Economists always like to talk about the ideal situation of perfectly competitive markets. This is the world in which there are vast numbers of buyers and sellers so that no individual buyer or seller can affect the price. In this world, every producer is a price taker. This means that the price is set by the market, and they can sell as much as they want to produce at the prevailing market price.
In the real world, this is not an accurate description of most markets, which have a relatively limited number of sellers. The one market that does seem to fit the competitive story reasonably well is agriculture. Farmers see a price in the market for corn, wheat, soybeans, etc. and they can sell as much as they choose at this price.
Unfortunately, the Post apparently does not believe that agriculture is a competitive market. It reports today that the United States is trying to open up markets in developing countries in order to give U.S. farmers something to offset the loss of subsidies in a new W.T.O. agreement. Sorry, this doesn't make any sense.
Farmers can already sell all they want in the market today at the prevailing price. It is unlikely that farmers will feel any better if the wheat they sell at $2.50 a bushel is going to Zambia than if it's going to Pennsylvania.
Perhaps the article meant that by opening up markets in Zambia, and other developing countries, the price of wheat would rise. It doesn't seem very likely that the new markets would produce any substantial rise in price (the new entrants would be relatively small compared to the existing world market), but this would be a qualitatively different effect than simply an increase in the quantity of wheat sold. It would mean that all of us would be paying more for wheat. This could lead a more efficient world market, but it would also mean higher prices for consumers in the U.S. If this is the intended outcome from an new W.T.O. agreement, shouldn't the Post be telling its readers?