No-till farming does NOT save carbon and is NOT a carbon offset

The list of very knowledgeable folk who still are pushing no-till farming as a greenhouse gas mitigation strategy even though science passed them by a while ago include:

I buried the science in the McCain post, but it deserves higher visibility. As a major review article from Agriculture, Ecosystems and Environment, Tillage and soil carbon sequestration–What do we really know?” concluded:

In essentially all cases where conservation tillage was found to sequester C[arbon], soils were only sampled to a depth of 30 cm or less, even though crop roots often extend much deeper. In the few studies where sampling extended deeper than 30 cm, conservation tillage has shown no consistent accrual of SOC [soil organic carbon], instead showing a difference in the distribution of SOC, with higher concentrations near the surface in conservation tillage and higher concentrations in deeper layers under conventional tillage.Long-term, continuous gas exchange measurements have also been unable to detect C gain due to reduced tillage. Though there are other good reasons to use conservation tillage, evidence that it promotes C sequestration is not compelling.

[Conservation tillage is “broadly defined as any tillage method that leaves sufficient crop residue in place to cover at least 30% of the soil surface after planting.]

This is actually not especially new research. The review article went online in June 2006, and, of course, as a review article, it was based on even earlier research — including a 1981 (!) study that came to the same exact conclusion:

That study compared “SOC and microbial biomass in long-term plowed and no-till cereal plots. They found no differences in either parameter between the two treatments when they sampled to 40 cm on an equivalent depth basis (equal mass per unit area), and concluded that no-till

has little effect on soil organic matter, other than altering its distribution in the profile.

Even worse, the review article notes

Studies that have involved deeper sampling generally show no C sequestration advantage for conservation tillage, and in fact often show more C in conventionally tilled systems.


Time to scrap no-till farming as a carbon offset or greenhouse gas mitigation strategy.

* I confess that I relied on the Princeton “stabilization wedges” analysis myself for including this as one of the 14 or so needed to stabilize carbon dioxide concentrations below 450 ppm (see here). It was only at this April American Meteorological Society seminar, “Biofuels, Land Conversion & Climate Change,” where I learned of this review article. It just goes to show you that you should always check things yourself as much as possible with primary sources. That’s why I am trying to go through all of the major climate solutions (and non-solutions) this year as thoroughly as possible with numerous links to primary sources.

26 Responses to No-till farming does NOT save carbon and is NOT a carbon offset

  1. Carol says:

    I didn’t realize no-till was being pushed as a C-sequestration strategy. I always understood it as a water conservation method, and watershed protection method, which are also important goals. Anything that disturbs the soil will release C.

  2. drwoood says:

    Joe, I have a question related to US emissions from land use, land use change and forestry (LULUCF), that maybe you could shed some light on.

    According to the EIA, in 2005, LULUCF was a net sink for 828.5 Mt CO2. Of this 828.5 Mt, 698.7 Mt was from ‘forestland remaining forestland’. It seems to me that unless the forest is growing back significantly, with the trees getting much bigger, the emissions from ‘forestland remaining forestland’ would be zero. Normally one would expect the carbon flux from land use change to be much larger than the carbon flux from land use.

    In Australia, where I am from, and with a country with a roughly similar area to the US, the emissions from LULUCF are estimated to be 30 Mt CO2, with 50 Mt from deforestation and about 20 Mt from new forests. Looking at countries around the world, while some like Indonesia and Malaysia are emitting similar amounts of CO2 as the US is supposedly sequestering, I see no other countries sequestering anything like as much CO2 through LULUCF. I have also looked at maps of which countries are planting forests and which are chopping them down, and the most forests planted appears to be in China, with the US not appearing to be significant.

    So my question is: is the US doing some amazing land use to be sequestering all of this carbon, or is this the result of different account (which could be to do with the US not being a signatory to the Kyoto protocol), or are these figures completely bogus?

  3. Stephen Mulkey says:

    Joe –

    It is useful to raise the issue of whether or not conservation tillage can improve soil carbon stocks, but it is too soon to reach the conclusion in your headline. The article that you cite by Baker et al. is a commentary, not a regular article. As such, it draws on the authors’ reading of a relatively limited set of studies.

    I would suggest that we need additional gas exchange and SOC analysis to determine how conservation tillage may function in various soils. In Florida, because of warm temperatures and abundant rainfall, much of the SOC is leached to lower levels. I would expect total SOC to be higher under no-till because less carbon would be lost from the surface due to runoff and microbial respiration. In effect, the longer surface carbon stocks remain in place, the more opportunity for carbon to be leached to lower soil layers where it could be sequestered long term.

    We need more study of this issue, and your strongly worded conclusion may serve to further polarize opinion about the value of offsets in the lay community. I suggest that we call instead for a comprehensive study and review of North American agricultural soils. We need to know more, and this can be said about most forms of offsets from forestry and agriculture. In general, we must establish a credible baseline and quantify real additionality before offsets can be marketed. The manual by the Nicholas Institute makes this point. Offsets should be established on a case by case basis, after appropriate analysis of local conditions and existing management practice. It seems that the carbon market in the US is running ahead of the science and ahead of the development of official regulations.


    Stephen S. Mulkey, PhD
    University of Florida
    Gainesville, FL 32611

  4. Joe says:

    Dr. Mulkey — I’m sure you are infinitely more knowledgeable on soil science than I am, but I stand by the headline.

    Given all the studies casting doubt on the carbon benefit of no till going back many, many years, I’m afraid to say that one or two new studies would not justify diverting billions of dollars from real proven carbon-reduction measures. Agricultural soils are well worth studying, but it looks to me like the climate policy community has been sold a pig in a poke.

    It is precisely because the soil carbon issue is such a complicated matter, whereas the consequences of failing to stabilize below 450 ppm are painfully uncomplicated, that no till as an offset strategy must be put on the shelf for the foreseeable future.

    This debate should have been aired in the policy community a while ago.
    I confess to have been stunned at the AMS seminar to hear an expert explain that no-till doesn’t sequestered carbon. The article I cite is Not what I would call a commentary, but rather a review article.

    If the next ten major studies on the subject all show conclusively a statistically significant carbon benefit, then perhaps the issue should be revisited. But we have simply run out of time for questionable solutions.

  5. Bob Kopp says:


    I agree with Stephen Mulkey — the commentary doesn’t seem to justify the headline. It does suggest that the uncertainties on carbon removal associated with no-till are larger than commonly assumed in the policy community — something which is, of course, very common for many offsets. The commentary agrees with the conclusion that no-till reduces erosion, which in and of itself increases carbon storage, though less than increased carbon flux into the soil would. But its main conclusion is not that no-till farm does “NOT save carbon”, but that more research is needed: “While conservation tillage practices may ultimately be found to favor soil carbon gain, the data reported to this point are not compelling.”

    All offsets should be examined with a critical eye, something well understood in the scientific community but not perhaps in all the policy community.

  6. Stephen Mulkey says:

    Joe –

    The article is labeled as a commentary, and not as a review article. There are fundamental differences in how journals treat such articles. I do agree that there are more than a couple articles that fail to find evidence of the putative effect of conservation tillage on SOC. I suggest that this is likely to vary from place to place, depending on existing conditions and management practice.

    That aside, you and I differ very little in our positions. I argue that because of the warming in the pipeline, we must manage carbon stocks in order to achieve stabilization below 450 ppm. The rush to market offsets is inappropriate until the local studies are done, and these studies can be done expeditiously and need not result in a delay in action. The same is true for forestry offsets. We need to examine the regional carbon stocks and radiant energy balance before deciding on a strategy for specific forests.

    I admire and share your passion. Again, my position is that the science shows that we must manage terrestrial carbon stocks if we are to effectively mitigate climate change. I refer you to the special feature of Nature Vol 451, Issue 17, 2008. Managing SOC is part of this portfolio. Conservation tillage may be appropriate in some cases, while inappropriate in others.

    Thanks for your reply. Let’s continue the dialog.


  7. If no till reduces erosion and keeps more moisture in the soil, then I would expect it to prevent further loss of carbon from soil, which is also a benefit. Whether soil carbon is added to is another matter, but would probably depend on what else is done with it and on vegetation cover. (e.g., if it gets compacted, less water will infiltrate and without water it won’t hold organic matter…) I’ll be reading more on this but would not be so quick to write it off.

  8. drwoood says:

    I have had a bit more of a look at US LULUCF emissions related to ‘forestland remaining forestland’ and they do include sinks from other land being converted to forestland. They do seem unusually high, but there isn’t anything obviously wrong with them – I have an open mind, Interestingly if Australia converted sequestered as much carbon dioxide through afforestation, then it could completely offset all of its emissions.

    Afforestation, avoided deforestation, and other LULUCF policies such as reduced grazing and overgrazing could play a very important role in climate change mitigation. There are sometimes also cobenefits from restoring habitat which could lead to climate change causing less species loss. The problem is that the uncertainties in measurement are huge.

    Peter Wood
    Dept Applied Mathematics
    Australian National University

  9. Andy says:

    Soil Organic Carbon is a tough one. I can think of some scenarios where conventional tillage could increase carbon sequestration on soils such as those in Florida because the dead plant material is being buried by the plow. Likewise, with high rates of erosion, a lot of carbon maybe sequestered through burial in anoxic stream sediments. Isn’t one of the goals of conservation tillage is to keep nutrients and organic carbon within reach of crop roots to reduce the need for fertilization and manure application?

    Regarding sequestration and forests. A possible explanation is that these numbers could change from year to year depending on where in the cycle of harvest of pine timber from private lands in the SE U.S. we are. During growth phases, a lot of carbon can be sucked up by young pines. I know we just ended a huge harvest phase due to losses from H. Rita and Katrina, and high rates of harvest due to the now over housing boom.

    Joe: how about a post on prairie restoration and carbon sequestration? The Ecological Society of America posted a position paper on the use of prairie grasses for biofuels. That could be a start. I would think that due to the very deep growth of prairie plant roots, and the apparent build up of organic carbon under prairie soils, that this could be a solution. Perhaps there’s some literature on this. Iowa recently converted many of their mown roadsides to prairie. Is there a carbon sequestration value there? What if all roadsides were converted to prairie? Would this be significant? What if the 100’s of millions of acres of degraded range lands were restored to native grassland? We don’t get a lot of beef off of those acres now. It could be done.

  10. Steve says:

    Does this relate to the claim that organic farming will sequester more carbon that conventional farming?

    And if so, how does it relate?

  11. David B. Benson says:

    Around here, dry-land soft white winter wheat is the predominant crop. No-till reduces soil loss significantly, reduces tractor diesel fuel consumption some and has become the prefered farming method. With the greaterly increased costs of diesel fuel I suspect the hold-outs will rapidly be moving to no-till techniques.

    This has nothing to do with SOC. In this area nitrogen (and its run-off effects) are the most important issue.

  12. drwoood says:

    The excess nitrogen from fertilizers not only ends up in the sea creating dead zones, it also forms nitrous oxide and adds to global warming.

  13. No-till and conservation tillage are important techniques, especially if organic no-till methods are developed and used (some no-till techniques substitute chemical inputs for tillage). They reduce farmings dependence on fossil fuels and reduce the carbon intensity of food production. This doesn’t mean they sequester carbon in the soil, which I am not competent to comment on.

    We desperately need agricultural scientists to work on new techniques that increase the energy efficiency of food production and enable the rapid introduction of electric and eventually renewable-energy powered farm equipment. Reducing the need for tillage is one important area for R&D.

    This is a really a matter of immense importance that has slipped under the radar.

  14. Finnjor says:

    As you know, soil CO2 is a big global issue. In Finland peat covers 50 % of the land, and most of it has been dried and forested or cultivated. So these peat lands have heavy CO2 emissions and are no CO2 sinks. Even the peat is taken up and burned, in large scale, and emissions worse than from coal.

    Homo idioticus is a global nuisance, as you see.

  15. No-till for reducing CO2 may be marginal but there are still virtues to the two other aspects: no ag fires (lofts soot which then warms air) and the top layer of crop residue holds soil moisture.

  16. Michael Plumer says:

    After 34 years of no-till research, I will have to say everything that is quoted in the article is and the listed research is “out of Context”. I have no-till research trials comparing no-till to conventional to converted conventional tillage to no-till. This will be the 40th year of the study. We have found that soil carbon has INCREASED 3270#/ acre each year over the 40 years. Compared to the conventional tillage soil that has lost 0.4% of the soil organic matter. The soil profile to 25cm has exactly the same carbon levels at 25 cm as it does at 5 cm. The most detailed soil respiration data has been done by USDA ARS lab in Minnesota which shows soil repiration is no-till is significantly less than conventional.

  17. Dano says:

    I agree with many of the above commenters.

    Joe, I find this yet another post of yours that ululates something that is too early to conclude.

    My undergrad is in EnvHort, and allows me to I agree with many of the above commenters regarding AVOIDED carbon (your ‘saving carbon’), SOC stocks, and Sylvia’s point that loss of soil carbon is the point – industrial ag is very good at losing soil carbon.

    Lastly, I reiterate that the tone and antagonism here is a self-marginalizing issue for your efforts. I have serious issues with RPs Jr and Sr, and think they are borderline FUD enablers, but if the person behind Dano were debating/presenting with them in public, I wouldn’t take your approach.

    Jus’ sayin’.



  18. David B. Benson says:

    Michael Plumer — Thank you. A question: when you write “soil respiration” are you referring to SOC, soil organic carbon?

  19. It’s worth noting that soil carbon makes up 46% of all offsets issued by the Chicago Climate Exchange from its launch in 2003 till December 2007 according to Ecosystem Marketplace’s 2008 “State of the Voluntary Market” report.

    Moreover, the financial additionality of these credits has been openly questioned in both the New York Times and the Washington Post.

    A debate for another day, perhaps, but soil carbon is looking less and less appealing as an offset type.

  20. Joe says:

    I’m glad there are many studies showing the benefits of conservation tillage. it sounds like a useful practice to promote. unfortunately, the catastrophic outcomes we are facing under global warming are becoming increasingly certain. if we are to avert catastrophe, we must invest heavily in strategies to reduce emissions that are even more certain. No till just does not make the cut at this point.

    Sorry if people don’t like the tone of this post, but I personally feel duped about this whole matter. Now we have the possible next president of United States using the 100% offsets as his primary cost-containment method in his cap&trade, featuring on offset that has not been conclusively proven to reduce carbon, and which some studies suggest may increase carbon.

    Sorry people, as I have said many times, the time to act is now, if not yesterday. We need to cut the wheat from the chaff, to use an agricultural metaphor, ASAP.

    DANO — you miss the point of this post I think. Absent a very high degree of scientific certainty, one must stick with the null hypothesis on an issue of this importance.

  21. Dano says:

    DANO — you miss the point of this post I think. Absent a very high degree of scientific certainty, one must stick with the null hypothesis on an issue of this importance.

    Joe, again I gnash my teeth after clicking on this bookmark.

    My default is that if someone p!sses off both sides they must be doing something right, but in this case you are engaging in binary logic: an either/or assessment of a strategy.

    There is no reason to reject no-till as a mitigation strategy. That is your argument as I read it.

    First, in an adaptive environmental management strategy (see Sylvia’s blog or here for more) – where we’re headed even tho the IPCC isn’t doing a good job introducing scenarios into popular dialogue – having a 95% CI [especially when *ahem* certain pundits insist we need to start yesterday] isn’t a luxury.

    Second, your read of the literature isn’t from an ag or hort standpoint. I suggest you check with a few experts. An analog: I’m a green infrastructure guy. There are folks who are promoting urban forests as carbon sequesters based on a misunderstanding read of just a couple of papers and concluded promoting aboveground C sequestration is a way to increase tree canopy cover – they wish to promote urban forests, which is laudable for many reasons. But the scant literature says “it depends” wrt climate, and in the Front Range, it ain’t gonna happen although some folk don’t want me to say that.

    Now, here, for whatever reason, you have – just as some urban forest proponents have done – misread a couple of papers and come to a conclusion. I’m not as familiar with the literature as some in this thread – my formal education that included soils and crop science ended some years ago – but its clear that wrt this topic “it depends”, not “no way”. I suggest you contact some soil researchers to have them explain where and when particular tillage techniques give a better chance at soil C sequestration (SCS).

    Next, consider that in an adaptive management regime there is a multitude – a basket, if you will – of channels that contribute to the sequestration basket. In that basket, let’s say that some smart person sets up a bunch of different funds (like we have today to choose stocks) and that some funds have soil C sequestration with a factor – say .25 that allows you to offset your C. Meaning some methods are better than SCS to sequester carbon, but you can still choose soil if you want. You have a bunch of options to choose from.

    That is: soil C sequestration isn’t the only egg in the basket, and it isn’t a whole egg because it isn’t the best strategy. But the head of your company’s dad was a farmer and they want to promote ag, so your company’s offset goes into this fund. SCS gets traded, promoted, talked about, chosen among a rich variety of choices. Just like we do Socially Responsible Investing today.

    Your negativity-laced yammering often gets in the way of creating innovative solution sets, Joe, in my view. Not always, but more often than I care to see.

    SCS is one way to go. It’s not a silver bullet, and it may not be great, but it helps to create a dialog that helps to create market choices. So it doesn’t do everything you think you want. Sheesh. Hello.




  22. David B. Benson says:

    There are varying degrees of permanence. For example, palnting lots and lots of trees will take up some carbon. Until the trees die. But that might easily be a century from now. So it buys time to determine what else to do with the carbon.

    Something of the same sort might be true of SOC. In any case, no-till saves on diesel fuel.

  23. Joe,
    Catastrophe or not, people are going to need to eat. Agriculture is not going to go away. Whatever you have been sold about no till and conservation tillage as a method of carbon sequestration, they are promising methods of reducing agricultural energy use and thereby emissions and agriculture’s dependence on fossil inputs.

    The problem I have with your tone is that agricultural ergonomics is a matter of life and death both now and in the future. Furthermore its connection (via rising fossil fuel prices) with rising food prices and technical solutions are not discussed much in the public sphere. You are working on an issue of a higher profile and your dismissive comments will become attached to these practices in a way that may mislead the public about their value. People, and it seems like you as well, do not think enough about how food gets on their table.

    So, whether or not no-till is a key method of carbon sequestration, it is a key energy solution in an area that is more vital for your survival than your daily commute. So, no-till and low-till are part of the wheat not the chaff…unless you have devised a more efficient agricultural energy solution…

  24. John Wendt says:

    Interesting discussion. As a soil scientist, and one who has been involved in measuring changes in soil properties, I have read perhaps hundreds of journal articles on the effects of tillage. I also concur with the conclusion of the above-mentioned article–simply put, that no-till;s value in increasing C sequestration is inconclusive.

    What amazes me the most, however, is the quality of studies that end up in published literature. There are hundreds of studies on no-till vs. till that restrict the depth of measurement to some 15 cm, often less. I am stunned that fellow soil scientists could be so…”shallow.” It is blatantly obvious that tillage mixes the soil, and that tillage below 15 cm will result in dilution of C in the upper 15 cm of soil (as C decreases with depth generally), thus under-estimating its total content in tilled treatments. Furthermore, soil scientists are, in general, ignorant of errors associated with depth layer determinations. Correct assessments must be based on equivalent soil mass layers (as per Ellert and Bettany 1995, for example), and not depth layers, which has distorted numerous assessments.

    I sometimes lament at the lack of intelligence demonstrated in so many publications, and am further amazed at how these errors get past reviewers and editors in top soil science journals. To reach any conclusion regarding total carbon sequestration in a study only involving the upper 15 cm of soil is impossible, and such studies by simple logic should be summarily excluded. Regrettably, they form the majority of studies that support increased no-till carbon sequestration. One wonders if studies–and journals–are looking for research to support a foregone conclusion.

  25. Thomas O'Donnell says:

    I hope to find time for a more thorough analysis of the statements regarding sampling of soils deeper than 30 centimeters. My initial reaction is that this is great information but does not negate carbon sequestration through no-till as an excellent way to reduce CO2 in the atmosphere. I have read recent analyses of no-till as a viable and important carbon sequestration practice. I agree with the conclusions of these investigations.

    Data that I have seen support the increase of carbon in soils undergoing conservation tillage, and highlight that the increased carbon begins in the upper layers. It may take many more years for the carbon build-up to reach deeper layers. I suspect that the deeper carbon is much older, which if true supports the finding that no-till leads to increased carbon storage.

    Aside from the scientific data, it makes sense and is logical – if you reduce oxidation of soil carbon more will cycle to humic materials and eventually kerogen-like resistent carbon compounds.

  26. cawblr says:

    i think you are all full of shit and should go to hell!!!!!