Farming carbon: part of the solution?

This column was published in the Waikato Times on July 14

dairy-farmCould New Zealand agriculture be part of the solution to climate change?  We know all too well that it is part of the problem – and that’s not an accusation, by the way, just a recognition.  But problems are there to be tackled, and what is called carbon farming looks like one way in which agriculture can substantially contribute to climate change mitigation and at the same time improve the soils on which it depends.

The concept is simple.  It is to increase the carbon content of soils, so that a greater proportion of the atmospheric carbon dioxide absorbed by plants remains stored in the soil. Globally, there is huge potential for enhanced carbon storage through management changes and soil restoration. Widely employed it could lead to a significant lowering of atmospheric carbon dioxide levels. The benefit for the soil is that a high carbon level greatly improves its structure, aeration, porosity, water holding capacity and nutrient holding capacity, all of which enable better growing.

Hamilton soil scientist Robin Janson, of Ecosynergy Research, works on biochemical indicators, measuring soil microbial activity. High activity tends to correlate well with high soil carbon levels. He is helping set up a New Zealand carbon farming association to get the message out that increasing soil carbon can be a practical consequence of good agricultural practice.  He explained that by world standards many NZ soils already have exceptionally high levels of carbon, which, depending on agrotechniques, can increase or decrease. Indeed some think that the soils are at maximum capacity and in a steady state whereby the carbon taken in through photosynthesis and the carbon released back into the atmosphere balance at an optimum level.  He agrees this may well be the case when considering standard soil tests, where only the top ten centimetres are measured. Under high fertiliser and/or tillage, increases below ten centimetres are rarely seen. Dr Janson says there is ample scientific and field based evidence supporting the building of higher levels of carbon at these depths.

How is this achieved?  Through a variety of management practices, which may vary depending on the purposes for which the land is being farmed and the way soils respond.  The range of possibilities is wide, and the few mentioned here should not be thought of as complete. Full ground cover is important to prevent soil being blown or washed away and to improve the conditions for those microbes and small animals that engender soil health. For pastoral farming this means avoiding overgrazing, pugging, and heavy chemical fertilisation. Light rather than heavy grazing is also important to enable plant roots to go deeper into the soil where they help create more carbon.  Where crops are being planted, no-till methods are preferred (the majority of Canada’s crops are managed under no till today). Farmers abandon ploughing and plant seeds by dropping them into ruts which barely disturb the soil. Disturbing the soil releases soil carbon. The more stable forms of soil carbon tend to build up more when least disturbed.

The message is that careful and knowledgeable management aimed at substantially increasing the carbon content of soil can and does succeed. Innovative farmers have already proven this to be so.  Some are already looking at the prospect of trading carbon as the substantial build-up in their soils is certificated – a welcome supplement to farm income.

Carbon farming is a win win approach, another reminder that there are ways still open to us of restoring the balances which enabled human civilisation to develop on Earth.  Sustainability can be for real if we make the changes good science points us to.

19 thoughts on “Farming carbon: part of the solution?”

  1. Interesting article.

    The big question really is the scale – how much carbon can be soaked up by a typical farm at what rate? ie what is the net carbon credit per hectare per year on an average number of stock units, with/without other technologies such as nitrogen fixers? How much land would need to be carbon-farmed to meet a “40 by 20” target in Agriculture alone?

    Is there a limit to how much carbon can be contained in the soil, or does it just keep piling up?

    1. Sam, I’ve checked with Robin Janson. He reports that the answer to your first set of questions unfortunately is “it depends”. This is because the issue is complicated, and the “depends” relates to what soil types, what land management, what climatic region etc. Your valid questions can’t be fully answered without long term research under local NZ conditions.

      The answer to the question in your second paragraph is easier. Carbon levels will build up to an equilibrium point depending on those same factors above. It will not keep “piling up”, and in fact in some soils may already be at maximum potential levels for the given farming or natural environment. Other soils, for instance the Pukekohe soils, have lost so much organic matter (read Carbon) that their potential to sequester carbon is much higher, but would require a change in farming practice.

      1. I think farmers need to realise this point. Yes, there is a possibility you can make a profit in the short term with carbon farming, but long term the profits will disappear (same as forestry carbon farming).

        And if you ever change back to the old management practices, you will have to pay all the carbon back.

        That is the message that needs to be told. Not this, farmers are the answer garbage.

        1. R2D2 you completely overlook the essential importance of carbon farming, which is that it appears to offer the possibility of taking CO2 from the atmosphere while at the same time improving soil fertility. This is not garbage, as you describe it, but a serious prospect in the battle against global warming. The possibility of carbon trading was a minor consideration in the column. Your comment is pointlessly destructive.

        1. Depends on how much carbon you want the soil to contain. Topsoil mining through turf farms is a sad practice in some of the best farmland in the world. Very little carbon in that soil, compared to that of the old growth forest that used to exist in many of these places. And very little in the shallow root structure of turf. The problem is here, is the best way to get beneficial carbon back in the soils, and there is much more naturally present in functioning, biological soils.

  2. There is about twice as much carbon in the world soils as there is in the worlds vegetation (1200 to 1600 Gt). So raising the percentage of carbon in soil by even a small amount would make a significant difference. The trick it seems, as far as NZ soils is concerned, is to lower the depth to which the carbon is stored. Some of the farming practices are highlighted above. The CSIRO has been making a significant contribution to the study (Australian soils obviously – quite different to ours) but their website is well worth a visit.

  3. Soils do, indeed, hold a lot of carbon and if a few simple changes in farming practices could lead to the sequestration of additional carbon that would be great news. But as a farmer with no-till experience, I know that things are rarely so simple.

    Consider that the carbon in soil is in a variety of forms — some ancient and relatively stable, some very recent and transitory. Standard soil tests do not discriminate, lumping it all together as Organic Matter. How much of it is stable? We don’t know. No-till farming has saved countless tons of topsoil over the last three decades, which has had the effect of keeping carbon in the soil rather than in a river delta, for instance. But does it directly sequester carbon? I have my doubts — anecdotal evidence notwithstanding.

    Leaving plant residue on the surface exposes it to the elements and considerable biological activity. Since no-till practices concentrate nutrients near the surface, many soil scientists recommend that no-till farmers take shallow soil samples — only 5 to 10 cm deep, rather than the traditional 20-cm “plow layer” depth. As a result, farmers (and scientists) may see an increase in soil OM — but they are sampling only the highest-carbon part of the soil now. Very little research has been done on the effects of no-till to carbon throughout the entire soil column.

    And shallow carbon is vulnerable carbon. A single pass of cultivation (to heal ruts left by a soggy harvest, perhaps) will release years of recent, fragile carbon to the atmosphere. I don’t know how such things could be monitored by a carbon board, nor do I know many U.S. farmers who would sign away the right to till their soil, if necessary.

    Another issue is that one of the first things dedicated no-tillers do is to drain their wet ground. Soil carbon is in balance with several factors, including mean annual temperature, annual rainfall, soil texture, and cultural practices. When you see dark (high-OM) soil, it is usually because it has been wet for thousands of years and carbon has accumulated under anoxic conditions. Drain that soil and the carbon begins to leave. One of our farms had drain tile installed waste-deep a century ago. Today, the tile is near the surface.

    The practice of no-till farming has been very successful in conserving topsoil and often reduces the cost of production. But the headaches surrounding verification of a “carbon farming” scheme and the very real question as to whether it even works leave me wanting more information before we sign off on such a plan.

    1. Perhaps we should be considering the basic structure of our farms more closely – for instance in the past few years I have had a rather wet piece of land on my farm (about a 2 hectares) – that had been previously drained but the drainage needed replacing. Instead of installing new drainage I have fenced it off, and reverted that land back to what it was originally – wetland. Planting sedge, rapo, and other wetland species has lead to a significant improvement in the environment of the farm. Wetland birds are returning. The stock have more shelter. The run-off is not straight into the stream and river. Of course it cost me something to do – but maybe there could be incentives funded from carbon credits for others to do likewise.

      1. There is a very interesting concept called a “biodiversity offset” that you appear to have stumbled on accidentally. See here for one initiative. At its most basic it involves compensating for loss of diversity through development (the sort of trade-off that often happens in the RMA process), but it is being extended into a sort of “super carbon offset” (example). Something that dairy farmers in NZ might like to consider…

        1. It wasn’t accidental Gareth. I was surprised at just how rapidly it did all happen, but it was planned and intended. I wasn’t aware of the “super carbon offset” however. I hope it gathers some legs! Reading the Frogblog post tonight on the difference between “town and country” however makes me think that the majority of our farmers have a long way to go, and we won’t get there until there is a change of heart.

  4. Irrigating the dry parts of the coutry is one way to greatly increase the carbon content of the soil. This is one argument in favour of the rpoposed Central Plains Irrigation scheme in Canterbury.

    1. Cropping in such ways that conserve soil moisture seems to be a better way to go. Name one irrigation scheme on land that is usually dry that does not have eventual severe problems with salt loading in the soils, leading to massive soil failure.

  5. I agree that land management approaches are the most effective way of influencing organic matter levels in our soils. But probably the one that has the biggest effect is the nature of the crop. Pasture and grassland are most effective in accumulating soil organic matter. Cropping actually lowers organic C levels – and that goes for forestry too.

    I think the positive effect of pasture/grassland is due to physical protection of organic matter. We researched this several years ago, with respect to decline of organic matter and release of nutrients from organic forms, in pasture soils converted to forestry. This had been thought due to biological activity of soil fungi under pine but our results showed higher activity under pasture. Soil physical data supported a protection mechanism from grasses.

    Mind you, we can’t convert all cropping soils to grassland for economic reasons. And pastoral farming has its negative effects, anyway.

    The idea of trapping atmospheric carbon by conversion to charcoal and incorporation into soil has been raised here previously. There has not been much work on charcoal addition here but it could be worth pursuing. I am thinking particualrly of handling wastes such as biosolids (sewage sludge) in this manner. Consideration has been given to applying biosolids directly to soil – and there are issues. A safer way could be to added biosolids after conversion to charcoal. (The conversion process would probably yield other useful products like oils and nutrients).

    This would help solve the current problem of biosolid disposal.

    Anecdotal evidence of positive effects of charcoal addition may not be relevant to NZ agriculture(I wish someone would check this out), especially as most of our soils are high in organic matter . But it is unlikely to be harmful. And its just possible that charcoal could be used as a carrier for fertiliser nutrients or other soil amelioration chemicals such as lime so application may not involve extra work. I think this idea could also be worth some research investment.

    Personally, I think we have got to try and incorporate waste management into problems like this. It seems a pity not to recognise the resources existing in many waste products, while at the same time we lament the facts of resource depletion.

  6. My (Robin Janson’s) tuppence to the debate here. In short, we know relatively little about the factors predisposing a soil carbon buildup. One of the problems overlooked is that we talk about carbon as if it were in one form. There are literally thousands of identified (and probably more unidentified) chemical compounds containing carbon (therefore organic compounds) that have very different dynamics in the soil environment. We need to better understand the factors leading to those stable fractions that will lead to an increase in carbon. All this can only really be practical when the end result is better for farmers AND the environment. In the case of building soil organic matter, we solve many problems farmers face such as nutrient retention and cycling, soil structure, aeration disease control etc. Do we have the perfect set of protocols to achieve this? Not really, and we probably never will have. Also, not all activities leading to more C capture are necessarily beneficial from a soil health perspective, so its not a panacea. The important point here is that by going for the goal of more C in the soil, we concomitantly achieve improved agroecological outcomes. We (humanity) win. Although we do have enough information to go on to say “this is the right direction”. and finally. true to that eternal statement emanating from scientists, there is that perpetual need for more research…….

  7. Kia ora katoa, it’s great to see these soil carbon sequestration issues being discussed in the public domain. My special interests are plant biology, mycorrhizas, symbiosis, no-tillage / no-dig no-weed, revegetation & restoration of disturbed soils, cover crops, organic farming & biochar. I agree that we’ll always need more research, but the non-scientific expertise of organic gardeners also has to be acknowledged in the need to manage soil organic matter. There is no getting past the need to “FEED THE SOIL”.
    The contestable funding regime that most institutional scientists have been dependent on has led to far too much attention placed on research that is tied to the development (R&D) of technologies that can provide an economic ‘return’ of the research ‘investment’ … & too little attention being focused on “Public Good Science” research or basic science required to understand improve the quality of human management of our environment.
    Even when New Zealand scientists do come up with environmentally ‘friendly’ technology, they are likely to be up against the vested interests of larger global corporations. Universities don’t always encourage academic freedom or assist inter-disciplinary relationships that protect intellectual property or put the most valuable lessons from research information into the public domain. New Zealand has developed some of the most effective no-tillage technology, see
    The production of Biochar doesn’t necessarily have to be high tech, (e.g. Carbonscape). Nor does the use of biochar as a soil carbon sink have to be high tech, however, I believe that no-tillage technology is likely to have a significant role in assisting the effective placement of biochar into the upper soil layers.
    Current research by Dr Robert Hill & others at Lincoln University’s BioProtection research unit is indicating a significant potential technology role for inoculating nursery seedlings Trichoderma. Biochar could potentially be used to replace commonly use nursery commodities such as expanded clay minerals vermiculite, perilite & zeolite. My personal interests in mycorrhizas leads me to be hopeful that biochar could also make an effective “carrier medium” for broad-acre no-till inoculation of biologially & physically degraded soils & plants for revegetation of habitats in Australia, Africa, China, North & South America.

    New Zealand is indeed RELATIVELY fortunate that our production soils usually have good levels of soil organic matter & humus. This doesn’t mean that we couldn’t produce & use biochar locally & for export. Biochar can adsorb organic compounds & mobile nutrient ions that may otherwise cause eutrophication or pollution of soil water & surface waterways. This idea may not be attractive to the economic interests of the mainstream soluble fertilser industry, (or is it?) … Perhaps this vested interest group could be encouraged to ‘invest’ in more sustainable nutrient technologies that recycle crop & animal wastes, as well as urban organic waste streams, in a model similar to how BP has sought to invest in a technological future “Beyond Fossil Fuels”.
    There is no pancaea or single simple technological fix, but we need to do the best we can to understand how to better maintain & encourage biologically active soils. Yes this global warming is serious & depressingly little is being done to prevent matter getting any worse than they already are, we need to act ASAP. If politicians or their advisors are paralyzed into inaction by complexity, then we need to show them as many ways forward to protect & save our precious natural inheritance.
    Kia kaha katoa

  8. Great comments! It’s good to read the article.

    It is essential to study many of the questions brought up here – if we don’t know what we are measuring, we can never protect the integrity of any carbon sequestration scheme so that people are assured that they are getting good value for money from carbon sequestration projects.

    Two things:

    Spreading sewage sludge around has been proposed for forestry in BC, and water from the sewage treatment plant in Cranbrook, BC is being used for irrigation on cattle ranches in the area.

    I have grave reservations about spreading sewage sludge that has hormones, plastics, latex, ammonia, and who-knows-what from everyone’s sink, at least until we understand what a toxic waste problem that we have created with our attitude towards throwing things “away,” as if such a place existed. I understand that you are talking about carbon created from sludge, with a treatment process. But until we can count on our sewage being clear of ANY substance that will harm “any child, of any organism, for all time,” to paraphrase architect William McDonough, we would merely be treating a problem at the end of the pipe, again, resulting in an expensive, industrial process. Potential for failure in trying to benefit natural systems through industrial solutions is unacceptably high.

    Second: though this vein of continuing research is important, we should simply get on with it. The benefits to society, the economy and to the environment of forest restoration strategies is clear and understood. We can fund some of it through carbon offsets, a potentially huge deal. But we should get on with planting multiple species, take advantage of young saplings and trees for forest products, develop engineering standards for timbers from young trees, and fix as much carbon as possible, soon. The amount of forest that has been removed within the past 200 years is staggering. That is all we need to know right now to get with it and start restoring. There are many ways this could be done.

    One: while the research is being hammered on farming carbon, windrow management could be enhanced through carbon offsets for planting more trees, and native trees at that, on more of a farmer’s total land area. Income can result for the farmer, for both the carbon offset and forest products from sustainably managed small forest tracts.

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