While the hemp cannabidiol industry is expanding rapidly, there is still a lack of information on fertilizer recommendations for optimal production. Therefore, a recent study evaluated the eﬀects of nitrogen (N) fertilization on bud biomass and CBD yield. To determine the eﬀect, the researchers carried out a two-year ﬁeld study, evaluating the impact of 4 rates of nitrogen fertilizer on plant growth, bud biomass, CBD, and leaf tissue concentrations. The study was done on two high-yielding CBD hemp varieties (Spectrum and Therapy) under field conditions in North Carolina, USA.
Increased bud biomass and CBD
While both hemp varieties responded to the nitrogen fertilization, the Spectrum variety produced higher bud biomass than the Therapy variety. The study indicates that the Therapy variety may require greater amounts of fertilizer for maximum growth. The diﬀerence in the rate of nitrogen predicted for the two varieties suggests that the nitrogen uptake and use eﬃciency of the two varieties are diﬀerent.
Still, the results showed that the fresh dry bud weight of both varieties increased quadratically with nitrogen fertilization. The CBD yield also increased while being diﬀerent for both the varieties; Spectrum, with higher dry matter biomass, had a higher CBD yield than the Therapy variety. The optimal nitrogen application rate for maximum CBD yield ranged between 130 and 250 kg N ha−1 for the Spectrum variety and 200 kg N ha−1 for Therapy.
According to the researchers, this is one of the first studies to report the effects of N fertilizer application rates on CBD hemp in field conditions. “With the results showing that N fertilization increases fresh and dry bud biomass as well as CBD yield, this study could serve as a preliminary guide for CBD hemp production.”
To read the complete study, go to www.researchgate.net