Stacey Roberts, UC Davis staff researcb associate, makes a point about the agronomic performance of some rice varieties under study during Rice Field Day at Biggs.

VERY EARLY TESTS

Eight advanced breeding lines and nine commercially available cultivars that reach 50 percent heading in 90 days or less were compared in three very early tests. At each location 26 preliminary breeding lines were also evaluated.

The highest yielding cultivar in the advanced test was M-201, followed by the breeding lines 88-Y-774 (released as L-203), 88-Y-124 and 89-Y-375. The variety M-203 was lowest yielding, due to lodging.

Average yields of the advanced lines and commercial standards at the Sutter County site exceeded 10,600 pounds per acre, significantly higher than yields at the other sites.

EARLY TESTS

Eleven advanced breeding lines and nine commercially available cultivars that reach 50 percent maturity within 90 to 97 days were compared in five early tests. Twenty-six experimental lines were also evaluated.

"A recently released long grain, L-203, performed well in statewide testing."

Several advanced breeding lines produced yields over 9,000 pounds per acre, but none was significantly higher than M-201. Entry 88 Y-317 ranked first in yield, averaging close to 9,600 pounds per acre.

Over all locations, M-201, L-202 and Valencia 87 ranked highest. M-203 ranked lowest among commercial varieties in four of five sites, again due to lodging. Of the preliminary breeding lines, 90 Y 82 yielded 10,200 pounds per acre, the highest in four of five locations.

INTERMEDIATE AND LATE TESTS

Five standard cultivars and eight advanced breeding lines that reach 50 percent heading in more than 97 days were compared in three intermediate-late tests. Twenty preliminary breeding lines were also evaluated at each location.

Commercially available varieties S-301, A-301,' M-202, M-401 and M-203 ranked first, third, tenth, twelfth and thirteenth, respectively, in comparison to the advanced breeding lines. Several preliminary lines averaged more than 10,000 pounds per acre.

NITROGEN FERTILIZER STUDIES

In 1989 and 1990, fertilizer studies were conducted to evaluate the response of new rice varieties in comparison to several ongoing commercial varieties.

Eight rates of nitrogen were added 'in 30 pound per acre increments up to 210 lb/A. M-203 was the most sensitive to overfertilization with nitrogen.

In 1990 the long grain cultivars, including the experimental 88-y-774 (since released as L-203), were most responsive to nitrogen. Over all varieties, the optimum nitrogen level was between 90 and 120 lb/A in the off-station tests but only 60 lb/A at the Rice Experiment Station.

In general, levels of nitrogen beyond those needed for optimum yield delayed heading, increased lodging and increased moisture at harvest.