Study: Irrigation Levels Influence Hemp Biomass, But Not Cannabinoid Concentrations

The multi-year field trials compared autoflower and full-season cultivars under varying irrigation rates, measuring biomass, flower structure, and cannabinoid yield. The findings show that hemp consistently produced its main flower even under drought conditions, with primary flower size and cannabinoid concentration remaining steady regardless of water levels. Increased irrigation primarily boosted plant height, leaf and stem biomass, and secondary/tertiary flower growth. However, floral biomass and CBD yields plateaued once irrigation reached about 80% of the site’s potential evapotranspiration. Beyond that threshold, additional water had little effect on cannabinoid yield.

The study also revealed that autoflower and full-season cultivars responded similarly, though autoflower plants tended to have a higher proportion of floral biomass relative to stems and leaves. Importantly, hemp was able to survive and produce flowers with little or no supplemental irrigation, highlighting its adaptability to dry environments.

According to the researchers, while moderate irrigation increases yield, water use beyond a certain level provides diminishing returns. The results suggest that in regions with limited irrigation resources, hemp cultivation can still be viable, with irrigation decisions best guided by water availability, production costs, and market conditions.