On-Farm Rice Drying Guidelines Developed by Arkansas Agricultural Experiment Station’s Rice Processing Program
Arkansas rice farmers are adopting technologies that allow more efficient drying of rice on the farm. The Arkansas Agricultural Experiment Station’s Rice Processing Program has taken data collected since 2013 to develop new recommendations for on-farm rice drying. (UA System Division of Agriculture photo)
Griffiths Atungulu
Interim Director of the AAES’ Rice Processing Program and Associate Professor of grain processing and post-harvest system engineering for the experiment station
Contact Griffiths Atungulu
The Problem
Storing rice with too much moisture can lead to the formation of mycotoxins, especially aflatoxin. These are known carcinogens that pose a severe health hazard to humans and animals. Conversely, over-drying the grain can make it brittle and lead to decreased head yield from broken kernels.
Rice growers commonly harvest rice once it reaches 20 percent moisture content. Rice producers store the rice in silos and begin the drying process to further reduce the moisture content to an optimum range of 12.5 percent to ward off mold growth and help maintain the rice’s structural quality for improved head yield, said Griffiths Atungulu, interim director of the Arkansas Agricultural Experiment Station’s Rice Processing Program.
Most on-farm drying systems in Arkansas use fans to blow either natural or slightly heated air to dry freshly harvested rice, Atungulu said. However, weather conditions come into play when determining the duration required to achieve that 12.5 percent optimum moisture content.
The Work
Atungulu, an associate professor of grain processing and post-harvest system engineering for the Experiment Station, the research arm of the University of Arkansas System Division of Agriculture, and his team used data compiled over nearly a decade to create the chart that offers new guidelines for rice drying on the farm.
The chart accounts for rice initial moisture content, typical airflow rates of 0.5, 1, 1.5, and 2 cubic feet of air per minute per bushel (cfm/bu), fan control strategy, and drying start date. Fan control strategies include the traditional continuous natural air system (CNA) along with computer-assisted Equilibrium Moisture Content systems with both natural air (EMC-NA) and heated air (EMC-H).
The chart states that “suitability” does not factor in “quality” issues but instead focuses on “attaining safe storage,” which is 12.5 percent moisture content, drying duration of fewer than 30 days, maximum dry matter loss (DML) of less than 0.5 percent, and an over-drying rate of less than 10 percent.
The Arkansas Agricultural Experiment Station’s Rice Processing Program has taken data collected since 2013 to develop new recommendations for on-farm rice drying with traditional and modern systems. (UA Rice Processing Program)
The Results
Based on this research, Atungulu said rice with a moisture content of 18 to 19 percent at harvest is now recommended for on-farm, in-bin drying systems. Harvesting at this moisture content can save energy to dry the grain to the optimum storage level. The new recommendation is at a moisture content that is slightly lower than common practice.
The rice drying guidance chart shows that sensory technology systems with heated air capabilities offer the broadest range of optimum drying periods. A low-energy fan can also do the job when used with a heater. However, farmers do not like to introduce heat into the rough rice because the heat uses more energy and can compromise quality, Atungulu said. A more robust fan achieves optimum drying periods without heated air.
The Value
Atungulu said the cost to set up a new on-farm, in-bin drying system with moisture-sensing technology, a weather station, and a fan controller is about $14,000 for the first 48,000-bushel bin.
It becomes more cost-effective as more bins get linked to the system because only one weather station is needed. The cost reduces to about $10,000 for each subsequent bin. Atungulu said most Arkansas rice farmers do not opt for the air heaters, but they are not a significant expense to add to a system.
This University of Arkansas Rice Processing Program research expands the knowledge of a burgeoning practice of on-farm, in-bin rice drying for the nation’s No. 1 rice-producing state. Information gathered by the program with industry partners can lower energy usage in drying the rice by knowing when to shut fans down as the air becomes too humid to dry it. This will help maintain the rough rice’s structural integrity for maximum head yield after milling.
Armed with the decision tool, producers will be in a better position to evaluate their rice drying needs, Atungulu said.
Funding
Rice check-off funding administered by the Arkansas Rice Research and Promotion Board and contributions from the Rice Processing Program’s corporate sponsors supported the research in association with the Arkansas Agricultural Experiment Station.
About the Researchers
Griffiths Atungulu
Associate professor of grain processing and post-harvest systems engineering in the Department of Food Science and interim director of the Rice Processing Program
Ph.D. − Iwate University, Japan (Agricultural Engineering)
M.S. − Iwate University, Japan (Agricultural Engineering)
B.S. − Jomo Kenyatta University of Agricultural and Technology, Kenya (Agricultural Engineering)
Atungulu’s work focuses on food processing and post-harvest systems engineering to improve grain processing efficiency, automated quality monitoring and processing controls for better grain quality and shelf-life, as well as mitigation of mycotoxin formation. His rice research spans the areas of drying, chilling, aeration, milling, storage, and value-added processing. Heutilizeslab-and field-based experiments, computerized mathematical modeling and simulations to generate conclusions that advance science and positively impact the food, grain feed and pet-food industries.