FRESNO — California farmers and ranchers will get $24 million in 2011 to replace aging diesel machines as part of an ongoing effort to improve air quality, federal officials said Monday.

The U.S. Department of Agriculture program splits in half the cost of buying new, cleaner-running farm engines and equipment.

In the past two years, the program has replaced 814 old tractors and other farm equipment, and reduced emissions of nitrogen oxide — a key component of smog — by 1,349 tons.

That amount is equivalent to removing 408,000 cars from California highways, said Ed Burton, state conservationist for the USDA's Natural Resources Conservation Service.

Demand for the program has overwhelmed available funding over the past two years. During that time, the NRCS received more than 5,000 applications to replace diesel engines but was able to fund only 814, at a cost of $43.4 million.

"The fact that landowners were stacked up seven deep for available funding indicates the strong ethic to improve air quality in California," Burton said.

Dairy farmers Dan Souza and his sister, Sandra Tavares — operators of Souza Dairy in Fresno County — used the federal program to replace two older front-end loaders with one newer model. The family saved $63,000.

"The new machine does the work of two machines, and it runs much more efficiently," Tavares said.

San Joaquin Valley Air Pollution Control District officials see this as helping to reduce smog significantly.

"We are well on our way to having one of the cleanest fleets of farm vehicles in farming," said Rick McVaigh, deputy air pollution control officer.

U.S. Rep. Jim Costa, D-Fresno said he and other valley elected officials will keep pushing for funding the program that was part of the 2008 Farm Bill.

The program aims to help farmers and ranchers achieve air-quality conditions set by the National Ambient Air Quality Standards.

Producers in 36 California counties that are not in compliance with one or more of these standards are eligible for the program.