UC Cooperative Extension, in partnership with the California Rice Experiment Station, has released results from the 2025 rice variety trials. The San Joaquin County Delta served as one of eight statewide testing sites and is unique for being the only drill-seeded location. This site is used to test very-early and early maturing rice varieties due to its cooler climate compared to other rice-growing regions in California.
The trial was conducted on April 18th using a seeding rate of 150 pounds per acre in a field planted with M-206, focusing solely on medium grain varieties. Each variety was tested in three replicated plots measuring 150 square feet each. The grower managed fertility and pest control according to standard practices for the field. Harvesting took place on October 9th, with yields measured by hand-harvesting a designated area from each plot.
Results indicated that M-206 remains the most widely grown variety both in the Delta and across California because of its strong agronomic traits, consistent quality at various harvest moistures, and leading average yield among commercial varieties over the past five years. However, “M-206 will be phased out in a couple of years, so growers should be trialing other varieties now to help them determine which varieties to grow when M-206 is no longer available.”
Another commonly planted variety in the Delta is M-105, recognized for its very early maturity and second highest average yield over five years at this location. Its susceptibility to blast disease may explain fluctuations in yield performance. Growers are encouraged to consider M-210 as well: “Growers should consider trialing M-210, which has the third highest average yield in the Delta, closely behind M-206 and M-105. M-210 is early maturing, has blast resistance, and would be a good option in the Delta, particularly on farms where blast has been observed.” Additionally, it offers stable yields similar to those of M-206.
Other varieties such as M-209 have shown variable results due to their longer growing period and sensitivity to low temperatures. Both M-211 and M-521 have also produced inconsistent yields; notably, “M-211 is not well adapted to cooler environments, and its quality tends to decrease below 18 percent harvest moisture.” Meanwhile, “M-521 is also known as ROXY rice and is oxyfluorfen resistant,” but use of this herbicide technology still awaits approval from regulatory agencies.
Comprehensive results from all eight testing locations will soon be accessible through the UC Rice Research and Information Center website (https://agronomy-rice.ucdavis.edu/).
Acknowledgment was given to participating growers and financial support provided by the CA Rice Research Board: “Special thanks go to the cooperating grower and the CA Rice Research Board for financially supporting statewide variety testing.”
For further information about these trials or Delta rice production practices, interested parties are encouraged to reach out directly.
