Study Finds Moderate Drought Can Considerably Reduce Marijuana Water Use Without Hurting Flower Production or CBD Yield

Marijuana plants subjected to moderate water restrictions during flowering used less water without suffering reductions in flower production or CBD yield, according to a new study published this week in the journal Frontiers in Plant Science

For the study, researchers from the University of Hohenheim and the University of Applied Science examined two CBD-dominant medicinal marijuana genotypes grown indoors under well-watered, moderately water-stressed and severely water-stressed conditions.

During moderate drought treatments, researchers allowed growing media to dry before providing enough water to prevent the plants from wilting. The process was repeated during early, middle and late flowering. Plants subjected to severe drought received no additional water until wilting occurred.

The researchers found that moderate water restrictions lowered water consumption while maintaining both inflorescence biomass and CBD yield. Neither flower biomass, CBD concentration nor overall CBD yield was significantly affected by the irrigation treatment.

Severe drought provided no comparable advantage. Although severely stressed plants temporarily became more efficient at conserving water at the leaf level, photosynthesis declined substantially and plants experienced leaf loss and other signs of stress. Researchers concluded that the apparent increase in water-use efficiency represented a survival response rather than an improvement in production efficiency.

The experiment also found that genetics had a substantially larger impact on marijuana productivity than irrigation strategy. The Terra Italia genotype produced approximately twice as much flower biomass and around five times the CBD yield of the Kanada genotype.

Moderate drought also did not significantly stimulate additional cannabinoid production. Although CBD concentrations increased modestly under moderate stress at the final harvest, the differences were not statistically significant.

Researchers said the results indicate that carefully managed deficit irrigation could provide marijuana cultivators with a practical way to reduce water consumption without sacrificing productivity.

“We conclude that moderate deficit irrigation is a viable and sustainable means of reducing water use in indoor medicinal cannabis production without compromising yield or quality,” the researchers said.

The authors cautioned that the experiment involved only two CBD-dominant genotypes grown indoors during a single flowering cycle. They said future research should include THC-dominant and balanced THC-CBD varieties and examine whether the findings hold across additional growing conditions and cultivation cycles.