The “Dirt” on Carbon Emissions

Is the secret in the soil? We often think of carbon as only being in the air – as emissions, what we exhale, what plants inhale; but a great deal of carbon is also stored within our soil. Plants absorb and store carbon in the soil. So, when today’s industrial farming methods use tilling to overturn the soil, it actually releases large amounts of carbon into the air.


According to journalist and writer Kristen Olsen, we can help reverse climate change by returning to no-till farming methods, which will leave the soil undisturbed and will keep that carbon trapped underground. In fact, David Johnson, a scientist at New Mexico State University, estimates that we could potentially offset all of our current carbon dioxide emissions by returning just 11% of the world’s cropland to no-till farming. If that’s true – wow!


Tilling soil can also release the nitrogen applied as fertilizer. On average, crops absorb only 30-50% of the nitrogen applied to the soil, so tilling can cause significant amounts to enter the atmosphere as nitrous oxide. Unfortunately, nitrous oxide (N2O) is a much more potent greenhouse gas than CO2. N2O has a lifetime of 120 years in the atmosphere, and its global warming potential (GWP) is 310 times greater than CO2 over a 100-year timespan. Still not as potent as artificial refrigerants like HFCs, but N2O emissions are certainly worth limiting! Add to that the fact that tilling is a major source of soil erosion, one of the key contributing factors to the Dust Bowl in the 1930s, and it seems like a no-brainer that our farmers should go “no-till.”


But, what are the benefits of tilling? If it were such an easy practice to give up, wouldn’t all farms have already switched to no-till practices? In fact, no-till farming is growing in the United States at about 1.5% per year and 35.5% of American cropland has at least some no-till portions, but only 10% of American farms are full-time no-till operations.


Tilling can help stop weed growth because turning over the soil tears up existing weeds and buries weed seeds resting on the surface deep enough so they can’t sprout. In this way, tilling reduces the amount of herbicides farmers need to kill weeds. These herbicides increase farmers’ costs while also having a negative impact on the environment. Although, new organic (i.e. non-chemical) ways of practicing no-till farming are on the rise.


So – to till or not to till?? While I am a huge proponent of reducing carbon emissions to mitigate climate change, I know that maintaining both economic and agricultural sustainability are critical to our wellbeing. As is often the case, I think it will be important to find a happy medium. Earthbound Farm (producer of organic salad greens) employs a “low-till” methodology, whereby they turn up only half an inch of soil, rather than the traditional six inches, in between plantings. The small amount of tilling helps bury weed seeds enough to prevent them from sprouting, but it releases only a fraction of the carbon into the atmosphere. In fact, Earthbound estimates that the organic soil in their fields absorbs 123.2 million pounds of CO2 each year (61,600 tons or the equivalent of taking 11,200 cars off the road).


Will low-till farming be the wave of the future? I’m not an agricultural expert, but it seems to hold potential. I think what I like best about the idea of low or no-till farming, though, is that it reminds us there is more than one way to reduce our carbon footprint. Switching to renewable fuels will undeniably be an important factor in mitigating climate change. But, such a complex and multi-faceted problem will also have many and diverse solutions.


Agriculture accounts for 10-12% of global emissions, according to the IPCC, so it seems natural that we should consider ways to reduce agricultural emissions as well as emissions from energy production and vehicle travel. And, no-till farming doesn’t require fancy new technology to achieve these reductions – rather a return to a more traditional method of farming.


So, let’s invest in our innovators and creators who are championing new fuels and energy systems, but let’s also remember how much we as a society already know and reach into our own thinking caps for practical solutions to combat climate change.

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