Preliminary Comparative Anatomical and Compositional Screening of the Pressed Fiber Fraction of Soybean (Glycine max L.) Green Biomass from Different Varieties Under a Single-Year Experimental Condition.

The present study aimed to characterize soybean pressed fiber obtained through wet fractionation of green biomass and evaluate the effects of variety and vegetation window on its composition and valorization potential. Four soybean varieties (Advisor, Bólyi 612, Isidor, and Pannónia kincse) were investigated across two distinct vegetation windows using anatomical, cell wall, biochemical, and pigment analyses. Significant variety-dependent differences were observed in several anatomical traits related to biomass quality. Isidor exhibited the greatest leaf blade thickness, while Advisor showed favorable stem structural characteristics and enhanced cuticle development. Cell wall analysis revealed significant differences in xylan, arabinan, and Klason lignin between vegetation windows, while glucan content was affected by both variety and vegetation window, with the highest value observed in Advisor during the first vegetation window. Photosynthetic pigment composition remained relatively stable among varieties and vegetation windows. Because the two vegetation windows occurred during different calendar periods, the observed differences may reflect both plant developmental status and seasonal environmental conditions and cannot be exclusively attributed to harvest timing. This one-year exploratory study provides baseline information on soybean pressed fiber as a potential secondary biomass resource. Further multi-year and multi-environment studies are required to assess the stability and environmental consistency of these findings.