|Variety Trials - 97
Project Leader and Principal UC Investigators
James E. Hill, Extension Agronomist and Chair Department of Agronomy and Range Science, UC Davis
C. Mick Canevari, UC Cooperative Extension Farm Advisor San Joaquin County
Randall "Cass" Mutters, UC Cooperative Extension Farm Advisor Butte County
Steven C. Scardaci, UC Cooperative Extension Farm Advisor Colusa/Glenn/Yolo counties
John F. "Jack" Williams, UC Cooperative Extension Farm Advisor Sutter/Yuba counties
R. L. Wennig, Staff Research Associate UC Cooperative Extension UC DavisStacey R. Roberts, Postgraduate Researcher UC Cooperative Extension UC Davis
University of California scientists in
cooperation with public and private plant breeders conducted 17 rice variety evaluation
trials in 1997 on farms throughout the rice growing region of the state. Six similar
tests, including two from each maturity group, were conducted at the Rice Experiment
Station at Biggs. Yields ranged from about 8,700 pounds/acre in the early and intermediate
tests to nearly 10,000 pounds/acre in the very early tests, with some advanced lines
reaching 12, 000 pounds/acre in individual tests. Commercial standards continue to rank
high in yield against new entries, demonstrating the difficulty in making further yield
advances. However, this testing - under a wide range of planting dates, environments,
disease levels and cultural practices -provides a crucial test that new cultivars must
pass before considering them for release.
This project is also examining cultural practices affecting varietal performance. A rice straw management and winter flooding study is continuing at Maxwell and the Rice Experiment Station. In Butte County another study is looking at nitrogen management to maximize yield and grain quality of premium quality Japanese varieties. Additional studies focused on whether potassium could reduce stemrot disease. The following narrative summarizes highlights of research in this area.
Very Early Tests
Eleven advanced breeding lines and nine commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading). In addition, 18 preliminary lines were compared to the standards L-204 and the Japanese variety, Akitakomachi at each location.
Grain yields in the advanced tests averaged 10,890 pounds/acre at San Joaquin, 8,860 pounds/acre at Sutter and 11,200 pounds/acre at Yolo. Over the four locations the highest yielding entry was advanced line 95-y-271, followed by M-202, which ranked first, second and eighth in yield at Yolo, Sutter and San Joaquin sites, respectively. Entry 92-y-624, an advanced medium-grain, highly ranked in previous years, was the overall fourth highest entry and the second of the advanced lines. Other commercial varieties ranking in the top 10 included M-201, S-102, M-204, L-204 and Cal Mochi-101.
Eleven advanced lines and nine commercial varieties were compared in five early tests (90-97 days to 50 percent heading). Twenty-three preliminary lines were compared to L-204 in separate tests at four of the five locations.
Yields in the advanced line tests averaged 10,460 pounds/acre at the Rice Experiment Station, 8,050 pounds/acre at Durham (Butte County), 8,110 pounds/ acre at Colusa, 7,540 pounds/acre at Yuba and 9,190 pounds/acre at the additional "blast trial" in Glenn County. The medium-grain cultivar 94-y-615, which was the average highest yielding advanced cultivar in 1996, yielded nearly 12,000 pounds/acre at the RES in 1997 and was again the highest yielding entry over the five locations in 1997.
Leading commercial varieties included S-201, M-204, M-201 and M-202. L-204, released in 1995, yielded 8,300 pounds/acre and ranked tenth.
Eight advanced lines and six commercial varieties were compared in three intermediate-late tests (more than 97 days to 50 percent heading). Twenty preliminary lines were also evaluated in separate tests at each location.
Average yields in the advanced line tests were 10,630 pounds/acre at the RES, 7,320 pounds/acre at Glenn and 8,040 pounds/acre at Sutter. An advanced medium-grain, 95-y-60, was the highest yielding entry at the RES and at Glenn overall and the second highest yielding in Sutter. The premium quality medium grain variety M-401 ranked second overall at an average 9,520 pounds/acre, followed closely by the early standard M-204 at an average yield of 9,310 pounds/acre. A-301, an aromatic long grain, yielded 8,010 pounds/acre in the 1997 intermediate-late tests.
Rice Straw Management
Researchers established a 75-acre rice straw management trial near Maxwell in the fall of 1993. The study is examining various combinations of burning, incorporation, rolling and baling under flooded and non-flooded conditions.
Results thus far are mixed. Straw and water treatments had a significant impact on yield some years but their effect varied from year to year. For instance, straw practices affected yield significantly in 1994 and 1996 but not in 1995 or 1997, while water practices were only significant in 1995. The variation is probably due to differences in the type and severity of crop production problems each year. Production problems likely to impact yield include salinity, hydrogen sulfide injury to rice and, most significantly, grass weed competition. Competition from barnyardgrass and watergrass in the non-flooded, incorporated plots has been consistently observed and may intensify over time.
Fertility In Japanese Varieties
Premium quality Japanese rice varieties such as Akitakomachi and Koshihikari do not respond well to traditional California nitrogen management strategies. This study sought to determine the optimal rate and timing of nitrogen application to maximize yields and grain quality. A second objective was to establish explore the value of a chlorophyll meter as a nitrogen management tool.
In 1996 and 1997, researchers examined 21 different nitrogen treatments on these two varieties. Ammonium sulfate was applied at different stages of plant growth and in a split application. One of those stages, pollen meiosis was chosen because it corresponds to when Japanese farmers typically fertilize.
In both years nitrogen applied preplant at the 80 pounds/acre rate produced the highest yields for Akitakomachi - 6,330 and 6,700 pounds/acre. A split nitrogen application - 20 pounds preplant and 20 pounds at heading - produced the highest, yield for Koshihikari (6,770 pounds/acre in 1996, 6,010 pounds/acre in 1997). However, overall yields for Koshihikari were lower in 1997 than in 1996. Researchers suspect the difference may be attributed to residual nitrogen from previous years.
Taste scores were higher at the lower nitrogen rates for both varieties. The chlorophyll meter showed a strong relationship to leaf tissue nitrogen, indicating that it may be possible to use this as a management tool for determining nitrogen needs.
Potassium, Nitrogen And Disease
Research from 1996 showed that potassium- deficient fields could see an increase in stemrot severity and that correcting that deficiency could reduce disease
severity. In 1997 scientist established three trials to determine whether potassium fertilization provided any disease protection to fields that weren't deficient. This study concluded that fertilizer potassium does not provide protection against stemrot in soils that have adequate levels of soil, potassium.