Excerpts: Improved technology in agriculture has had a major influence on the size of the corn crop and on the competitive position of corn in farming systems. On some soils, farmers have found it profitable to substitute commercial nitrogen for legumes and to maintain a higher percentage of the land in corn. Increased use of fertilizer has taken the form of higher rates, higher percentages of acreages fertilized within areas, and extension of use to new areas (table 1). Use of fertilizer on corn in the United States has expanded markedly in recent years but considerably higher rates of application would be profit able on most farms in the principal corn-producing areas. In the Corn Belt, at projected crop price-fertilizer cost relationships used in this analysis, rates per acre could be increased nearly threefold before passing the point of minimum total cost of production per bushel. The corn crop estimated as needed by 1975 could be produced on fewer acres than were harvested during the World War II years of 1943 and 1944, if fertilizer were applied on the same acreage that was fertilized in 1954 at rates that would result in a marginal, return of $2.50. For the Corn Belt, this rate would be associated with minimum cost of production per bushel. In terms of plant nutrients, fertilizer used on corn would need to be about double that applied in 1954.