ISU research complicates cover crops


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Cover crops hold onto soil and carbon during the off-season (via Creative Commons).

Julia Poska| November 13, 2019

Though cover cropping has proven advantageous for soil and water conservation in Iowa, the practice’s benefits to atmospheric quality may be negligible, new research from Iowa State University found.

When farm fields are left bare during the winter and spring, wind and water transport soil and nutrients off the land and into streams and rivers, degrading both the field and water quality. Exposed soil typically releases carbon into the atmosphere at increased rates compared to planted areas, contributing significantly to climate change.

Cover cropping involves planting alternative crops like rye or clover to cover and nourish the land throughout the off-season. The conservation practice holds soil in place, pulls atmospheric carbon into plant material and adds carbon back into soil upon decomposition. Sequestering carbon in plants and soil is key to combatting climate change.

That carbon may not remain in the soil for long, however. The new study, published in Global Change Biology Bioenergy,  found that the added soil carbon stimulates microbes in the soil that emit carbon dioxide back into the atmosphere as they digest the organic matter.

The research — conducted by ISU assistant professor of ecology, evolution and organismal biology Steven Hall and grad student Chenglong Ye —  highlights the need for a variety of solutions for the planet’s numerous natural resource problems. While cover crops are a proven protectors against water pollution, we will need to implement other strategies to make farming carbon neutral, too.

Climate change and soil: sink or source?


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Peatlands, or bogs, are wetlands where partially decomposed vegetation accumulates saturated in water. The soil is very rich and productive and contains huge amounts of carbon (flickr). 

Julia Poska| November 29, 2018

The world’s soils hold massive amounts of carbon from decomposed plants and animals. In this way the soil acts as a sink, storing carbon that could otherwise end up in the atmosphere, but soil is a source of carbon emissions.

Two studies published this month highlight just how helpful and harmful the the soil’s carbon storage capacity might be in the face of climate change.

The first, published in Proceedings of the National Academy of Sciencesexamined the changing role of peatlands, also known as bogs or mires, in the carbon cycle. According to author Qianlai Zhuang of Purdue University, peatlands cover about 3 percent of the Earth’s surface but contain 30 percent of soil carbon. This major sink, though, has begun to release large amounts of carbon, too.

When peatlands are drained for human uses like agriculture or mining, they release some of that carbon into the air. The rate of carbon loss is predicted to increase with climate change, even for untouched peatlands.

Northern-hemisphere peatlands in Canada, Siberia and Southeast Asia have already begun releasing significant amounts of carbon, but Zhuang and PhD candidate Sirui Wang found that Amazonian peatlands may soon follow suit, according to a Purdue University media release. The researchers estimate that by the end of the century, peatlands in that area could release an amount of carbon equal to 5 percent of current annual emissions worldwide.

The second study, published in Nature Climate Change, found increased capacity for carbon storage deep within the soil. Much of the soils carbon is stored in a dissolved form; the carbon leaches downwards in the water and attaches to minerals over 6-feet underground.

Little is known about this method of storage, but Washington State University researcher Marc Kramer and Oliver Chadwick from the University of California Santa Barbara have looked at it closely and believe humanity could take advantage of the process to bury more atmospheric carbon deep inside the earth. Unfortunately, they believe climate change will limit this capacity in tropical rainforests, currently the best locations for dissolved carbon storage.

Check out our 2018 Iowa Climate Statement to learn more about the impacts of climate change right here at home.