You can expect a larger yield of corn following a soybean crop than if the field had been in corn the previous year with conditions as they were in 1942.
Norum, Enoch B.
"Do Beans Hurt the Soil?,"
Farm Science Reporter: Vol. 4
, Article 4.
Available at: http://lib.dr.iastate.edu/farmsciencereporter/vol4/iss1/4