|Factors Affecting Rice Milling
Quality and Yield-03
Project Leader and Principal UC Investigators
Randall "Cass" Mutters,UCCE farm advisor, Butte County
James Thompson, Extension Specialist, Dept. of Biological and Ag. Engineering, UC Davis
Scientists working on this project have determined that certain
meteorological conditions - dew formation and drying winds, in
particular-have a big impact on head rice yield.
A controlled experiment at the Rice Experiment Station with M-202 medium grain showed that good head rice yield could be kept high even at low harvest moisture if the rice is not subject to rehydration from dew. Test plots were drained on September 12 (early), 18 (normal) or 26 (late) and harvested on September 30, October 6, 13 and 16, respectively. Each plot was hand harvested in six to eight locations and threshed with a small plot thresher. Rice moisture for each harvest location was determined with a single grain moisture meter.
Findings confirmed that north winds in the Sacramento Valley cause rapid rice drying in the field and prevent dew formation, allowing head rice yields above 55 pounds per hundredweight in moisture ranges of 16 to 18 percent. These conditions produce rice with high value and low drying costs. After windy conditions stop and dew returns, harvest moisture must be above 22 to 24 percent to maintain head rice yields above 55 percent. Otherwise, head rice loss caused by rehydration of kernels below 16 percent will most likely occur. Early field draining resulted in lower rice moisture at harvest and contributed to lower head rice yield compared with normal and late drain times.