Research HighlightsDigging Deeper into Nematode Soil Samples
By Laura Temple
Many university extension programs offer soil testing for soybean cyst nematodes, or SCN, so that soybean farmers understand the potential threat buried in specific fields. However, Horacio Lopez-Nicora, assistant professor of soybean pathology and nematology at Ohio State University, has begun digging much deeper into soil samples submitted in Ohio.
“While we know SCN hurts soybean yields, we would like to understand more about how their populations change,” he says. “At the same time, a wide variety of other nematodes — both parasitic and free-living — reside alongside SCN in our soils. We want to learn more about those species, as well.”
Farmers throughout the state receive bags and instructions on how to collect soil samples during winter meetings, thanks to support from the Ohio Soybean Council. Lopez-Nicora says his team asks them to take soil samples both at planting and at harvest in both soybean and corn fields, along with yield estimates.
“With this additional information, we can see SCN population changes and create a reproduction factor for the specific types of SCN in a given field,” he explains. “Tracking SCN populations over time will show growers the value of rotation to non-host crops and adequate selection of SCN-resistant soybean cultivars.”
At the same time, his team derives a wealth of additional information from these soil samples.
They quantify populations of several other parasitic nematodes, including lesion, pin, lance, stunt and spiral nematodes. Lesion nematodes can be an issue in corn, and some species also feed on soybeans. Very little information exists about the pin nematode, which was first reported on Ohio soybeans in 2017.
Lopez-Nicora monitors the samples closely for root-knot nematode species as well. He knows they can be found in high tunnels growing vegetables in Ohio, but as of the 2023 growing season, they have not yet been found in any commercial soybean fields.
The team also identifies free-living nematodes, or species that do not feed on plants. Some nematodes feed on bacteria, fungi or other nematodes, and these species can serve as bioindicators for characteristics of soil and microbial community health.
“We want to understand the entire nematode community assemblage and relate that to other soil health parameters,” Lopez-Nicora adds.
To make those connections, his team gathers soil characteristics from the samples, including soil texture, major nutrient content, pH, respiration, cation exchange capacity and more.
“This data provides a more complete picture of nematode pressure and rate of reproduction,” he says. “That includes the whole biology of the soil they live in. We can look at the physical, chemical and biological aspects of the soil and associate them with characteristics of nematode populations.”
He says farmers and researchers can use this information to better manage SCN and other nematodes in the field. It should also help them stay a step ahead of shifts in SCN virulence to resistant soybean genetics.
“This detailed soil data can be layered with another SCN study one of my students is working on to use near infrared imaging to detect potential SCN hotspots in a field,” Lopez-Nicora adds. “For example, those images could potentially guide farmers to spots that need to be included in future soil samples.”
Published: Nov 6, 2023