This is the third installment in the series "Agriculture and the Abatement of 'Record' CO2 Emissions Levels." So far, we've looked at the problem -- record emissions levels -- and one (pseudo-)solution: no-till. To recap, no-till may have some promise in allowing agriculture to contribute to the abatement of climate change because carbon offsets may be earned through carbon sequestration. However, the practice is highly problematic for three general reasons: permanence; saturation; and effectiveness. In short, there are a lot of problems with using no-till that may end up limiting its use (or even ability) in reducing fluxes of greenhouse gases.
* * * * *
If a farmer told you he was about to "plant the hairy vetch," one might presume something unsavory was about to occur. Actually, however, the farmer would simply be referring to a cover crop -- usually a dense type of grass or legume that occupies the farm field in between crops. Hairy vetch is one type of cover crop, but there are several others.
Traditionally, the chief merit of a cover crop was that it would reduce erosion from water and wind. Further, certain varieties can reduce the need for nitrogen fertilizer by fixing nitrogen from the atmosphere. Still others could help improve water quality by sucking up excess soil nitrogen and other nutrients.
Some recent evidence, however, shows that their value extends to the abatement of greenhouse gases. Some researchers posit that cover crops can reduce the impact of freeze-thaw cycles on agricultural soils. Since these cycles are responsible for a significant loss of nitrous oxide (N2O) -- a potent greenhouse gas -- to the atmosphere, cover crops that minimize the cycles can help to abate global climate change. Leguminous varieties that fix nitrogen to the soil can drastically reduce N2O loss, not only by mitigating the effects of freeze-thaw cycles but by reducing farmers' dependence on chemical nitrogen fertilizers, portions of which are inevitably lost to the atmosphere.
While it is accepted that cover crops can reduce fluxes of greenhouse gases to the atmosphere, there is not much research that demonstrates the effectiveness of the practice in terms of the total quantity of GHGs reduced. Some results from ecological simulation models employed in my thesis suggest that the practice can be quite effective, at least initially (see the red line in the picture) [1].
From a policy standpoint, cover crops are a fairly dependable tool for policymakers' toolboxes as their use is easily enforced; if a farmer were to sign a contract through a federal conservation program to implement a cover crop, it's extremely easy for regulators to certify that the farmer followed through on the contract.
The use of cover crops offers an exciting potential for farmers to contribute to the abatement of greenhouse gases and expands the portfolio of practices they have available to them beyond the use of the questionable no-till. Climate policy has been a little slow to recognize their potential, however; as I mentioned before, there's not a whole lot of reliable data on cover crops obtained from long-term studies, etc. Further, most of the effort at including row crop agriculture into climate change mitigation has focused on CO2 instead of the much more potent N2O, so it's possible that many of the practices that are most useful for reducing fluxes of greenhouse gases have flown under policymakers' collective radars.
----------------------------------------------
1. Please don't use these results outside the context of my thesis. Also, don't put too much stock into the accuracy of them. Remember, I'm an agricultural economist, not an ecological modeler. I will post a link to the thesis once it's been officially accepted by Purdue if you are interested in using the results for any particular reason. In the interim, the citation for the above graphic is: Reeling, C. 2011. Using Carbon Offsets to Fund Agricultural Conservation Practices in a Working-Lands Setting. MS Thesis, Purdue University.
Some recent evidence, however, shows that their value extends to the abatement of greenhouse gases. Some researchers posit that cover crops can reduce the impact of freeze-thaw cycles on agricultural soils. Since these cycles are responsible for a significant loss of nitrous oxide (N2O) -- a potent greenhouse gas -- to the atmosphere, cover crops that minimize the cycles can help to abate global climate change. Leguminous varieties that fix nitrogen to the soil can drastically reduce N2O loss, not only by mitigating the effects of freeze-thaw cycles but by reducing farmers' dependence on chemical nitrogen fertilizers, portions of which are inevitably lost to the atmosphere.
From a policy standpoint, cover crops are a fairly dependable tool for policymakers' toolboxes as their use is easily enforced; if a farmer were to sign a contract through a federal conservation program to implement a cover crop, it's extremely easy for regulators to certify that the farmer followed through on the contract.
The use of cover crops offers an exciting potential for farmers to contribute to the abatement of greenhouse gases and expands the portfolio of practices they have available to them beyond the use of the questionable no-till. Climate policy has been a little slow to recognize their potential, however; as I mentioned before, there's not a whole lot of reliable data on cover crops obtained from long-term studies, etc. Further, most of the effort at including row crop agriculture into climate change mitigation has focused on CO2 instead of the much more potent N2O, so it's possible that many of the practices that are most useful for reducing fluxes of greenhouse gases have flown under policymakers' collective radars.
----------------------------------------------
1. Please don't use these results outside the context of my thesis. Also, don't put too much stock into the accuracy of them. Remember, I'm an agricultural economist, not an ecological modeler. I will post a link to the thesis once it's been officially accepted by Purdue if you are interested in using the results for any particular reason. In the interim, the citation for the above graphic is: Reeling, C. 2011. Using Carbon Offsets to Fund Agricultural Conservation Practices in a Working-Lands Setting. MS Thesis, Purdue University.
No comments:
Post a Comment