An analysis of all known research (100 studies from around the world) that reported corn yields, N rates, plant densities, and whole-plant N uptake was performed to compare “Old” (1940 to 1990) versus “New” (1991 to 2011) corn hybrids for their yield relationship to whole-plant N uptake, and their associated N use efficiency (NUE). This summary confirmed that NUE gains in “New” hybrids were primarily achieved by increased grain yields per unit of N stored in the plant at maturity. The accompanying reduction in grain N concentrations over time suggests that future NUE progress in corn should not overlook nutritional quality of the resulting grains
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