PepsiCo Inc. yesterday announced it will contribute $1 million over the next decade to the United Negro College Fund. It is the largest multiyear corporate donation ever pledged to the fund's annual campaign.

"President Reagan has challenged private enterprise to help offset reductions in financial aid that were necessary at the federal level," Donald M. Kendall, chairman of both PepsiCo and the U.S. Chamber of Commerce, said at a ceremony yesterday at chamber headquarters.

Students at the 41 private, historically black colleges supported by the fund will lose at least $3.9 million in scholarships and aid as a result of Reagan administration budget cuts, a fund spokesman said.

More than half the 50,000 students come from families that earn less than $12,000 annually. "Any reduction in student aid hit these colleges very hard," said Christopher F. Edley, director of the fund.

The fund, founded in 1944, expects to raise a record $21 million this year, with 40 percent of the contributions coming from the private sector. In years past, PepsiCo had been contributing $25,000 a year to the fund.

"I hope Pepsi's grant will encourage still other companies to raise the levels of their own charitable contributions," Kendall said.

Meanwhile, the Exxon Education Foundation, which committed itself two months ago to giving $15 million to support engineering education at 66 American colleges, announced that it would also give $1.8 million to engineering schools at six traditionally black colleges.

The grants will amount to $100,000 a year for three years, beginning in 1982, to support faculty development, the foundation said in New York.

Recipients will be Howard University of Washington, D.C.; North Carolina A&T in Greensboro; Prairie View A&M in Prairie View, Tex.; Southern University in Baton Rouge, La.; Tennessee State in Nashville, and Tuskegee Institute in Tuskegee, Ala.