Project Update
BIFS rice survey: Status of straw and weed management, opportunities for input reduction in rice

California has 500,000 acres of rice and the highest yields in the world. The state’s rice farming system is highly mechanized and reliant on agrichemical inputs. Components of this system face several challenges: The insecticide carbofuran is no longer registered for use in rice, straw burning has been severely restricted to protect air quality, and herbicide-resistant weeds have appeared. In addition, lower profit margins and the potential reduction in federal subsidies make the use of high-cost agrichemicals less attractive. The rice Biologically Integrated Farming Systems (BIFS) project addresses some of these problems by refining and promoting alternative farming practices through on-farm demonstration trials. The project uses results from previous University of California research on winter flooding, straw incorporation, cover cropping, summer water depth management, and drill-seeded rice to reduce the need for pesticides and synthetic nitrogen.

The rice BIFS project recently conducted a survey of 213 rice growers to garner information on the extent to which conventional and alternatives techniques are practiced and valued two years into the project. The survey also asked about project recognition and sources of information. This “snapshot” of practices, attitudes, and information flow can be used as a baseline against which progress will be measured when a second survey is conducted after the project is finished. This report focuses on non-chemical weed control strategies based on water management, and the reduced use of chemical fertilizer through the use of alternative nitrogen sources. This report helps to identify areas of opportunities for future extension efforts.

Methods

SAREP staff, a Cooperative Extension farm advisor and a professional survey worker developed a four-page questionnaire that was pre-tested on 10 rice growers. A mailing list of 900 recipients was generated by combining the lists of three different Sacramento Valley UC Cooperative Extension farm advisors. In March 2001 we mailed a cover letter, the questionnaire and a business-reply return envelope to 900 recipients in nine counties. A reminder card was sent two weeks later. We received 213 valid responses but not everyone responded to all questions. Short telephone interviews with 53 non-respondents showed that non-respondents were not statistically different from the 213 respondents in their age or farm size distribution. The names and addresses of respondents are confidential. A comparison of the location of survey respondents to official rice acreage figures shows that our sample is geographically representative of the state’s rice growing population (Table 1).

For the purposes of this report, only those results relevant to weed, straw, and soil fertility management are discussed.

Weed management, herbicides

Weed management is key to maintaining high yields in rice and most of the concerns with pesticide risks focus on herbicide use. The California Department of Pesticide Regulation (DPR, 2001) reported several continuing problems related to herbicides: aerial drift, phytotoxicity to non-target crops, weed resistance to rice herbicides, aquatic toxicity, sediment accumulation, and drinking water concerns.

Nearly all California rice growers depend on herbicides. The extent of this dependence is evident in the results where 98 percent of respondents use herbicides. This group uses herbicides on an average of 95 percent of their acreage. Even though most growers do not find herbicides affordable (68%), most find them reliable (71%) (Figure 1). The 29 percent of growers who do not find herbicides reliable may reflect the increased problems with weed resistance to herbicides. Pesticide inputs account for 15 percent to 20 percent of production costs and most of these costs are from herbicide use. The large percentage of growers who do not find herbicides affordable indicates that there are opportunities to promote cheaper reliable alternatives.

UC trials demonstrated that watergrass was effectively controlled with increased water depth (Williams et al., 1990). The BIFS project demonstrated in several field trials that deeper water controlled weeds often without affecting yields. However, interest in this method is low. The survey results show that most growers consider non-herbicide weed control methods neither affordable (72%) nor reliable (88%) (Figure 1).

We find, however, that attitudes toward non-herbicide methods of weed control may depend on farmers’ experience with these methods and the inherent risks associated with these techniques. For example, high winds during the deepwater period may result in seed drift, stand loss, or breakdown of the levies that retain the water in the fields. A grower must weigh the costs associated with both non-chemical and chemical weed control strategies.

Obviously, growers with organic acreage have some experience with non-herbicide weed control methods. At the time the 2000 trials were set up, only growers with organic rice acreage were willing to try this method. Of course, organic growers do not have the option of chemical use and lower yields in organic rice are offset by higher prices as compared to conventionally grown rice. Nonetheless, additional efforts to demonstrate and to provide opportunities to experience the effectiveness of non-herbicide methods of weed control are warranted.

In addition to deep water/dry down, other non-herbicide weed management methods are available. Even though they may not be appropriate to all farming systems, the survey found a number of growers using these methods on some of their acreage. Respondents reported practicing crop rotation (24%), summer fallow flood then plow down (9%), and drill or dry seed with dry down (4%).

Straw management, reduced nitrogen input

Rice grower Eric Tenhunfeld (third from left) shows Butte County farmadvisor Randall “Cass” Mutters and interested farmers photos of a drill-seeded field. R-L: Greg Massa, Mutters, Tenhunfeld, Eric Lundberg, Nancy Schlieger, and Nic Greco. (photo by Macro Barzman)

Straw management is a long-standing challenge for California rice growers. In 1991, due to air quality concerns, the California Legislature enacted the Rice Straw Burning Reduction Act, which mandated a scheduled phase-down in rice straw burning. The California Air Resources Board (2001) reports that the rice acreage burned in the Sacramento Valley has decreased from 303,000 acres in 1992 to 139,000 acres in 2000. The survey showed that in the 2000 season at least 44 percent of respondents burned straw over an average of 36 percent of their acreage (Table 2). Starting in 2001, all rice growers will have to comply with a straw burning limit of 125,000 acres basinwide or 25 percent of each individual grower’s fields, whichever is less. Burning is permitted only if the disease levels in the field are determined by inspection to reduce yields.

Incorporating straw into the soil is the most common alternative to burning, even though the cost of this practice is estimated at $43 per acre, compared to approximately $3 per acre for burning (California Air Resource Board, 2001). In the survey, a large majority (89%) reported incorporating straw during the 2000 season on an average of 80 percent of their rice acreage, while only 11 percent did not incorporate any straw (Table 2).

Growers gather around drill seeding machine at rice BIFS field day at Wallace Ranch in Dunnigan, Yolo County. (photo by Macro Barzman)

Straw incorporation, particularly when it is combined with winter flooding, can generate a number of benefits. Studies have shown that this practice can reduce rice water weevil populations and stem rot inoculum levels (Godfrey et al., 1998; Webster et al., 1999), while improving straw decay and soil quality. In conventional systems, nitrogen fertilizer is incorporated as aqueous ammonia or as dry fertilizer a few days before pre-plant flooding at rates of 150 pounds per acre, sometimes followed by a nitrogen topdressing later in the season. Altogether, fertilizers account for 10 percent of total operating costs (Williams et al., 2001). Incorporating straw in the soil can replace some of this inorganic fertilizer because it increases soil organic nitrogen, a major form of nitrogen used by rice plants. The rice BIFS project now has three years of data from farmer-managed on-farm trials showing that nitrogen rates can be reduced by 30 pounds per acre with no reductions in yields (Mutters et al., 2000).

A large percentage of respondents (78%) reported following soil incorporation with winter flooding on at least some of their acreage, while 12 percent reported not flooding any of their acreage after soil incorporation, and 11 percent reported not incorporating any straw (Table 2). Among other benefits, flooding rice fields during the winter creates habitat for wildlife. The University of California has encouraged this practice for at least 10 years (Brouder & Hill, 1995). In our survey, 73 percent of growers reported using winter flooding as a way to enhance wildlife habitat.

For the majority of respondents (i.e., for the 78 percent who incorporate straw and flood), the conditions were met for reducing their synthetic nitrogen input. During the 2000 season, 33 percent of respondents reported reducing their nitrogen application on at least some of their acreage in combination with incorporating straw and flooding. A few respondents (11%) reported having used this practice in the past but chose not to repeat it this last season (Table 2). The reasons these growers did not to repeat this practice should be investigated to determine the reliability of the practice and the obstacles to its adoption. The survey did not collect data on how many growers chose to repeat the practice. The rice BIFS project’s trial results, along with the high percentage of growers already using the prerequisite practices for nitrogen reduction, are encouraging.

For more information, contact Marco Barzman at msbarzman@ucdavis.edu, or Cass Mutters at rgmutters@ucdavis.edu.

References

• Brouder, S.M. and J.E. Hill. 1995. Winter flooding of ricelands provides waterfowl habitat. Cal. Ag. 49(6):58-64.
• California Agricultural Statistics Service. 2000. California Agricultural Statistics 1990-1999, A ten-year report.
• California Air Resources Board. June 2001. Report to the Legislature. Progress Report on the Phase Down and the 1998-2000 Pause in the Phase Down of Rice Straw Burning in the Sacramento Valley Air Basin.
• California Rice Research Board. 2001. Sacramento Valley Fall Burn Report - 2000. http://www.syix.com/rrb/00rpt/FallBurn.htm
• Department of Pesticide Regulation. 2001. http://www.cdpr.ca.gov/docs/surfwatr/programs.htm Last updated Apr. 25, 2001.
• Godfrey, L., D. Cuneo, and D. Palrang. 1998. Agronomic effects of winter flooding on rice straw decomposition and rice production: Effects on pest arthropods. In: Winter flooding and straw management: Implications for rice production, 1994-1996
• Mutters, R.G., J.W. Eckert and D.T. Parks. 2000. Biologically Integrated Systems in Rice Progress Report, November 2000.
• Webster, R.K., C. Greer. 1999. Cause and control of rice diseases. Annual Report to the California Rice Research Board.
• Williams, J.F., S.R. Roberts, J.E. Hill, S.C. Scardaci, G. Tibbits. 1990. Managing water for weed control in rice. California Agriculture 44 (5):7-10.
• Williams, J.F., R.G. Mutters, K.M. Klonsky, R.L. DeMoura. 2001 Sample costs to produce rice - Sacramento Valley. UCCE.