S06 - Session P8 - Salinity effects on yield and nutrient uptake in Cannabis sativa

Authors: Rob Baas *, Diek Wijnen

Cannabis sativa is a relatively fast-growing crop cultivated in hydroponic systems both outdoor and indoor. However, nutritional requirements and salinity tolerance have only been little documented, particularly with respect to cultivation in closed nutrient systems. Therefore, in greenhouse trials the effects of salinity and nutritional requirements were investigated using nutrient solutions with EC levels from 1,8-12 mS/cm. EC was increased either with macro nutrients (N, P, K, Ca, Mg, S) or with NaCl above a base-EC of 1,8. During the experiment, EC levels in the rockwool were monitored and maintained by drain management and flushing. The growth and eventually bud yield of Early Queen Haze decreased above 3 mS/cm in the nutrient-enhanced EC treatments, and at 13 mM NaCl (corresponding to 3 mS/cm) in the NaCl-enhanced EC treatments. THC/CBD concentrations were not significantly influenced by salinity or NaCl. Necrosis of the older leaves occurred only in the highest NaCl treatments of 111 mM at 12 mS/cm. Cannabis proved to effectively exclude Na since Na uptake did not exceed 30 mmol/kg DM. In all treatments remarkably high Ca ( > 2200 mmol/kg DM) concentrations were found. Relatively low P-concentrations ( < 50 mmol/kg) were observed in particularly the low EC-treatments, which could be related to pH levels higher than 7.5 in the root environment. In conclusion, optimal growth in cannabis was obtained between 1.8 and 3 mS/cm and at NaCl concentrations lower than 13 mM. The relatively low sodicity offers possibilities for prolonged cultivation in closed nutrient systems. Under these conditions, pH control needs further attention in order to avoid P-limitation.