and Trichoderma. The number of spores per gram is impressive. The world standard is 40 spores per gram but Platform® contains at least 500 spores per gram along with at least 1500 to 2000 infective hyphae per gram. This equates to a total of 2000 to 2500 propagules per gram. The standard application rate is 200 grams per hectare, which supplies a minimum of 400,000 propagules per hectare. The cost of this inoculum will be less than $20 (AUD) per hectare. A good application strategy is to include a few kilograms of NTS Soluble Humate Granules™ per hectare, along with a little Tri-Kelp™ Soluble Seaweed Powder (300 grams per hectare) to feed the introduced workforce. It is always a good idea to send the workers off to work with a lunchbox if you want to maximise colonisation and minimise attrition.
We have developed over 300 products at NTS over the past 16 years, but I have rarely felt this excited about the introduction of something new. Food production seems to get more difficult each year as input prices increase and profit margins shrink. We are relentlessly seeking solutions to improve the lot of the planet’s most important profession and I am convinced that this new inoculum can achieve this goal. For the first time ever, an AMF inoculum is available that is cost effective for every crop, from pasture and broadacre to all horticulture crops.
The beauty of this inoculum is that, unless you do something to kill off the new recruits, you only need to inoculate once. When the massive network of hyphae is up and running, there is an enhanced supply of NPK and trace elements and each new crop plugs directly into this massive biological matrix. The platform is in place to store carbon in the soil rather than the atmosphere and farmers are set for a brighter more profitable future with less reliance on petrochemicals. Now that’s a reason to get excited!