[Terrapreta] No-till farming doesn't work as C-saver

[lou gold]

Please excuse my ignorance of farming practices but is there a way to
combine bio-char and no-till? I am asking because Brazil has a huge amount
of land already under no-till regimes and that is not likely to change.

===================================================

On Thu, May 22, 2008 at 4:59 PM, Biopact <biopact at biopact.com> wrote:

>  Interesting piece written by Joseph Romm, published today. It seems like
> no-till farming is *not* saving carbon and *cannot* be seen as a way to
> offset emissions (even though no-till farming is included in the Chicago
> Climate Exchange).
>
> No-till farming was one of the obvious ideas 'competing' with biochar over
> potential carbon credits. But now it seems soil C dynamics are more complex
> than previously thought and no-till does not seem to make a difference.
>
> Romm summarizes as follows:
>
> ==========================
>
> The list of very knowledgeable folk who still are pushing no-till farmingas a greenhouse-gas mitigation strategy -- even though science passed them
> by a while ago -- includes:
>
>    - Sen. John McCain
>    - Princeton University* [PDF]
>    - The Chicago Climate Exchange [PDF]
>    - The Nicholas Institute for Environmental Policy Solutions [PDF]
>
> I buried the science in the McCain post, but it deserves higher visibility.
> As a major review article [PDF] 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 percent 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 this:
>
> 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*.
>
> D'oh!
>
> 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.
>
> *This post was created for ClimateProgress.org, a project of the Center
> for American Progress Action Fund.*
>
> ======================
>
>
>
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>



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