Given the growing interest in multipurpose hemp crop, eight monoecious cultivars were compared in a two-year trial for quantitative and qualitative yield in a Mediterranean environment characterized by a temperate and humid climate with hot summers. All hemp cultivars were evaluated for yield potential of (i) seed plus stem at seed maturity, and (ii) essential oil yield from inflorescences harvested at full flowering. The second goal was set to test the ability of cultivars to supply new seeds after the removal of inflorescence at full flowering. Among the cultivars, Fedora obtained the best results for seed (0.79 and 0.52 t ha⁻¹) and vegetable oil yield (0.17 and 0.09 t ha⁻¹) normally and with inflorescence removed plants, respectively. Futura, conversely, showed the best results for inflorescence (3.0 t ha⁻¹), essential oil (9 L ha⁻¹), and stem yield at seed maturity (8.34 t ha⁻¹), as means across the two years. The cultivars studied generally reached the grain-filling stage during a period that was drier and warmer than the average of the same multi-year period, and this negatively affected seed quality. The oil fatty acid composition was mainly composed of polyunsaturated fatty acids (75% on average) and not affected by the cultivar. In conclusion, although the hemp grower should always clearly know the main production objective of the crop, the monoecious cultivars available today allow a multipurpose use of hemp crop, improving the sustainability of the cultivation activity.

Due to its possible utilization in cosmetics, medicine and crop protection, as a valuable alternative to petrochemical-derived products, hemp essential oil is now considered a product with high value added and a promising marketing potential. This experiment was conducted with the aim of evaluating the effect of four different locations of Northern Italy during two years (four environments) and three hemp monoecious varieties on the production and quality of essential oils (EOs) obtained by inflorescences harvested at full flowering of female flowers. The highest inflorescence yield was obtained at Maiano 2017, where a superficial groundwater layer (1.5 m) was present, with values that ranged from 1.69 of Fedora to 2.06 t ha⁻¹ of Futura. EOs production ranged between 3.4 and 4.9 L ha⁻¹, affected mainly by the variety effect. The terpene in EOs, very similar between varieties and environments, was mainly composed of sesquiterpenes (caryophillene and humulene, as the most abundant) rather than monoterpenes (α-pinene, β-myrcene and trans-β-ocimene, in particular). Phytocannabinoids, and in particular cannabidiol (CBD), were not removed from tissues by the steam during hydrodistillation, and if this is confirmed by further experiments, the residual biomass, now considered as waste, could assume significant importance as a source for further utilization.

The seed yield in hemp (Cannabis sativa L.) is strongly influenced, besides by genotype, by environment and the genotype x environment interaction, so establishing the fitness and stability of hemp cultivars in multiple environments is necessary. The purpose of this study was to investigate the performance and degree of stability and variance of seed yield, the main related traits, and the correlation among the traits in five hemp monoecious cultivars cultivated in six different environments. The environments resulted from the combination of four locations, two years, and two delayed sowings in a Mediterranean area of north-eastern Italy, and the stability index of the weighted average of absolute scores (WAAS) was used in order to identify the most productive and stable genotypes on the basis of their deviation from the average performance across environments. In this studied area, early varieties, such as Fedora and Felina, proved to be the best performing and stable for seed yield and both increased their yield in correspondence to delayed sowing times, opening up the possibility of cultivating hemp as a second crop. Among the climate parameters, high temperatures during the early grain filling period led to a progressive decrease in seed yield. For a dual-purpose crop, a good compromise could be a late monoecious cultivar (like Futura, in the present experiment), which, if sown early, could certainly provide notable biomass production and acceptable seed yield.

Considering the effects of increasing heat waves already underway, especially in several areas of the Mediterranean region, the study of the effect of temperature on the qualitative yield of hemp oil becomes necessary. Given this, an experiment was conducted in order to evaluate the effect of temperature during the grain-filling period on fatty acid accumulation and composition in hemp seed, comparing two locations with different temperature regimes, two years, two sowing times and two monoecious hemp varieties, characterized by different earliness. The accumulation of different fatty acids in hemp seeds at maturity seems to depend on the genetic background of the two genotypes studied. However, high temperatures also affect the activity of desaturase Δ12 and Δ15, which are responsible for the production of polyunsaturated fatty acids, in particular if greater than an 18 °C minimum night temperature and 30 °C maximum daily temperature, respectively. This result makes it possible to orient, even if partially, the qualitative characteristics of hemp oil for different uses, by identifying the suitable cultivation environment. Considering the Mediterranean area, hilly and foothill environments would favor the percentage of polyunsaturated fatty acid in the oil, with an improvement of the n-6/n-3 ratio, while the plain and warmer area, characterized by heat stress during the grain-filling period, would give an oil with an increased percentage of monounsaturated acids to the detriment of polyunsaturated fatty acid.