Unique production system evolved to meet California’s special needs, resulting in high yields and quality and with an eye on the environment.
By Whitney Brim-DeForest, Luis Espino and Cass Mutters
Changes in agronomic practices improved production efficiencies and the economic sustainability of the crop while decreasing the environmental impacts of production.
The California rice industry is a model of environmental stewardship. The industry works closely with regulatory agencies and conservation groups to ensure that rice production enhances wildlife habitat while promoting sound stewardship of water resources.
A long history of grower support
Since the establishment of the California Rice Experiment Station in 1912, rice growers have supported all aspects of rice research, with a special emphasis on developing varieties well adapted to the growing conditions in the Sacramento Valley. Before the 1960s, there were only three major public rice varieties: Calrose (medium-grain), Caloro and Colusa (both short-grains).
The advent of the Cooperative Rice Research Foundation in 1968 launched an accelerated breeding program for medium-grain varieties that led to the release of nine new varieties within a decade.
Major improvements during that period included the release of varieties with smooth hulls, semi-dwarf height and early maturity. The development of cold-tolerant varieties, released in 2000, allowed for the further expansion of acreage into cooler areas of the state.
Prompted by the discovery of blast in California in 1998, blast-resistant varieties were released in 2005 and 2006. Since 2000, varietal improvements include increases in milling yield and yield stability, as well as significantly higher yield potentials compared to earlier varieties.
Not just medium-grain
Short- and long-grain varieties also have been improved in the past 50 years. In 1980, the first smooth-hulled, short-statured short-grain variety was released. Long-grain varieties are an important component of the California rice market, but early breeding efforts with Southern rice varieties proved difficult.
Starting in the 1970s, several high-quality long-grain varieties were released, including two aromatic types and a basmati-type. The focus of breeding efforts for the long-grains is for taste and cooking quality.
The advent of chemical fertilizers in the 1950s along with the widespread adoption of aerial seeding marked a dramatic increase in yields. During the 1970s, laser-guided leveling was introduced, resulting in the change from contour levees to parallel levees, improving water-use efficiency.
The introduction and widespread adoption of the corrugated roller to finish the seed bed before flooding contributed to better stand establishment and uniformity.
More recently, GPS-guided leveling has allowed growers to level fields almost yearly. The combination of varietal and agronomic improvements resulted in average yields increasing from approximately 3,000 pounds per acre in the 1950s to close to 9,000 pounds per acre in 2016, the highest in the United States.
Focus on water quality
During the 1970s, problems with offsite movement of herbicides from rice fields into the Sacramento River prompted the industry to develop practices to manage herbicide residues in rice field drain waters.
Water-holding periods after pesticide applications, designed to allow pesticide degradation before drain water left fields, were developed and widely adopted, and are now required by pesticide labels.
During the 1990s, recirculating and static-water irrigation systems were introduced to further reduce off-site pesticide movement. Growers have become experts at holding water and eliminating drainage after a pesticide application.
Currently, the rice industry and California regulatory agencies collaborate in monitoring water quality and work together to maintain residue levels in rice drain water below levels of concern for wildlife and human consumption.
The use of water holding periods has reduced the movement of pesticide residues into the Sacramento River by 97 percent since the inception of the program.
Winter flooding a boon to waterfowl Before the 1990s, burning was the most common method to dispose of straw residue after harvest. In the early 1990s, air quality concerns led to the introduction of state laws restricting straw burning.
As a result, growers started incorporating straw residues in the fall after harvest, followed by flooding of fields during the winter to encourage straw decomposition.
This has resulted in the creation of additional habitat for migratory waterfowl, which has been valued at more than $1 billion.
The environmental benefits of straw incorporation and winter flooding have been recognized by the rice industry and environmental groups, who now work closely to preserve them. Moreover, this method of straw decomposition provides about 25 pounds of nitrogen per acre, allowing many growers to reduce the amount of pre-plant applied N. Currently, only about 10 percent of rice acreage is burned for straw disposal in a given year.
The introduction of chemical herbicides in the 1950s and ’60s provided effective weed control for three decades.
However, since the early 1990s, an increasing number of weeds with herbicide resistance have posed major challenges for growers.
Weed management has become complicated and expensive, relying heavily on herbicide mixtures and an increasing number of applications. Herbicide stewardship is critical to delay the evolution of resistance to new modes of action.
With the monocropping system of rice cultivation and the limited number of new herbicide modes of action, herbicide resistance is one of the major production challenges growers currently face.
Thanks to the strong relationship between rice growers and the research community, the rice industry in California is poised to be at the forefront of agronomic and varietal advances in rice production far into the future. With grower support, the California rice industry will continue to meet the increasing environmental and economic challenges it faces.
Dr. Whitney Brim-DeForest is a University of California Cooperative Extension farm adviser serving Sutter, Yuba, Placer and Sacramento counties. She may be reached at firstname.lastname@example.org. Dr. Luis Espino is a farm adviser serving Colusa, Glenn, Yolo and the Sacramento Capital Corridor. He may be reached at email@example.com. Dr. Cass Mutters is county director and farm adviser for Butte County. He may be reached at firstname.lastname@example.org.