Research Highlights

Research Highlights
Biochar as a Soil Amendment May Help Battle Soybean Seedling Diseases

Biochar results from burning certain plant materials such as corn cobs and stover, or grasses like miscanthus, under low or no oxygen. It is a byproduct of biofuel manufacturing, and scientists in the ag industry are discovering its soil health benefits. Photo: Leonor Leandro

By Carol Brown

Biochar has existed on Earth as long as there have been plants and fire. The byproduct of burned trees and plants, interest in this charcoal-like material continues to grow. Farmers can add biochar to their fields to improve soil health, increase carbon sequestration, improve water infiltration and retention, and more. Scientists are studying additional ways biochar can benefit farmers and the agricultural industry.  

Iowa State University plant pathology professor Leonor Leandro is studying biochar for its possible role in reducing soybean seedling diseases. Leandro’s exploration of biochar for this purpose is part of a larger United Soybean Board-funded project that is looking at several management practices to curtail these pathogens.

“My first exposure to biochar was in 2014. I collaborated with colleagues in the ISU agronomy department,” explains Leandro. “I helped with the trials David Laird and Natalia Rogovska were conducting with biochar and its effect on soybean sudden death syndrome, which is one of the diseases I focus on.”

They added biochar to the soil at different rates and achieved a 60% reduction in the root rot phase of SDS, compared to 90% root rot without using biochar. Leandro and some of her students are revisiting biochar to reduce seedling diseases caused by Pythium and Fusarium, as well as continuing their work on SDS. 

Biochar Benefits

Simply put, biochar is the product of burned plants. The biochar production process, called pyrolysis, is achieved by burning organic waste or plant material under low or no oxygen. Biochar is a byproduct of biofuel production and was originally considered a waste product, but now biochar’s economic value is being realized.

Biochar can be incorporated into a field by broadcast spreading and then tilling into the soil. Biochar stays in the soil for hundreds of years and can nurture microbial communities, increase organic matter, and improve water infiltration and carbon sequestration. Photo source: Daniel Warnock, Michigan State University

“Biochar is a solid material that looks like charcoal, but with a range of textures smaller and finer than charcoal, depending on the biomass that was burned and how finely it is ground. Biochar also has specific characteristics,” says Leandro. “It is a high-carbon compound, its microscopic structure is very porous, and it is resistant to microbial decomposition. When biochar is added to the soil, it lasts for a long time. It stays in the soil because the decomposition is minimal. It doesn’t need to be added annually.”

Encouraged by the positive results Leandro observed using biochar to reduce SDS, she and her research team are also exploring its efficacy against Pythium sylvaticum and Fusarium graminearum. She is conducting greenhouse tests, amending the soil with different rates of biochar to find the proper amount that will combat these pathogens effectively and whether the amounts are feasible for field application.

“We’re mixing biochar into the potted soil at 5 to 10% rates. Then we inoculate the pots with the pathogen and grow the soybeans,” she explains. “After a few weeks, we take the plants down and look for disease symptoms in the roots, and measure shoot and root size.”

Preliminary results are promising, Leandro says, and they will conduct the experiments in the greenhouse again before expanding to field plot studies.

“So far, we have seen that a 10% biochar concentration reduced root rot caused by F. graminearum by about 50%,” she says. “For the Pythium study, we are testing biochar from different sources using a 5% concentration, and seeing similar reductions.”

The larger USB-funded project is exploring how to mitigate several seedling diseases through different management methods including cover crops and seed treatments as well as Leandro’s work with biochar. The multi-state project also includes research on how seedling diseases impact seed quality and testing different soybean varieties for disease tolerance.

For more information about previous results from this project, go to the National Soybean Checkoff Research Database:

Published: May 15, 2023