South Africa on edge

White South Africa is worried, and with reason. Last week's official ban on black protest meetings acknowledged the extent of the government's concern that this month's episode of violence by Africans could spread, gain momentum, and assume serious proportions.

Approximately 40 Africans, the most since 1976-77, have been killed since the beginning of September in a succession of violent protests directed at the newly installed white government of President Pieter W. Botha, at white-appointed black officials in the African townships or ghettos, against recent rent increases in the townships, and generally against the meaninglessness for Africans of the political reforms recently introduced for Coloreds (peoples of mixed descent) and Asians.

Nearly 4.6 million white South Africans rule 22 million Africans, 2.6 million Coloreds, and 8 million Asians. Last week Mr. Botha, previously prime minister, was installed as the country's first executive president; this week the new tricameral Parliament sits for the first time, 160 whites voting in one chamber, 80 Coloreds in another, and 40 Asians in a third.

Last month Colored and Asian representatives were chosen in separate elections. Fewer than 30 percent of the registered voters, and fewer than 20 percent of the eligible voters, cast ballots. The white chamber carried over from the country's former legislature.

South Africa's police and Army have overwhelming firepower, and can thus contain and, if they wish to risk heavy casualties, end violent protest movements in individual townships. But taking that course would forfeit whatever positive results the government has achieved locally and worldwide following its devolution of some power to Coloreds and Asians. Massacre headlines would alarm the world, and also upset the United States during the presidential election season. South Africa is very eager that President Reagan win a second term.

Banning meetings and public gatherings, even funerals for riot victims, stops just short of a declaration of public emergency. Black high schools, a focus of discontent and rage, have also been closed. Shortly the government may need to rescind the rent increases, which have added up to 25 percent to the already heavy burden poorly paid Africans bear in recessionary South Africa.

Thus far the riots have largely been confined to hardscrabble black townships near Vereeniging, south of Johannesburg, and several smaller ones east and west of Johannesburg. The 1.5 million people of Soweto, the largest black city in the country and the main labor reservoir for Johannesburg and adjacent gold mines, have not erupted into violence as they did in 1976.

But residents of Soweto dislike their local black officials - the clients of the white government, or ''stooges,'' as they are called - as much as the recent rioters of Sharpeville, Tembisa, and Sebokeng. They have also been upset by rent increases. And for a year schoolchildren in Tembisa and near Pretoria have been protesting third-rate facilities and poor teaching, boycotting classes for those and more political reasons.

South Africa is thus ripe for more widespread revolt. The precipitating factor was the heavy-handed final inauguration of the new Constitution and Parliament. It worsens the position of Africans, as conceivably it may ultimately benefit Coloreds and Asians, although only positive results will make that case. It also denigrates Africans, denying them any form of national political participation while giving Coloreds and Asians a little.

Even if the revolt spreads, it need not add up to a revolution. White South Africa is too strong, and it is determined to retain power and survive. But when Africans have protested militantly they have won concessions.

They have obtained significant modifications of apartheid when their protest has been supported by Western diplomatic pressure. Thus, only if the Reagan administration now chooses to stiffen its attitude to white South Africa, and wishes to turn the events in South Africa to Washington's advantage, will this month's desperate attacks by Africans achieve much in the way of desirable social, economic, or political betterment.