Farmers, faced with low prices and a global wheat glut, are slashing wheat acreage by 10 percent this year, the government said Friday in its first gauge of the impact of the new farm policy law.

The law gives farmers more freedom to decide which crops to grow, but it also makes 15 percent of a farmer's wheat, feed grain, cotton and rice land ineligible for federal subsidies.The Agriculture Department estimated 51 million acres were sown to winter wheat, compared with 56.9 million acres planted for the 1990 crop. Winter wheat accounts for three-fourths of U.S. wheat production.

In a companion report, the department presented its final estimate of last year's harvest - 7.98 billion bushels of corn, 1.92 billion bushels of soybeans and 2.74 billion bushels of wheat. The corn and wheat figures were unchanged from a November estimate while soybeans were up 19 million bushels or 1 percent.

The wheat crop was the third largest on record and 35 percent larger than the freeze and drought-damaged 1989 crop.