Just what are healthier soils? How do they impact crop growth? Nester points to more earthworms and better soil structure. Sundermeier points to water infiltration and increased organic matter. Hatfield points to biological components that can offset challenges to the plant.

“We are still working out how to bring together biological, chemical and physical measurements to evaluate both the soil and plant components,” says Hatfield. “For example, in cover crops, the growing roots supply fresh root material for the microbes to eat throughout a longer period of time.”

Senyu Chen, plant pathologist, Southern Research and Outreach Center, University of Minnesota, has taken that concept even further. He’s identified endoparasitic fungi that can biologically disrupt SCN. These friendly fungi seem to be more common in continuous-soybean than in corn-soybean rotations. He’s researching whether the endoparasite can be introduced into non-suppressive soils, whether in more common corn/soybean rotations, continuous corn or continuous soybean rotations.

Searching for a better understanding of SCN, Chen’s research team has identified SCN-suppressive soils. He defines them as soils that naturally contain physical, biochemical and biological factors that suppress SCN. These factors include fungal parasites of SCN, such as one that forms a special device that can catch nematodes in the soil, and extracellular enzyme activity related to suppression.

“We are mainly looking at SCN, but also at other nematodes, including those that act on corn,” Chen explains. “We are asking why one field is suppressive to SCN and others aren’t. What is the cooperating system of rotation and tillage that can influence suppression?