Agronomy Fact Sheet Series 1999-3

Authors

S.T. Tseng, plant breeder, Rice Experiment Station, Biggs, CA

C.W. Johnson, plant breeder, Rice Experiment Station, Biggs, CA

K.S. McKenzie, plant breeder and director, Rice Experiment Station, Biggs, CA

J.E. Hill, Chair and Extension Agronomist, Dept. of Agronomy and Range Science, UC Davis

W.M. Canevari,  R.G. Mutters, S.C. Scardaci, and J.F. Williams are Farm Advisors, UC Cooperative Extension, San Joaquin, Butte Colusa/Yolo /Glenn and Sacramento/ Sutter/Yuba counties respectively

Introduction

L-204 is a new long-grain rice variety released for commercial production in California in 1996. It was produced by growers in 1996 to 1998 and reports about its agronomic performance and milling yields have been favorable. The following information is based on research and experience and is intended to assist growers in optimizing the yield and quality of L-204.

Description

L-204 is a photoperiod nonsensitive, early maturing, semi-dwarf, long-gain rice variety. Seedling vigor of L-204 approaches that of the medium-grain varieties M-202 and M-204. L-204 is tolerant to thiobencarb (Abolish and Bolero) and molinate (Ordram) herbicides like other current California rice varieties. L-204 is about 2 to 5 days earlier that L-203 and M-202, requiring about 88 days to 50% heading. L-204 like medium-grain varieties requires about 40 to 45 days from heading to harvest (130 to 145 days from planting to harvest) at a grain moisture content that favors maximum milling yield in warmer areas. It has excellent straw strength and lodging resistance. L-204has smooth leaves and hulls and its leaves are darker green and more erect than L-203. The narrow erect leaves of L-204 cause what may appear to be slower emergence and less seedling vigor than medium grains. The visibility of more open water early in stand establishment (less leaf surface above water), however, does not mean L-204 is less vigorous. L-204 like medium-grain varieties is susceptible to stem rot, aggregate sheath spot, and the IG-1 race of the rice blast disease fungus prevalent in California.

Performance

The average grain yield of L-204 was 9,570 lb/acre compared to L-203 and M-202 ields of 9,300 and 9,910 lb/acre, respectively, in Statewide Yield Tests conducted by University of California Cooperative Extension (UCCE) in 1992 to 1997. L-204 has performed similar to medium grains like M-202 in warmer locations, but L-204 yields have been significantly lower in cool locations like the Escalon-Valley Home area of San Joaquin County. reports of agronomic characteristics and grain yields have been favorable based on foundation seed and grower production on L-204. The head rice milling yields of L-204 have been better than previous California long-grain rice varieties. Average head and total rice milling yields of L-204 from samples harvested twice per week sequentially at grain moisture contents of 22 to 13% in 1996 to 1998 were 57.0 and 68.7%, respectively, as shown in the following table. Maximum head rice and total milling yields of L-204 were obtained at 16 to 17% grain moisture at harvest in these studies. Milled rice of L-204 has physical and chemical characteristics similar to typical southern US long grains, but it cooks slightly softer when grown in California.

Grain Moisture at Harvest and Milling Yields
L-205 at RES

1 - Samples harvested twice per week, thrashed, and dried to 12-13% grain moisture for milling yield determination.

Management Guidelines

The following guidelines are based on research, observation and experience acquired in the development and testing of  L-204. These suggested cultural practices are intended to assist in the production of optimum yields and quality of L-204.

• Uniform water depth, fertility, seed distribution and weed control are important because they affect uniformity of heading, harvest moisture and in turn grain and head rice milling yield.
• Fertilizer rates and management should be like those used for medium-grain varieties. Although L-204 is resistant to lodging, excessive N is undesirable because it results in excessive leafiness, increased susceptibility to blanking and diseases, and reduced grain yield and quality. All or most of the N required and all of the P and K required should be incorporated preflood into a dry soil.
• Preferred seeding date is May 1 to 15 with earlier seeding dates increasing the risk of stand establishment problems and later seeding dates increase the risk of low temperature induced blanking. L-204 should be seeded at a rate of 130 to 150 lb/acre. L-204 seed is lighter than medium grains, and consequently the number of seed/lb of L-204 is greater than M-202 and other medium grain varieties. Stand densities greater than 20 plants/ft² may result in reduced yields because of increased diseases and competition. Early season water depth should be maintained uniformly at about 2 to 4 inches for optimum tillering and stand density.