The effect of plant density and fertilization regime on primary and secondary hemp fibers

Natural fibers requests from the market are always rising; to date, little information is available about the influence of cultivation practice on the morpho-anatomical characteristics of hemp stems. We investigated the effect of sowing density and NPK fertilization on primary and secondary fibers abundance, cell wall thickening and lignin distribution in stems of two monoecious cultivars (Futura 75 and Felina). Plant height, stem diameter and percentage of secondary fibers were affected by fertilization in Felina, while in Futura 75 the sowing density had a prominent effect. Cell wall thickening in primary fibers was higher in Futura 75 in both low density and fertilization, and in Felina grown in low fertilization; regarding the secondary fibers cell wall thickening, Felina maintained the same trend, while in Futura 75 higher values were detected in high density and fertilization. The intensity of fluorescence related to lignin presence was similar in the two kinds of fibers, higher values were observed in high density and low fertilization conditions. This study highlights that optimizing fertilization and sowing density can enhance hemp fiber yield by promoting taller plants with longer fibers and low lignin content, while emphasizes the importance of cultivar-specific responses to fine-tune cultivation practices.