In the world of poverty, one law is constant: when the rich tire of sharing with the poor, let the shoulders of other poor strap the load. This appears to be happening again.

As part of the House-passed legislation that would give the Nicaraguan contras $100 million to continue murdering civilians and burning farms, another $300 million is to be given for unspecified economic development in El Salvador, Honduras, Guatemala and Costa Rica.

The $300 million would be transferred from African famine-relief programs and Food for Peace. "Transfer" is the polite word. Raid is more like it. Africa's food-short nations, where quiet deaths from starvation provided the western media with the international news story of 1985, have had most of their emergency bins filled. But there is no greening of the Sahel, no stopping of the desert's advance in countries like Niger, no easing of the locust plague in Gambia, Chad and Senegal, no rains to end Botswana's fifth year of drought, and no denying that, although the response of donor nations has been large, thousands of African communities remain in critical condition because of health, agricultural, water and transportation needs. Postemergency Africa remains critical Africa.

To transfer unspent famine-relief and Food for Peace money from Africa is, first, a kick in the hollowed ribs of that continent's hungry. It also increases the imbalance that now exists. The Congressional Research Service for the Library of Congress reports that American aid per capita to Africa in 1985 was $3.83 (slightly more than a penny a day), while per capita aid for Central America totaled $51.20. For 1981-85, the growth rate for aid to Africa was 19 percent, for Central America more than 400 percent.

Little of this was discussed in the House when the contra handout was debated. The language in the bill that provided for the $300 million to Central America was, as they say, "little-noticed." It's being noticed now, though. Several farm-state senators, led by John Melcher (D-Mont.), have announced plans to alert the Senate that the Reagan administration is deviously abandoning Africa's hungry in favor of bankrolling a political agenda for Central America. Food for peace is becoming food for politics. Melcher intends to offer an amendment blocking the $300 million transfer when the Senate takes up the contra bill.

The concern of the farm-state senators is that a closed African market means a lost export opportunity for American farmers. Melcher points out that "last month saw agricultural imports exceed agricultural exports for the first time in nearly two decades." When Willie Nelson sings "On the Road Again" on behalf of Farm Aid, the money he is raising compensates in a small way for the larger sums being lost because farmers lack outlets to sell food to programs for the hungry. July is the preharvest month when final applications are made for Food for Peace purposes, but if the money is in doubt, as it is with the Senate yet to vote, then farmers will naturally feel further impoverished with no export guarantee.

Others besides Melcher are opposed to the $300 million transfer. Bread for the World, a Washington public-interest group that lobbies for the world's hungry, argues that even if Africans did not need the aid the question would remain: What will the money be used for in Central America? Congress doesn't know and the proposed legislation doesn't say. The administration has earned no one's trust on the issue of getting money to the people it is intended for, if the well-publicized corruption surrounding the last shipment of money to the contras says anything.

Three of the four Central American governments in line for the $300 million remain black holes of violence. In Guatemala, with six months of a civilian reform-minded president, a continuing run of political assassinations and disappearances suggests that the army and security forces have not backed off.

Honduras is Fort Benning South. More than 1,000 U.S. soldiers are stationed at Palmerola Air Base. Five airfields -- as well as warehouses and other Pentagon projects included in the $288 million in U.S. military aid since 1981 -- are turning the country into the ideal staging ground for combat should the Reagan administration be overcome with the war impulse that led to Grenada and Libya.

El Salvador is still El Salvador, burdened with a weak president, a ruthless military and a civil war with no end in sight.

In a ranking of 17 industrial nations based on foreign aid as a percentage of the GNP, the United States, with 0.24 percent, ranks last. This absence of generosity to the world's poor is one shame. The proposed hustle to take money from Africa's hungry to bolster the Reagan agenda for Central America is another.