Carbon Connections - 2 05/21 06:20
Calculator Shows Little Impact on Global Warming
DTN Staff Agronomist makes an estimate of his farm's impact on the
environment. He sees room for improvement, but is pleasantly surprised his farm
is sequestering more carbon than it produces.
By Daniel Davidson
OMAHA (DTN) -- There is a lot of talk about carbon footprints in industry,
manufacturing and farming. With concerns over greenhouse gas emissions and
global warming, we have to be aware of our carbon footprint and make an effort
to reduce it.
The question is, do I use more carbon in my farming operation from field
activities, transportation costs and inputs purchased than the carbon I put
back in the soil?
Crops, especially high biomass crops like corn or perennial switchgrass,
capture a lot of carbon from the atmosphere. Soil experts call this carbon
Historically, agriculture's carbon budget has been in the red. Extensive
tillage released carbon from the soil, and those multiple tillage passes
required inefficient, smoke-belching machines.
Today farmers can reduce or eliminate tillage, cut the number of field
passes and sequester more carbon while reducing the carbon expended when
farming. But first, each farmer needs to know where he or she stands.
CURRENT CARBON STATUS
In the 1990s, my father farmed with a 50-50 corn-soybean rotation, drilling
soybeans into disked cornstalks and no-tilling corn into soybean stubble.
My brother and I took over nine years ago, and converted to a 100 percent
no-till corn and soybean rotation. We sold all the tillage equipment except for
a plow to plow the garden. Our passes include fertilizing, planting, harvesting
and two for spraying.
I soon realized soybean profits were meager, and we converted to continuous
no-till corn. I already knew the switch greatly increased soil organic matter.
In nine years, organic matter has nearly doubled from 1.5 percent to just under
Higher organic matter means more carbon being sequestered though growing
continuous no-till corn is a challenge. Ample crop residue immobilizes nitrogen
and can interfere with planting and seed germination.
To remedy that, I apply a residue digester, which requires another field
pass. We bale about 30 percent of the corn residue on about 30 percent of the
acres and recently ran a vertical tillage tool across the field to process the
stalks. So, while my organic matter and soil quality is increasing, it requires
carbon expenditures to achieve that.
OUR CARBON FOOTPRINT
To test our carbon footprint, I used the web-based Fieldprint Calculator
(http://www.fieldtomarket.org/tool-home.php) to evaluate a single field.
I selected a 155-acre field that has been in no-till corn for five years,
hasn't had a cover crop and yielded 155 bushels per acre in 2009. I entered
data on state, crop, season, soil slope and type, tillage practices, rotation
and conservation practices, fertilizer use and pesticide passes.
I learned, based on that field at least, that our operation has a
significantly smaller carbon footprint than the Nebraska state average, and
that our state's farms have a smaller footprint than the national average. As
hoped, our farm's no-till continuous corn creates a carbon budget in the black
-- we sequester more carbon that we expend.
Our land use index was 49, similar to the state and national averages,
meaning we have only mediocre average production. However, if corn production
could be increased to 250 bushels, the index would drop to 30 as our resource
efficiency increases. Achieving that yield in this field is impossible at the
moment, but the calculator allows you to examine such "what if" scenarios.
While we do not use terraces, contour farming or buffer strips on this
field, we had a soil loss index value of 15, lower than the state's 33 and the
nation's 50. Our energy use index was 7, compared to 46 for the state and 50
for the national average. We were spending 6003 BTUs of energy per bushel of
According to the calculator, this field has no impact on the environment:
our Climate Impact Index score was zero compared to 47 for the state and 50 for
the nation. We are sequestering 6.778 pounds of carbon dioxide per bushel
produced of corn produced. Our carbon budget is in the black.
CONCLUSIONS AND ADVICE
I am proud of what we have accomplished, even though it was driven by
improving our bottom line and not sequestering more carbon. Still, are there
things I can do to improve our footprint?
The results do need to be taken with a grain of salt. This calculator, while
simple and easy to use, is really designed to look more at the sustainability
of a farm than to specifically look at its carbon footprint. It doesn't take
into full consideration the carbon used to make and apply the inputs we use.
It also doesn't account for other greenhouse gases, such as nitrous oxide
and methane that can be released as nitrogen fertilizer breaks down in the
soil. It did ask about fertilizer rates and whether nitrogen stabilizers were
used but using them didn't make a significant difference.
The results I discuss here are also based on one example field. In other
fields we performed some vertical tillage to deal with the results of a wet
harvest and to reduce the amount of residue. I would need to account for the
fuel used and the carbon released during that tillage for a whole-farm score.
I know there is other room for improvement. We still run '80s vintage
tractors that aren't as fuel efficient as modern machines and we pull smaller
implements that take us longer to complete the job.
I also did not account for baling that 30 percent of the corn residue on a
third of the acres every year. That would change the carbon budget, but it sure
makes growing continuous corn easier. On the plus side, we are starting to
plant a rye cover crop on that acreage each fall to remediate that residue
loss, reduce soil erosion potential and add some carbon back to the soil.
Any further changes to lessen our footprint will have to pay off in profits.
Yet it is interesting to see how field activities change your carbon footprint
and allows you to set some realistic goals.
Go to the website, complete the questionnaire and see where you stand.
Daniel Davidson can be reached at firstname.lastname@example.org
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