Soil conditions significantly influence the levels of cannabinoids and terpenes produced by cannabis plants, according to a first-of-its-kind study.
The research, published in the Journal of Medicinally Active Plants, compared hemp extracts from two cultivars grown in fields with different soil preparation methods and found “significant differences in specific cannabinoid and terpene concentration”.
Funded by the U.S. Department of Agriculture’s (USDA) National Institute of Food and Agriculture, Penn State College of Medicine and cannabis research company PA Options for Wellness, researchers grew two crops of cannabis. One with the Tangerine cultivar and another with a cultivar named CBG Stem Cell; both cultivars contain high levels of cannabigerol (CBG).
The cultivars were planted in two separate fields that received no fertiliser or supplementation, and similar amounts of rain and sunshine. No.1 field was known as the cover crop (CC) field, and No.2 field was a conventionally tilled field (CF).
The CC field had crops of hairy vetch, triticale, winter oats, and crimson clover grown on, which were then tilled into the field before the cannabis cultivars were planted. The CF field was tilled conventionally and had no crops grown or tilled into it prior to cannabis being planted. The researchers hypothesised that the CC field would yield the cannabis with the highest amounts of cannabinoids and terpenes.
To analyse the findings, the team extracted compounds from 200 hemp plants using an ethanol-based extraction technique to produce a wax concentrate from the cultivar’s inflorescence (the complete flower head of a plant, including stems, stalks, bracts, and flowers). They then used third-party laboratories to perform statistical analysis of the concentrate to determine the quantities of cannabinoids and terpenes.
The results revealed that while total cannabinoid content remained constant across both fields and both cultivars, the individual cannabinoid content varied. In the CC field, the cultivar Tangerine produced higher levels of CBDA and lower levels of CBD. However, for the cultivar CBG Stem Cell, the opposite was found; it produced higher levels of CBD and lower levels of CBDA.
Terpene profiles also varied between cultivation methods, with more pronounced differences observed in conventionally tilled fields.
“Our study adds to a growing literature demonstrating that cannabinoid and terpene profiles are strongly influenced by cultivation conditions, notably cultivation system (indoor vs outdoor), soil quality, and light exposure,” the study said.
The findings demonstrate that soil quality significantly affects the production of bioactive compounds in cannabis plants, though researchers acknowledge that further investigation is needed to understand the underlying mechanisms.
“The outcome of this study provides outdoor growers with information on the effects soil health can have on cannabinoid and terpene content in hemp,” the study concluded.
“Poor soil quality (CF) appears to result in higher levels of THC production, whereas higher soil quality (CC) may result in higher levels of the precursor cannabinoid, CBG. Further studies that incorporate synchronised soil and plant analyses across multiple time points, as well as studies with isolated treatments of the characteristics that contribute to the health of the soil are required to delineate the main driver between soil health and hemp cannabinoid and terpene content.”
