How to Celebrate 25 Years in a Soil Carbon Project - Part Five of Six - Nurture and Enhance
Agronomic Evolutions
Progress never stands still. Agronomic challenges are continually being solved and exciting opportunities always present themselves when change is at foot.
Once a grower is in a 25-year soil carbon project, there is a clear financial reasons to care about seriously building soil carbon. Carbon is now on the balance sheet! The question becomes, “what else can I do to grow carbon in my soil?”
Foundational Practices for Carbon Sequestration
Best management conservation farming practices provide great foundational operations to underscore a soil carbon project. The three principles we are aiming to achieve are;
Low soil disturbance - protect aggregate stability…because that’s where the carbon is stored. Aggregate stability (water stable aggregates) is the centerpiece of soil efficiency. Fungi hyphae provide the physical mechanism that wrap up and bind soil particles into stable aggregates. I call these fungi the dung beetles of the fungi world.
Moisture management - water grows crops and carbon. A well aggregated soil can absorb more water, hold more water and drain more water when there is too much, keeping soil moisture conditions in the sweet spot for plants. A balance of macro aggregates and microaggregates allows optimized soil function and moisture conditions. Soil peds are evident as discrete structures.
Nitrogen management. Grow your own nitrogen - legume nitrogen is King for growing carbon and grain yield (and reducing emissions and fertiliser costs).
The practices that support these principles are well known and broadly adopted and include;
Stubble retention - protect soil surface from the drying sun and winds for fallow moisture conservation. Standing stubble also helps protect from heavy rain events with stubble root channels ushering rain into the soil to greater depths as well as slowing run off and erosion.
Min & zero till- tillage breaks up the microaggregates and exposes the trapped aggregate carbon to oxidation and loss. Small pores or capillaries create a network for stored water (capillary water) Large pores allow drainage to avoid water logging and hydrolysis (loss) of the more labile soil carbon fractions. Tillage destroys the important pore structure in soil.
Controlled traffic - broadacre machinery is heavy and heavy stuff squashes the critical pore structure out of soil…making it harder for roots to perform their function and for carbon to be fixed in the soil…simples.
Legume rotations - naturally fixed nitrogen from legumes helps drive carbon sequestration. Most farmers will attest to the fact that legume nitrogen outperforms synthetic nitrogen regarding crop health and yield. Indeed, kilogram for kilogram, legume nitrogen is ~4 times as effective for plants compared to synthetic N.
Legume nitrogen is beneficial for carbon sequestration also. To build soil carbon you need nitrogen, and legume nitrogen is the preferred source for amplified carbon sequestration.
Soil Ameliorants - Lime & gypsum applied strategically to modify soil pH and sodicity respectively are well understood practices that can remediate soil constraints, plant growth, root expression and in turn support soil carbon sequestration.
Mindset - what physical practices are adopted on a farm are initiated in the neural pathways and synapses of the farmers mind. Following a principle of first asking “will this improve my soil health and fertility” is the genesis of great farming outcomes. Yield, quality and climatic resilience of crops inevitably comes from the state of the soil.
A 25-year soil carbon project gives stronger financial feasibility to spending money on soil health inputs and strategies because ACCU’s are now also on the balance sheet to add to the ROI.
Agronomic Ideas for Further Exploration
Outside CarbonBuilder fungal inoculum which has been discussed in the previous Carbon.Calling blogs, some of the emerging practices that deserve further attention and research towards supporting a soil carbon / ACCU generating project include;
Multi-Species Cover crops - There is much merit to utilizing multispecies cover crops in rotation when the opportunity arises. A variety of rooting depths and root exudates deliver significant beneficial structural changes in one season that could not be achieved with steel and diesel.
In combination with CarbonBuilder inoculation, MS cover crops in a dedicated ‘carbon + nitrogen accumulation rotation’ and either browned out at Springtime, grazed or cut for hay could provide a significant lift in soil carbon accumulation particularly in combination with CarbonBuilder inoculation that helps secure the extra carbon load into long term carbon pools.
Designing the mix to suit your geography is important and swaying the mix towards legume dominance could be very important towards maximising legume nitrogen fixation that will amplify the yield and carbon build in future rotations.
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Compost & Compost Granules - two new players in the market are Mort and Co compost granules made from composted feedlot manure, and Southern Cross Nutrients compost granules made from composted FOGO (food waste). Compost granules applied at sowing at 100-200 kg per ha into the furrow may help root biomass accumulation and improve the efficiency of nitrogen and other nutrients according to early university research.
Compost granule research in repliczted strip trials conducted in 2023 by SoilCQuest showed promising results (research soon to be released).
Root stimulants - The main way carbon is transferred from the air into the soil is via the roots, either as root biomass or as the exudates that leak from actively growing roots. Root exudation is by far the largest contributor to the carbon flow into the soil. This liquid carbon pathway requires fungi in the soil in order to stabilise this easily-lost carbon into long term fractions of recalcitrant soil organic carbon. By stimulating a crop to produce bigger roots with greater exudation surface area into the soil profile means greater potential for carbon sequestration.
There are a number of commercial products and specific compounds that stimulate root growth. Research is continuing at SoilCQuest into the influence of a number of these products and their potential influence on carbon sequestration.
High Intensity Legume Rotations - dedicated high intensity legume rotations where the crop is selected specifically for the nitrogen contribution to the rest of the rotation has a lot of potential. Feasibly the N demand of an entire rotation could be catered for by one season of a high biomass legume crop.
For example;
2.5T/ha canola crop requires ~100 kg of nitrogen
6T/ha wheat crop requires ~120 kg of nitrogen
6T/ha of malting barley crop requires ~ 100 kg of nitrogen
TOTAL for rotation = 320 kg of nitrogen required.
Given a well-inoculated legume crop should fix 30 kg of N per tonne of above ground biomass, we would need to grow a 10t/ha biomass legume crop to comfortably grow enough N for the following three rotations in this scenario.
Winter vetch, clover and medic varieties and summer legumes such a Lab Lab, Cow Pea and Pigeon pea are potential choices to consider.
For those thinking about the potential of going carbon neutral and attracting associated grain premiums, reducing or eliminating urea would be high on the agenda given the high carbon emissions associated with that product, and the high cost of this fertiliser in a cropping program. With ACCU's now on the balance sheet in a carbon project, the economics of a legume rotation helping to create more carbon credits start to add up.
Of Black Swans and Black Elephants
A black swan event is an unknown and unpredictable risk or disaster. A black elephant is an extremely likely and highly predicted risk or disastrous event that is usually ignored by many or society as a whole. The phrase comes from a combination of a ‘black swan’ and the ‘elephant in the room’.
Unequivocal and convergent global scientific consensus combined with demonstratively escalating and intensifying climate extremes around the world tell us we will be farming into a changing climate of increasing extreme weather events. Building resilience into the farming system has never had a downside, however the importance of resilience is now a critical business decision in order to buffer against future extreme weather events.
Building soil health and soil carbon levels is a fundamental way to build resilience into your cropping business. Soils that can absorb more water, hold more water and provide drainage when there is too much water allow crops to better manage through tough conditions.
Of course, food security into the future will rely on increasing farming resilience. Soil health has never been more important. A carbon project commits the farm business to building soil and crop resilience year by year. It's like a commitment to a savings plan...it simply automates good decision making.
At the same time, a carbon project draws heat trapping carbon dioxide from the atmosphere where we don't want it and solidifies it into the soil where we do…year in year out... taking the farm and the broader industry incrementally but inevitably in a positive direction.
A 25-year carbon project is simply being on the front foot. A carbon project delivers a true win-win-win for the farmer, the environment and the legacy for the next generations from which we all borrow the land we farm.
Keep an eye out for the sixth and final part of
'How to Celebrate 25 years in a Soil Carbon Project'
Legacy
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For more information contact Guy R Webb