The soybean (Glycine max [L.] Merrill) uses both combined nitrogen from the soil and symbiotically fixed nitrogen from the air if effective nodules are present on its roots. Both sources of nitrogen are required for maximum yields at reasonable costs. In the absence of nodules, yields can be brought up to the level of those where effective nodules are present, but only with a high rate of nitrogen fertilizer application.
Hadley, Henry H. and Attiey, Koffi
"Research notes: Variation in percent seed oil in related nodulating and non-nodulating
F2 plants and F3 progenies from three soybean
Soybean Genetics Newsletter: Vol. 6
, Article 17.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol6/iss1/17