Forty years of research has helped secure the viability of California rice

In 1969, the California Rice Research Board was created to fund scientific investigations that would enhance the profitability of rice farming.  In the 40 years since, the investment of millions of dollars in grower assessments has produced 42 new rice varieties, improved crop protection and management practices, tapped new markets, created value for waste products, and given the industry the ability to approach environmental concerns proactively.

When the program began, the rice industry relied on three tall-statured varieties: Caloro, Colusa and Calrose. Average yields (1967-69) were about 5,250 pounds/acre. As newer varieties came into use, that figure jumped to 6,450 pounds/acre within 10 years.  By 1985, average yields topped 7,400 pounds/acre. In 2008 the statewide average yield was 8,320 pounds/acre, now fairly typical. While rice quality and harvest characteristics have improved significantly over the years, yields began leveling off in the 1990s because of weather uncertainties, the loss of some chemical tools, and the phasing out of rice field burning.

Progress in the development of new rice varieties and improved agronomic practices is reported each year in this annual report. A look back at some highlights from the last 40 years demonstrates the flexibility the industry created for itself in responding to changing needs and seizing on new opportunities.

Systematic variety development

Thousands of crosses have been made by plant breeders with rice cultivars and related wild species from throughout the world. Increases in grain yield of short- and medium-grain rice were early successes. Development of long grains, followed by specialty rices such as the aromatics (A-301) and sticky types (Calmochi-101) increased market opportunities. A timeline below shows the year each new California variety was released.

 In 1970 an irradiation-induced mutant of Calrose paved the way for higher yielding short-statured, early-maturing varieties. Calrose 76 – a full 10 inches shorter than 46-inch Calrose – was the first, released in 1976.

Geneticists identify sources of disease resistance, cold tolerance, improved grain characteristics, and other desirable traits. The advent of molecular marker technology in the 1990s greatly accelerated their work. This research also examined genes associated with hybrid rice, submergence tolerance, and improved salinity tolerance.

In 1978 a varietal naming system was created. The prefixes L, M, and S designate grain type. Group numbers (100, 200, 300, 400) refer to maturity, with the lower groupings relating to earliest maturity. The last two numbers indicate the order of release. For example, M-202, is a medium grain of early maturity and the second release of this grain type. This system has proven valuable in variety selection, harvesting, storage, and milling.

Once an experimental line has passed muster in statewide trials and is recommended for release as a new variety, it is grown out as foundation seed at the Rice Experiment Station. Seed growers then produce registered seed from foundation seed and certified seed from registered seed for industry-wide use.

Crop protection advances

Until the late 1960s, propanil was an effective and widely used rice herbicide. However, incidents of herbicide injury to other crops resulted in propanil being banned throughout most of the Sacramento Valley in 1971.  Subsequent research resulted in a new nozzle design that greatly reduced the problem. A new product formulation, in addition to Board-funded drift research, has kept propanil a valuable weed control tool and given growers an option for avoiding herbicide resistance.

In the mid-1980s, the new broad-spectrum, broadleaf herbicide Londax® showed great promise. Not only did Londax® work effectively in water, but it didn’t persist in the environment. Its “silver bullet” image wouldn’t last long when in 1992 resistance to this herbicide began to appear in weeds such as ricefield bulrush and smallflower umbrella sedge, as well as the broadleaf aquatics.

As chemical control of weeds became more challenging, weed management strategies shifted toward biological interactions between rice and weeds. In 2003 a major, long-term experiment was begun on alternative systems for establishing rice to evaluate the benefits of rotating stand establishment methods in rice-only rotations to manage herbicide-resistant weeds. Ongoing research has further refined this strategy, which utilizes variations of traditional water-seeded and drill-seeded systems and alternating herbicides with different modes of action.

The most serious disease of California rice is stem rot, which causes infected stems to die or to produce small panicles and shrunken kernels. Research in the 1970s determined that the most effective way to control stem rot was a fall burn, followed by moldboard plowing. But rice field burning became severely restricted because of air quality concerns. Numerous rice varieties and wild plant relatives have been screened in search of resistance to stem rot and other fungal diseases such as aggregate sheath spot.

In 1996 the disease “blast” was discovered in California. Plant pathologists and rice breeders devoted substantial time and energy to learning more about blast and launched a special project to tap known sources of blast resistance. Blast-resistant M-207 was released as early as 2005 and was quickly followed by an even more resistant variety, M-208.

In 1999 another new disease – Bakanae – appeared in California. While not as threatening as blast, it was cause for concern and stimulated research that quickly showed a chlorine seed soak could effectively limit this disease.

Research into rice water weevil (RWW) control focuses on weevil biology and chemical, cultural and biological control strategies. With the deregistering of Furadan®, other methods of RWW control were needed to keep it from becoming a major problem. Newer compounds requiring post-flood applications came into use in the late 1990s and necessitated research into updated RWW control thresholds.

Soil fertility studies

Soil and plant-tissue tests conducted after the introduction of semi-dwarf varieties helped establish new critical levels for nitrogen. The need for rapid identification of soil fertility problems led to the development of colorimetric tests and eventually the leaf color chart.

Early studies also examined zinc, iron, and manganese deficiencies and their relationship to “alkali disease.” This research showed that a zinc treatment following rice on alkali-problem soils helped rotation crops.

As rice growers implemented new straw management practices in the 1990s, knowledge of changes in soil fertility became more important. Research on purple vetch, long used by some rice growers, showed that incorporation increased soil microbial activity and accelerated decomposition of straw.

Research begun in the 1990s has shown that nitrogen becomes more available under consistent straw incorporation, making it possible to reduce fertilizer applications. Winter flooding and rolling were also shown to increase nitrogen availability.

Environmental stewardship

Early research found cleaner ways of burning rice straw that significantly reduced smoke. In April 1970 funds became available to study smoke dispersal during rice field burning in the Sacramento Valley.  A network of automated meteorological observing stations – “AMOS” – provided knowledge of local weather conditions and laid the groundwork for a highly successful program that further reduced haze, smoke, and citizen complaints. For its efforts to reduce smoke, the rice industry received two clean air awards from the American Lung Association in 1984.

Since early on, studies have been conducted on the disposition of fertilizers, herbicides, and pesticides in the environment. In 1972, for instance, experimental water management practices – static, flow-through and recycled – were examined for their effects on water quality. Environmental toxicology field and laboratory studies have also helped ensure public safety.

In 1976 an extensive “accounting” of the herbicide MCPA showed that the herbicide readily shifted to nontoxic fragments in water from the action of sunlight and microbes. Without this research, continued registration of this important herbicide would not have been possible.

The Bottom Line This figure shows the relationship between rice varieties, grain yield, research costs, and financial return on rice research. Benefits from breeding research began accruing to growers in 1979 when the first semi-dwarf varieties Calrose 76, M7, and M9 were grown on about 30 percent of the California rice acreage. The accrued gross financial return to tice growers attributed to research (with no value added economic multiplier) increased to $1.45 billion through 2007. This cumulative return is based ont he assumption that 60 percent of the actual rough rice yield increase is the result of improved varieties. total grower expenditures for rice breeding research since 1969 totaled $32.5 million through 2007.

Improving milling yields

Next to field yields, milling quality is the most important factor affecting what price growers get for their rice crop. As the industry began to shift from late-maturing to early-maturing varieties in the 1980s, milling quality declined. This prompted research into the effects of cultivar type, time of drainage, and rate of nitrogen application on the growth and development of panicles, kernel uniformity and head rice yields. Selection of breeding lines with measurable milling quality traits became increasingly important.

More recent research on variability in milling appraisals found that rice variety is a key factor affecting production of total and head rice yield. Studies on how harvest conditions affect milling quality and yield have shown that M-205 and M-206 can be harvested at a wide range of moisture levels while retaining quality.

Rice utilization and product development

For many years, rice bran was a milling byproduct used only for livestock feed, but it gained new respect when USDA researchers developed a procedure for stabilizing it in the 1980s. California mills adapted the process and bran became a healthy addition to breakfast cereals and extruded snack foods. Studies reported in the 1990s showed that rice bran, rich in antioxidants, reduced cholesterol and lesions leading to heart disease.

 In the 1970s, USDA and UC Davis food scientists conducted studies to extract rice oil from bran, reduce stickiness in cooked rice, expand use of rice flour, and develop other new products such as instant rice made from freeze-dried Calrose. Research from this period also utilized short and medium grains in puddings and snack foods. Rice soy milk was developed as a food for infants in the early 1980s.

Finding economic uses for rice straw has long been a priority. In 1973, studies examined systems for harvesting, transporting, stockpiling, and processing rice straw for energy generation. Recent USDA research experimented with rice straw in a biorefinery prototype.  Other studies on rice straw have examined its use in livestock rations, grazing potential, straw forage quality, nutritional differences among varieties, and many other areas. Work also has been conducted on feedlots and, more recently, at California dairies.