Soybean farmers looking for the best way to improve soil health now have a clear way forward, thanks to a study funded by USDA’s National Institute of Food and Agriculture (NIFA) and co-led by the University of Kentucky. By analyzing data from 21 long-term field trials across the United States, researchers found that cover crops deliver some of the strongest, most consistent gains in soil health.
Researchers studied trials ranging from four to 50 years old, focusing on soybean-based cropping systems and the top 15 centimeters of soil. They compared four common management practices: crop rotation, tillage, cover crops and artificial drainage by measuring soil indicators – namely biological activity, soil structure, nutrient levels and pH.
When the results were combined, cover crops were most consistently linked to improvements – specifically, they increased carbon and boosted soil microbes.
Two-crop rotations delivered higher phosphorus levels than single-crop rotations. However, beyond that, rotation diversity, tillage method and drainage didn’t show clear, consistent results across all sites.
While the study tracked soil-health indicators, it didn’t measure yield or profit. However, Hanna Poffenbarger, associate professor of soil nutrient management at the University of Kentucky and a co-author of the paper, said that emerging research is establishing that link.
“This study helps tighten up the evidence on which practices are showing up in the soil tests across a lot of real, long-term systems,” Poffenbarger said. “Then the next step is pairing that with work that connects soil improvements to outcomes farmers care about day to day.”
About the study
The study, published in Agriculture, Ecosystems & Environment, was co-led by researchers at the University of Kentucky’s Martin-Gatton College of Agriculture, Food and Environment, in collaboration with other universities across the United States and with support from a subaward from the University of Wisconsin.