Want a new tractor? Ask Obama - he'll pay half

California farmers and ranchers are helping lower air pollution in the San Joaquin Valley and other smog-laden regions by embracing a federal program that replaces old diesel tractors with cleaner-running farm equipment. In the last two years, the U.S. Department of Agriculture's Natural Resources Conservation Service has helped farmers replace 814 aging machines with more modern equipment. Federal officials say next year they will invest $24 million in the program, which splits the cost of upgrading equipment with owners...more