Variety Trials - 2005




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Project Leader and Principal UC Investigators

James E. Hill, UCCE Specialist, Dept. of Agronomy and Range Science, UC Davis




UC Cooperative Extension conducted sixteen on-farm rice variety evaluation trials throughout the rice-growing regions of California in 2005 in collaboration with the Rice Experiment Station plant breeders. These trials perform an essential role in exposing 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, two from each maturity group. Average yields across varieties and locations in the advanced-line tests ranged from 8,090 pounds/acre in the very early trials to about 7,800 pounds/acre in the early tests. In the intermediate to late test, the advanced lines yielded more than 8,660 pounds/acre.

Similar to the exceptionally wet 2003 planting season, the 2005 season resulted in reduced planted acreage and lower average yields. A two-week period of temperatures over 100 degrees Fahrenheit helped shorten the days to harvest but it may have been too much, too late. Rice plants could not compensate for delayed plantings and yields were off. Statewide yields averaged 7,300 pounds/acre on 511,000 planted acres.

Several advanced lines in 2005 produced high yields and showed improvement toward other important breeding goals, such as disease resistance and grain quality. Testing advanced and preliminary lines under a variety of conditions remains a critical aspect of releasing varieties adapted to changing cultural practices, markets and pests.

A long-term experiment on rice stand establishment continued for a second year at the Rice Experiment Station. Five different methods of stand establishment were evaluated for their impact on weed management. One of the important findings is that nitrogen losses can be high when water is removed. This work is described in more detail below.

Very Early Tests

Ten advanced breeding lines and eight commercial varieties were compared in four very early advanced tests. Additionally, 32 cultivar lines were tested in the preliminary trials at each location.

Grain yield in the advanced tests averaged 7,980 pounds/acre at RES, 7,650 pounds/acre at San Joaquin, 7,410 pounds/acre at Sutter and 9,330 pounds/acre at Yolo. Over all locations, the highest yielding entry on average was the advanced long grain 99-Y-041 (8,780 pounds/acre), followed by short grain S-102 (8,690 pounds/acre) and L-205 (8,390 pounds/acre). Other top-yielding commercial varieties included M-206, M-202, CM-101 and L-204.

Days to 50 percent heading for most varieties in 2005 were two-to-five days fewer than in 2004. A significant percentage of the rice acreage was planted later than normal due to frequent spring rains that delayed field preparation.

Over a five-year period and across locations, S-102 continues to be the highest yielding very early variety, at 9,653 pounds/acre, followed by M-206 at 9,326 pounds/acre.

Early Tests

Ten advanced lines and 11 commercial varieties were compared in four early tests. Thirty preliminary lines were also evaluated in separate tests at each location.

Yields in the advanced lines averaged 7,780 pounds/acre at RES, 8,070 pounds/acre at Colusa, and 7,550 pounds/acre at Yuba. Butte County yields were not included in the over-locations yield due to heavy bird damage. The advanced Newrex type long grain 01-Y-655 was the highest yielding entry (8,490 pounds/acre) when averaged over three locations in 2005. Other consistently high-yielding entries included M-205, 99-Y-529, 99-Y-041, L-205, M-204 and M-206.

Days to 50 percent heading ranged from 77 days at the Yuba County test to 89 days at the Colusa County site. Commercial standard M-202 headed at 77 days at RES and 91 days at Colusa. As in the very early tests, 50 percent heading was two-to-13 days less than in 2004.

Over a five-year period and across locations, M-205 continues to be the highest yielding commercial variety at 9,529 pounds/acre, followed by M-206 at 9,118 pounds/acre.

Intermediate to 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.

Yields in the advanced lines averaged 9,170 pounds/acre at RES, 7,960 pounds/acre at Glenn and 9,100 pounds/acre at Sutter. The over-location average yield was 1,400 pounds/acre less than in 2004. M-204, the highest yielding commercial variety, ranked fourth overall at 10,040 pounds/acre in Sutter County. M-202 and

L-205 were the next highest yielding commercial varieties across locations. Long grain Newrex entry 03-Y-151 was the highest yielding advanced entry across locations at 9,470 pounds/acre

Days to 50 percent heading ranged from 81 days at the Sutter County site to 89 days at the Glenn County and RES locations. The number of days to 50 percent heading was about six days less than 2004 because of an unusual two-week, exceptionally hot spell in July.

Over a five-year period and across locations, M-205 continues to be the highest yielding commercial variety in this group at 9,930 pounds/acre. M-205 and M-402 produced 107 percent and 98 percent, respectively, of the M-202 yield on average over the last five years.

Cultural Practices

A long-term stand establishment trial was begun at the Rice Experiment Station in 2004. The purpose of this study is to investigate the influence of different stand establishment methods on rice stand establishment, weed management and nitrogen use efficiency.

The five systems included conventional water seeded; conventional drill seeded; spring-tilled, delayed water seeding; no spring-till water seeding; and no spring-till drill seeding. The two no-till treatments and the spring-tilled treatment were temporarily flooded to germinate weeds, drained and treated with Roundup® to remove the weeds prior to planting. Weeds in the no-till, water-seeded treatment were greatly reduced. This treatment had the advantage of needing very little additional weed control. Prowl was used in the drill-seeded treatments, thus introducing another herbicide as an alternative to combat weed resistance and to lower herbicide costs. The impact of these treatments on weed management is reported in the Weed Control in Rice section of this annual report.

Because nitrogen requirements are expected to differ among stand establishment methods, various rates and timing of nitrogen application were tested. In both years the highest yields were observed in the conventional, direct-seeded treatment and the lowest yields were in the spring-tilled, delayed water-seeded treatment. Researchers speculate that the early season flush of water to germinate weeds may have resulted in high native nitrogen losses compared to the conventionally water-seeded treatment.

A study to develop a degree-day model for scheduling field management decisions was begun in 2005 at locations in the northern and southern Sacramento Valley. Two medium grain Calrose varieties—M-202 and M-206—are being used in this work. Initial results indicate rate of leaf development to be similar for both cultivars at each site.


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