Salinity effects on yield and nutrient uptake in Cannabis sativa L.

In order to study the salinity response of Cannabis sativa L. (C. sativa), nutrient solutions for hydroponic cultivation with electrical conductivity (EC) levels of 1.8, 3, 6, 9 or 12 mS cm^-1 were applied in rockwool. EC was increased either by increasing the nutrient concentrations N, P, K, Ca, Mg, S or by the addition of NaCl to a nutrient solution EC of 1.8 mS cm^-1. Shoot and bud weight of the C. sativa ‘Early Haze’ decreased linearly with the increase of EC when nutrient-increased ECs were higher than 3 mS cm^-1, and when the NaCl-increased ECs were higher than 1.8 mS cm^-1. The concentrations of Total THC and CBD were not affected by EC or nutrient composition. Highest cannabinoid yields were obtained at 1.8 and 3 mS cm^-1 at NaCl concentrations ≤13 mM. Leaf necrosis occurred only in the 9 and 12 mS cm^-1 NaCl treatments. Despite high Na supply, leaf Na concentrations did not exceed 30 mmol kg^-1 DM. In contrast, remarkably high Ca (>2200 mmol kg^-1 DM) concentrations were found in all treatments. Besides, low P-concentrations (<50 mmol kg^-1 DM) in particularly the low EC-treatments were found and could be related to pH levels >7.5 in the rootzone. The results are discussed with respect to the possibilities for the cultivation of C. sativa in closed nutrient systems.