Variety Trials-99


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Project Leader and Principal UC Investigators

James E. Hill, Extension Agronomist and Chair, Department of Agronomy and Range Science, UC Davis

Michael D. Carriere, Interim CE Agronomist, Department of Agronomy and Range Science, UC Davis

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

Randall "Cass" Mutters, UC Cooperative Extension Farm Advisor Butte County

Steven C. Scardaci, UC Cooperative Extension Farm Advisor, Colusa/Glenn/Yolo Counties

Raymond L. Wennig, Staff Research Associate, UC Cooperative Extension, UC Davis

Stacy R. Roberts, Post-graduate researcher, UC Cooperative Extension, UC Davis

Michael W. Hair, Post-graduate researcher, UC Cooperative Extension, UC Davis

James Eckert, Post-graduate researcher, UC Cooperative Extension, Butte County

Sixteen rice variety evaluation trials were conducted on farms throughout the rice growing regions of California in 1999 by University of California scientists in cooperation with public and private plant breeders.  These trials expose commercial standards and advanced and preliminary experimental cultivars to a range of environments, cultural practices and disease levels.

variety 13d.jpg (22097 bytes)Six similar tests, including two from each maturity group, were conducted at the Rice Experiment Station in Biggs.  Average yields across varieties and locations ranged from about 7,700 pounds/acre in the early and intermediate tests to about 9,030 pounds/acre in the very early tests.  Unusually cool early season conditions lengthened time to maturity and caused cold-induced sterility, which decreased yields in varieties exposed to cool weather during late July and early August.  In these weather conditions, nonetheless, several advanced and preliminary lines appeared to yield well relative to the commercial standards, demonstrating the importance of statewide testing under a variety of conditions.  As in previous years, the commercial standards ranked high in yield.   Testing advanced and preliminary lines under a variety of conditions is crucial in the development of varieties well-suited to changing cultural practices, markets and pests.

This project also examined varieties Akitakomachi and Koshihikari under different nitrogen rates and timings, underscoring the need for unconventional management to maximize yields, grain quality and taste of these increasingly popular Japanese premium quality varieties.

A study was conducted at RES to provide growers with initial guidelines for nitrogen management of the recently release varieties M-402, L-205, Calmati-201 and Calihikari-201.   Results of these trials are summarized below.

Very Early Tests

Nine advanced breeding lines and nine commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading).  In addition, 23 preliminary lines were compared to Akitakomachi at each location.

Grain yields in the advanced tests averaged 10,160 pounds/acre at Biggs, 8,980 pounds/acre at Sutter, 7,950 pounds/acre at Yolo and 4,520 pounds/acre at San Joaquin.   Yields from the San Joaquin location were excluded from the over-locations analysis because of the very low overall yield and high variability.  Over the other three locations, the highest yielding entry was S-102, followed by the advanced line 96-Y-196, a waxy, short-grain and M-103. Other commercial varieties ranking in the top 10 included Calmochi 101, L-204, M-202 and L-205, ranked fourth, sixth, ninth and tenth, respectively.   Two of the preliminary lines, 97-Y-187 and 97-Y-182, ranked higher than any entry in the advanced test.  Heading was slower than in past years.

Early Tests

Eleven advanced lines and nine commercial varieties were compared in four early tests (90-97 days to 50 percent heading).  Twenty preliminary lines were evaluated in separate tests at each location.  Yields in the advanced line tests averaged 9,920 pounds/acre at Biggs, 5,590 pounds/acre in Butte County, 8,510 pounds/acre at Colusa and 6,820 pounds/acre at Yuba.

The short "waxy" cultivar, 96-Y-203, was the highest yielding entry averaged over the four locations.  Other top entries were S-102, Calmochi-101, M-103 and M-202.  M-202 yielded 8,950 pounds/acre and ranked fifth.  None of the preliminary lines exceeded the top-yielding experimental line in the advanced tests but several yielded slightly more than M-202.

Intermediate-Late Tests

variety13b.jpg (18295 bytes)Eight advanced lines and six commercial varieties were compared in three intermediate-late tests (more than 97 days to 50 percent heading).  Nineteen preliminary lines were also evaluated in separate tests at each location.

Average yields in the advanced-line tests were 8,720 pounds/acre at Biggs, 7,300 pounds/acre at Glenn and 7,330 pounds/acre at Yuba.  An advanced medium-grain line, 97-Y-413, was the highest yielding entry overall.  The highest yielding commercial variety was M-204, followed by M-402 and M-202.  The premium quality medium-grain variety M-401, which ranked second overall in 1997 and eleventh overall in 1998, again ranked eleventh.  The overall yield of preliminary line 98-Y-644, a medium grain, was higher than any entry in the advanced tests.  Average time to heading across all varieties and locations was 101 days, with              M-401 taking much longer to head than any other entry.

Nitrogen Management

The Rice Experiment Station recently released four new varieties, with another due out in 2000.   This research was conducted to provide growers with initial guidelines for nitrogen management of these new varieties.  The results summarized below should be taken in the context of individual farming operations and cropping year.

The experiment at the RES involved eight varieties grown with six different nitrogen rates applied as ammonium sulfate.  Varieties included the four new releases (M-402, L-205, Calmati, and Calhikari), one advanced line (Y-615) and three standard varieties (M-202, L-204 and S-102).  Y-615 will be released this year as M-205.   In general, stem rot increased with increasing amounts of nitrogen for all varieties.   Conversely, the incidence of aggregate sheath spot declined with increasing amounts of applied nitrogen.   Stem rot levels in M-202 and Calhikari were the most responsive to changes in nitrogen. Specific results show:

• M-202 showed a maximum yield response at the 135 pounds N/acre rate, compared to 120 pounds N/acre for the other two medium grains, Y-615 and M-402.

• Among the long grains, L-204 yielded highest at 125 pounds N/acre, compared to 140 pounds N/acre for L-205.  Blanking contributed to Calmati being the lowest yielding long grain.

• S-102 proved to be the highest of all varieties tested.  Maximum yield response occurred at the 135 pound N/acre rate.  The new Japanese-type premium short grain, Calhikari, yielded highest at an N rate of 110 pounds N/acre.

Color Chart for N

A prototype color chart for visually estimating leaf tissue nitrogen in California rice varieties has been under development for several years.  Last year we reported that leaf color of a short (S-201), medium (M-202) and long (L-204) grain variety grown under different levels of nitrogen had been quantified using a colorimeter.  The results have been used to develop a series of color acrylic color panels corresponding to a range of tissue nitrogen concentrations.  Final assembly of the panels was to begin in spring 2000.

Potassium Study

generic2.JPG (16516 bytes)The phase down in rice straw burning has changed the way farmers manage rice residue and is, consequently, affecting nutrient cycling in ways that scientists are just beginning to understand.  Soil incorporation is currently the most common alternative, but straw removal is expected to increase.   The amount of straw removed by baling for off-site use can exceed 100 pounds/acre, removing potassium in the process.  When straw is removed continually, this practice could show a pronounced effect on the available potassium levels in soil. 

Preliminary studies at the Rice Experiment Station had previously suggested that potassium near the soil surface declines significantly.  This study, a three-year project partially funded by the California Department of Food and Agriculture Fertilizer Research and Education Program (FREP), set out to determine how potassium fertility affects rice yield and rice diseases.  After one year of straw removal on a field near Marysville, researchers observed significantly more available potassium in the straw incorporated portion of the plot versus straw removal. 

This study is also examining the role of nitrogen in relationship to potassium fertility.  There was a strong nitrogen fertilizer response and grain yield increased from 6,015 pounds/ acre with no N fertilization to 9,150 pounds/acre with a high rate of nitrogen.  The yield under no nitrogen fertilization was 350 pounds higher in the incorporated plot, suggesting a small nitrogen carry over from the residue. 

Straw yield also increased 1,000 pounds per acre when residue was incorporated.   As grain yield was not affected by straw incorporation or removal, the increase in total biomass was due solely to the increase in straw production.

Potassium fertilization had no effect on total grain yield across all nitrogen rates, despite the difference in extractable potassium levels in the spring following straw incorporation.  A soil test conducted in the spring underestimated potassium availability.

Aggregate Sheathspot disease declined as nitrogen levels increased.  The rate of potassium application showed no effect on Aggregate Sheathspot.  Because there was absence of a potassium response on yield, the levels of potassium in the soil were sufficient and this may have precluded any effect on potassium on aggregate sheathspot.

Management of Japanese Premium Quality Rice

Proper nitrogen management in the Japanese varieties Akitakomachi and Koshihikari is essential for producing superior quality rice.  For three years researchers studied plant productivity and quality response of these varieties to different rates and timing of nitrogen applications.  To test the applicability of previous years’ results to the Sacramento Valley, a large, multi-county test of the top producing nitrogen treatments was conducted in 1999.

Akitakomachi was grown near Richvale, Pleasant Grove and Colusa.  Koshihikari experiments were conducted near Richvale, Yuba City and Willows.  Akita was grown at six different nitrogen treatments and Koshi at eight.  Nitrogen was applied entirely preplant or as preplant/topdress applications.  Conventional cultural practices were used.  Researchers report no significant differences in Akita or Koshi yields between treatments at any location.   Highest yields for Akita were observed in split applications of 40 pounds preplant, 40 pounds panicle initiation(PI) and zero at heading.   The 60 pound preplant and the 50-50-0 preplant/PI split application also performed well for Akita.  The 50-25-25 split application produced the highest Koshi yields.

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