Field burning is already one of the most heavily regulated activities imaginable. Farmers must pay $10/acre, not burn within buffer zones along major highways, standby ready for countless hours in hopes that they will get the call that they can burn a field, and post flaggers at both ends of any adjacent roads that will be impacted by smoke. The Oregon Dept. of Agriculture (ODA) monitors weather conditions and only allows burning on about 10 days each summer during the best wind conditions possible to achieve good lift and transport of the smoke out of the area.
Over 500,000 acres used to be burned annually, but since legislation in 1991 phased that down, a maximum of 65,000 acres can now (before the just passed ban) be burned. The total acres burned for most of this decade averaged around 50,000 acres, dropping to 32,000 in 2007 and 38,000 in 2008.
The Oregon Department of Agriculture - Natural Resources Division's Smoke Management Program publishes an annual summary report on field burning. The ODA has Nephelometers, to measure smoke impact, located in Portland, Salem, Corvallis, Carus, Lyons, Sweet Home, Eugene, and Springfield. Going back to 2002, with only the exceptions of 2 hours in Corvallis (2006), 2 hours in Eugene (2005), 4 hours (2005) and 1 hour (2002) in Springfield, and 1 hour in Carus (2004), the only nephelometers to record any smoke at all were in Sweet Home and Lyons. The smoke impact is reported as light (no impact to visibility), moderate (12 miles visibility), or heavy (5 miles visibility). Since 2002, about 2/3 of the measured smoke impact is light and 1/3 is moderate. Obviously, there are other areas that would have been affected by smoke and not measured, but there is no way that field burning smoke, measured at about 2% of air pollution each summer, is today a major problem.
The annual summary reports also list the number of complaints broken down by city. Unfortunately, they are not broken down by day so that they can be cross-referenced to see if there was even any open field burning on that day. Eugene, who remember has only had 2 hours of measurable smoke since 2002 and none in the last 2 years, is consistently a top complainer, registering 134 of 463 total complaints in 2008 and 368 of 776 in 2007. Sweet Home and Lyons, in comparison, have relatively few complaints.
The field burning ban will force farmers to use more pesticides and increase ground tillage, expanding even more the summer haze of dust that now comprises 80% of summer air pollution. Even with these more expensive measures, crops will not grow as cleanly and some farmers will be driven out of business.