Postwar hybrid corn

Glenn Stone's picture

I'm investigating the breeding of fertilizer-intensive hybrid corn in the 1950s in the US.  Two questions:

One source (Steele 1978, "The hybrid corn industry in the United States") says by 1955 some hybrids were being marketed as especially bred for high plant densities.  I need to track down this marketing material -- adverts, speeches, brochures, anything. 

I need a good source on the details of this breeding effort: which entities were doing the breeding, what lines were they using, who was paying for it, what were the first products put on the market, etc.  I'm sure there is a good source on this but I can't seem to find it.  The info I want is not in Kloppenburg, Fitzgerald, Steele.

Any leads appreciated

Glenn Stone