Crops don’t grow by themselves. Otherwise we’d call them something else. That’s where you find the difference between cultivation and foraging: work. Lots and lots of work.
If you want to grow crops, whether it’s corn, cotton or cabbage, you’ll need to put in a variety of resources and effort to produce a harvest. And if agriculture is the cornerstone of civilization, the trick is to produce many, many harvests.
Ideally, your next harvest is better than your last.
But what exactly does “better” mean? For the Carbon Harmony movement, it’s a novel, maybe heretical concept: Zero Carbon Corn. Some think this just might be the summit of agriculture in our time.
According to National Geographic, with the dawn of agriculture, “cities and civilizations grew, and because crops… could now be farmed to meet demand, the global population [rocketed] from some five million people 10,000 years ago to more than seven billion today.”
There’s at least one thing modern farmers share with their ancient forebears: with each new season they want more yield with less input.
That’s not easy. It takes a lot of careful, experimentation and study. The good news is that modern growers have the benefit of 10,000 seasons of both. And of course science.
These days, corn famers know a lot about the resources that go into each crop. And there are costs — not just in investments, but in outcomes. Consumption of energy and other inputs required to plant, protect and harvest a crop results in emissions you’ve probably heard of: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Collectively, those emissions are known as “greenhouse gasses,” or GHGs. They’re a uniquely modern challenge. The biggest is the carbon in the form of CO2.
Environmental scientists calculate the “carbon footprint” of modern production processes like farming, construction, shipping, manufacturing or power generation by accounting for the total inputs of all energy and resources that activity consumes — and their output in carbon emissions.
For farmers of every kind, GHGs have now entered their productivity equation: a carbon footprint is a new indication of performance in that pursuit of higher yields from lower inputs. To the extent farmers want to get more with less, this means reducing that footprint.
So where do you find the big inputs that affect the size of a grower’s carbon footprint? On the farm, they include diesel fuel and gasoline used by tractors, sprayers, and harvesting machinery during field activity; electricity, propane and natural gas used for farm shops and crop drying/handling; diesel fuel and gasoline used to transport harvested grain from farms to market, as well as to move fuel, fertilizers, pesticides, etc. to farms for use.
Then there’s the energy used to mine and manufacture fertilizers, pesticides and machinery prior to farm arrival. The use of fertilizer nutrients to keep crops healthy results in significant soil GHG emissions such as carbon dioxide, nitrous oxide, and methane.
The U.S. Department of Energy and the U.S. EPA have teams of scientists that build and refine models to calculate total GHG emissions resulting from the “cradle-to-grave life cycle analysis” of the production of all manner of modern products, including crops. In the case of corn production, this is referred to as “field to market” life cycle analysis. The most widely used and prestigious life cycle GHG accounting model is the Greenhouse gas and Regulated Emissions and Energy use in Transportation (GREET) model developed by the U.S. DOE Lab at Argonne, Illinois. The GREET model is available to the public. Farmers can use the GREET model to calculate the carbon footprint of their operation.
Here is an example of the 2016 GREET model assessment of “Mid-West Average” corn production as estimated by Argonne National Energy Lab scientists:
This GREET model analysis demonstrates that GHG emissions from the use of nitrogen fertilizer is the dominant source of GHGs during corn production
So at first blush it looks like there’s a whole bevy of inputs that lead to GHG outputs. But that’s only half — and if you’re interested in the concept of Zero Carbon Corn, at most half and maybe even less than half — of the story. Here’s why.
For more than three decades Ron, his brother Larry, and now Keith have specifically managed their crops and soils to build soil organic matter. When soil organic matter stocks are building, carbon dioxide is removed from the atmosphere. If soil organic matter stocks build at a fast enough annual rate, it can offset some, all or even more than all of the carbon dioxide emissions that have been emitted during corn production.
“We’ve used several keys to achieve our carbon footprint goals,” explains Keith. “Strategies like precision fertilizer management to reduce losses and emissions, and ridge plant and continuous corn to build soil organic matter. It’s a big investment of time, money and focus. But it’s paid off for us and has improved out soil’s productivity and health.”
In the ridge plant system, Keith explains, crops are seeded into permanent seedbed “ridges” that are “high and dry” when normal spring weather is cool, moist and not friendly to early crop development. This elevated seedbed makes it possible to grow high residue producing crops like corn continuously and economically and at high yields with minimal tillage.
High yields are a critical factor in achieving Zero Carbon Corn. That’s because “C4” plants like corn photosynthesize and assimilate an incredible amount of atmospheric carbon dioxide in plant material per unit of land — far more than other commonly grown crops in the Mid-West United States, such as wheat and soybean. A portion of this new root and and above ground unharvested plant material can become soil organic matter.
But how does this carbon in above ground unharvested plant material become soil organic carbon? Doesn’t it just decompose and fly off into the air? Soil is teeming with life….some critters big enough to see, like worms, and lots of critters that are too small to see, like bacteria and fungi. These critters grab this plant material and pull it into the soil, and eat it to get their carbs and protein. Large critters like night crawlers, can pull this material down deep into the soil. Watch this:
Follow a ridge-till regimen like the Alversons’ and grow corn continuously on any given parcel of land, and you pull more carbon out of the air each year and deposit it in the soil in the form of plant material much more effectively than if you rotate other crops on and off that parcel. As the Alversons have observed in careful measurements of their fields, this strategy leads to a positive carbon balance of the soil system. More carbon in the ground. Less in the air.
Suddenly that carbon footprint starts to shrink. With the production of high amounts of biomass from a C4 plant like corn — and the integration of it into the soil each season — the GHGs that are emitted during the production of corn is now offset by carbon deposition into the ground through biomass. Now you’re looking at the prospect of balance and a crop you can call “Zero Carbon”.
And there are big secondary benefits of improved soil carbon. As soil organic matter stocks build, so does water and nutrient holding capacity. A positive feedback loop kicks in……higher soil organic matter means higher yields, means even higher soil organic matter, means even higher yields……..
When the Alversons started to use the Ridge Plant system in 1983, soil samples were taken from each field and tested for soil organic matter content. On average the concentration of topsoil organic matter in those fields was about 3.3%. Now after more than 3 decades, soil tests during the past few years indicate that the topsoil in those same fields now average 4.8% organic matter.
Here’s a summary of the results of long-term soil organic matter testing done in several fields:
But Soil Scientists say the change in topsoil (0-6 in.) soil organic matter content is not conclusive proof that total soil profile organic matter/carbon content is increasing. Topsoil is just the “tip of the iceberg” so to speak. Soil organic matter/carbon must be measured throughout the full rooting profile of the soil. “In 1984 we sampled and tested soil in one field down to 40 inches in depth”, says Ron, “and then sampled and tested the soil in the same location again in 2015”. Here are the results:
“The results from this field perked our curiosity. We wanted to find out more”. So, in 2015 Keith contracted with a professional soil sampling firm to quantify the soil organic matter in the soil profile that is commonly impacted by crop roots, residue and tillage. Applied Ecological Services used soil type maps and landscape topography to select 110 sampling sites in K2 Farm land tracts that have been under various land use management scenarios over the past 2-3 decades. AES technicians extracted 0-40 inch, 2 inch diameter soil cores from these 110 locations and did a laboratory analysis for soil organic and inorganic carbon and soil bulk density. The chart below compares the total organic carbon (adjusted for soil bulk density) in soil under various land management practices:
AES found that the Alversons’ fields, using the “ridge plant” system and growing corn three out of four seasons on a given field, have been sequestering about 1.5 tons more atmospheric carbon dioxide in soil per acre each year for the past 32 years than fields that have been chisel tilled and grew corn rotated with soybeans. And the carbon content of long-term ridge-plant fields has been almost fully restored to current native pasture levels.
Now contrast the carbon capture power of the these fields with the GHG emissions from energy the Alversons consumed and the resources they used to produce the corn crop. When this soil carbon sequestration credit is coupled with precision energy and fertilizer use efficiency practices, the result is better than a zero-carbon crop of corn — it’s actually carbon negative.
Put another way: on an annual basis, the Alverson corn production enterprise sequesters enough atmospheric carbon dioxide in soil to offset all GHGs tied to the operation — along with the carbon dioxide emissions from 370 cars.
That realigns the age-old pursuit of higher yields with fewer inputs and costs — and sets a precedent that should help agriculture keep civilization going another 10,000 growing seasons.
Carbon footprints are also sustainability report cards. When energy and resources are used efficiently and soil carbon stocks are rising, environmental impacts are minimized and crop/soil productivity and resiliency improves.