October 23rd marked the end of the 2023 hemp fiber field season, with the collection of the final data points in our retting sensor trial. This trial aimed to monitor localized temperature and moisture at the site of fiber actively dew-retting on the ground. These sensors arrived a bit later in the season, but luckily one of our longer-season varieties was able to lend itself to the last-minute experimental design. That variety was none other than the mighty Yuma; a towering dioecious variety native to China with broad leaves and heights reaching 14 feet, sourced from Kanda Hemp.
Prior to data collection, the NWCS team hand-harvested all 400sqft of Yuma, trucked it to where the sensors were installed, and got to work forming 32 retting piles (8 piles per 4 reps). This was all quite a feat as the plants were nearly twice the size of the 8-foot farm truck bed. Samples of five stems were collected from corresponding piles and photographed twice weekly for 8 intervals spanning 5 weeks.
Photos collected over the course of the experiment show the alchemy of the retting process. Retting is the natural process by which microorganisms colonize the hemp stalks and feed on the pectin and lignin that bind the outer “bark” layer of bast fiber to the inner woody core, known as the hurd.
In the second sample photo (on right), it is possible to see the bast fiber pulling away from the hurd as those natural glues diminish within the stalk. All the samples were then dried and sent for lab testing in hopes that we can gain a better understanding of what is happening within the stalks while they ret, and how this activity corresponds with temperature and moisture at the ground level.
For many in Vermont it was a tough growing season, but the monster stature of the Yuma and all of its giant neighbors in the variety trial managed to put a smile on our faces every day. Stay tuned this winter for the corresponding research reports that are sure to shed even more insight on how our fifteen 2023 hemp varieties expressed themselves this year. Our research reports can be found at www.uvm.edu/extension/nwcrops/research.