By Graeme Sait

Nutrition farming is about managing minerals, microbes and humus, and understanding their interplay. No mineral is an island, and no mineral is less singular than the all-important calcium. This mineral directly impacts the plant availability of seven other minerals. That’s why we try to address calcium before any other corrective, when developing productive nutrition programs.

There is another reason, beyond enhanced mineral uptake, that further increases the supreme importance of calcium. Calcium determines your soil’s capacity to breathe. The single most important element for high-production fertility is not N. It’s not P, or K, or even calcium. The driver of plant productivity is oxygen.

You are managing gas exchange above all else. How freely can oxygen diffuse into the soil and then, after the roots and microbes have breathed in oxygen, they breathe out CO2. That outbreath, now accumulates in the rootzone, diffuses out of the soil and into the waiting stomates (the entry point for this gas). There, in conjunction with water and sunlight, we have the basis of photosynthesis, the most important process on the planet. The better you manage gas exchange, the better you do. The beneficial impact of this intake of oxygen and outbreath of CO2 is dependent upon the friability of your soil. That breathing capacity is determined by the calcium to magnesium ratio.

Calcium is a large ion with two positive charges (a divalent cation). Picture it as a beachball with a positive charge on either side. Clay is the main vehicle for calcium storage in the soil. The clay colloid has negatively charged sites, a little like Velcro, that attach either side to the beachball. This effectively pushes apart the clay and the soil breathes (flocculation).

Magnesium is like a golf ball compared to that beachball. It also features two charges, grabbing the negatively charged clay on either side. However, instead of pushing apart that clay, high magnesium tightens the soil so that you have platform shoes when working in the wet. These soils do not breathe well. In fact, they are sometimes called “Sunday soils”. You work them on Saturday and plant them on Sunday because they have often closed over and become impenetrable by Monday.

You might well ask, “Why worry about magnesium, if calcium is the key to an open breathing soil?” I sense you thinking? Well, the fact is that you can’t ignore magnesium, because it is the centerpiece of your other major farm management issue. You are managing gas exchange and you are also managing chlorophyll, the green pigment that houses the little sugar factories, called chloroplasts. Magnesium is at the centre of that molecule, so it can never be ignored.

It turns out that there is an ideal ratio between calcium and magnesium, based upon the amount of clay in your soil. This ratio ensures that there is sufficient magnesium to drive chlorophyll, while providing enough calcium to allow the soil to breathe and flourish. A light, sandy soil might require three parts calcium, to 1 part magnesium (a 3:1 ratio). This tighter ratio is because we need extra magnesium to provide a little structure to a soil that has none.

Conversely, a high clay soil might require a 7:1 ratio, because more calcium is needed to open up all that clay. Your soil will be somewhere between those extremes and a good soil test (NTS Soil Therapy) will provide the ideal cal/mag ratio relevant to your paddock.

Calcium and magnesium have a unique relationship, where one can displace the other from the clay colloid, where they are stored. The base saturation percentages on your soil test reflect relative storage of key cations (bases) on the clay colloid. This happens on a one-to-one basis, until balance has been achieved, and then it slows right down. It’s almost as if this desirable balance is a natural law and the message, “we’re there now mate”, goes out when optimal balance has been achieved. For example, if you had 58% calcium base saturation (when you need 68%) and your magnesium base saturation was 22% (when you need just 12%). The addition of the appropriate amount of calcium would provide 10% calcium while displacing 10% magnesium. This takes about 12 months, and then you have achieved the perfect calcium to magnesium ratio.

The Cal/Mag ratio and nitrogen requirements

A high magnesium soil struggling for breath will always require more nitrogen to achieve the same outcome. In fact, it can require 50% more N to get the same yield. There are a quartet of things at play here;

1. Nitrogen fixing bacteria have a particular hunger for oxygen. In fact, azotobacter are the most aerobic creatures on the planet.
2. Nitrogen cycling slows considerably in a tight, closed soil, because some of the nitrogen mineralising creatures struggle in these soils. Beneficial nematodes, for example, have a 100 to 1 carbon to nitrogen ratio. They are genetically keyed to maintain this ratio. A nematode must consume 20 bacteria with a 5:1 C:N ratio to get their 100 units of carbon. However, they only need one unit of N, so they spit out the excess 19 units from those 20 bacteria, and the plants sing “you beauty!” It turns out that these beneficial nematodes hate compacted soils, so they soon disappear, and so does their nitrogen cycling function.
3. High magnesium antagonises uptake of other cations through competition. This directly affects ammonium nitrogen
4. Excess Mg also impacts calcium availability which affects root hair production. This compromises uptake of nitrate nitrogen.

Hopefully you are beginning to recognise that it might be a good strategy to improve your cal/mag ratio.

Cal/mag dynamics

1. The first thing to understand is that you don’t need to perfect this ratio to benefit. You might have a heavy clay soil where the ideal ratio is 7:1, but you currently have a 1:1 ratio, with the extreme soil tightness that this undesirable ratio confers. What we see in this scenario is measurable benefits at every stage of the journey. If you can only afford to move your 1:1 ratio up to 2:1, you will still be rewarded for your efforts.
2. A second consideration relates to light sandy soils. Here, you forget about base saturation ratios all together. In a CEC below 5, you simply shoot for 500 ppm of calcium and 120 ppm of both magnesium and potassium. This is what works!
3. The next consideration relates to how you can best address a poor ratio. Here are some guidelines:

Gypsum is calcium sulphate. In the soil, these two minerals ionise (they break apart) and the newly liberated sulphate forms magnesium sulphate and sodium sulphate. These happen to be the most leachable forms of these two minerals. Hence, gypsum is often termed, “the clay breaker”, because both excess magnesium and excess sodium contribute to soils struggling for breath.

However, there are problems, if gypsum is over supplied, because there is the potential to remove more than what is intended. Gypsum can inadvertently serve to demineralise your soil, if it is misused. The associated sulphate excess can also impact the uptake and availability of the other major cation, phosphorus. This is a big price to pay, and this is why we try to achieve a 1:1 phosphorus to sulphur ratio.

The rule of thumb is to never apply more than 2.5 tonnes of gypsum per hectare (1 tonne per acre), in a single application.

A combination of gypsum and lime is often the best approach to improve the cal/mag ratio. The gypsum moves out some of the excess magnesium, and the lime (with twice the percentage of calcium found in gypsum) can serve to displace magnesium from the clay colloid, to complete the job. This relates to the phenomenon I mentioned earlier, where calcium can displace magnesium on a one to one basis. I.e. if you increase calcium base saturation by 10% with lime, 12 months later you will note the displacement of 10% magnesium, detached from its clay storage place.

If it is not feasible to apply appropriate amounts of either of these correctives, then there is a much less expensive option. Here, you can fertigate, or liquid inject micronised versions of gypsum or lime directly into the root zone. This is a great strategy to make an impact where it really matters. That’s what’s made our Gyp-Life product one of our top five sellers around the globe.

The biological link to a breathing soil.

Enhancing gas exchange can involve more than improving the all-important cal/mag ratio. Let’s now look at how biology might help. The key creatures here are beneficial fungi. They create the larger aggregates that are the basis of crumb structure, the most desirable of all soil conditions. However, we can never take it for granted that this workforce is poised for action in our soils, because most soils are seriously lacking these organisms. A Microbiometer measures the fungi to bacteria ratio, so it will give you an indication of your fungal status. In most cases, you will find you are seriously lacking fungi. They don’t like tillage, fungicides, nematicides or herbicides so they are on the back foot in most fields. The next question becomes, “how can I improve my fungi to bacteria ratio?”

One of the most effective strategies involves introducing more legumes, in pasture, beneath cereal crops, and within cover crop mixes. Legumes produce acid exudates, which create the preferred lower pH habitat for fungi to proliferate.

Here’s a really important message that’s not well understood amongst many consultants and farmers. You need to be checking your legumes for nodulation and you need to know that those nodules are red within. Over half the fields I walk, house legumes with no nodules, or no blood (leghemoglobin). There is a huge price to pay here, because your legume becomes more of a liability than an asset at this point. Let me explain.

The lack of nodules is commonly related to a lack of sulphur, although zinc and iron deficiency can also play a role. Most soils are sulphur deficient, because we no longer harvest free sulphate from industrial sulphur emissions, and we have lost much of the humus, that is the storehouse for sulphur in the soil.

The reddish coloured pigment within the nodule indicates whether or not that plant is fixing nitrogen. This substance is appropriately called leghemoglobin and it is, in effect, the blood that determines most of the beneficial characteristics of legumes. If your nodules are an anaemic grey colour, you are not accessing what I call, “the free gift”- the 74,000 tonnes of nitrogen gas hovering above every hectare.

However, there is another negative outcome. Your legumes are also not creating the acid exudates that break the bond between locked up calcium and phosphate in your soils. This is a huge role of legumes and it is critically important for the cereal crop above the clover, or the grasses and cereals in pastures and cover crops. Calcium and phosphorus are the two most important minerals for the most important of all plant processes, photosynthesis. It is a serious issue when legumes lose this bond-breaking side-effect.

Perhaps I had best explain why the plant releases these beneficial acid exudates. It relates to the fixation of ammonium nitrogen within the legume. When a plant uptakes a cation, like ammonium nitrogen, it must release a cation, to maintain internal, electrical balance. There would be no point in taking in one cation required for nutrition and releasing another food source, so the plant always releases a non-nutrient cation called hydrogen. Hydrogen is the acid element that determines low soil pH, but here it relates directly to the acid exudates. If you are not fixing nitrogen and stimulating this hydrogen release, you are unable to release locked up calcium and phosphate, with these acidic exudates, but, more importantly, you do not create the acidic home base for fungi.

So, we have determined that it’s pretty damn important to have blood within your nodules, so why is it so often missing?

That comes down to a little neglected trace mineral called, molybdenum. Molybdenum is missing in 8 out of ten soils we test, and it is required for the nitrogenase enzyme that catalyses the conversion of atmospheric nitrogen into ammonium nitrogen in the soil. Only small amounts are required, and shortages can be addressed with seed treatment, liquid inject and foliar applications of sodium molybdate or liquid molybdenum fertilisers.

The second suspect in bloodless nodules, is boron, and sulphur can also play a role. Molybdenum, boron and sulphur are lacking in most soils, so there is no surprise that our legumes are compromised. A simple foliar corrective might involve 1 kg of Solubor (sodium borate), 50 grams of sodium molybdate and 4 kgs of ammonium sulphate per hectare.

As mentioned, the biggest outcome from this lack of leghemoglobin, and the associated acid exudates, is the impact on fungi and their creation of crumb structure. In this particular “house that Jack built”, a sulphur shortage limits nodule development, and missing molybdenum prevents the blood, that creates the acid exudates, that feed fungi, that solubilise calcium and phosphate, that live in the house that jack built. That’s a pretty strange nickname for God, but you get the picture. The essence of Nutrition Farming is to work with Nature - the perfect blueprint, to understand these interrelationships, and to increase your profitability.

The role of humates and beneficial anaerobes

Humates are another effective strategy to boost fungi, to aggregate your soil and to improve gas exchange. Humic acid, in particular, offers multi-level benefits. Humic acid is the most powerful stimulant of all-important fungi, and it also buffers the negative impact of sodium, that can accumulate in a closed, tight soil. Humic acid has also been shown to be a soil conditioner that can seriously improve soil structure and associated gas exchange. It’s important to select a product based on Leonardite rather than lignite. Our product, NTS Soluble Humate Granules is the best of these products in Australia, but, of course, I’m a little biased.

Beneficial anaerobes like EM, or our product BAM, can almost be seen as pioneer species in a heavy soil with a poor calcium to magnesium ratio. These soils struggle to breathe, so a consortium of organisms that thrive without oxygen, can pave the way in terms of biological improvement of soil structure. BAM can be easily brewed on farm to make it a super cost-effective soil conditioner.

In conclusion….

The gifts bestowed from creating a living, breathing soil, include both increased resilience and enhanced infiltration. These are two of the single most desirable qualities determining both productivity and farming fun. The calcium to magnesium ratio is the mineral link to creating this outcome. The fungi to bacteria ratio monitors the relevant microbial contribution, and humates highlight the humus link. This further demonstrates the importance of understanding the relationships between minerals, microbes and humus in the Nutrition Farming playbook.

Wishing you all some autumn moisture and a breathing soil, to kick off a good winter.

Warm regards,

Graeme

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Integrated micronised mineral blend to promote structural strength, optimise base saturation, and brix lift.

Supa Synergy™ is an integrated micronised mineral suspension designed to strengthen plant structure, optimise base saturation and lift Brix across a wide range of crops. It delivers highly available calcium, silicon, phosphorus, sulphur, boron and magnesium to support cell wall integrity, resilience and efficient nutrient uptake and translocation. Supa Synergy™ can be applied via soil, fertigation, liquid injection or foliar spray, making it a flexible tool for both soil regeneration and in-crop nutrition. Regular use supports improved soil health, stronger plants and more productive, resilient farming systems.

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Key Performance

• Humic acid is a powerful fungi promotant.
• Stabilise nitrogen and improve nitrogen efficiency (ideal as an additive with urea).
• Promotes root growth.

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