Fertilization and soil pH affect seed and biomass yield, plant morphology, and cadmium uptake in hemp (Cannabis sativa L.)

The phytoremediation potential of industrial hemp (Cannabis sativa L.) becomes a new target of hemp cultivation. The ability to accumulate cadmium depends on genetic, anatomical and physiological characteristics of the varieties. The published data show that the level of fertilization affects many metabolic pathways, the development of plants and cannabinoid concentration. In addition, there are inconsistent data on the cadmium accumulation capacity depending on the mineral nutrition and pH. A study was carried out to assess the potential of two hemp varieties (‘Henola’ and ‘Białobrzeskie’) as a decontaminator of cadmium, depending on soil pH and phosphorous fertilizer level. The influence of pH, fertilization and cadmium concentration in the soil on plant morphology and on the yield of seeds and biomass were also assessed. The soil with two different pH was used in the experiment: acidic (pH 4) and alkaline (pH 7.5). Two concentrations of aqueous solution of cadmium nitrate (Cd(NO3)2) were added to the soil to obtain final concentration of Cd: 4 mg/kg and 8 mg/kg of soil, respectively. The phosphorous fertilizer was supplied in the amounts of: 50 kg/ha, 100 kg/ha, 150 kg/ha. The cadmium content in soil and in hemp plants was determined with a flame atomic absorption spectrophotometry and a plasma optical emission spectrometry (ICP-OES), respectively. Based on two years of experiments, the highest cadmium concentration in seeds and biomass, were revealed for Henola variety, when fertilizer was applied in the amount of 150 kg/ha. The results revealed that the fertilization ant pH level are important factors in the cultivation of hemp. They affect the intensity of cadmium uptake from the soil. Higher soil pH was correlated with the highest concentration of Cd in seeds and straw of Białobrzeskie variety. Such a relationship has not been demonstrated in the case of the Henola variety. The highest BCF (bioconcentration factor) value was calculated for Cd uptake in ‘Henola’ biomass. Increased cadmium concentration in the soil did not adversely affect development and growth of two hemp varieties studied. The phytoremediation potential of individual hemp varieties is different. Higher pH increases the cadmium uptake by some hemp varieties, but in the case of other varieties this relationship is reversed. It is necessary to assess the phytoremediation potential of each hemp cultivar in different agrotechnical conditions.