President-elect Ronald Reagan reportedly has settled on Illinois farm official and farming entrepreneur John R. Block to be the next secretary of agriculture.

Sen. Bob Dole (R-Kan.), who had vigorously promoted Block's candidacy,, said yesterday the appointment looked pretty certain based on unofficial reports from the Reagan camp. Block phoned him after an apparently decisive meeting with Reagan in California Friday, Dole said, adding that Block was "very excited" and has made plans to come to Washington Monday, presumably for the formal announcement.

Reagan transition team officials yesterday refused to confirm published reports in the New York Times and the Washington Star that Block definitely has been chosen over the other top contender, Richard Lyng, who was being pushed for the post by trade groups, some members of Congress and former agriculture secretary Earl Butz.

Block, 45, a West Point graduate who became a successful large-scale farmer and is now the Illinois state director of agriculture, is a "real live producer" who practices "hands-on" farming, according to Dole. He is also the only midwesterner appointed so far to the Reagan Cabinet, which Dole said was probably an important factor in the selection.

Block's candidacy raised concern on the part of Sen. Jesse Helms (R-N.C.), the likely new chairman of the Senate Agriculture Committee, according to one report. This report suggested that Helms was worried that Block might not be sufficiently sympathetic to the needs of southern agriculture, which continues to depend on generous government subsidies for such crops as tobacco, peanuts and cotton.

Block runs a 3,000-acre corn, soybean and hog farm near Gilson, Ill., which he had expended from its original 700 acres since the early 1960s."He even runs in the Boston marathon," Dole said gleefully. "He's a fresh face. eHe's had no other administration experience so he'll be a Reagan man."

Block has established a good record in Illinois, from the farmers' point of view, on soil conservation, preservation of farmlands and other issues.

He is expected to draw some fire from consumer groups for his positions in favor of higher price supports for farm products and against any more than minimal government interference in such issues as meat safety and nutritional policy. His is a "down-the-line, vested-interest position," according to a representative of one Washington comsumer group.

Regarding the controversy over the use of nitrates in pork as a preservative, Block is on record with sharp criticism of federal regulators, calling the well-publicized inquiry into the cancer-causing properties of the substance "an almost ridiculous charade" that proved unnecessarily costly and unfair to farmers.

He offered in that context the results of tests he said were conducted recently by Southern Illinois University showing that "vitamin D is extremely carcinogenic [cancer-causing] and yet we put it in milk."

Block also has opposed the issuance by the Agricutlure Department of guidelines to schools for lunch menus. Those guidelines are already in the works.

And on the subject of the food stamp program, which is administered by Agriculture, Block has said he is "not opposed in principle but . . . it's really getting out of hand." The program's rate of growth, he said, must be halted.

Some consumer groups have said they view Lyng as more accessible to them, a man with Washington experience who they could work with even though they often disagree with him.

Lyng previously served Reagan as California's director of agriculture. His most recent Washington service was as a representative of the meat-packing industry. He has drawn support from factions in the industry who favor someone more attuned to the needs of processors, the grain industry and agribusiness in general than to the needs of the farmers.

Based on his approach in his state job, Block favors maximum emphasis on agricultural trade and exports. He has promoted food exports in Illinois and points out that his state is the nation's largest exporter of agricultural products.