Zambia's economic blockade of the white-dominated biracial government of neighboring Rhodesia has ironically resulted in its own economic strangulation and face-losing surrender to the hard realities of a landlocked central African country.

President Kenneth Kaunda's controversial decision earlier this month to reopen Zambia's southern route to the Indian Ocean through Rhodesia and South Africa, after a nearly six-year boycott, was taken as it became clear that the country stood to reap a disastrously small corn harvest next spring if at least 90,000 tons of a total 170,000 tons of essential fertilizers did not reach Zambia farmers before the rains begin next month.

The decision came in the midst of growing Zambian discontent over the never ending half-empty shelves in food stores throughtout Zambia and just two months before a general and presidential election that threatens to see an embarrassingly small turnout of voters to reelect Kaunda for another five-year term.

However, it now appears the Zambian decision to reopen its southern route has come to late to get the fertilizer here in time anyway, raising the likelihood of a serious shortage of the essential staple corn crop next year.

Meanwhile, the decision has greatly angered both Rhodesia's nationalist guerrillas, now aiming more than ever to cut Rhodesia's communication lines, and Zambia's two most important so-caled frontline allies, Tanzania and Mozambique. More importantly, the decision deepens the already evident rift among all five front-line states involved in the Rhodesia dispute and to isolate Zambia politically.

Simply put, Zambia reached the end of its economic and political thether before Rhodesia did. While the Rhodesians learned to turn the adversity of United Nations sanctions into a powerful stinulus, for development, the Zambians failed to do as much in the face of a similar economic trial.

Instead, Zambia has succumbed to a combination of fallen copper prices, gross mismanagement of its domestic economy and an acute lack of outlets to the sea. Even the Chinese-built, 1000-mile "Uhuru" (freedom) railroad linking it to the Tanzanian port of Dar es Salaam could not save this country from slow economic asphyxiation.

Rhodesia has lived frugally but productively with U.N. sanctions since shortly after its unilateral declaration of independence from Britain in November 1965 and with the closing of the Zambian border since January 1973.White Rhodesian authorities have long regarded Zambia as the weak link in black Africa's economic blockade of Rhodesia and their calculations now seem largely justified.

On the other hand, Zambia has probably sacrified the most of any front-line African state by closing its border with Rhodesia and the government here calculates its economic loss at more than $1 billion over the last six years.

The decision to partially reopen its border with Rhodesia has been generally a popular one at home if not so in the rest of black Africa. "We are happy with it," was one typical Zambian reaction. "We have suffered long enough for Zimbawe". Zimbawe is the black nationalist name for Rhodesia.

Underlying Zambia's current economic crisis has been a longstanding political rivalry between Kaunda and Tanzanian leader Julius Nyerere for leadership of the five front-line states involved in the Rhodesia dispute.

Zambia and Tanzania have been trading charges over the Chinese-built TAZARA (Tanzanian-Zambian) Railroad for months now, imputing political motives to the noticeable lack of cooperation between the two countries in getting the new rail link to work at full capacity. Both have come up with solid evidence of the failings of the other, suggesting the blame can probabily be shared about equally for the congestion at the Dar es Salaam port and the poor performance of the new rail line.

Since the closure of Angola's Benguela Railroad during that country's 1975-76 civil war, Zambia has had no other rail link to the sea other than the TAZARA.

The fertilizer crisis now plaguing Zambia has been in the making since early last spring. The Zambian government first began negotiations with Mozambique in March for the shipment of 235,000 tons of various vital commodities through their port, rail and road network. The possible use of Dar es Salaam was apparently excluded from the beginning because of the existing backlog of Zambian cargo.

More than 60,000 of the 170,000 tons of fertilizer was bought in the United States under a $30 million import loan. The rest came from Japan and European countries under similar arrangements.

From the outset, Zambia was months behind in making its purchases and arrangements for getting the fertilizer into the country on time. Normally, it should have been here six months before the rains begin several weeks from now, according to Western Economists here.

Mozambican authorities said the Zambians proposed to bring 32,000 tons of fertilizer a month by rail and road from the Mozambican port of Beira into Zambia and 7,000 tons of it via Malawi.

But by mid-April, the Zambians already reportedly realized this would never work because of their own inability to truck more than 10,000 tons a month from the Mozambican railhead of Moatize.

Apparently well informed about the gathering fertilizer crisis the Rhodesians, at the end of August, ambushed the road leading from Moatize in northern Mozambique into Zambia, killing two Zambian drivers and halting all traffic for three days. They also triggered shooting around Kazangula, the end of Zambia's second route through Batswana that closed down the transport ferry there repeatedly, according to the Mozambican account of what happened.

With only a few weeks before the rains begin, there are still 50,000 tons of fertilizer piled up in Beira and another 45,000 ton in Maputo. Only 32,000 tons recently rerouted from the Mozambican capital to East London in South Africa seems likely to reach Zambia in time along the reopened southern route.

Western economists here now estimate that altogether about 30 to 40 per cent of the total fertilizer needed before the rains begin will be available to farmers, meaning next year's corn crop will probably not cover the country's needs.