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

This ongoing project plays a vital role in supporting the efforts of plant breeders with the Rice Experiment Station by providing them with information to help evaluate, compare and identify potential new rice varieties for the California rice industry.

Several experiments conducted in cooperation with other investigators received assistance with planting, fertilizing, herbicide application, harvesting and data analysis from this project. These experiments, reported in the section on the Rice Breeding Program, included work on nitrogen fertility and the relationship between straw management and nitrogen.

Eight uniform advanced breeding line trials and eight preliminary breeding line trials were conducted throughout the major rice producing areas. Six additional tests, including two from each maturity group, were conducted by the rice breeders at the Rice Experiment Station.

Several of the experimental lines had been tested and screened in previous years and some lines were in advanced stages (i.e. two or more years). The seed for public varieties and experimental cultivars was provided by the Rice Experiment Station. Following are the key findings from the 1995 variety trials.

Very Early Maturity

Very early maturity rice reaches 50 percent heading in less than 90 days. Ten advanced breeding lines and 10 commercial varieties were compared in four very early tests. Twenty preliminary lines were also evaluated at each location.

Grain yields in the advanced tests averaged 9,750 pounds/acre at Biggs, 9,820 pounds/acre at Yolo, 8,680 pounds/acre at Sutter, and 8,300 pounds/acre at San Joaquin.

Over the four locations, the highest yielding entry was industry standard M-202, which ranked first, second and third in yield at the Yolo, RES and Sutter sites, respectively. Entry 91-y-381, an advanced medium grain, was the highest yielding entry at Sutter and ranked second in the four-location summary. Of the other very early commercial varieties, M-204 and M-201 ranked fourth and 10th, respectively, over all locations, and M-201 was the second-highest yielding variety in the Sutter test.

The early premium quality variety M-203 continues to perform very well in the San Joaquin test and in other locations where severe early lodging is avoided.

Early Tests

Rice termed "early" reaches 50 percent heading between 90 and 97 days. Eleven advanced lines and nine commercial varieties were compared in four early tests. Twenty preliminary lines were also evaluated in separate tests at each location.

Grain yields in the advanced line early tests averaged 9,400 pounds/acre at the RES, 8,090 pounds/acre at Butte, 7,870 pounds/acre at Yuba and 8,820 pounds/acre at Colusa. The medium-grain cultivar 92-y-624 exceeded 10,000 pounds/acre at Biggs and was the highest yielding entry over the four locations.

Other leading entries in the test included M-204, 93-y-589 and M-201. M-204 ranked third at the Rice Experiment Station and Colusa and sixth in yield at Butte, and was below average at Yuba.

L-203, released in 1991, continued to show improvement over L-202.

Preliminary medium grain lines showing improvement included 94-y-274, 94-y-354 and 94-y-615 - all of which yielded more than 10,000 pounds/acre.

Intermediate And Late Tests

Intermediate to late rice reaches 50 percent heading in more than 97 days. Six advanced lines and six commercial varieties were compared in three intermediate to late tests. Twenty-four preliminary lines were also evaluated in separate tests at each location.

Average yields in the advanced line tests were 8,900 pounds/acre at Biggs, 9,600 pounds/acre at Sutter, and 8,050 pounds/acre at Glenn. An advanced medium grain, 93-y-42, was the highest yielding entry at Sutter and Biggs and was first in the over location summary. The commercial variety M-204 produced higher yields than M-202 at each location and ranked third in yield in tests in Sutter and Glenn counties. Premium quality M-401 ranked eighth, ninth and fourth in yield at Biggs, Sutter and Glenn, respectively.

Rice Straw Management

Scientists established a 75-acre rice straw management trial near Maxwell in the fall of 1993. The study examined various combinations of burning, incorporation, rolling and baling under flooded and non-flooded conditions.

Results from the second year of the study show significant differences. Flooded plots yielded about 1,000 pounds/acre more than unflooded plots with no differences between straw treatments. The reason for this difference is unknown at this time.

Researchers also found greater rice injury from the thiocarbamate herbicides molinate and thiobencarb in burned and baled plots compared to the incorporated and rolled plots. The difference became apparent in seedling vigor ratings. However, grass weed control was significantly better in the burned and baled plots than it was in the incorporated and rolled plots. A variety of factors may account for the differences in herbicide injury and weed control; further studies are planned.

Soil/Water Salinity Studies

Researchers surveyed the salinity of 27 rice fields in Colusa and Glenn coun- ties during 1995 in an effort to determine the effect of salinity on rice. Last season was the third year for the project, which is funded by a USDA water quality grant.

Preliminary results show that soil and water salinity levels are significantly higher in the bottom basins of surveyed fields. Top basin water salinity is typically similar to that of inlet water delivered by irrigation districts and water companies.

These results are similar to those observed in the first two years of the study and indicate that salts are concentrating in the bottom basins of fields. Grain yields are significantly lower in bottom basins. Researchers note that water management can affect water salinity levels.