Project Leader and Principal UC Investigators
Randall "Cass" Mutters, Interim CE Agronomist and UCCE Farm Advisor, Dept. of Agronomy & Range Science, UC Davis
Jim Hill, Extension Agronomist, Dept of Agronomy & Range Science, UC Davis
University of California scientists in
cooperation with public and private plant breeders conducted 16 on-farm rice variety
evaluation trials throughout the rice growing areas of California during 2000. 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 in Biggs. Average yields across varieties and locations ranged from about 7,520 pounds/acre in very early trials to about 10,530 pounds/acre in the intermediate tests. Midseason temperatures were favorable for good floral development. Very little blanking was observed - in contrast to 1999.
As in previous years, the commercial standards ranked high in yield against advanced and preliminary entries, demonstrating the difficulty in achieving higher yields. However, a few advanced lines in 2000 produced very high yields and exhibited good plant development characteristics. 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 study was conducted at three locations to provide growers with initial guidelines for nitrogen management of five recently released varieties - M-205, M-402, L-205, CT-201 and CH-201. Progress has also been made on the development of a leaf color chart to aid in nitrogen management decisions and another study examining how rice straw removal affects potassium fertility and, consequently, yield and disease incidence. Highlights are discussed below.
Very Early Tests
Nine advanced breeding lines and 10 commercial varieties were compared in four very early tests (less than 90 days to 50 percent heading).
Grain yields in the advanced tests averaged 9,700 pounds/acre at Biggs, 9,360 pounds/acre at Yolo, 9,300 pounds/acre at Sutter and 6,840 pounds/acre at San Joaquin. Over the four locations, the highest yielding entry on average was S-102 (9,300 pounds/acre), followed by an advanced line, a long grain and an experimental premium quality medium grain. Commercial varieties remaining in the top 10 included M-104 (fifth), M-202 (seventh), L-205 (eighth) and
M-103 (ninth). Heading was sooner than in 1999, with an average of 90 days after seeding (DAS) in advanced lines, yet slower than the 84 DAS in 1998 and 89 DAS in 1997.
Eight advanced lines and 11 commercial varieties were compared in four early tests (90-97 days to 50 percent heading). Twenty-two preliminary lines were also evaluated in separate tests at each location.
Yields in the advanced line tests averaged 10,040 pounds/acre at Biggs, 8,050 pounds/acre at Butte, 8,280 pounds/acre at Colusa and 8,610 pounds/acre at Yuba. Newly released medium grain M-205 was the highest yielding entry (10,060 pounds/acre) over the four locations in 2000. Other consistently high yielding entries included two experimental lines, and M-204 and M-202. Several lines in preliminary yield tests exceeded M-202 and the top-yielding advanced line. Time to 50 percent heading averaged 84 DAS for all entries and locations.
Eight advanced lines and six commercial varieties were compared in three intermediate-late tests (more than 97 days to 50 percent heading). Nineteen preliminary lines were also evaluated in separate tests at each location.
Average yields in the advanced line tests were 9,980 pounds/acre at Biggs, 7,970 pounds/acre at Glenn and 9,730 pounds/acre at Sutter - up substantially from 1999. The advanced long-grain line 98-Y-511 was the highest yielding entry overall (10,330 pounds/acre). The highest yielding commercial variety was M-205, followed by M-202 and M-402 at 10,190 pounds/acre, 9,600 pounds/acre and 9,080 pounds/acre, respectively. The overall yield of the preliminary medium grain line 98-Y-425 was higher than any entry in the advanced tests. Average time to heading across all varieties and locations was 86 DAS, with M-402 taking the longest to head (96 DAS).
Highest yield of any commercial variety at any location was M-204 (11,200 pounds/acre) in the RES Early Variety Trial. This variety was also the highest yielding entry across all locations (9,285 pounds/acre), followed by M-205 (9,190 pounds/acre) and M-202 (9,025 pounds/acre)
Varietal Nitrogen Study
Scientists conducted a nitrogen management trial on six varieties last year - M-202 and the five recently released varieties (M-402, L-205, CT-201, CH-201 and M-205). Ammonium sulfate was applied preplant at six different rates (0,40, 80, 120, 160 and 200 pounds/acre). Growers should evaluate the results in the context of their individual operations and cropping year.
Yields, considered either at the individual location or averaged across location, trended upwards with increasing rates of nitrogen. Maximum yields were observed for varieties
CT-201, L-205, M-104 and M-202 at the 200 pound/acre rate at the Yuba City and Richvale locations. M-104 and M-202 responded similarly at the Pleasant Grove site. These findings contrast sharply with 1999 results, where optimal rates of preplant nitrogen from 110 to 140 pounds/acre. Higher nitrogen rates in 1999 depressed yields in all tested varieties. The reason for the discrepancy is unclear. The experiments will be repeated in 2001.
M-205 lodged the least in this study - regardless of nitrogen rate. This confirms previous observations that M-205 is very resistant to lodging.
Leaf N color chart
A simple, easy-to-use leaf color chart was made available to growers and PCAs late in summer 2000 (see photos).
The color of individual color panels is based on actual rice leaf color when grown at different nitrogen levels. The chart is made of acrylic plastic designed to withstand temperatures up to 190 degrees. Color panels will not fade. The chart is extremely durable and field ready. Most importantly, it predicted leaf nitrogen with a very high degree of accuracy using a single leaf at panicle initiation. Possible refinements to be studied in 2001 include sampling the three upper most leaves to calibrate the chart for whole field evaluations.
The second year of a study funded by the CDFA Fertilizer Research and Education Program (FREP) is looking into how rice straw removal affects potassium fertility and ultimately rice yield and rice diseases.
Plots with straw removed showed a slight yield increase when supplemental potassium was added, suggesting the straw removal is depleting this nutrient. This study also suggests that continued rice straw incorporation could help offset the loss of nutrients from removing straw. The duration of this effect depends on the number of years of straw incorporation and native soil fertility.
Aggregate sheath spot was the only disease present in this trial. More of the disease was observed in the straw removed plots than in the straw incorporated plots. This disease reacted differently from how stem rot would be expected to react in two ways. First, it tended to decrease with increasing nitrogen, while stem rot tends to grow more severe with higher nitrogen levels. Second, its severity increased when straw was removed. This could be a reaction to gradually lowering fertility of the straw removed plots, which tends to increase the severity of this disease.
This project has one more year to run. Fertilizer potassium and nitrogen requirements have increased each year of straw removal and are expected to do so in the last year of the study. This information will be quite useful should California begin to use significant quantities of straw, particularly for rice farms on the eastern side of the Sacramento Valley where soil potassium is low.