Title : Biomass and seed yield of industrial hemp varieties under Mediterranean conditions
Abstract:
Industrial hemp (Cannabis sativa L.) has been increasingly recognized as a sustainable agricultural crop, adaptable to different edaphoclimatic conditions and suitable for low-input systems, due to its rapid growth, high water-use efficiency, and reduced need for fertilization and plant protection products (Amaducci et al., 2015; Cosentino et al., 2013). In Mediterranean climate regions, characterized by hot and dry summers, evaluating hemp performance across different growing seasons is particularly relevant, as climatic variability can significantly influence biomass and seed production (Struik et al., 2000). The present study was conducted at the National Institute for Agrarian and Veterinary Research (INIAV), in Elvas, Portugal (38°52' N; 7°09' W), in a temperate climate region with annual precipitation between 500 and 600 mm and average annual temperatures ranging from 15.0 °C to 17.5 °C (Agencia Estatal de Meteorología, 2011). The trial was established on a loamy-sand soil with a pH between 7.0 and 7.5, considered suitable for hemp cultivation. Four certified commercial hemp varieties—Futura 75, Fibror 79, Mona 16, and Santhica 27—were evaluated over two consecutive growing seasons (2024 and 2025). The experimental design included four replicates per variety, in plots of approximately 12 m². Sowing was carried out using a row seeder with an inter-row spacing of approximately 15 cm, and irrigation was provided through a drip system. No fertilizers or phytosanitary products were applied. After harvest, plant components—stems, leaves, and seeds—were separated and weighed individually to allow detailed biomass production assessment. The results revealed significant differences between the two growing seasons, with consistently higher biomass production in 2024 and a marked reduction in 2025. This decrease was observed across all plant components and was statistically significant for stems (p=0.0002175), leaves (p=0.000149), and seeds (p=0.00047). Varietal responses to interannual variability differed. While the Mona 16 variety showed a pronounced reduction in leaf and seed production in one replication, Santhica 27 exhibited the highest overall average reduction in stem, leaf, and seed production between the two years. Seed yield was the most affected component, with reductions exceeding 84.7%, indicating high sensitivity to the environmental conditions recorded during the 2025 growing season. These findings highlight the strong influence of interannual climatic variability on industrial hemp productivity and emphasize the importance of varietal selection and adaptive management practices to enhance crop resilience in Mediterranean low-input agricultural systems.
