Wichita ? The effectiveness of a new plan to manage smoke from the annual spring prairie burning in the Flint Hills is being questioned after smoke from some planned burns drifted over Wichita in late March.

The haze in Wichita on March 24-25 will be discussed when the new smoke management plan is analyzed at the end of April, The Wichita Eagle reported Monday.

“We’ll go back and do a post-mortem analysis of what happened during this burn season once it’s over,” said Josh Tapp of the smoke management division of the Environmental Protection Agency. “We’ll collect all the data and evaluate if the smoke plan is being effective or needs to be revised or improved.”

Ranchers’ annual burning of the prairie prevents trees and invading plants from growing in the grass, improves productivity of the rangeland and helps cattle who feed on the grass.

The Flint Hills Smoke Management Plan is a pilot project that allows the ranchers to continue their planned burns but with restrictions designed to prevent smoke from drifting and increasing ozone levels in urban areas, particularly Kansas City and Wichita. The cities could face new regulations if ozone levels consistently are above the recommended levels.

“Unfortunately, right off the bat, it didn’t work,” said Mike Holder, a Chase County extension agent who helped coordinate the plan. “We’ve yet to see whether this will work all the time.”

The smoke management plan, approved in December by the Kansas Department of Health and Environment and more than 80 interested parties, allows ranchers to continue burning grasslands in the spring but restricts other burning in 12 counties in the Flint Hills and four near Kansas City and Wichita.

The plan tries to encourage people to start burning in March, Tapp said, to prevent having too many fires on any given day.

The smoke did not cause any serious health concerns in Wichita, health officials said. It raised hourly pollution readings from 20 parts per million volumes of air to 140, which is under the 150 reading the EPA considers dangerous.

Spokespeople for Via Christi Health and Wesley Medical Center said they saw no increase in patients coming to emergency rooms with respiratory problems.

The number of fires on March 24 and 25 wasn’t unusual for Kansas this time of year. On March 24, about 60 controlled burns were set in Sedgwick County, as well as others in surrounding areas. On March 25, Chase County had 19 fires burning over 20,000 acres, and Butler County — the source of most of the smoke that drifted into Wichita — had 35 controlled burns.

“Everybody is doing the best they can with this smoke management plan,” Holder said. “There will be days like (March 24-25) when even though we minimize the burning, we could have some air quality problems in urban areas.”

Agriculture experts estimate that by the end of April nearly three-quarters of the 4.5 million acres of native tallgrass prairie in the Flint Hills will be set on fire.