The farm financial crisis continues to close in on the business partners of Secretary John R. Block back in Knox County, Ill.

This time it involves Rolland E. Main, who has filed for protection from creditors under the federal bankruptcy code. Main's petition for protection while he reorganizes his business listed debts of $2.78 million.

Main, recognized as an Illinois Master Farmer in 1977 for his farming skills, is also the trus- tee of a blind trust that Block set up last year when his own financial troubles were making news. Block said at the time that he was attempting to remove himself from some of his complex business partnerships.

Earlier, Block partner John W. Curry filed for bankruptcy protection. Curry became a front-page figure last year when he obtained a $400,000 emergency loan from the Farmers Home Administration, which is under Block's control.

The loan stirred up a political storm, with legislators such as Sen. Tom Harkin (D-Iowa), then a House member, charging that Curry got favored treatment. But Block denied knowing about or having any role in the loan and survived that flap.

Curry, however, later was unable to repay the loan and moved in the bankruptcy court to insulate himself from efforts by the FmHA and other creditors to collect on his debts. Meanwhile, he is helping make ends meet by advising other farmers on ways to deal with bankruptcy.

FAMILY INC. . . . Yes, department researchers say, there are more corporate farms than ever before, but they are not the kind of giant absentee-owner operations popularly believed to be threatening to take control of the nation's food production.

Between 1974 and 1982, the number of corporate farms rose from 1.7 percent to 2.7 percent, mostly because more and more farm families found incorporation advantageous for tax and estate-planning reasons.

But the report said there actually was a decline in nonfamily corporate operations during that same period and their share of total farm production fell dramatically from 9.1 percent to 6.5 percent. Nonfamily corporate farms made up 0.4 percent of total farms in 1974; 0.3 percent in 1982.