Rationing
Rationing is the act of intentionally using a good in an amount that would be less than normal. Sometimes it is a personal decision, sometimes it is imposed upon a person or group. The most well known incidents of rationing in the United States would be the rationing of gas during the oil crisis of the 1970s and the rationing of World War II.
Speech Relevance
From 'Encroaching Control':
But what is being proposed in Washington, well a farm program is being lobbied which says the only answer to the farm problem is to take the 80% of free agriculture into a program of government regimentation, requiring the licensing of every farm in the United States, requiring the government establishment of production quotas and prices. And then they frankly admit this will mean the employment of thousands and thousands of new employees in the agricultural department, a permanent government subsidy and the raising of food prices between 15 and 25%. And in order to do this, they admit they will also create, artificially, a shortage of foodstuffs to the point that meat alone will be in supply about equal to what we knew under rationing in World War II. Thomas Jefferson said, "If we let Washington tell us when to sow and when to reap, the nation shall soon want for bread."
World War II was such a massive undertaking for all involved that certain goods or materials couldn't be produced fast enough. Rubber, nylon, steel, gas and certain kinds of food were deemed necessary for the war effort and, thus, rationed for civilians. Reagan is saying that greater government intervention into agriculture would reduce output to the point that the people would feel like they were back in the 1940s.