The World Bank said last week it will lend $81.2 million to five African nations, including $30 million to Tunisia to support an agricultural credit project.

The bank said the money will pay for investments by Tunisian farmers, cooperatives and agricultural industries as well as modernization and strengthening of the National Bank of Tunisia, which makes farm loans.

The bank will lend $19.7 million to Guinea to help improve the government's ability to plan health programs, prevent disease and provide basic health care to rural residents.

Niger will get $5.5 million worth of no-interest loans to back the development and administration of a government agency that promotes public enterprises.

Zaire will get a similar type of aid, totaling $11 million, to help the government develop long-term strategies for higher education. Some money will pay for studies to improve educational administration, while other cash will be used to buy university library books, textbooks and teaching equipment.

The Central African Republic's cotton industry will undergo significant changes with the help of a $15 million loan from the World Bank. The cotton market collapsed in 1985, and the loan money will be used to make the industry competitive again by helping reduce inefficiency and making the pricing system more flexible.

The bank also reported that it approved $17.6 billion worth of loans in the 12-month period ended June 30, including $292 million for rural development in Brazil.

The bank said the amount of loans rose to $14.2 billion in 1986-87, compared with $13.2 billion in fiscal 1986.

The amount of credits -- no-interest loans with generous repayment terms -- made to the world's poorest countries rose to $3.4 billion in the last fiscal year, compared with $3.1 billion in 1985-86.

The loans include five grants worth $292 million for projects designed to assist rural development projects in northeast Brazil as well as control livestock diseases in 15 states.