During my recent visit to New Zealand, I encountered a frightening scenario where the entire Kiwifruit industry was seriously impacted by a virulent bacterial pathogen not unlike the citrus canker that threatened the Australian citrus industry a few years ago. I offered my help based upon almost twenty years of problem solving experience in diverse crops around the globe. In the process of developing an integrated program for this industry I realised that the principles are relevant to all crops and should be shared with our Nutrition Matters readers.
The keystone concept here involves the understanding that there are no silver bullets. Resilience is multi-factorial and success is most likely when we cover as many bases as possible. Nutri-Tech Solutions (NTS) has specialised in integrated programs to maximise plant and soil resilience in over forty countries for many years. Enhanced resilience is an essential requirement for proactive disease management and the following document will outlay the mechanics of a comprehensive resilience program. Here we will consider a five-pronged approach involving a combination of mineral management, biological inoculums, immune supporters, photosynthesis enhancers and a cell-strengthening strategy.
1) Mineral Management
The key strategy here involves the principle that no mineral is an island. Every mineral affects the uptake of at least one other mineral and the secret is to work toward an optimum balance where the availability of all minerals is maximised. A second mineral management strategy involves a recognition that a broad spectrum of minerals are required to build a resilient plant and most of the less researched minerals are not included in many nutrition programs.
We suggest growers utilise our Soil Therapy™ service, as this soil testing and programming service is based upon a proven mineral balancing philosophy. There are a number of key ratios we seek to achieve in your soil but the most important of these include the following:
The ideal calcium to magnesium ratio – This will vary based upon the clay component of your soil and will often involve the addition of either of these minerals or sometimes both of them. This mineral ratio governs the efficiency of gas exchange. This is arguably the most important process in plant growth and soil health, as it involves the entry of oxygen into the soil (to feed the roots and the army of protective organisms living around the roots) and the exit of CO2 as the roots and the organisms breath out. This CO2 diffuses from the soil and is captured by the tiny pores called stomata, which line the underside of the leaf. The CO2 is then utilized for the all-important process of photosynthesis. The better the Ca/Mg ratio, the better the gas exchange, the healthier the soil life and the happier the plant.
Equal ppm of magnesium and potassium – if this can be achieved you will see optimum uptake of both of these minerals (as evidenced by a leaf test) and luxury uptake of phosphorus. Potassium, in excess, negatively affects the uptake of both magnesium and phosphate, while excess magnesium antagonises potassium. Magnesium is also a phosphate synergist, which enhances phosphate uptake. If you can get this ratio right, you will achieve the best possible uptake of all three minerals. It must always be remembered that phosphorus is a key fuel for the plant’s immune system as it provides the ATP that is required for all of the enzymic reactions that drive defence. We rarely see the luxury levels of phosphate we are seeking in the leaf to maximise plant immunity and this particular balancing strategy is a great way to address this issue.
A phosphorus to zinc ratio of 10 to 1 – These two minerals have a major impact on each other and maximum uptake of both is possible if you can achieve this 10 to 1 ratio. Remember the importance of phosphate in immunity and recognise that zinc is the trace mineral that governs the production of auxins, which in turn govern leaf size. The leaf is the solar panel that determines productivity and plant health.
Nitrogen Management and Resilience
Nitrogen is the mineral most mismanaged in modern horticulture. It is invariably over-supplied and often in the wrong form. It is critically important to ensure that the plant is not packed with nitrate nitrogen if we are seeking to avoid disease pressure. Nitrate nitrogen is always carried into the plant with water and there is an associated dilution factor involved. High nitrate nitrogen always spells low mineralisation because of this dilution effect. A broad spectrum of minerals are involved in the plant’s immune response and the levels are compromised by excess nitrates.
Aside from this dilution effect, excess nitrate nitrogen also reduces the uptake of two key minerals that are important for resilience. One of these is calcium, which is so important for cell wall strength and associated disease resistance. The other mineral impacted by high nitrate nitrogen is potassium. Potassium is the most expensive fertiliser input in agriculture and it makes little sense to inadvertently induce a shortage of this mineral by over-supplying another expensive input (nitrogen). Nitrogen is critical for maximum production, so it easy to understand why growers so regularly succumb to the “moron” approach (if a little nitrogen is good then let’s put more on). The “Goldilocks” approach is most productive here, but getting your nitrogen “just right” involves close monitoring.
The best tool to help maintain ideal levels of nitrate nitrogen is a Horiba Nitrate Meter. This simple and accurate tool can supply immediate, in-field information about nitrate nitrogen levels within your crop. The mantra becomes “how low can I go”, to maintain maximum yield potential without compromising plant health. Nitrogen is the most abundant mineral required for plant growth so it is critically important that it is not under-supplied. Conversely, it is the mineral that is most often oversupplied, so precision in nitrogen nutrition is invaluable.
In the dairy industry, for example, it has been found that rye grass is healthiest and most productive when nitrate levels are maintained at 2600 ppm (using a Horiba Nitrate Meter). The previous practice of broadcasting up to 150 kg of urea every six weeks (after each grazing) was delivering 7000 ppm to 8000 ppm of nitrates and this was creating plant and animal health problems. In the Dutch strawberry industry, agronomists working with this approach have discovered that just 1350 ppm of nitrate nitrogen is the “just right” level that maximises plant health and production in that crop.
Research is required to determine ideal nitrate nitrogen levels in your crop. Growers should not simply accept the advice of Horiba, as those suggestions are based upon existing industry practices and these are very often wrong!
Molybdenum and Nitrogen
Molybdenum is a critical trace mineral for nitrogen management, which is frequently overlooked. In my recent visit to New Zealand, a vast majority of Kiwifruit growers had never soil tested for this mineral. We find in our work in over forty countries, that molybdenum is deficient in over 80% of the soil tests we analyse. It is a serious oversight if you lack molybdenum and it has no small role in an integrated resilience program. If excess nitrates and nitrate accumulation within the plant can reduce resilience then the obvious goal is to increase the amount of naturally sourced ammonium nitrogen within the plant while reducing nitrate accumulation within the leaves. Both of these strategies involve molybdenum.
Molybdenum is a crucial component of the nitrogenase enzyme, the tool used by nitrogen-fixing organisms to convert nitrogen gas in the atmosphere into ammonium nitrogen in the soil. You simply do not have access to 74,000 tonnes of free nitrogen in the atmosphere (which helps ensure the desirable 3:1 ratio of ammonium nitrogen to nitrate nitrogen in the plant) if you have neglected your molybdenum. Similarly, your crop will accumulate nitrates in the leaf and become more susceptible to disease if molybdenum is not present to provide the critical building block for the nitrate reductase enzyme, which serves to convert nitrate nitrogen through to protein. In my opinion, growers involved in intensive horticulture should be monitoring molybdenum in both the soil and the leaf on a regular basis. Broadacre growers and graziers might monitor this mineral in the soil and leaf every two or three years.
The Recipe for Nitrogen Fixation
The efficient accessing of free nitrogen from the atmosphere ensures the delivery of the most desirable nitrogen form on an ongoing basis, with obvious plant health and cost-saving implications (particularly in the face of a peak oil scenario where commercial nitrogen is set to rise and rise in price). However, there is more to accessing “the free gift” than just molybdenum. There is a five-part recipe that determines your access to the 74,000 tonnes of free nitrogen hovering above every hectare and here it is:
Ensure that you have a minimum of 0.5 ppm of molybdenum in your soil (based on a Brookside-style soil test).
Aim for a minimum 2 ppm of cobalt, based on the same test. Cobalt is now considered as “mothers milk” for nitrogen fixing organisms and it is also the building block for vitamin B12, which may yet prove to be an unrecognized immune elicitor.
Improve the calcium to magnesium ratio in your soil to ensure that there is adequate oxygen to fuel N-fixation. Azotobacter, one of the most prolific free-living nitrogen-fixing organisms, is the most aerobic (oxygen dependent) of all oxygen-dependent organisms.
Iron is the second component mineral of the nitrogenase enzyme. This is the most abundant mineral in the universe but in cold and compacted soils it can become unavailable. Humic acid is the best tool to reclaim this availability. New European studies have even reported dramatically increased iron availability to chlorotic plants in freezing conditions.
Soluble phosphorous is the final requirement in this five-part recipe. This can be achieved via the application of small amounts of soluble phosphate fertiliser, but it is vastly preferable to source your soluble phosphate biologically. The indisputable phosphate king, in the world of soil microbes, is mycorrhizal fungi. Most of the agricultural soils we analyse are lacking mycorrhizal fungi and yet this shortage can be addressed for a nominal cost. This organism increases your root zone surface area by up to 500% and the massive network of tiny filaments is constantly releasing biological acids to break the bond between calcium and phosphorus enabling enhanced delivery of both minerals to the plant.
The first cell that oozed from the pre-Cambrian ocean contained 74 minerals and it is a safe bet to assume they all have a purpose in the perfect blueprint that is Nature. Soluble kelp and liquid fish are the mainstay of the biological approach, partly because they still contain that full range of minerals. The science of plant immunology is still in its infancy but I believe that we will eventually discover that immune elicitation involves more than the seventeen minerals currently considered. Selenium is a good example. This mineral is never tested and yet new research suggests it serves as an antioxidant within the plant to counter the oxidation associated with 12 hours of unbridled sunshine each day. Antioxidants are invariably protective on many levels and that is one of the reasons that we have been one of the first companies to include 250 ppm of selenium in our best-selling foliar fertiliser, Triple Ten™. The practice of broad-spectrum mineralisation offers more than increased plant health. It also stimulates and nurtures the micro-organisms that are an integral component of resilience.
2) Microbe Mastery – Inoculums for Disease Management
The use of biological inoculums amounts to re-charging the life force in the soil to reap the benefits of a new, task-specific workforce. There are specific inhibitory bacteria or predatory fungi that are the mainstay of resilient soils and plants. The five organisms with most promise in this context include mycorrhizal fungi, Trichoderma, Pseudomonas fluorescens, Bacillus subtilis and Azotobacter.
Mycorrhizal fungi are a critical component of this protective team. There is comprehensive research linking plant resilience to mycorrhizal colonisation. Part of this increased defence capacity comes from the biological delivery of phosphate (arguably the most important mineral for plant immunity, as it fires glucose production and is the building block for ATP which fuels the multiple enzymic reactions involved in resilience). There is also evidence that mycorrhizal fungi produce biochemicals that support an immune response in the plant. We have witnessed many cases of improved plant health and resilience following mycorrhizal colonisation.
Trichoderma is a cellulose-digesting, free living fungi, which is often compromised by farm chemicals, including copper. Trichoderma does more than build humus, however, it is also a beneficial fungi that feeds upon a wide range of other organisms and it produces metabolites that further compromise the organisms. It releases acids that solubilise locked-up phosphate in your soils and most importantly, in this context, Trichoderma supports plant defence mechanisms via the production of protein-based immune supporters.
Pseudomonas fluorescens is a ubiquitous, protective bacteria that is seriously compromised by glyphosate and as this herbicide is widely used in all forms of agriculture, there is a question mark about the disease-suppressive capacity of these soils. These organisms produce a variety of anti-social compounds including hydrogen cyanide. However, Pseudomonas fluorescens offer protection-based benefit involving frost events. Frost crystals are caused by ice nucleating bacteria and organisms that predate on these bacteria can effectively halt frost damage. Pseudomonas fluorescens is a competitive antagonist that lacks the ice nucleating protein and it has proven highly effective as a tool to reduce frost damage. Here is a frost protection strategy that has worked well for us:
The NTS Frost Protection Recipe (rates per hectare)
- 1 kg of Nutri-Life Sudo Shield™
- 300 grams of Tri-Kelp™
- 100 grams of NTS Fulvic Acid Powder™
- 2 litres of K-Carb 35™
- 250 mL of Cloak™ Spray Oil
The rationale here is that the hormones in kelp have been shown to offer a couple of degrees of frost protection and kelp also stimulates the colonisation of Pseudomonas fluorescens. Fulvic acid also stimulates this inoculum, while the concentrated potassium source serves as an electrolyte to keep the plant fluids moving and less likely to freeze. Some Kiwifruit growers use urea for this purpose but we have found this form of potassium to be more effective. The spray oil enhances the efficacy of this mix.
Bacillus subtilis is a much researched bacterial species that can offer multiple benefits. We find that a good strategy to improve the consistency and performance of all introduced inoculums is to send them off to work with a lunchbox. Providing a food source with the introduced organisms encourages their colonisation and provides a kick start to achieve the desired response. The best lunchbox for Bacillus subtilis involves a combination of fish fertiliser (Nutri-Sea Liquid Fish™) and fulvic acid (NTS Fulvic Acid Powder™). Bacillus subtilus forms a stable, extensive bio-film and secretes a biochemical called surfactin, which, together, can boost soil and plant resilience. Surfactin is powerful lipopeptide but this versatile organism also produces a substance called acetoin, which has also been found to help in the promotion of a disease resilient soil.
Inoculums involving blends of the nitrogen-fixing organism, Azotobacter, can provide up to 20 kg of ammonium nitrogen per hectare while also offering a suite of other benefits. We have been working with Azotobacter inoculums in agriculture for over 15 years. We have developed inexpensive blends for inoculating both the soil and the leaf. We have clients who source the majority of their nitrogen from these organisms. Our leaf-dwelling Azotobacter, marketed as Nutri-Life Bio-Plex™, are remarkably effective at supplying nitrogen directly from the atmosphere into the leaf. They generate a rich green leaf and a tremendously healthy plant in vine crops like passion fruit and grapes and in most orchard crops we find that if we supply a foliar fertiliser containing iron, molybdenum, cobalt and phosphorous with the azotobacter inoculum, we have covered all the bases to ensure maximum performance of the introduced organisms. Two litres per hectare of our all-inclusive foliar fertiliser, Triple Ten™, with Nutri-Life Bio-Plex™ (for the leaf) or Nutri-Life Bio-N™ (for the soil) seems to deliver the desired response.
Task-Specific Microbe Blends
A cost-effective strategy that is widely employed in horticulture and broadacre cropping involves multiplying or “brewing” your own organisms and applying them as a biological fertiliser/resilience enhancer. The NTS product, Nutri-Life 4/20™, for example, contains four of the “big five” organisms mentioned above (Azotobacter, Bacillus subtilis, Pseudomonas fluorescens and Trichoderma) along with co-factor species that stimulate existing soil-life. It is multiplied over a 24-hour brewing process using inexpensive brewing equipment and applied at 100 litres per hectare. A food source called Liquid Microbe Food (LMF™) is added during brewing at the rate of 1 litre per 100 litres and it is possible to select for either bacteria or beneficial fungi with the addition of a second liquid called Dominate-F™ or Dominate-B™. The addition of Dominate-F™ during the brewing of Nutri-Life 4/20™ at 1 litre per 100 litres, for example, delivers a tank full of Trichoderma spores which allows a luxury dose of these organisms at a very low price.
3) Immune Elicitors
This is an area that the industry research bodies are focusing upon at present. This is recognition that the plant has a defence system not unlike our immune system and that there are substances that have proven to boost immune responses. It is part of the “give and you will receive” deal, so commonly seen in nature, where the plant gives up 30% of its photosynthates to feed the root zone organisms and these creatures respond with a vast range of benefits. Part of this payback involves the production of a suite of biochemicals to elicit plant immunity. The organisms have vested interests in looking after their provider, of course. The healthier their host, the greater the glucose delivery.
There are substances that elicit an immune response that are not produced by microbes to look after their host. One of the most powerful of these immune sparking, non-biological substances is salicylic acid. Aspirin was developed as a synthetic form of salicylic acid to mimic the pain-killing capacity of plants that are naturally rich in this substance, like willow bark and aloe vera. Salicylic acid is a phenolic phytohormone that is intimately involved in the hormone response. Aloe vera is the highest plant source of salicylic acid (hence the sunburn quenching capacity of the gel) and it is increasingly used in agriculture. You can even dissolve aspirins at a rate of one aspirin per four litres of water and apply it as a foliar spray to boost plant immunity. If you buy home brand aspirin in bulk at the local supermarket you should be able achieve the desired concentration at a cost of less the $20 per hectare.
Kelp is another recognised resilience builder and this is part of the reason that seaweed is an integral part of any biological program. Kelp contains luxury levels of the four plant growth promotants required by every plant. In fact it contains 40 times more of these essential health factors than any other plant. Tri-Kelp™ from NTS features a unique blend of three different kelp species. A standard 10% kelp solution (the industry standard for kelp), made by adding 100 grams of this powder to one litre of water can be achieved at a very low cost.
The other much-researched substance that supports immunity is chitinase, which is sourced from prawn shells and is now available in commercial preparations.
4) Photosynthesis Enhancement
Photosynthesis is the most important process on the planet, as the green plant is literally the only food source. Anything that significantly boosts photosynthesis, increases plant health and resilience. Chlorophyll is the green pigment within the tiny sugar factories (chloroplasts) that perform this miracle. Chlorophyll management is the principle role of growers. The greater the chlorophyll density, the higher the production and the lower the problems. We use a refractometer to monitor dissolved solids (brix levels) in the crop leaves and this amounts to a direct guideline as to chlorophyll density. It was with this understanding that I became very excited when I first discovered research into a plant-based substance called triacontanol. This substance is found in the outer waxy coating of the lucerne plant and can be sourced from the wax of bees working lucerne plantings. Prize winning rose growers in the US often refer to the growth enhancing benefits of alfalfa tea without realising that the lacto fermentation process they recommend is successfully extracting triacontanol from the alfalfa (lucerne).
This is the first fatty acid that has been found to promote plant growth and it does so in the healthiest possible fashion. Most PGP products are based upon some sort of hormonal manipulation and they often deliver increased growth but reduced nutrient density. Dairy farmers, for example, are currently playing with gibberellic acid to increase the production of rye grass. However, they often produce more grass with less nutrition and a net gain is debatable. Triacontanol, by contrast, boosts chlorophyll density and magnifies production of the phosphate-based enzymes responsible for photosynthesis. In one important study a researcher named Reis reported a 31% increase in chlorophyll density.
When we first trialled a range of triacontanol products from around the world we were amazed at the standout response achieved from a single product from India. When we tried to secure an import permit for this product, our efforts were thwarted due to the reluctance of the manufacturer to reveal the technique they used to solubilise the beeswax from which the active ingredient is derived. Their reluctance to share was understandable considering the fact that they had obviously discovered the secret of solubilising wax. We eventually decided to import our own wax and commission a chemist to solubilise it. We were never able to achieve quite the performance of the original Indian liquid source but it was still good enough to justify adding it to our most popular foliar fertilisers to boost their performance.
Earlier this year we decided to try again. We sourced a more concentrated form of triacontanol and commissioned an accomplished chemist to do his best. The end result is a new triacontanol product that is as good as that original standout from a decade ago and we are delighted. The researched benefits of triacontanol include the following:
- Bigger leaves and roots
- Induction of flower buds and flowering
- Enhanced photosynthesis with associated brix increases
- Production of more robust and resilient plants
- A kick-start for seedlings or young plants produced from cuttings
- More flowers, more fruit and thicker foliage.
- Increased crop resilience
Nutri-Stim Triacontanol™ from NTS is remarkably cost-effective and it is applied at just 8 mL per 100 litres.
5) Resilience Through Cell Strength
When you witness a disease spreading from cell to cell under a microscope the first thought relates to increasing cell strength as a means of containing the destructive invaders. The cell wall is the obvious physical barrier that can slow the flow of disease. The two minerals that determine the strength of the cell wall are calcium and silica. Calcium is the mineral we find most difficult to build to the luxury leaf levels required to maximise cell strength. Calcium has terrible mobility in the soil and in the plant. In fact, it is a slug of a mineral! Silica has been shown to increase the mobility of calcium in its role as the chief mineral involved in building phloem and xylem (the pathways into and around the plant). All fruiting crops respond well to calcium foliar sprays as this practice sponsors the direct delivery of calcium into the fruit.
However, it is the second cell-strengthening component, silica, which is so often the missing link in modern horticulture. Silica is the second most abundant mineral on the planet but something we have done to our soils has hindered the flow of water soluble silica (mono silicic acid) from the sands and clays of which it is a primary component. We need to see 100 ppm of silica on our particular soil test, but most soils present with just 20 to 40 ppm. Silica has become the flavour of the month in agriculture following two International Silica conventions at which hundreds of new research papers were presented. It turns out that silica is much more than a cell-strengthening mineral. It is actually an immune supporter of profound importance. It also boosts photosynthesis and protects the plant from sodium and heavy metal toxicity.
Silica can be applied as potassium silicate via fertigation or as a foliar, but it usually involves a standalone application. Silica is incompatible with almost everything except kelp and humic acid and there have been many a curse from growers who have discovered this the hard way. There is, however, one form of silica that allows more versatility with combinations and less stress. In fact, the NTS product Dia-Life Organic™ can be combined with almost anything. Dia-Life Organic™ is based upon organic liquid micronised diatomaceous earth. Diatoms are ancient microscopic creatures that congregated in pools in great numbers. Their exoskeleton consists of 85% silica dioxide and when their community eventually died out, the abrasive outer shell is all that remained. More recently it was discovered that if this material was micronised down to 5 microns, it delivered plant available silica to the plant.
We like to monitor silica levels with leaf analysis and we see substantial rises in silica in the leaf following modest applications of Dia-Life Organic™ to the soil, via fertigation. An initial application of 20 litres per hectare should be followed by a further 5 litres of Dia-Life Organic™ every ten days. It is important to deliver some plant-available silica to the soil solution as often as possible because the plant draws upon this silica source when it is attacked and moves it to the attack site. The goal is to strengthen the walls of the surrounding cells to support resilience. Silica is rapidly incorporated into the cell walls when plants absorb it, so it is important to provide an ongoing supply.
You have just read over 5000 words and are, perhaps, wishing that life could be easier. It may not be necessary to put all of these strategies in place to achieve success but plant and soil resilience is multi-faceted and the more bases you cover the better. Here is a seven point checklist you can tick off to mark your progress:
The Resilience Checklist
Test your soil and leaves with a lab that understands the balance concept, ensuring that the key ratios have been addressed.
Monitor your nitrates and ensure that the recipe for nitrogen fixation is in place.
Include fish emulsion and kelp in your program to achieve broad-spectrum mineralisation.
Master microbes by introducing the key five organisms we discussed.
Introduce proven immune supporters like aspirin, kelp, Aloe vera and chitinase.
Enhance photosynthesis with triacontanol.
Strengthen cell walls with silica and calcium.