Variety Trials-92



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Project Leader and Principal UC Investigators

James E. Hill, extension agronomist, Agronomy & Range Science Extension, UC Davis

James R. Webster, staff research associate, Agronomy & Range Science Extension, UC Davis

Carl M. Wick, UC Cooperative Extension farm advisor, Butte County

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

Steve C. Scardaci, UC Cooperative Extension farm advisor, Colusa/Glenn
/Yolo counties

W. Michael Canevari, UC Cooperative Extension fame advisor, San Joaquin county

Bill L. Weir, UC Cooperative Extension farm advisor, Merced/Fresno counties


Last year researchers conducted 18 rice variety evaluation trials on nine farm sites throughout the rice growing regions California. Six similar tests, including two from each group, were conducted on the Rice Experiment Station at Biggs. Several advanced and preliminary breeding lines show promise in improved yields and other agronomic characteristics. Researchers also conducted experiments on nitrogen and potassium fertility, straw management, drill-seeding of rice, herbicide and water depth interactions and green manuring. The following narrative summarizes their significant findings.

Very Early Maturity

Thirteen advanced breeding lines and 11 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 9,810 pounds/acre at Biggs, 9,700 pounds/acre at Sutter, 8,900 pounds/acre at Butte and 8,550 at San Joaquin.

Variety.jpg (96421 bytes)Over all locations, the highest yielding entry in the advanced test was 89-Y-103, a short grain, at 10,290 pounds/acre. This entry, previously tested as a preliminary line, was the highest yielding very early entry over four locations. This experimental line will undergo seed increase and expanded quality and market evaluation in 1993.

Other very early advanced lines that performed well and produced high yields included 90-Y-479 (long grain), 91-Y-193 (short grain) and 90-Y-233 (medium grain). Several preliminary lines produced yields in excess of 10,000 pounds/acre and showed improvement in other plant characteristics.

Early Maturity

Fourteen advanced lines and 10 commercial varieties were compared in five early tests (90-97 days to 50 percent heading). Twenty preliminary lines were also evaluated at each location. Grain yields in the advanced line tests averaged 9,580 pounds/acre at Biggs, 10,320 pounds/acre at Yolo, 9,470 pounds/acre at Yuba, 9,710 pounds/acre at Colusa and 10,060 pounds/acre at Merced. Other significant observations from the early maturity tests include:

  • M-202 was the highest yielding variety over all locations, ranking first at Yolo, Yuba and Biggs.
  • The advanced line 91-Y-322 (short grain) and 90-Y-423 (medium grain) each produced yields in excess of 10,000 pounds/acre at all five locations.
  • L-203, released in 1991, continues to show improvement over L-202 in seedling vigor, earliness and yield.
  • Preliminary medium grain entries 91-Y-381 and 91-Y-231 show excellent yield potential and other favorable agronomic traits.

Intermediate to Late Maturity

Nine advanced lines and seven commercial varieties were compared in three intermediate-late tests (more than 97 days to 50 percent heading). Nineteen preliminary lines and the Japanese short-grain Koshihikari were also evaluated in separate tests at each location.

Yields in the advanced lines tests were high, averaging 9,820 pounds/acre at Biggs, 10,770 pounds/acre at Sutter and 10,620 pounds/acre at Glenn. The medium-grain lines 90-Y-686 and 89-Y-544 were the highest yielding entries over the three locations, exceeding 12,500 pounds/acre in Glenn County.

In the preliminary line tests, yields of 91-Y-413, 91-Y-581 and 91-Y-356 were consistently high across the three locations and ranked first, second and third, respectively, in yield. These lines also showed excellent lodging resistance. Six of the 19 preliminary lines produced yields above 12,000 pounds/acre in the Glenn Count test, with 91-Y-581 exceeding a hefty 13,000 pounds/acre.

Fertilizer Studies

At the Rice Experiment Station, researchers conducted two fertilizer experiments involving six commercial rice varieties at seven nitrogen levels from zero to 180 pounds/acre. Most varieties produced their highest yields in the 120 to 150 pounds/acre range. Yields generally declined above that rate; heading dates were also delayed at higher nitrogen levels. Grain moisture at harvest, plant height and lodging all increased with greater nitrogen levels.

In the second study, researchers examined the role of potassium applied in combination with four levels of nitrogen (zero to 180 pounds/acre). Potassium appeared to have no significant effect on yield, regardless of nitrogen or potassium level. Although lodging scores did not differ significantly between potassium rates, it occurred earlier with increased potassium rates. Mature plant height was also slightly increased. Potassium appears also to have a significant effect on leaf tissue at mid-tillering and panicle initiation. Studies of potassium nutrition will continue in 1993.

Researchers also conducted 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.

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