General Description

Acreage and principal growing areas
Commercial rice production began in Butte County, California in 1912 and is now an important field crop in acreage and value. Rice acreage fluctuates annually according to changes in price, government programs, and changes in water availability (fig. 1). For example, rice acreage increased to over 500,000 acres in 1975 when the government removed mandatory acreage control but then declined to 308,000 acres in 1977 because of a severe 2-year drought (fig. 1). Relatively high prices led to a record 605,000 acres in 1981. World rice surpluses, low prices, and acreage reduction incentives offered by the US Department of Agriculture reduced the acreage by nearly 50 percent in 1983. Acreage typically ranges between 350,000 to 450,000 acres.

More than 90 percent of California's rice acreage is located in the Sacramento Valley; the remainder is in the north to central San Joaquin Valley. In the southern San Joaquin Valley rice is occasionally grown to reclaim sodic and saline soils. The leading rice producing counties are Colusa, Butte, Sutter, and Glenn (fig. 2).

Climate, soils, and water
California rice is grown under a Mediterranean climate characterized by warm, dry, clear days, and a long growing season favorable to high photosynthetic rates and high rice yields (fig. 3). Compared to tropical and subtropical rice-growing areas, the climate is cool, but warm summer nights during panicle development, when pollen formation takes place, helps to avoid cold-induced floret sterility. Low relative humidity throughout the growing season reduces the development, severity, and importance of rice diseases. However, cool weather and strong winds during stand establishment may cause partial stand loss and seedling drift.

Figure 3. Seasonal average rainfall and temperature patterns in the Sacramento Valley of California. Hatched area indicates the California rice production season from seeding to harvest.

Rice is grown mostly on fine-textured, poorly drained soils with impervious hardpans or claypans. These soils are principally in three textural classes: clays, silty clays, and silty clay loams ranging from 25 to 70 percent clay. A few of the soils are loam in the surface horizon but are underlain with hardpans. These soils are well suited to rice production, since their low water permeability enhances water use efficiency. Most of the irrigation water for California rice comes from winter rain and snow-fed reservoirs of the Cascade, Klamath, and Sierra Nevada mountain ranges. Less than 10 percent of rice irrigation water is pumped from wells in areas where surface water is not available, or as a supplement to surface supplies. The high cost of pumping well water prevents its widespread use in rice production. Surface water and most groundwaters are of very good quality for rice irrigation.

Yields
Improved varieties and cultural practices have contributed significantly to yield increases since 1955 (fig. 4). The most important of these practices include 1) more efficient nitrogen management adopted in the 1950s, 2) herbicides to control broadleaf and grass weeds adopted respectively in the 1950s and 1960s, 3) precision land leveling with laser-directed equipment widely adopted in the 1970s, and 4) development of semidwarf rice varieties introduced in the late 1970s and early 1980s.

Figure 4. Annual average rice yields in California and agronomic and management changes which have contributed to increased yields since 1955.

 Before 1950, statewide yields were 2,500 to 3,000 pounds per acre; by the early 1990's average California rice yields exceeded 8,500 pounds per acre with some field yields exceeding 10,000 pounds per acre. Yields from experimental tests have exceeded 13,000 pounds per acre of paddy rice (at 14 percent moisture).

Varietal selection
A wide range of varieties is adapted to the rice-growing areas of California, made available by an aggressive, industry-funded rice improvement program. These include short-, medium-, and long-grain varieties, as well as such specialty market varieties as glutinous (also called mochi, sweet, or waxy) and aromatic types. Nearly all varieties are semidwarf and respond to high nitrogen levels.

Season length, from seeding to harvest, ranges from the very early, at approximately a 130 days, to the late, at about 175 days. However, the naming system and maturity group of California varieties is based on days to 50% flowering (heading) at the relatively warm environment of the Rice Experiment Station in Biggs, CA and season length for the same variety may vary greatly from warmer to cooler locations in the state. Choice of variety depends on environment, planting date, quality, marketing, and harvest scheduling. For example, cold-tolerant very early and early varieties are selected for cooler regions and late planting. The same varieties selected for warmer environments may mature during extremely hot weather and produce poor-quality rice. In 1979, the California rice industry developed a uniform naming system for publicly developed rice varieties based on grain type, maturity, and order of varietal release (table 1); however, privately developed varieties are named by the proprietor. The public varieties grown in California are principally short- and medium-grain japonica types with origins from the cooler rice climates of the northern latitudes.

Long-grain rice, historically adapted to subtropical and tropical climates, has only been produced on a commercial scale in California since the 1980's. Long-grain varieties grown in the southern United States are not well adapted to California's cooler environment. However, notable improvement through plant breeding has provided enough cold tolerance to achieve long-grain yields in California comparable to short- and medium-grain yields. In addition, marketing opportunities play a major role in determining the grain type produced and less than 2 percent of California's rice production is long grain. Although long grain types dominate US rice production, medium grain production prevails in California (fig 5), California rice production by grain type.

Figure 5. Recent California rice production by grain type.

More information on choosing California rice varieties.

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