The phase-down of rice straw burning in California's Sacramento Valley began in 1991 after the passage of the Connelly-Areias-Chandler Rice Straw Burning Reduction Act.

This year growers are allowed to burn no more than 125,000 acres or 25 percent, whichever is less, for disease control as specified under the “Safe Harbor” clause in the law.

In coordination with the California Department of Food and Agriculture (CDFA) and Sacramento Valley Air Basin Control Council (BCC), officials of the Air Resources Board (ARB) developed a conditional rice straw burning permit regulation. The Conditional Rice Straw Burning Advisory Group, established in 1996, made recommendations to the ARB to use in developing the regulation.

Proposed regulations for the “Safe Harbor” provision were completed in the fall of 2000. Paul Buttner, air pollution specialist with ARB, was the principal author of the regulation, which establishes a framework for a local program to be adopted by the BCC in early 2001.

The BCC's program sets forth the procedures under which growers will have to prove a significant and quantifiable reduction in yield to qualify for a conditional burning permit.

“We actually went through a process to determine mathematically what we believe to be a significant impact on yield,” Buttner says.

Sack per acre

“Through this process, we established a level of significance to be about one sack per acre. Using information on the impact of disease on rice yield, we estimate that a 15 percent incidence of aggregate sheetspot or stem rot, and a 1.8 percent incidence of blast causes a significant impact on yield.” An average field produces 75 to 80 sacks of rice per acre.

Growers with significant disease in their fields will have to file for a conditional burn permit. The following is performed to obtain a permit:

  1. Contract to have a field inspected or conduct self-inspection (inspector certification required)

  2. A detailed inspection report, using an easy-to-use form, is completed.

  3. Grower submits an application to burn and sends an inspection report to the local agricultural commissioner.

  4. The inspection report is reviewed and evaluated for accuracy by the agricultural commissioner.

  5. If approved by the agricultural commissioner, the application is sent to the air pollution control officer (APCO).

  6. The APCO may than issue a permit.

With the assistance of the University of California Cooperative Extension, local training sessions will be offered to growers and others interested in becoming certified inspectors. The training session consists of about two hours of class time and two hours of field time. It is expected that classes will be made available at several locations in the north valley and coordinated with county agricultural departments.

Don Bransford, chairman of the industry affairs committee for the California Rice Commission, foresees most growers going through the certification process.

“We have a certain amount of education we have to do on an annual basis anyway. Growers should be able to do this fairly easily since most walk their fields on a regular basis during the growing season. They're already able to identify the diseases, which are visually very evident.”

Fees for the conditional burn permits will vary from county to county, but are estimated to be less than $100, according to Harry Krug, agricultural commissioner for Colusa County.

During this year and next, the program specifically requires the quantification of disease. Data will be evaluated as to the overall incidence of disease in the valley. If the level of disease is determined to be significant, or at least 25 percent of the fields routinely effected by this disease, quantification will no longer be necessary, provided the BCC's program is amended to delete the quantification provision.

Four inspection methods have been suggested in the program. Through pilot programs, the first method, biased/unbiased, had the most advantages in the implementation, including being reasonably rapid and reliable, Buttner says.

Four samples

In this method, four samples are taken from a field of 50 acres or less, six from fields greater than 50 acres. One of the samples can be biased, that is, taken from a section obviously diseased.

The location of the remaining three unbiased samples are predetermined by the method. The results from all sites are averaged for an estimate of the disease threshold. There is a slightly inflated disease estimate because of the biased sampling, and it requires the collection of up to 200-300 stems per field. If significant disease levels are found in the first few sample sites, the remaining samples may not be required.

The second method uses multiple soil samples taken from the seedbed prior to flooding. The samples are evaluated to measure disease significance thresholds developed by Robert Webster of UC, Davis. Early tests of this method indicate it may be cost-prohibitive for widespread use, fairly difficult to implement, and have a narrow time-window for sampling.

The third is a single-sample biased method that looks only at one highly diseased area in the field. The ARB staff recommended this method be merged with the biased/unbiased method.

The fourth method is a visual inspection of the field without sampling. An inspector visually inspects and scores the percentage of diseased plants. This method generally had a high variability of results and an underestimation of disease.

Through observation and trial runs, Krug found all fields he inspected during the 2000 season would have qualified for burning under the current regulations. If disease in the field exceeds the 125,000-acre cap, the ARB and CDFA could authorize an act of God special release. However, Krug says, “It would have to be an overwhelming problem for them to do that.”