Hemp farmers know the importance of monitoring THC content in their crop. With the USDA guidelines set to take effect soon, it’s important that farmers understand the difference between delta-9 THC, and total THC. If you’re a little fuzzy on this, visit our FAQ for more details.
One simple ratio is also critically important for hemp farmers: the ratio of CBD to THC in a hemp plant. By understanding the significance of this ratio, farmers will have better knowledge of their potential yields, because they can predict the CBD content of their finished biomass.
To determine the CBD to THC ratio, simply divide the percentage of total CBD by the percentage of total THC on a dry weight basis. In the example COA below, there is 6.48% total CBD and 0.24% total THC. We divide CBD by THC, and our ratio is 27:1.
If we had a sample from another plant that contained 6.75% CBD and 0.27% THC, it might on first glance seem like a more valuable plant because the CBD percentage is higher, with only a marginal increase in THC. But by doing some quick division, we can see that our ratio is only 25:1. This tells us that the first sample is more valuable, because it contains more CBD for a given concentration of THC.
You can now see how using the CBD to THC ratio is the only way to compare the potential yields of different cultivars. This ratio is especially valuable because it remains fairly constant throughout several weeks of flower development. This means you can even compare the certificate of analysis (COA) of a less mature flower to the COA of a finished flower, and understand which plant will yield the most CBD while remaining compliant.
To make financial forecasts, farmers need to be able to predict the CBD content that a compliant crop will yield. This forecast can be achieved with the CBD to THC ratio. Knowing that biomass must test at 0.3%, and given a CBD to THC ratio, we can work backwards to determine the CBD our biomass will yield. Simply multiply your ratio by 0.3% to obtain the % CBD you will see at 0.3% THC. For example: 0.3%(25:1) = 7.5% CBD to 0.3% THC.
You have probably seen claims of hemp producing a CBD percentage of 18% or more. While this might be possible, there is no way to accomplish this while remaining compliant. The best hemp genetics on the market consistently produce a ratio of about 25:1 in the field with best management practices. As we just saw, that means a compliant crop will contain 7.5% CBD. To produce 18% CBD, and remain total THC compliant, the plant would need to have a ratio of 60:1—genetically, this simply does not exist. When you are looking at your options for the coming season, be mindful of the CBD percentage that plant providers promise you on a compliant crop. Do some quick ratio math, and if the ratio is substantially higher than 25:1, start asking questions!