Substrate Management Effects on Biomass Yield and Cannabinoid Profile in Cannabis Sativa L. under Controlled Cultivation in Argentina

Abstract

Cannabis sativa L. has recently been legalized for industrial and medicinal production in Argentina; however, agronomic information relevant to horticultural systems in general and to the La Plata Horticultural Belt (CHP) in particular, remains limited. Substrate selection is a key factor influencing vegetative growth, biomass accumulation and cannabinoid synthesis. We conducted a factorial randomized experiment using three C. sativa varieties grown in three substrates: (i) conventional horticultural soil, (ii) organic horticultural soil, and (iii) a commercial peat-based substrate. Plants were cultivated under controlled greenhouse conditions with standardized irrigation and fertigation. Biomass yield, Harvest Index (HI), nitrogen status (SPAD), and cannabinoid composition (THC, THCA, CBD, CBDA, CBN) were assessed. Cannabinoid quantification was performed via HPLC-UV. Variety had a significant effect on biomass production and cannabinoid profiles, whereas substrate type did not significantly influence these variables. Variety B exhibited the highest total dry biomass (75.1g plant⁻¹), flower biomass (27.8g plant⁻¹), and HI (0.38). Substrate did affect nitrogen status, with the peat-based substrate showing the lowest SPAD values. Cannabinoid profiles were strongly genotype-dependent: Variety A accumulated higher CBD/CBDA, Variety B was THC/THCA-dominant and Variety C displayed an intermediate chemotype characterized by elevated CBN. Overall, genetic background was the primary determinant of yield and cannabinoid composition, outweighing substrate effects. These findings underscore the critical role of variety selection in optimizing cannabinoid production under controlled environments and indicate that conventional and organic horticultural soils may serve as viable alternatives to commercial peat-based substrates.