VNR: Can Hawaiʻi grow rice again? Yes, and faster than in Japan

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Last fall, University of Hawaiʻi at Mānoa researchers asked the question: Can Hawaiʻi grow rice again? Now, a new study published in Frontiers in Agronomy has given a data-driven answer: Yes, and the quality might be higher than expected.

The report is the work of scientists from the UH Mānoa College of Tropical Agriculture and Human Resilience (CTAHR) and the Tokyo University of Agriculture and Technology. They found that high-quality Japanese rice types can thrive in fields with traditional irrigation systems, instead of traditional flooded paddies.

The collaboration evaluated two of Japan's premier short-grain varieties, Koshihikari and Hitomebore, during the 2025 summer season.

The team tested upland cultivation in fields in Kapaʻa, Kauaʻi, owned by farmer Jerry Ornellas, a former CTAHR field technician. Yields in Kapaʻa reached 3.79 to 4.01 tons per hectare, comparable to many fields in Tokyo. Surprisingly, while the crops in Japan required 134 days to mature, Hawaiʻi's crops were harvested in 97 days. Shorter tropical daylengths accelerated their growth.

"This was an excellent start to the collaborative research to explore the potential of bringing back rice farming to Hawaiʻi," said Professor Tomoaki Miura of CTAHR's Department of Natural Resources and Environmental Management.

Hawaiʻi's stable temperatures and abundant sunshine generated heavier grains, yielding an outstanding grain-filling rate of up to 93.9%. The island-grown rice also achieved a superior whole-grain ratio and a lower protein content, a trait highly prized for creating a softer, stickier eating texture.

Hawaiʻi imports 100% of its rice, totaling 140 million pounds a year. Because residents consume three times the national average, establishing local production can play a major role in the state's food security.

B-ROLL (Credit: Tokyo University of Agriculture and Technology) :
- Researchers harvesting rice grown on Kauaʻi.