ALMOST 20 years ago, the biggest movement of food between two nations in history took place when the United States used 600 ships to provide India with grain.
The monsoons had failed in India in 1965-66, and the country was desperate.
Today India is self-sufficient in grain. The reasons: more incentives to farmers, better weather, thousands of new irrigation wells in the Ganges Plain - and a Green Revolution which produced new ''miracle'' hybrid seeds, and new chemical fertilizers by the ton to boost their yield.
The Green Revolution also lifted Latin American food production. But so far the revolution has not come to Africa. Why?
* African conditions are poorer and more diverse.
Sub-Saharan Africa alone is three times as large as the United States. It contains some 46 countries ranging in population from a few hundred thousand to 90 million (Nigeria).
* Extended drought in the Sahel and down the length of East Africa has dried up water tables, blighted crops and lifted valuable topsoil into dust clouds of erosion. Still-high petroleum prices make it difficult for African countries, deep in foreign debt, to buy petroleum-based chemical fertilizers.
* India and Latin America have large numbers of trained manager-class civil servants; Africa does not. Even simple record-keeping and accounting skills are often lacking.
* African populations are rising so fast - ''the fastest growth of any continent in history,'' according to Lester Brown of the Worldwatch Foundation in Washington - that food gains are being wiped out.
* Too many nations have preferred ''show'' projects such as dams and highways rather than promoting agricultural reforms and incentives.
* Farming methods are still primitive even in relatively advanced nations such as Kenya, where 84 percent of all cropland is cultivated by hand, usually by women using digging sticks and hand hoes. Twelve percent of Kenyan land is worked by oxen. Only 4 percent is tilled by tractor.
* Soil is poor in many areas. No Ice Age enriched it eons ago. Overgrazing and erosion are frequent in the Sahel, in Ethiopia, and elsewhere.
* Twenty-seven of the UN's 37 ''least-developed'' countries are in Africa. Twenty-six African countries earn more than half their foreign exchange on a single mineral or export crop, for which prices are now low.
Thirty-seven countries depend on one or two items for as much as 80 percent of overseas earnings. By the late 1970s, 75 percent of Senegal's export earnings came from peanuts, and four-fifths of Chad's were generated by raw cotton.
* Average sub-Saharan per capita income in 1982 was $491 a year. Lowest was Chad ($80). Highest was Gabon ($4,000), then Mauritius ($1,242). Nigeria, where one in every five sub-Saharan Africans live, was $860.
(Western Europe averages $12,000 a year and the US in 1982 was $13,160. India was only $260 because of its huge population of 750 million, but was self-sufficient in food).
* Urgently needed to generate an African Green Revolution:
l. More basic research into high-yield, drought-resistant sorghum and millet seeds. Promising work is being done in Ibadan, Nigeria, at the International Institute for Tropical Agriculture (IITA) into new farming systems and on improvements in rice, maize, cowpeas, yams, sweet potatoes, and cassava.
2. Better training of farmers, as the US and the World Bank are trying to do.
3. Fewer rigid government monopolies on buying and selling food, and more private initiative.
4. More incentives to farmers to grow subsistence food as well as cash crops for export.
5. Better farm management on a continent where agriculture still employs more than 70 percent of the population.
6. More irrigation canals, but only if Africans can be trained to manage and maintain them. Irrigation is expensive. The failure and under-use rate of African projects is high, donors ruefully report.