Gas Exchange – How to Maximise your Money Maker

There is one mechanism in your soil that has more impact on production, sustainability and profitability than any other. If you get it right you will have better soil structure, higher production, enhanced crop quality and reduced need for expensive, chemical intervention. “What is this magic bullet?”, I hear you say “and how can I access it?”, well this one doesn’t come from a bag or bottle. I am talking about the most important process in agriculture – it is called gas exchange.

A Breathing Soil

Gas exchange is not a reference to faulty digestive processes, cruel Dutch ovens or the replacement of barbecue bottles. I am referring here to the all-important movement of oxygen into the soil and the movement of CO2 out of the soil. This “breathing” process represents the mechanics of photosynthesis, the most important process on the planet. Oxygen is required to fuel every root function and it is also the life breath for the billions of aerobic organisms surrounding those roots. The roots and the beneficial biology breathe in the oxygen and the by-product of oxygen metabolism is CO2. The CO2 rises from the soil and is captured by the tiny breathing pores, called stomates, on the underside of most plant leaves. Here, in the sugar factories called chloroplasts, this CO2 is combined with water (H2O) and sunlight to produce glucose (C6H12O6), the building blocks for all life as we know it.

The equation for the grower is quite simple. The better that gas exchange works the greater the photosynthetic potential and the higher the production. Food producers are chlorophyll managers and the more dense this green pigment, the more the productive potential of the plant. But how do we maximise the breathing capacity of our soils to reap these associated benefits?

The Bounty of Breath

The key to optimum gas exchange is to achieve an open, friable soil where the two life gases can flow freely. Soil friability involves cation balance, a vital, diverse soil-life community and humus.

Cation balance refers to the relative percentage of the key, positively charged minerals (cations) that are attached to the clay in your soil. Clay is negatively charged and it serves as the main storage system for calcium, magnesium, potassium and sodium. It has been determined that there is a productive balance of these major cations on the clay colloid and the ratio between these cations has a big influence on how well a soil can breathe. The most important ratio is the Ca:Mg ratio. Calcium opens (flocculates) the soil because it is a large ion with two charges that pushes apart the clay colloids and holds them apart. Magnesium also has two charges that can stick clay colloids either side of the ion. This mineral, however is much smaller than calcium and if there is too much magnesium in relation to calcium, the soil will be tight and closed. A high magnesium soil is not conducive to thriving, aerobic soil life because a lack of oxygen becomes the limiting factor. The ideal calcium to magnesium ratio in a heavy clay soil might be 7:1 while in a light soil that might be 3:1 (in favour of calcium). In light sandy soils, we actually want relatively more of the soil tightening, magnesium mineral to give a little more structure.

It is not just the Ca:Mg ratio that determines gas exchange potential. Both sodium and potassium are also cations but they each have just a single positive charge. This means they cannot serve as the meat between the sandwich like calcium and magnesium. In fact, if they are oversupplied, they tend to disperse the clay, destroying rather than improving soil structure. High sodium soils (higher than 3% base saturation) or soils with excess potassium (greater than 7%) can also create soils that struggle for breath.

Soil Crumbs Boost Breath

Soil life is the other determinant of good gas exchange. Soil bacteria, in their billions, exude a sticky substance than binds together soil particles to create a mini aggregate. Fungi grab these particles with their tentacle-like strands (hyphae) and mould them into larger soil crumbs and this creates crumb structure, the most desirable of all soil conditions. Earth worms and beneficial nematodes can move freely through these soils, conferring all of their associated benefits. Plant roots, and the mycorrhizal fungi attached to them, can grow unimpeded. Moisture moves easily in, from above and below (the water table), and frustration becomes fascination for those of us lucky enough to be working with these soils. The higher the humus levels of your soils, the greater your likelihood of crumb structure because humus is both the home base and the manifestation of the soil creatures that confer crumb structure.

How do I Optimise Gas Exchange?

The starting point is to use a good soil test and consultant as a guideline to achieve the ideal cation balance in your particular soil. Unfortunately, there are quite a number of soil labs and advisors out there who have yet to understand the cation balance concept. You may well wonder at the reasons for that apparent lack of “understanding” because the science is there and yet it is still ignored. The obvious cynical assumption is that there are more inputs required in an unbalanced soil (nitrogen and farm chemicals) so why would the input suppliers choose to help you reduce your inputs and their profits!

The popular NTS Soil Therapy™ service is ideally suited to those seeking a more productive path. The NTS Agronomy team are leaders in the understanding of both mineral and microbe balance and they share this information with our farmers. Following a Soil Therapy™ report you will understand exactly how to achieve a high production soil and you will have a game plan to achieve that goal. Contact the Agronomy department at NTS on +61 7 5472 9900 or email to get your soil breathing again.

Compost is an amazing tool to fast track the biological aspect of gas exchange. Compost is not just a humus source and an inoculum of wonderfully diverse soil-life, it is also a triggering mechanism for the production of humus. New research suggests that compost is  a previously unrecognized stimulant of mychorrhizal fungi and this is a critically important creature that is missing in action in many soils. It is now understood that glomalin, the sticky substance produced by mycorrhizal fungi is a major synergist in the humus building process. In fact, 30% of all of the planet’s humus comes from this amazing fungi.  

Platform for Better Breathing

Mycorrhizal fungi offer much more than humus to improve gas exchange. They effectively provide a massive root extension (ten times more root surface area) allowing more access to minerals like phosphorus, zinc, potassium and calcium. Everything the roots offer the plants is magnified ten-fold and a  more resilient, more productive plant is the ultimate outcome. The replacement of these organisms in the soil used to be an expensive process, as the spores must be laboriously harvested from live plant roots to produce inoculums. Platform® from NTS is the exciting, exception to this rule. This inoculum is the product of innovative new growing and harvesting technology which allows the replacement of these missing creatures from as little as $10 (AUD) per hectare. It is no longer just high value crops that can be reinvigorated with a new root extension. Everything from pasture to broadacre crops can now be boosted and this is good news when we understand the role of humus in averting climate chaos.

Humates for Crumbs

Humates are a great substitute for compost and are a user-friendly, humus-building tool to create crumb structure. It is fungi that are often the missing link in the soil crumb equation.  Soil-life analysis from virtually every conventionally farmed soil reveals a lack of beneficial fungi. It is so common that there is almost no point in testing those soils because the results invariably reveal the same shortage. The development of crumb structure and the associated improvement in gas exchange is not possible in the absence of fungi to bind up the larger aggregates. Humic acid is the most powerful known fungi promotant. It is a rich source of the long-chain carbohydrates that are the favoured food of beneficial fungi. NTS Soluble Humate Granules™ are leonardite-based, high quality humic acid granules that have been proven performers over fifteen years in Australia and in over forty other countries. They can be combined at 5% with granular fertilisers to both magnify and stabilise these expensive inputs.  These granules can also be used to create an, inexpensive D.I.Y liquid humic acid by dissolving the granules in water at the rate of 1 kg per 10 litres of water. This liquid humic acid, which costs less than 30 cents a litre, can be fertigated at 10 to 30 litres per hectare, to great effect. Humic acid can have more impact upon soil structure and gas exchange than any other substance.

In Conclusion

A soil that can breathe is a soil that will produce healthy, resilient plants with much less need for chemical intervention. The majority of pathogens are anaerobes that do not particularly like the oxygen in-breath. The capacity of the plant to resist pathogens is also higher when the soil breathes out and  the plant has access to luxury levels of CO2 for photosynthesis. It all becomes so simple when we understand these basics. Improve your gas exchange with mineral balance, microbial inoculums and humates and the building blocks for profitability are in place.

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