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Research looks at effects of biochar on prairies

Posted December 3, 2012

As optimism grows about the benefits of applying biochar to farmland, researchers have turned their attention to a neglected topic: how biochar affects natural ecosystems.

Biochar, a carbon-rich material similar to charcoal, is created as a byproduct of burning feedstock at high temperatures in a low-oxygen environment, a process to make biofuel called pyrolysis. When applied to crop fields, biochar has many of the same benefits for soil health as fertilizer, and also sequesters carbon underground for decades or centuries.

“There’s been a lot of attention on biochar as this new miracle product that can solve multiple problems in terms of energy and environment,” Harpole said. “But there isn’t really much information about its effect on things other than crops.”

As a fine powder, biochar can easily blow from agricultural fields into nearby prairies, forests or waterways. The investigators hope their research will lay the foundation for best management practices for applying biochar that will benefit both farmland and the surrounding ecosystems.

In a pilot study in a greenhouse, Biederman found that biochar applications seemed to reduce prairie biodiversity, especially in belowground microbial communities. To test this on a field scale, Biederman set up plots at ISU’s Western Research and Demonstration Farm in the Loess Hills.

“That was our expectation going into this experiment—that we might see a loss in diversity—but we actually see the opposite,” Biederman said.

The researchers established 30 replicated plots treated with one percent or three percent additions of biochar, with or without manure. Next they planted a diverse mixture of tallgrass prairie species. Preliminary results from the first two years of the experiment suggest that biochar has a positive effect on plant and soil biodiversity, contrary to the results from the greenhouse.

However, Biederman noted that while plants thrived in the three percent plots, mycorrhizae, important soil fungi that have symbiotic relationships with plant roots, diminished. “The jury is still out,” she said. The researchers will continue collecting field data for at least one more year.

Uncertainty also surrounds the effects of biochar on aquatic systems. In a basic laboratory test, Harpole discovered that biochar dissolved into water killed algae. He is now working to design a more realistic experiment that mimics how biochar moves through soil into waterways.

“The experiment is so new that it’s too soon to tell what will happen,” Harpole said. “Biochar has so many different ways that it can work in the environment that you’re never sure which is going to be the important one.”

In a related experiment, ISU Environmental Sciences and Agronomy student Erich Sneller is applying biochar to Sun Gold cherry tomatoes at a research plot on TableTop Farm, an organic vegetable farm near Nevada. The experiment compares plants growing with and without biochar, either inoculated with mycorrhizae or sterilized. Sneller tracks germination, growth and fruiting data on the tomatoes, and collects data on plant productivity and plant and soil nutrients.

The researchers envision that farmers could supply future biofuel plants with feedstock and receive biochar in return, creating a cycle that would continually improve soil health. Potentially, biochar could be useful for prairie restoration projects as well, depending on the results of this research.

The project, started in 2011 with a competitive grant from the Leopold Center for Sustainable Agriculture, is led by Stan Harpole and Lori Biederman, Iowa State University Ecology, Evolution and Organismal Biology.

Source: ISU Leopold Center for Sustainable Agriculture

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