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Capturing Carbon and supporting soil - ten top tips from Graeme Sait on building carbon

23rd Jan 2018

This blog was written by Graeme Sait and published on the nutri-tech blog on the 9th November 2017, you can access it in its original form here

I am driven to travel to dozens of countries each year in the hope tha tI can make a positive difference in the global warming challenge. I am one of the thousands who understand that the soil may be out only saviour. We can cut all carbon emissions tomorrow morning and, in 200 years' time the offending CO2 excess in our atmosphere drops down to 1975 levels. Unfortunately this is still too high and our oceans will continue to warm and acidify. so is it all over bar the shouting?

The answer is a resounding NO!!! Here are five key facts to better understand this equation:

1. We cannot make new carbon. There remains the same number of carbon atoms present on the planet since the very start of time, and they move between three storage systems. Carbon is stored in the soil as humus, in carbon-based life forms (e.g. plants, animals and humans), or in the atmosphere (as CO2 and methane). Carbon moves between these three storehouses in a phenomenon called the carbon cycle.

2. The lion's share of this carbon resource is stored in soil. In fact, there is almost double the amount stored in the soil as orgnaic matter, compared to that stored in the atmosphere (1550 gigatonnes vs 800 gigatonnes).

3. Two thirds of the carbon that was once int he soil is not in the atmosphere. Global organic matter levels have dropped from an average of 5% down to 1.5% during decades of blind extraction with the industrial farming model.

4. This carbon lode, which was historically soil-based, is now the primary culprit in thickening the blanket of greenhouse gases that trap the heat, warm the oceans and dramatically impact our climate.

5. The solution is to put it back whence it came. When we build organic matter in our soils, we are effectively stepping into the carbon cycle and sequestering carbon into the soil, whiuch would have otherwise returned to the atmosphere.

Farmers are the only people who can save the world, but they need some support from the soil creatures responsible for building stable organic matter. Unfortunately, modern farming practices have seriously impacted these humus building helpers. The central mantra of a more biological approach to food production involves a recognition of a "give and you will receive" relationship. You look after your soil workforce and that interralted system will look after you. The question remains "which of the workforce is most worthy of our support, in relation to the urgent building of stable carbon?"

Fungi to the rescue

You can make compost from lawn clippings, apply a generous dose to your farhen and observe the soil darkening with the introduction of the compost. However when you return to that soil six months later, it has often reverted to the original colour. This active carbon produced by bacteria can oxidise and return to the atmosphere. Stable humus is created by fungi, and this form of carbon remains in our soils (and out of the atmpshere) for at least 35 years. The concerning part of this story involves our new understanding that the beneficial fungi responsible for stable carbon storage are sadly missing in our soils. We have killed them off with fungicides, herbicides, nematicides, excessive tillage, long fallow periods, and acid / salt fertilisers. One group of these creatures, mycorrhizal fungi, has been decimated to the point that just 10% remain.

There is a desperate need to feed our remaining fungal workforce with humates, kelp and cover crops, while introducing a new workforce that includes mycorrhizal inoculums and fungal dominated compost teas.

Mycorrhizal fungi release a sticky carbon -based substance called glomalin, which is responsible for 30% of all the humus in the soil. These critically important creatures can be reintroduced and should be government subsidised to encourage a rapid response from all farmers.

However while global entepreneurs dream of colonising a barren red desert called Mars, we barely understand the biological essence of a gloriously beautiful precious jewel called planet Earth. We have identified and named 20,000 nemtodes, for example but DNA analysis reveals that more than one million different  nematode species exist in that barely understood world beneath our feet. Surely we should be directing some of those billions destined for space exploration into developing a better understanding of the space that grows our food - the soil that can save us.

We need to band together and return carbon to the soil. We need to embrace humus building as a sacred mission.

Ten humus building tips

1. Don't burn down your cover crop - a cover crop contains a rich lode of carbon, nitrogen and sulphur, but all three of these minerals will revert to their gaseous form following a herbicide burndown. This trio is desperately needed in most soils, so it is farm more productive to lightly work the cover crop itno the A horizon (the top few inches of your soil).

2. Include legumes in every pasture and under every cereal crop - legumes like clover tend to feed the fungal component of your soil foodweb. It is this network of hyphae that bind humus and clay colloids to create the holy grail of soil health - crumb structure. These aggregated soils breathe more freely while allowing humus building maestros, like earthworms to deliver their gifts unimpeded. The clovers under your cereal crops also deliver nitrogen, and they release acide exudates to prize apart the two most important minerals (calcium and phosphorus) for the most important of all plant processes, photosynthesis.

3. Plant cocktail cover crops whenever you can - we now understand that the combination of five plant families in a cover crop blend sponsors a remarkable phenomenon. The plant roots begin to message each other before initiating an outpourint of phenolic compounds into the surrounding soil. Just as our body cells thrive in the presence of similar compounds from green tea and dark chocolate, the soil - life slips into hyperdrive. Soil structure changes, humus creation hastens and this cover crop boosts all of the benefits bestowed by beneficial microbes. The five plant families include grasses, cereals, brassicas, legumes and chenopods. The latter two are included as small percentage so fthe total blend because they release biochemicals that dissuade friendly fungi. however they must always be part of the package to create the desired response.

4. Discover humates - humic acide is the most powerful promoter of the beneficial humus - building fungi that are missing in most soils. These fungi seek the long chain carbohydrates and complex compounds that are abundant in this natural substance. When suitably restored this mising link creates the stable carbon that will stay in your soil, and out of the atmosphere for most of your remaining lifetime. 

5. Embrace compost - compost is much more than a conglomerate of humus substances created through fast - tracking and optimising the natural process of decomposition. Compost provides vast diversity and numbers of beneficial organisms to reclaim the capacity of your soil to build humus. There can be five billion organisms in every teaspoon of compost, involveing over 30,000 different species. Much of this workforce has been compromised with acid / salt fertilisers, farm chemicacls and mismanagement of our soils. Compost restores these key players so that the end result in terms of soil carbon increases becomes many times more than the humus added in the compost.

6. Minimise tillage - the component of our soil biology so despeately in need of nurturing does not favour the intrusion of cold steel. Tillage slices and dices beneficial fungi like the ragged claws of a brown bear knee deep in schooling salmon. Every time we open the soil we also introduce oxygen, which oxidises a percentage of our precious humus. If we choose to work the soil when it is wet, then that loss is magnified several fold. The major issue with no-till farming revolves around the dependence of glyphosate. It is hard to envisage glyphosate free, no till, but we will surely develop roller crimpers, cover crops and other alternatives to compensate for this loss. 

7. Bring back your earthworms - these gut like segmented tubes are effectively the 'intestines' of the soil. They serves as part of the plant's external stomach by digesting crop residues, producing plant food and incubating a unique group of beneficial bacteria without which your soil life community is sadly incomplete. Most soils contain a fraction of their original earthworm population and there is a big price to pay for this loss. Earthworms are little fertiliser factories because the composted material emerging from their rear ends differs hugely from the surrounding soil. In fact, it contains tem times more potassium, seven times more nitrogen, five times more phosphorus, three times more magnesium and 150% more calcium. The earthworm composts crop residues and other organic material four times faster than any other form of decomposition and it aerates the root zone and transports minerals from beyond the root's reach, to boost plant growth and resilience. If you could achieve the holy grail of 25 earthworms per shovelful of soil, this squiggly workforce will produce 300 tonnes of earthworm castings per hectare per year. . Earthworm compost retails for around $100 (AUD) per tonne, so you hav just secured $300 (AUD) worth of free fertiliser. You have literally struck pay dirt!

8. Incorporate livestock - Rudolph Steiner, the founder of Biodynamics, stated that a farm was not a farm in the absence of cattle. Many crop producers have discovered the wisdom of these words. Pasture cropping and cell grazing often combined are proven humus building tools. In fact they may be amongst the most powerful ways to reclaim organic matter as they both involve minimum soil disturbance and that is where the fungi thrive.

9. Enhance stubble digestion - in a truly active soil, your crop residues should become an integral part of the soil within siz weeks. If they are still there months after harvest they you still have some work to do. The sooner this stubble can be converted to humus the better as the residues will otherwise gradually revert to the gaseous form and we have lost a wonderful humus building opportunity.

10. Provide oxygen for your workforce - the single most important element for crop vigour and resilience is not N, P or K. its the gas that grants life to microbes, plants, animals and humans - oxygen. The calcium to magnesium ratio is paramount amongst several key ratios, because it physically helps create the open structure that allows the soil to breath. Gypsum can be an immensely valuable tool in this context, as this clay - breaker removes excess magnesium and sodium from the equoation. These minerals are key players in tight, closed, unproductive soils.

In Conclusion

We are confronted with our greates ever challenge, but climate change is reversible. The good news is the win/ win situation linked to this eneavour. When we build humus in our soils we sequester atmospheric CI2 and thin the greenhouse blanket. We also reduce soil erosion, increase soil health, boost profitability and improve the quality and medicinal value of the food we produce. It sounds like a compelling list to inspire the adoption of humus building strategies on your farm.