This study examined the dynamics between potassium (K) supplementation, soil microbiome interactions, and their cumulative impact on the physiological, morphological, and phytochemical attributes of a tropical/subtropical cultivar of industrial hemp (Cannabis sativa L.), namely ECO-0015, bred for Australian climatic conditions by Ecofibre Ltd. The experiment, conducted in a controlled glasshouse environment, endeavoured to interpret the K-nutritional demands of the variety and the resultant physiological repercussions.
We compared the effects of escalating dosages of conventional liquid K fertilisers against a novel slow-release potassium formulation (SRK), integrated with a consortium of select soil microorganisms (courtesy of Troforte, Sunpalm Fertilisers, Australia). The experimental design encompassed a comprehensive suite of physiological and morphometric parameters, including but not limited to, photosynthetic efficiency in response to varying levels of photosynthetically active radiation (PAR) and ambient carbon dioxide (CO2) concentrations, along with cannabinoid profile quantification.
Our findings indicated that SRK application, in synergy with the soil microbial environment, significantly enhanced morphometric parameters such as stalk diameter, plant height, and shoot biomass, compared with the conventional K treatments, which did not result in any marked differences.
Physiological assessments revealed an inverse relationship between higher K concentrations and photosynthetic efficiency, implying a potential escalation in plant stress under such conditions. Furthermore, phytochemical analysis revealed a notable increase in cannabidiol (CBD) and cannabidivarin (CBDV) levels at elevated K concentrations. The integration of SRK with the soil microbiome resulted in an increase in Δ9-tetrahydrocannabinol (THC) and analogous cannabinoid compounds.
This study illustrates the complex interplay between nutrient supplementation, rhizospheric microbial dynamics, and their collective influence on the growth and cannabinoid biosynthesis in Cannabis sativa L., presenting key insights for optimising cultivation practices in tropical and subtropical environments.