Sixteen on-farm rice variety evaluation trials were conducted throughout the rice-growing regions of California in 2007 by UC Cooperative Extension in collaboration with public and private 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 8,790 pounds/acre in the very early trials to about 9,540 pounds/acre in the early tests. In the intermediate-to-late test, the advanced lines yielded more than 8,170 pounds/acre.

Planting of the earliest rice fields was delayed a week to 10 days because of rain; however, the majority of rice acreage was planted in a timely manner. Statewide yields in 2007 averaged 8,220 pounds/acre on 533,000 harvested acres, according to USDA statistics.

Several advanced lines in 2007 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 rice cropping systems experiment on stand establishment continued for a fourth year at the Rice Experiment Station. Five different methods of stand establishment are being evaluated for weed control and fertility management. This work is described in more detail below and in the weed control section of this annual report.

Very Early Tests

Ten advanced breeding lines and seven commercial varieties were compared in four very early advanced-breeding tests. Additionally, 34 cultivar lines were tested in the preliminary trials at each location.

Grain yield in the advanced tests averaged 9,530 pounds/acres at RES, 10,660 pounds/acre at Sutter, 7,220 pounds/acre at Yolo, and 8,120 pounds/acre at San Joaquin. Over all locations, the highest-yielding entry on average was an advanced medium grain, 05-Y-724 at 9,920 pounds/acre, followed by S-102 and M-206 (9,830 and 9,750 pounds/acre, respectively). Top-yielding commercial varieties included L-206, M-104, CM-101 and M-202.

Days to 50 percent heading for most varieties in 2007 were two weeks to 17 days longer than in 2006, the result of moderate daytime and cooler night temperatures. This also reduced lodging. In spite of modest rain delays, most planting was completed in a timely manner.

Over a five-year period and across locations, S-102 continues to be the highest yielding very early variety, followed by M-206 at 9,396 pounds/acre and 9,111 pounds/acre respectively.

Early Tests

Ten advanced lines and eight commercial varieties were compared in four early tests. Preliminary tests included three commercial varieties and 33 preliminary lines evaluated in separate tests at each location.

Yields in the advanced lines averaged 8,420 pounds/acre at RES, 8,220 pounds/acre at Butte, 6,810 pounds/acre at Yuba, and 9,280 pounds/acre at Colusa. M-206 was the highest-yielding entry (8,850 pounds/acre) averaged over four locations in 2007. (Over-location yields were lower than expected in the early tests because of herbicide damage at the Yuba site.) Other consistently high-yielding entries included 99-Y-529, M-205, 03-Y-559, L-206, 01-Y-655, and 06-Y-333.

Days to 50 percent heading ranged from 85 days at RES to 92 days at the Yuba County test site. Commercial standard M-202 headed at 91 days at RES and 96 days at Yuba.

Over a five-year period and across locations, M-205 continues to be the highest yielding commercial variety at 9,235 pounds/acre, followed by M-204 at 8,944 pounds/acre.

Intermediate to Late Tests

Eight advanced lines and five commercial varieties were compared in three intermediate-to-late tests. Preliminary tests included four commercial varieties and 18 preliminary lines evaluated in separate tests at each location.

Yields in the advanced lines averaged 9,530 pounds/acre at RES, 9,530 pounds/acre at Glenn, and 9,540 pounds/acre at Sutter. All locations yielded higher in 2007, with the average advanced test yield increasing almost 2,600 pounds/acre at Glenn. The over-location average yield was 1,370 pounds/acre more than in 2006.

M-205 was the highest yielding commercial variety at 10,270 pounds/acre, second overall. L-206 and L-205 were the next highest-yielding commercial varieties across locations. Stem rot-resistant short grain entry 05-Y-657 was the highest yielding advanced entry at 10,410 pounds/acre.

Days to 50 percent heading ranged from 87 days at the Sutter County site to 92 days at the Glenn County location. The number of days to 50 percent heading was about four- to six-days longer than in 2006. As in the previous two years, M-402 took the longest time to reach maturity among the commercial varieties (average is102 days).

Over a five-year period and across locations, M-205 continues to be the highest-yielding commercial variety in this group at 9,571 pounds/acre. M-205 and M-402 produced 108 percent and 98 percent, respectively, of the M-202 yield on average over the last five years.

Stand establishment trials

A long-term stand establishment trial at the Rice Experiment Station continued for a fourth year in 2007. The purpose of this study is to investigate the influence of different stand-establishment methods on rice seedlings, weed resistance, and nitrogen use efficiency.

The five systems include 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 pre-flush irrigated and treated with Roundup®. Weeds were treated as necessary in the main plot areas, but one area remained untreated to evaluate weed germination and recruitment.

Various nitrogen rates and application timing were tested among stand-establishment methods. In the conventional water seeded and delayed spring-tilled stale seedbed treatments, where the soil is spring tilled, nitrogen was incorporated preplant as normal for water-seeded rice. In the drill-seeded stand, nitrogen was applied in splits. In the no spring-till drilled and water-seeded treatments, where soil disturbance would defeat the purpose of non-tillage with respect to weed recruitment, nitrogen must also be applied to the surface. Phosphorous was applied in the fall to the entire block and incorporated with fall tillage.

The two no spring-till systems yielded equally to the conventional systems. The spring-tilled, delayed water-seeded plot showed significantly lower yields than the other systems and will not be continued. Lower yields were attributed to nitrogen loss that occurred in the 10-14 days of drainage in this system. Both conventional drill-seeded and no spring-till drill seeded treatments gave slightly higher yields than the water-seeded treatments. More detail on stand establishment studies is reported in the Weed Control in Rice section of this annual report.

Rice growth and development

A rice growth and development study begun in commercial fields at the southern and northern ends of the Sacramento Valley continued for a third year. One short grain, CM-101, and three medium grain Calrose cultivars – M-104, M-202, and M-206 – were direct seeded in continuous flood at all three locations. The Glenn County site was planted nine and 14 days earlier than the cooler sites in Sutter and Yolo counties. Detailed information collected on leaf and reproductive stage development is being analyzed.