|Variety Trials - 93
Project Leader and Principal UC Investigators
James E. Hill, Extension Agronomist and Chair, Department of Agronomy and Range Science, UC Davis
James R. Webster, Staff research associate, Department of Agronomy and Range Science, UC Davis
Carl M. Wick, farm advisor, Butte County Cooperative Extension
John F. "Jack" Williams, UC Cooperative Extension Farm Advisor Sutter/Yuba counties
Steven C. Scardaci, UC Cooperative Extension Farm Advisor Colusa/Glenn/Yolo counties
C. Mick Canevari, UC Cooperative Extension Farm Advisor San Joaquin County
Bill L. Weir, farm advisor, Merced County Cooperative Extension Farm
|Each year a team of University of California scientists
evaluates experimental cultivars in cooperation with public and private plant breeders for
the purpose of rice variety improvement Last year 16 on-farm rice variety evaluation
trials were conducted throughout the rice growing regions of California. Six similar tests
were conducted at the Rice Experiment Station at Biggs. Several advanced and preliminary
breeding lines showed promise in improved yields and other agronomic characteristics over
existing varieties. In addition, several experiments were conducted on nitrogen and
potassium fertility and straw management-nitrogen effects. This section summarizes the
Very Early Maturity
Twelve advanced breeding lines and 10 commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading). Twenty-two preliminary lines were also evaluated at each location.
Grain yields in the advanced tests averaged 9,870 pounds/ acre at Biggs, 7,950 pounds/acre at Butte, 8,750 pounds/ acre at Sutter and 8,660 pounds/acre at San Joaquin. Lower average yields in the off-station Butte County test were attributed to thin stands that allowed for increased weed competition.
Over the four locations, the highest yielding entry was 91-y-177, a very early short grain that ranked first in yield in the Sutter and San Joaquin tests. Entry 89-Y-103, another advanced short-grain, was the highest yielding entry at Biggs and ranked third in the four location summary.
No entry produced yields statistically higher than M-202 at Biggs, Butte and Sutter. Yields of M-204 were similar to M-202 at Biggs and Butte but were 8 percent and 9 percent lower in the Sutter and San Joaquin tests, respectively. The researchers say this illustrates a lower degree of tolerance to the cooler conditions in San Joaquin County and the delayed planting date at Sutter. The early premium quality variety, M-203, continues to perform very well in the San Joaquin test and in other locations where severe early lodging is avoided.
Fourteen advanced lines and 10 commercial varieties were compared in four early tests (90-97 days to 50 percent heading). Eighteen preliminary lines were also evaluated in separate tests at each location. Grain yields in the advanced line tests averaged 9,950 pounds/acre at the Rice Experiment Station, 9,870 pounds/acre at Yolo, 9,270 pounds/acre at Yuba and 8,600 pounds/acre at Colusa.
The medium grain line 91-y-381 exceeded 10,000 pounds/ acre at Biggs, Yolo and Yuba and was the highest yielding entry over the four locations. Other leading advanced
lines included 89-y-103 and 90-y-253. The variety M-202 ranked first and third in yield at Yolo and Yuba, respectively, but was below average at Biggs and Colusa. The new variety M-204 exceeded the yield of M-202 at these locations.
The long grain variety L-203, released in 1991, continues to show improvement over L-202 at each location. Of the preliminary lines, 92-y-624 and 93-y-75 (medium grains) and 92-y-521 (long-grain) exceeded 10,000 pounds/acre and showed improvement in other agronomic traits.
Intermediate to Late Maturity
Nine advanced lines and seven commercial varieties were compared in three intermediate to late tests (more than 97 days to 50 percent heading). Eighteen preliminary lines were also evaluated in separate tests at each location.
Average grain yield in the advanced line tests were 9,210 pounds/acre at Biggs, 9,710 pounds/acre at Sutter and 9,350 pounds/acre at Glenn. An advanced short-grain,
91-y-581, was the highest yielding entry at Biggs and Sutter and ranked third in the over location summary. This entry had been advanced from preliminary testing in 1992. M-204 produced higher yields than M-202 at each location and ranked second in yield in the over location summary.
In connection with the variety trials, researchers also conducted two fertilizer experiments at the Rice Experiment Station. Scientists evaluated six commercial varieties at seven nitrogen levels, ranging from zero to 180 pounds N/acre. Grain yields of most varieties did not increase with more than 90 pounds N/acre, a somewhat "unexpected" response that may be explained by accumulated residual fertility. As in previous experiments, grain moisture at harvest, plant height and lodging all showed a tendency to increase with greater nitrogen levels.
In a second test, researchers continued to examine the role of potassium applied in combination with four levels of nitrogen (zero to 180 pounds/acre). Residual nitrogen was apparently at work in this study, as well, since average yield declined from the zero nitrogen level to the 60 pound rate. Higher N rates saw severe lodging and weren't harvested.
The second study's test found that applied potassium had no significant effect on yield. However, increased potassium resulted in increased harvest moisture, plant height and lodging. Applied potassium also showed a significant effect on leaf tissue at mid-tillering and panicle initiation. Significant interactions of nitrogen and potassium were also observed at panicle initiation.
Researchers conducted seven experiments in Butte, Colusa and Sutter counties to evaluate the role of nitrogen in different straw management scenarios. Their findings are reported elsewhere in this report.