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Soil health is a crucial yet historically underrated aspect of farming. However, many of today’s farmers realize that healthy soil leads to healthier crops and a more stable ecosystem. As Wisconsin heads into its third hemp farming season, how does soil health come into play with this old-yet-new-again crop?
Carrie Laboski is a professor and UW–Division of Extension soil fertility and nutrient management specialist. Through the College of Agriculture and Life Sciences (CALS) and the UW-Division of Extension’s hemp research program launched last spring, Laboski is working with her colleagues in agronomy to research best growing practices for hemp. Her research focused on hemp for grain and fiber.
Laboski emphasizes that this is the first time in generations that anyone could conduct hemp research in Wisconsin because the plant had been illegal for so long. Thus, researchers, as well as most in the industry, don’t have much knowledge or experience with the hemp crop. The research team was able to find literature from 80-100 years ago about how hemp was grown in Wisconsin for fiber. Laboski also pulled together some rough fertility guidelines for hemp with data extrapolated from more recent research done by universities in areas of the U.S. and Canada that had rolled out hemp research programs before Wisconsin. She looked at weather conditions and patterns, soils conditions and how hemp behaved compared to other crops like wheat.
The team conducted research at the UW-Madison Arlington Ag Research Station and in Buffalo and Chippewa counties. Initial screening trials seek to understand how crop management practices—such as variety, seeding rate and nitrogen fertilization—affect grain and fiber production in Wisconsin. For all of these practices, they are evaluating the impact on grain and fiber yield, as well as the tetrahydrocannabinol (THC) content.
Preliminary data suggests that hemp will require nitrogen additions, either as fertilizer or manure. “It’s not a crop you can just plant and ignore,” Laboski emphasizes. “We could see that if we didn’t apply nitrogen fertilizer, we had significantly less yields of grain or fiber, so that’s an important component.”
In addition to studying the effects of nitrogen on hemp, Laboski may eventually study how other macro-nutrients, such as phosphorus and potassium, affect hemp crops and THC content. She notes that she has concerns about soil erosion, which could happen if there’s not enough crop residue (such as dead leaves) covering the soil surface.
“You have to be careful with rotations to make sure you have enough plant residue covering the soils to minimize erosion potential,” she says. “We haven’t conducted research to determine if hemp increases the potential for soil erosion compared to other crops, but that’s something we have to think about.”
There’s still much work to be done with regard to hemp research and growing practices, and Laboski notes that, at this point, a great deal of professional judgement in required to provide best estimates until there’s more solid data in Wisconsin. “Everybody wants the silver bullet, whether it’s improving our health, helping the farm economy or cleaning up the environment, but a silver bullet doesn’t exist. Hemp might be part of a solution, though,” she concludes.
For more information on UW-Division of Extension’s hemp program, visit fyi.extension.wisc.edu/hemp.
