Effects of Nitrogen, Phosphorus, and Potassium on the Growth Physiology and Secondary Metabolites of Hemp (Cannabis sativa L.) under NaHCO3 Stress

Industrial hemp (Cannabis sativa L.) is a crop with high economic value due to its wide adaptability and significant resistance to stress. In the Songnen Plain of Northeast China, sodium bicarbonate (NaHCO3), the main component of the prevalent alkaline soil, poses a major challenge to plant growth. Although previous studies have explored the physiological and biochemical responses of industrial hemp to soil salinity and nutrients, research on the interactive effects of salinity and nutrients on its growth physiology and secondary metabolites remains limited. In this study, we used “Hemp No. 5” as the experimental material and employed the ‘3414’ experimental design method to systematically investigate the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilization on the growth physiology and secondary metabolites of industrial hemp under NaHCO3 stress in pot experiments. The results showed that under the N1P2K2 treatment, the dry matter accumulation and SPAD value of industrial hemp increased by 28 and 32%, respectively, compared to the control group. Additionally, this treatment led to a 22% decrease in malondialdehyde (MDA) content, indicating that appropriate fertilization can effectively alleviate the impact of alkaline salt stress. Concurrently, the contents of secondary metabolites, such as total flavonoids and cannabidiol (CBD), increased by 45 and 50%, respectively, compared to the control group under this treatment. However, excessively high concentrations of N, P, and K (N3P3K3 treatment) exacerbated the negative effects of saline-alkaline stress, resulting in a 15 and 18% decrease in biomass and chlorophyll content, respectively, compared to the control group. These findings underscore the importance of proper proportions of N, P, and K in enhancing the growth and stress resistance of industrial hemp in alkaline salt stress environments. The results of this study provide a scientific basis for rational fertilization of industrial hemp in saline-alkali regions, which can help optimize fertilization strategies and improve the production efficiency and economic value of this crop.