Scope and method of study. Delaying sidedress nitrogen (N) fertilizer application until later in the growing season has potential for increasing nitrogen use efficiency (NUE). Delaying N fertilization would also help to determine the amount of fertilizer N needed to be applied to achieve maximum grain yields based on the crops yield potential. This two-year study was conducted in 2005 and 2006 to determine the optimum nitrogen management strategy for corn by evaluating several combinations of preplant and sidedress N fertilizer applications at various growth stages.; Findings and conclusions. Higher corn grain yields and NUE's were achieved with preplant N applications followed by mid-season sidedress fertilization at V6-V10 growth stages. Grain yields were decreased when no preplant N was applied and sidedress N fertilization was delayed until the VT growth stage. Delaying N fertilizer until mid-season supplies N at the time when the crops need for N and N uptake are at maximum, and thus facilitates more efficient N fertilizer use. Results of this study suggest that preplant N followed by mid-season sidedress N application at or before the V10 growth stage is recommended for corn.
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