Exploring the influence of abiotic factors on the hemp field retting process: Moisture impact assessment

The industrial use of hemp fibres in construction materials, biocomposites, and technical textiles requires fibres with high quality, uniformity, and well-defined mechanical and biochemical properties. Retting is a key step in achieving these characteristics, as it promotes fibre extraction through the microbial degradation of pectic and structural components binding fibres to the woody core. This process depends on the colonization of hemp stems by diverse microbial communities, mainly bacteria and fungi, which produce specific enzymes that modify cell wall architecture. However, field retting remains largely empirical and highly sensitive to abiotic factors, particularly climatic fluctuations, which often lead to heterogeneous microbial activity and inconsistent fibre properties. Moisture, in particular, is expected to modulate both the structure and functional potential of retting-associated microbiota, thereby influencing fibre outcomes. This study examines the impact of moisture on the progression of field retting of hemp (Futura 75 variety) under a Mediterranean climate in Southern France. High-throughput sequencing (HTS) was used to monitor temporal changes in microbial community composition, diversity, and enzymatic functions over a six-week retting period. Complementary physicochemical and biochemical analyses were conducted on retted stems and extracted fibres to evaluate how moisture-driven microbial dynamics affect tissue degradation and fibre characteristics. The results reveal how moisture shapes the trajectory of bacterial and fungal communities and influences fibre quality parameters. These findings contribute to identifying environmental conditions that enhance retting performance and support the development of more controlled, predictable, and efficient field retting strategies for high-quality hemp fibre production.