A recent study from Cornell University has found no link between increases in the THC content in hemp with environmental or biological stresses. Guidelines from USDA’s Agricultural Marketing Service note that the threshold for THC content is 0.3 percent. USDA has recently raised what it considers to be a “negligent crop” from THC levels of .5 percent to one percent, reducing some risk for growers. Senior author of the study and professor in the horticulture section of the School of Integrative Plant Science in the College of Agriculture and Life Sciences, Larry Smart said that their findings should help to provide some comfort regarding the CBD to THC ratio in hemp.
The research project included control plots and five stress treatments that were applied to three genetically unrelated high-CBD hemp cultivars. The stress treatments included flood conditions, physical wounding, exposure to a particular plant growth regulator, powdery mildew, and herbicide. Over the four-week maturation period, tests showed that THC content increased proportionally for all of the different stress treatments imposed on the different cultivars. The study provides support for genetics being the determining factor for THC content in hemp plants rather than environmental stresses. Further research and breeding will be needed to better determine the appropriate genetics for achieving a high CDB content with acceptable levels of THC.
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