Impact of seed moisture and temperature on hemp seed germination

Abstract

Germination rates of commercial lots of hemp have been highly variable, resulting in poor stand establishment. Germination rates in some seed lots have decreased by 50% after only 1 year of storage. The objective of this trial was to investigate the impact of seed storage conditions on seed germination over time. Industrial hemp (IH) seeds (cv. NWG2730) were harvested from the field. The seeds were cleaned, sorted, and dried to specific moisture contents (MC) 6%, 8%, 10%, and 14%. Seeds were subdivided, placed in hermetically sealed packets, and stored at temperatures of −20°C, 4°C, 10°C, or 21°C for 3, 6, 12, 18, and 24 months. At each increment, seeds were removed from storage and sterilized using hot water and bleach treatment, and subjected to germination tests. A tetrazolium test (1% solution on a sub-sample of seeds [n = 50]) at 3 and 24 months was conducted. Results indicated an interaction between seed MC and storage temperature over time. At higher MCs (10% and 14%), germination decreased over time with the decline being more rapid at warmer temperatures. For viability, a similar trend occurred with a combination of higher temperature and MC resulting in lower seed viability. These results suggest that optimal storage conditions for intermediate storage of IH seed should focus primarily on keeping seed moisture at <8% and storing seeds at 4°C to10°C. Our data suggest that the variability in germination of commercial hemp seed lots may in part be attributed to loss of seed viability as a result of less-than-ideal storage conditions.