Finding the Optimal Drying Conditions for Seed Rice Germination, Vigor
Seed rice quality depends on germination rates and seed vigor, which are affected by drying conditions. Traditional drying guidelines focus on rice for consumption, leaving a gap in recommendations for optimizing seed rice drying. To find the optimal drying conditions for seed rice, researchers with the Arkansas Agricultural Experiment Station used X-ray imaging to explore how drying conditions affect rice seed quality. The research found that harvest moisture content has a greater impact on germination potential and seed vigor than drying temperature alone. By identifying the temperature and humidity ranges that preserve seed quality while reducing drying time, the findings offer rice producers and millers science-backed guidance for efficient postharvest management for rice intended to be used as seed.
The Problem
Improper drying of rice can damage the embryo inside the grain, reducing germination rates and seed vigor. Traditional drying guidelines focus largely on rice for consumption instead of rice destined to be used as seed. As the rice industry seeks more efficient and cost-effective methods for drying rice seed without damaging the seeds, guidelines for temperature and humidity are needed to balance drying speed and seed quality.
The Work
Under the direction of Griffiths Atungulu, Professor and Director of the Rice Processing Program for the Arkansas Agricultural Experiment Station, Ph.D. student Samuel Olaoni conducted a series of controlled drying experiments using two long-grain rice varieties. The experiment tested combinations of harvest moisture content (21% to 24%, 18% to 20%, and 13% to 16%), drying temperatures (100 to 140 degrees Fahrenheit), relative humidity (25% to 50%), and air velocity (0.66 to 1.65 meters per second). Using X-ray imaging, the researchers noninvasively examined grains for internal fissures before and after drying and then conducted germination and vigor tests over a 12-month storage period under controlled humidity and temperature conditions.
The Results
The study found that harvest moisture content had the greatest effect on seed quality. Seeds harvested between 13% to 16% moisture and dried at 122 degrees Fahrenheit with 35% relative humidity achieved germination rates of about 95% and strong seed vigor. Even drying at 140 degrees produced acceptable results with germination rates of 90%. The results offer evidence that processors may dry at a higher temperature for a reduced drying time with minimal seed damage. Lower relative humidity (25%) caused slightly more drying stress and lower germination than higher humidity (35% to 50%). Kernel fissuring showed only a weak correlation with seed vigor, with just a 3.5% difference in germination between highly and minimally fissured grains. During storage, seed vigor declined more for rice dried at higher temperatures, but overall germination remained strong when dried to 12.5% moisture before storage.
The Value
The study provides rice farmers and rice processors with data-driven parameters for balancing drying efficiency and seed viability. By safely using higher drying temperatures and optimizing humidity, processors can reduce turnaround times while maintaining seed quality.
Read the Research
Use of X-ray imaging to elucidate impacts of drying conditions and storage on seed rice germination and vigor
Drying Technology
Volume 43, Issue 10 (2025)
https://doi.org/10.1080/07373937.2025.2538177
Supported in part by
U.S. Department of Agriculture, National Institute of Food and Agriculture, Hatch Act funding.
About the Researchers
Griffiths Atungulu
Professor and Director of the Arkansas Rice Processing Program
Ph.D. in Agricultural Engineering, Iwate University, Japan
M.S. in Agricultural Engineering, Iwate University, Japan
B.S. in Agricultural Engineering, Jomo Kenyatta University of Agriculture and Technology, Kenya
Other Collaborators
Samuel Olaoni, a Ph.D. student in the Department of Food Science at the Dale Bumpers College of Agricultural, Food and Life Sciences, and Kaushik Luthra, Assistant Professor of Postharvest Processing in the Department of Biological and Agricultural Engineering, were co-authors.
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