Crop Management and Environ-
mental Effects on Rice Milling
Quality and Yield - 2006

 

 

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Project Leader and Principal  Investigators

Randall "Cass" Mutters, farm advisor, UC Cooperative Extension, Butte County

James Thompson, extension specialist, Dept. of Biological and Agricultural Enginering, UC Davis

Richard Plant, professor, Dept. of Plant Sciences, UC Davis

This is the fourth year of a project examining how rice moisture at harvest affects head rice yield and ultimately grower profitability.

A small plot at the Rice Experiment Station was divided into sections and planted with M-201, M-202 or M-206 rice at a seeding rate of 75, 150 or 225 pounds per acre. The rice was grown under identical cultural practices and harvested on October 3, 10, 13, 20 and 27 and then analyzed for rice moisture, head rice yield and yield.

Head rice yield was generally high even as harvest moisture decreased below 21 percent, the typical minimum moisture for high head rice yields. Weather conditions were dry during harvest, with little overnight dew and little rewetting of rice kernels. Seeding rate did not appear to affect head rice quality. Yield for the three varieties did not change during the harvest period in the test.

Results showed that M-206 had higher quality than either M-201 or M-202. This is a reflection of the higher total rice yield in the newer variety, M-206. It also appeared to be more resistant to fissuring at the low harvest moistures experienced at the later harvest dates. Average quality as measured by percent whole kernels for the Oct. 13, 20 and 27 harvest dates was M-201 (88.3%), M-202 (77.4%) and M-206 (92.2%).

The dry conditions of 2006 were not caused by the north wind, as in past years, but by generally low dew point temperatures. Weather during the four years of this project has varied greatly, with 2003 and 2004 being much more humid. The last two years were much drier and more conducive to good rice quality.

Daytime dew point temperature can be a good predictor of overnight dew formation and rewetting potential. If there is little chance of overnight dew, rice can be harvested at moistures below 21 percent with little loss in head rice yield but with good return to the grower because of reduced drying costs. Previous studies suggest that more than 11 hours of dew is necessary to completely rehydrate rice. Daytime dew point temperatures less than about 55 degrees will allow rice to dry with little loss in head rice yield.

 

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