Variety Trials, 2001

Sixteen on-farm rice variety evaluation trials were conducted on farms throughout the rice growing regions of California in 2001 by University of California scientists in cooperation with public and private plant breeders. These trials expose standard, advanced and preliminary varieties to a range of environments, cultural practices and disease levels.

Six similar tests were conducted at the Rice Experiment Station near Biggs (RES). Average yields across varieties and locations ranged from about 7,300 pounds/acre in the very early trials to about 9,900 pounds/acre, also in the very early trials. All the yields from other trials fell within this range.

VarTrial.JPG (24637 bytes)Midseason temperatures were favorable for good floral development, which resulted in comparatively less blanking than in the previous season. Two trials became heavily infested with weeds and required a hand rouging to ensure the integrity of the experiments.

As in previous years, the commercial standards ranked high in yield against the advanced and preliminary entries, demonstrating that further yield advances are increasingly difficult to attain. However, a few advanced lines in the 2001 variety trials produced very high yields and exhibited good plant characteristics. Testing advanced and preliminary lines under a variety of conditions is essential before releasing new varieties into an environment of changing cultural practices, markets and pests.

This project also examined optimal nitrogen levels for industry standard M-202 and four recently released varieties—M-205, M-402, L-205, CT-201 and M-104. Optimum nitrogen rates for these varieties ranged from 120 to 170 pounds N/acre. A recently developed leaf-color chart was also field tested by 29 growers throughout the valley. Read on for more detail on this work.

Very Early Tests

Nine advanced breeding lines and nine commercial varieties were compared in four very early advanced tests (less than 90 days to 50 percent heading). In addition, 30 cultivar lines were tested in the preliminary trials at each location.

Grain yields in the advanced tests averaged 9,900 pounds/acre at the RES, 8,560 pounds/acre at Yolo, 8,640 pounds/acre at Sutter and 7,880 pounds/acre at the San Joaquin site. Over the four locations, the highest yielding entry on average was S-102 at 9,770 pounds/acre, followed by the advanced waxy line 00-Y-175 at 9,560 pounds/acre, a medium-grain advanced line 98-Y-242 at 9,150 pounds/acre and the advanced long grain 00-Y-481 at 9,150 pounds/acre. Commercial varieties ranking in the top 10 included M-104, CM-101 and L-204. With yields curtailed at cooler locations, M-205 ranked 16th.

Early heading for several varieties was most likely caused by accelerated growth from early season high temperatures. The overall average was 86 days, compared to 90 days in 2000. Blast-resistant lines in the very early tests varied considerably in yield performance.

Early Tests

Nine advanced lines and 10 commercial varieties were compared in four early tests (90-97 days to 50 percent heading). Additionally, 34 preliminary lines were evaluated in separate tests at each location.

Yields in the advanced-line tests averaged 9,520 pounds/acre at the RES, 7,880 pounds/acre at Butte, 9,200 pounds/acre at Colusa and 7,630 pounds/acre at Yuba. Averaged over the four locations, newly released M-205 was the highest yielding entry at 9,080 pounds/acre. Other high yielders included S-102, 99-Y-041, M-104 and M-204. Among the preliminary lines, long grain 9942357 and medium grain 00-Y-410 exceeded the top yielding commercial and advanced experimental lines.

Time to heading averaged 83 days for all entries, one day sooner than in 2000. Yields for blast-resistant lines in these tests were also highly variable. The best performing line, Y-818, yielded 9,040 pounds/acre across locations.

Intermediate–Late Tests

Eight advanced lines and six commercial varieties were compared in three intermediate-to-late tests. Twenty preliminary lines were also evaluated in separate tests at each location.

Average yields in the advanced line tests were 8,910 pounds/acre at the RES, 7,930 pounds/acre at Glenn and 9,050 pounds/acre at Sutter. M-205 was the highest yielding entry overall at 9,440 pounds/acre. Advanced long grain 98-Y-511 topped experimental lines at 9,420 pounds/acre.

Average time to heading across all varieties and locations was 89 days. Average yields of blast-resistant lines ranged from 7,790 to 8,850 pounds/acre.

S-102 Tops Yields

The highest yield of any commercial variety at any location was S-102 at 10,260 pounds/acre in the early tests. On average, S-102 has been the highest yielding variety for the last five years at 10,262 pounds/acre. In 2001, and over the last five years, the highest yielding commercial variety in the early trials was M-205 at the RES. However, test results confirm that M-205 loses its yield advantage to other varieties in cooler locations and is thus recommended for areas north of Highway 20.

Nitrogen Trial

A small-plot nitrogen management trial comparing six varieties at six preplant N rates was conducted in a Sutter County commercial rice field. The varieties included M-205, M-402, L-205, CT-201, M-104 and M-202. Cultural practices included ammonium sulfate applied in a band 2-4 inches deep; rolled and flooded, then hand seeded May 10, 2001; continuous flood; Ordram, Londax, Grandstand and propanil for weed control; harvested October 5, 2001 with the UCCE plot harvester. Crop growth was good but yields were low due to weed pressure (primarily smallflower umbrellaplant) and herbicide injury. Optimal nitrogen rates ranged from 120 to 170 pounds N/acre at this location, a site already nitrogen deficient.

Leaf Color Chart

A leaf color chart to quickly and easily assess nitrogen status was tested in grower fields throughout rice country last year. Twenty-nine growers collected leaf samples and returned them to local Cooperative Extension offices for analysis. UC researchers collected additional samples for analysis. Preliminary results for M-202 indicate that grower evaluation of color was the most consistent at color panel five and below. Growers may be able to better discern leaf color differences at the lower nitrogen levels. However, more definitive conclusions await completion of laboratory analysis.

Project Leader and Principal Investigators

Randall “Cass” Mutters, Interim CE Agronomist, UC Davis Department of Agronomy and Range Science, UCCE Farm Advisor, Butte County Cooperative Extension

Jim Hill, Extension Agronomist, UC Davis Department of Agronomy and Range Science