A Frederick County, Md., dairy farmer has plastered an antinuclear missile message on his highest field in an effort to sway presidential policy.

Joel Anderson, a 30-year-old history graduate of Hood College who farms 450 acres, wrote "STOP MX" in 100-foot letters of lime on Saturday.

He said helicopters apparently carrying President Reagan to Camp David occasionally fly over his farm, which is near Thurmont, and he hopes Reagan sees the message on one of his weekend jaunts.

"He takes different routes for security, but he often flies over these farms," Anderson said yesterday. "Sooner or later he'll fly over that field. I don't know if the sign will still be there, but it's going to be there until April, anyway, when I plant corn."

Anderson said he sees "a direct connection between the U.S. deficit and farm problems."

"At the same time the administration is supporting the MX missile, Reagan vetoes a farm relief bill as a budget-buster. In my view, the MX is basically a boondoggle."

Anderson, a member of the Frederick County Nuclear Weapons Freeze Campaign, said he wrote "Freeze Now" in a field last year, but he formed the letters with barley plants and they didn't show up well against the brown soil.

This year, he made the letters of thick white lime, 100 feet high and 50 feet wide, and they show up perfectly, he said.

A government spokesman said the president's travel routes and schedules are not publicly discussed, but as far as he knew Reagan has not seen the message.

Anderson said the massive application of lime will not harm his farm. "Lime's good for the soil," he said.