Earlier this summer I wrote about adapting to new climate normals and what warmer temperatures, longer droughts and more extreme weather events mean for agriculture. It was a kind of bleak picture, and I felt bad about that because I’ve tried hard to make On Pasture an uplifting place to come to in a world that can be pretty hard. So, to make up for that, this month I want to give you something you can do right now to paint a brighter future while improving your soil, growing more forage, and increasing resilience in the face of extreme weather events: Spread compost.
I’ve been following the results of a long-running research project in California looking at what kinds of practices graziers can implement that address their needs and climate change as well. The research looked at key-line plowing, Adaptive Multi-Paddock (AMP) grazing, and applications of compost and compared the results to see which was most beneficial to graziers, and which was best at pulling CO2 from the atmosphere and sequestering in a durable form in the soil. It began in 2008 and measurements have been taken every year since. (You can read more on this project here.)
The results: Compost won hands down
Though the grazing treatment showed improvements in organic matter, when it came to durable carbon sequestration, it remains a carbon source all these years later. Likewise, the key-line plowed treatment did not show any improvements in long-term soil carbon increases. But compost showed improvements in all areas.
“When you add compost to soils, it increases plant growth, helps maintain water-holding capacity and nutrient supply, and reduces erosion,” says Dr. Whendee Silver, lead researcher on the project. “You end up with more organically rich soil and more nutrients, so the plants grow better, and those plants are pulling carbon dioxide out of the atmosphere and helping to slow climate change.”
With just one application of compost, researchers found that forage production increased by 50% in year one, and when they analyzed the soil, they found they had added a metric ton of occluded carbon per hectare (2.47 acres) to the soil. (That’s durable carbon that stays put for 30 to 100 years.) The next year — with no further treatment — the soil had captured another ton of carbon, the next year another ton, and so it has continued. In fact, fourteen years later, forage production continues to be better. In addition, the soil’s water holding capacity has increased, so even through the severe California drought, forage is greener and more productive.
If you’re a grazier, those are all great reasons to spread compost, regardless of how you feel about climate change. But, if you’d like to do something about warming temperatures, extended droughts, and extreme, unpredictable weather events, spread compost. A quarter inch of compost will continue sequestering durable carbon for twenty years before you need to do another application. In fact, a 2013 study by Silver found that adding compost to just 5 percent of California’s rangelands could sequester the equivalent of 28 million tons of carbon dioxide over a three-year period, offsetting nearly one year of emissions from the state’s agriculture and forestry sectors. Scaled up, this practice could make a significant contribution to preventing further climate change while providing plenty of food, fuel, fiber and flora.
As John Wick is fond of saying, by “carbon farming” we’re creating a system where we’re producing food, fuel and fiber, and the more we do and the more we buy the better the climate is. It’s a win-win.
Why Compost and Not Plain Manure?
Back in 2008 when the Marin Carbon Project began this research, the first step was to get a baseline understanding of how much carbon was already sequestered in the soils in the area. As they gathered soil samples, they found that the dairy farm practice of spreading manure increase carbon dramatically–50 metric tons of carbon per hectare.
Silver says, “This sounds exciting except that cattle manure is a really big source of greenhouse gas, especially when it’s stored in piles or in slurry ponds. In fact, EPA data shows that manure management is equivalent to coal mining in terms of methane emissions. Methane is a very potent greenhouse gas, and manure greenhouse gas emissions are equivalent to mobile combustion emissions of nitrous oxide out of your tail pipes. Nitrous oxide is 300 times more potent per molecule as CO2 over 100 years.”
After additional field sampling at the dairies, and computer simulation models assessing livestock and manure emissions vs carbon sequestration, they learned that the net effect of manure spreading is high emissions.
Silver says, “That’s why we turned to compost, because composting that material actually decreases emissions.” They’ve found that if you put manure in a compost pile and turn it weekly, the result is very low methane emissions and almost undetectable nitrous oxide. Once spread on the pasture, emissions remain low.
For those wondering about compost tea as a potential solution, it just doesn’t make muster. Tests of the product showed that it was not capable of providing the same benefits and on farm trials have shown the same. For more on the reasons why, here’s a good summary.
Solving the Food Waste and Compost Supply Problems – Two Birds with One Stone
So, we know compost improves long-term carbon sequestration, but where can we get all the compost we need? Fortunately, a part of the answer to that question solves another climate problem: Food Waste. Roughly one third of food produced for human consumption is wasted and much of it ends up in landfills where it produces methane as it deteriorates. The U.S. Environmental Protection Agency estimates (link here) that each year food waste creates the equivalent of 42 coal-fired power plants in greenhouse gas emissions. Solving that problem is as simple as composting food waste. Then, using that compost, we can also grow more food, fuel, and fiber while increasing carbon sequestration in the soil. It’s a win-win for us all!
But how do you get folks to compost? How do you get the compost to the farmers? Who will provide the technical and financial assistance for graziers and others implementing this practice?
We cover the answers to that here, with examples of processes and legislation you can adapt to your own region.
Moving on to Carbon Farming
While spreading compost is a good thing, it’s not the only thing. In fact, it is just one among a number of practices a farmer or grazier can implement to ensure that more carbon is going into the soil. This is called “Carbon Farming.” It is a whole farm/ranch approach to optimizing carbon capture.
If your head is reeling just a bit with all the new information I’ve shared here, I understand. It’s a lot. You don’t have to do all of this at once. But, if I might suggest, figuring out how to spread some compost on your pastures is a good place to start. It gets you outdoors where you can take a deep breath, you’ll grow more and better forage, and you’ll be doing something for the planet too.
And for that, I thank you!