Variety Trials - 98


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Project Leader and Principal UC Investigators

James E. Hill, Extension Agronomist, Department of Agronomy and Range Science, University of California, 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 Davis

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

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

J. Eckert, Post-graduate Researcher, UC Cooperative Extension, Butte County

Variety1.jpg (126463 bytes)During 1998 University of California scientists in cooperation with public and private plant breeders conducted 16 rice variety evaluation trials on farms throughout the rice growing region of the state. These trials exposed commercial standards and advanced and preliminary experimental cultivars to a range of environments, cultural practices and disease levels.

Six similar tests, including two from each maturity group, were conducted at the Rice Experiment Station in Biggs. Average yields ranged from about 7,300 pounds/acre in the early and intermediate tests to about 8,100 pounds/acre in the very early tests. The El Niħo weather pattern of unusually cool early season conditions and hot mid-season temperatures appeared to cause slow early growth followed by rapid internode elongation, shortened heading times, increased lodging and resulted in lower yields. In these weather conditions, 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 against the advanced and preliminary entries, demonstrating the difficulty in making further yield advances. However, testing advanced and preliminary lines under a variety of conditions remains a highly important step in developing varieties well-suited to changing cultural practices, markets and pest conditions.

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. Another study is continuing its examination of Japanese premium quality rice, including optimal rate and timing of nitrogen applications to maximize yields, grain quality and taste.

Very Early Tests

Ten advanced breeding lines and eight commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading). In addition, 22 preliminary lines were compared to the standards L-204 and the Japanese variety Akitakomachi at each location.

Variety2.jpg (237554 bytes)Grain yields in the advanced tests averaged 9,270 pounds/acre at Biggs, 7,440 pounds/acre at San Joaquin, 7,030 pounds/acre at Sutter and 8,710 pounds/acre at Yolo. Over the four locations, the highest yielding entry was S-102, followed by three advanced lines. Other commercial varieties ranking in the top 10 included L-204 (fifth), M-204 (seventh), L-203 (eighth) and M-202 (ninth). M-202, which normally ranks higher overall, ranked high (second) only at the Yolo site. Heading was more rapid than in past years in advanced and preliminary lines. Lodging among standard varieties and experimental cultivars was light to moderate; Akitakomachi, a tall Japanese quality variety was severely lodged.

Early Tests

Eleven advanced lines and nine commercial varieties were compared in four early tests (90-97 days to 50 percent heading). Nineteen preliminary lines were compared to L-204 in separate tests at each location. Yields in the advanced line tests averaged 9,300 pounds/acre at Biggs, 6,890 pounds/acre in Butte County, 6,980 pounds/acre at Colusa and 6,250 pounds/acre at Yuba.

The long-grain cultivar 96-Y-480 was the highest yielding entry averaged over the four locations. Other leading entries included experimentals 94-Y-615 and 96-Y-203. Leading commercial varieties included L-203, S-102, M-201, L-204 and M-204. M-202 yielded 7,310 pounds/acre. None of the preliminary lines exceeded the top yielding advanced entry but several yielded more than the commercial standard L-204. Heading in advanced tests was relatively rapid.

Intermediate-late Tests

Nine advanced lines and five commercial varieties were compared in three intermediate-late tests (more than 97 day to 50 percent heading). Twenty preliminary lines were also evaluated in separate tests at each location.

Average yields in the advanced-line tests were 9,060 pounds/acre at Biggs, 6,960 pounds/acre at Glenn and 6,540 pounds/acre at Yuba. An advanced long-grain line, 94-Y-633, was the highest yielding entry overall. The highest yielding commercial variety was A-301, an aromatic long grain. The premium quality medium-grain variety M-401 was fourth among five commercial varieties. Average time to heading across all varieties and locations was 91 days, with M-401 taking much longer to head than any other entry.

Rice Straw Management

Rice straw management studies are continuing on the 75-acre site near Maxwell. Begun in 1993 this trial is examining how various combinations of burning, incorporation, rolling and baling under flooded and non-flooded conditions affect rice production.

No clear-cut trends have emerged. Straw and water treatments had a significant impact on yield in some years but effects have varied from year to year. The variation is probably due to differences in the type and severity of crop production problems occurring at the site each year. Salinity, hydrogen sulfide injury and grass weed competition have all played a role in hampering rice growth and production at this site.

However, greater barnyardgrass and watergrass weed competition in the incorporated plots, especially the non-flooded incorporated plots, has been consistently observed, probably due to seed burial from birds and rodents. This increased weed competition has reduced yields in some years and may intensify over time.

Fertility in Japanese Varieties

Variety3.jpg (104149 bytes)Efforts continue to fine-tune nitrogen management strategies for premium quality Japanese rice varieties. Experiments indicate that Akitakomachi produces its highest yields with total nitrogen applied preplant, while Koshihikari produces its best yields with a split application of nitrogen. As observed in previous years, taste scores were higher for both varieties at lower nitrogen levels.

In these trials nitrogen applied preplant at 80 and 100 pounds per/acre produced some of the highest yields for Akitakomachi in 1996 and 1997, although yields were off in 1998. El Niħo also apparently affected Akitakomachi last year. Under the cool, wet conditions of 1998 best yields were observed with a split application of nitrogen at preplant and heading. In previous years best yields were observed in a split application at preplant and panicle initiation. Preliminary analyses indicate that head length and percent blanking accounted for the difference. Lodging, plant density and seed size were unaffected by treatment.

Grain analyses of Akitakomachi from 1996 and 1997 demonstrated that taste scores were highly correlated with protein content. Moreover, leaf tissue nitrogen at heading appears to be a good predictor of protein content in the grain. An entirely preplant nitrogen application resulted in a higher concentration of leaf nitrogen than a preplant/panicle initiation split application. Grain quality analyses for 1998 are continuing.

In contrast to Akitakomachi, Koshihikari responds more favorably to split nitrogen applications -- 20 pounds preplant and 20 pounds at heading produced the highest yields in 1996 and 1998. In 1996 and 1997 lower yields observed in some trials were associated with smaller head and grain size. Overall yields were lower in 1998. Factors affecting yield are still being analyzed.

Similar to Akitakomachi, nitrogen applied to Koshihikari at panicle initiation resulted in increased leaf tissue nitrogen content.

Color chart for N

A prototype color chart for visually estimating leaf tissue nitrogen in California rice varieties is under development. Leaf color of a short (S-201), medium (M-202) and long (L-204) grain variety grown under different levels of nitrogen was quantified using a colorimeter. The results are being used to develop a series of color acrylic color panels corresponding to a range of tissue nitrogen concentrations.

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