Variety Trials-94


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Project Leader and Principal UC Investigators

James E. Hill, extension agronomist, Dept. of Agronomy and Range Science, UC Davis

Michael E. Hair, postgraduate researcher, Dept. of Agronomy and Range Science, UC Davis

Timothy J. Kesselring, postgraduate researcher, Dept. of Agronomy and Range Science, UC Davis

John F. Williams, farm advisor, Sutter/Yuba Cooperative Extension

Steve Scardaci, farm advisor, Colusa County Cooperative Extension

C. Michael Caneveri, farm advisor, San Joaquin County Cooperative Extension

Variety.jpg (172597 bytes)The road to rice variety improvement leads through an important set of field trials conducted by a team of University of California scientists in cooperation with public and private plant breeders. Last year 16 on-farm rice variety evaluation trials were conducted throughout the rice growing regions of California. Six similar tests were conducted on the Rice Experiment Station at Biggs. Several advanced and preliminary breeding lines showed promise in improved yields and other agronomic characteristics over existing varieties. This project plays a vital role in supporting the efforts of RES plant breeders by evaluating, comparing and identifying potentially new rice varieties for the California rice industry. Several experiments conducted in cooperation with other investigators received assistance with planting, fertilizing, herbicide application, harvesting and data analysis from this project. These experiments included work on nitrogen and potassium fertility and straw management/nitrogen effects. This section summarizes 1994 variety trials.

Very Early Maturity

Ten advanced breeding lines and 10 commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading). Twenty preliminary lines were also evaluated at each location.

Grain yields in the advanced tests averaged 9,900 pounds/acre at Biggs, 10,900 pounds/acre at Yolo, 9,870 pounds/ acre at Sutter, and 8,570 pounds/acre at San Joaquin.

Over the four locations, the highest yielding entry was 91-y-171, a very early short grain that ranked second in yield in all four tests locations. Entry 93-y-195, an advanced short-grain waxy type was the highest N yielding line at Biggs and ranked second in the four location summary. No entry produced yields statistically higher than M-202 at Yolo and Yuba. Yields of M-201 were similar to M-202 at Biggs, Yolo and San Joaquin but nine percent lower in the Yuba test.

Early Tests

Ten advanced lines and 10 commercial varieties were compared in four early tests (90-97 days to 50 percent heading). Twenty preliminary lines were also evaluated in separate tests at each location.

Grain yields in the advanced line tests averaged 10,160 pounds/acre at the Rice Experiment Station, 10,880 pounds/acre at Yolo, 7,270 pounds/acre at Yuba and 9,730 pounds/acre at Colusa.

The medium grain line 91-y-381 exceeded 10,000 pounds/acre at Biggs, Yolo and Colusa, and was the highest yielding entry over the four locations. Other leading advanced lines were entries M-202, 92-y-521 and M-201. The variety M-202 ranked second and fourth in yield at Yolo and Biggs but was below average at Yuba and Colusa. L-203, released in 1991 continued to show improvement over L-202. Preliminary medium grain lines 93-y-240, 93-y-589, 93-y-218, 93-y-421 all exceeded 10,000 pounds/acre and showed improvements in other agronomic traits.

Intermediate-Late Maturity

Seven advanced lines and seven commercial varieties were compared in three intermediate-late tests. Twenty preliminary lines were also evaluated in separate tests at each location.

Average grain yields in the advanced line tests were 10,540 pounds/acre at Biggs, 9,040 pounds/acre at Sutter and 8,810 pounds/acre at Glenn. An advanced premium quality medium grain, 90-y-686, was the highest yielding entry at Sutter, ranked third at Biggs and was first in the over location summary. This entry was also the highest yielding variety over three locations in 1992 and the fourth highest in 1993. The commercial variety M-204 produced higher yields than M-202 at each location and ranked first in yield in the Glenn County test.

Fertilizer Studies

UC researchers also collaborated with Rice Experiment Station researchers to determine the nitrogen and potassium requirements of California rice varieties. In connection with the variety trials, researchers also conducted two fertilizer experiments at the Rice Experiment Station.

Six commercial varieties were evaluated at seven nitrogen levels ranging from zero to 180 pounds/acre. Grain yields of M-201, M-202, M-204, L-202, L-203 and S201 did not increase at nitrogen rates above 90 pounds/acre, which was probably due to residual fertility at the site. Even where no fertilizer was applied, grain yields were surprisingly high, averaging 7,160 pounds/acre. As observed in previous years, increasing nitrogen levels above the optimum led to increased grain moisture at harvest, days to heading, plant height and lodging.

A second study focused on how varying potassium rates interact with varying nitrogen rates. Test varieties were M-204 and L-203. Potassium did not significantly increase grain yields of either variety, although it did increase plant height slightly. The experiment showed that nitrogen is the dominant factor in determining grain yields, regardless of potassium levels. Average yields of both varieties with no additional nitrogen averaged 7,100 pounds/acre. At 120 pounds applied nitrogen, M-204 yield increased to 8,700 pounds/acre and L-203 to 9,700 pounds/acre, a 13 percent and 21 percent increase, respectively.

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