Ippolitos Gintsioudis

Hemp is a multipurpose crop that produces high amounts of lignocellulosic biomass. There are few studies dealing with hemp’s biomass production (lignocellulosic and fiber) under cropping strategies such as irrigation and nitrogen fertilizer. Therefore, the aim of the current study was to assess the effect of irrigation and N-fertilization on the lignocellulosic biomass of one of the most well-known industrial hemp (Cannabis sativa L.) varieties worldwide (Felina 32) under a typical Mediterranean climate. For the purposes of this study, a field experiment was conducted in central Greece (Thessaly region) over the cultivating years 2022 and 2023. We determined the produced biomass dry yield and the dry biomass yield vs. N-uptake relation, as well as quality characteristics for hemp (cv. Felina 32) under three irrigation (I1: 33%, I2: 66%, and I3: 100% ETo) and three N-fertilization levels (N1: 0, N2: 70, and N3: 140 kg ha⁻¹). A significant difference in the dry biomass yield was found, ranging between 10–11.2 t ha⁻¹ using I2 and/or I3 irrigation levels and remaining at 8.6 t ha⁻¹ with lower irrigation (I1). In terms of fertilization factor, it appeared that in samplings where statistically significant changes were observed, all degrees of fertilization differed from one another, with the N3 treatment exhibiting the highest production (11.4 t ha⁻¹). The average protein content varied between 10% in 2023 and 14% in 2023. A linear biomass yield–nutrient uptake relationship was found with high R², pointing to a nitrogen use efficiency of 55.15 kg kg⁻¹. Thus, it would seem that nitrogen fertilization and irrigation are both crucial factors of industrial hemp cultivation, helping to raise the crop’s overall yield of lignocellulosic biomass. The introduction of hemp into land-use systems necessitates thorough evaluation, as hemp shows considerable potential as a crop that can yield substantial quantities of above-ground biomass (lignocellulosic: stems and fibers). This is especially true in regions where irrigation is possible, and the application of nitrogen fertilizers can further enhance these yields.

Nowadays, the lack of cattle feed, particularly green fodder, has become a key limiting factor in the agricultural economy. Switchgrass appears to offer a viable solution to the feed shortage. An improved cultivation practice might be needed to boost switchgrass forage production all season long. This study was conducted to quantify the positive effects of introducing different legume crops (vetch and pea), optimally fertilized, on the production and quality of mixed harvested switchgrass–legumes hay in late spring (May) and switchgrass hay harvested once more in early fall (September). The studied intercropping systems, independently of the legume species used, increased forage productivity (almost threefold), reaching 7.5 t ha⁻¹ and quality characteristics, with protein content almost rising threefold, reaching 12.5%. The aforementioned practice can assist the perennial crop (switchgrass) in providing a high hay production during the early fall harvest, even without fertilization. The overall annual economic benefit for the farmers may be increased by 90–720 € per ha, depending on the prevailing weather conditions. Overall, it may be concluded that the suggested cropping system produces a significantly higher yield of cattle feed compared to traditional monocultures, improving the agricultural economy while reducing the negative effects of modern agriculture on the environment.