The Effects of Plastic Mulch and Irrigation on Hemp Chemistry and Leaf Endophytes

As an emerging crop, cultivation techniques for industrial hemp (Cannabis sativa L.) are still being developed and optimized. For example, irrigation and plastic mulching are some management practices that have been touted for their benefits in improving crop quality. Both techniques ensure ample water availability, which has often been attributed to improving hemp cannabinoid and terpene composition. In this study, we examined how supplemental irrigation implemented in a plastic mulch system influenced the cannabinoid and terpene profiles of one cultivar of CBD hemp, Lifter. We grew industrial hemp in field with plastic mulch and applied regular irrigation to one group while growing a control group without supplemental water. We found that the cannabinoid content and terpene profiles of industrial hemp did not differ between groups that received irrigation or not. We further examined the leaf endophytic fungal community, as another possible effect elicited by water availability, and found that communities did not differ between the two treatment groups. However, regardless of treatment group, hemp chemical composition was predictive of fungal community, suggesting that terpene and cannabinoid profiles shape or are shaped by the microbiome. Together, our results indicate that hemp is resistant to moderate changes in soil water availability and supplemental irrigation may not be necessary in a plastic mulch system. We encourage future studies to compare the chemical composition of hemp grown in bare ground vs. plastic mulch and in irrigated bare ground soil vs. non-irrigated soil to further improve hemp cultivation techniques.