The summer harvest was over.

Watching a machine crush the wheat stubble in the field, Gao Chengli recalled the days when he was choked by smoke from burning straw and wary of local officials' scrutiny.

"We didn't get it at first," said the 40-year-old Gao, referring to China's ban on burning waste stalks, which began in 1999.

"Farmers even set fires secretly because it was convenient."

In the run-up to the Olympics, Chinese farmers like Gao have shifted from matches to machines as the government strives to keep Beijing from being smothered by smoke.

Officials are using many approaches, ranging from the carrot of subsidies and the stick of fines to satellite monitoring and straw-to-power projects.

Beijing farmers had adopted the conservation farming approach, which leaves stubble in the soil to increase organic matter, on more than 80 percent of all farm land since 2006, said the Ministry of Agriculture on Monday.

"The achievement was significant for reducing dust in Beijing, cutting straw burning and improving the capital's environment for the Olympics," the ministry quoted Minister Sun Zhengcai as saying in a statement.

Straw burning in the Beijing suburbs, which extend far beyond the city center, used to cause thick smog in the capital proper, closing highways and disrupting airport operations.

Smoke from the farms south of Beijing was blown north last June, polluting the capital's sky for days.

For Gao, who owns about 0.38 acres of land in Zhengding County, Hebei Province, which borders Beijing, the solution was a crushing machine organized by the township government.

In Beizaoxian, another town in the county, 200,000 yuan (28,571 U.S. dollars) was allocated by the township government to subsidize farmers' purchase of farm machines, including the stubble-crushing machine.

"Farmers have gradually come to understand the harm of burning waste straw and voluntarily adopted crushing," said Zheng Wei, an official with the Zhengding government.

In some parts of China, the issue turned bitter for local officials. Four town-level officials were suspended last week for not doing enough to stop straw burning in Xi'an, capital of the northwestern Shaanxi Province.

To keep the sky clear for the Olympics, the central government expanded the no-straw-burning areas in May and imposed a full-scale ban in Beijing and eight regions neighboring or south of the city through September.

The China Meteorological Administration said that satellite monitoring picked up 1,762 fires set on farm land from June 2 to 15, down 22 percent from the period between June 4 and 17 last year.

Satellite technology was introduced in 2004 in an effort to reduce the outlawed practice of straw burning, and this system of monitoring detected 2,989 fires in 2007, up from 2,481 in 2004.

"Farmers had their own reasons." said professor Cheng Xu of the China Agricultural University (CAU).

Cheng said that farmers often had little time to clear the land of one crop before having to plant another, so fire was often the fastest option.

China's agricultural areas saw about 700 million tons of waste straw left after harvests each year.

By the end of 2007, mechanical stubble crushing had been applied on 327 million mu (21.8 million hectares) of farm land, about one sixth of the country's total, according to the ministry.

"About 30 percent of China's waste straw goes unused," said another CAU professor, Meng Qingxiang. "The waste straw is not 'waste' at all but a precious resource, and we must let people know that."

Straw has several uses, including livestock feed, methane production, a source of solid fuel or electricity generation, said Cheng.

Li Jing, deputy head of the National Development and Reform Commission's (NDRC's) resource conservation and environmental protection department, urged China to speed up the comprehensive use of waste straw.

China is considering ways to use more than 80 percent of its waste straw by 2015, according to officials with the NDRC.

(Xinhua News Agency June 25, 2008)