Wichita ? Millions of U.S. acres will no longer be part of a program that pays farmers not to plant crops, opening up new options for growers and raising environmental concerns.

About 4 million acres will be taken out of the Conservation Reserve Program on Sept. 20, many of them in the High Plains of eastern Colorado, western Kansas, Oklahoma and Texas, the Agriculture Department’s Farm Service Agency said Friday.

Regulations in the new farm bill mean about 2.5 million acres can’t be re-enrolled. Under the $2 billion-a-year federal program, the fields have been returned to native vegetation.

About 100,000 of the 4 million acres set to expire are considered environmentally sensitive, acting as buffer zones or filter strips to safeguard water quality, wildlife and tree plantings while protecting the land from soil erosion.

In Kansas, nearly 435,906 acres are set to expire, including 10,786 acres of environmentally sensitive land.

Most expiring acres could have been re-enrolled in the program before, but the new farm bill capped CRP acres at 32 million. That means the Agriculture Department can extend contracts on 1.5 million of the expiring acres, the agency said.

The Farm Service Agency in Kansas is offering three- or five-year contract extensions to those landowners whose acreage is considered to be the most environmentally sensitive. About 129,000 Kansas acres are eligible for extensions.

Rod Winkler, program specialist for the Farm Service Agency in Manhattan, said the contract extensions were being offered because government, wildlife and environmental groups were concerned about the huge number of acres coming out of CRP at the same time.

Winkler said it is still too early to tell how many farmers will be interested in re-enrolling acres, but he anticipated a good percentage of the western Kansas landowners would do so.

“When commodity prices jettisoned up last summer, there was a lot more interest, or a lot more talk or discussion I guess I should say, about these acres flowing out of the program. We didn’t see that. We did see a very small number flow out, but we didn’t see the overall outflow that everyone was scared of.”

He attributed that partly to drought that has been going on for a number of years in western Kansas and the fact that crop prices didn’t stay high for very long.