The protesting farmers say their demands are simple.

They say the federal government should take steps immediately to increase their income to offset what they say are the higher costs of producing food.

Their central demand is for farm price supports to be increased to 90 percent of parity, a figure based on farmers' buying power between 1910 and 1914.

Such an increase would raise corn prices to around $3.50 a bushel and wheat prices to more than $5 a bushel. Corn sold last week in Chicago for $2.34 a bushel and wheat went in Kansas City for $3.50 a bushel.

The 1977 farm legislation passed by Congress authorized the secretary of agriculture to raise price supports to as much as 100 percent of parity. However, Congress added a number of conditions that had to be met before that could be done.

The law says that price supports cannot be increased above their present levels if such a step made U.S. corn less competitive in world markets, or made U.S. wheat less competitive than other grains in U.S. and world markets.

Changes in cotton price supports are required to be determined by a complex formula involving average U.S. and World prices in previous years.

Department of Agriculture economist Howard Hjort said yesterday that these conditions would make it difficult for the department to approve the stiff increases sought by the farmers without new legislation.

In addition to the parity changes for grains the farmers also want higher income supports for cane and beet sugar growers.

Also sought are changes in laws on beef imports that would reduce the imports when domestic cattle prices are low and U.S. beef production is high.