Nitrogen Fertilizer Source, and Method and Time of Application Effects on No‐till Corn Yields and Nitrogen Uptakes1

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Abstract
The increasing use of both no‐tillage corn (Zea mays L.) production and urea‐containing fertilizers makes it imperative that we develop management strategies that maximize economic return from applications of these fertilizers to no‐till corn. A 3‐yr experiment was conducted on a Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludult) to determine the relative efficiencies (yield and N uptake per unit of N applied) of three common N sources [NH4NO3 (AN), urea, and urea‐ammonium nitrate solution (UAN)] used on no‐till corn. They were applied either as a surface band or as an injected band at or near the time of planting, or as a sidedress 26 to 31 days after plant emergence. Surface‐banded AN, injected AN, and injected urea all produced similar no‐till corn yields and N uptakes. The apparent NH3 volatilization loss from surface‐banded urea was strongly influenced by the number of days after application until a total of 10 mm of rain fell. Apparent losses ranged from less than 50 g kg−1 of applied N with 10 mm of rainfall within 2 to 3 days after application, to over 300 g kg−1 with 5 to 7 days of dry weather after application. Both surface‐banded and injected UAN were less efficient than AN or injected urea. Sidedress applications of N resulted in more efficient N fertilizer utilization with all sources, but particularly with urea‐containing sources. Shorter rain‐free periods after sidedress applications may have contributed to this effect. Surface applications of an experimental fertilizer, 3:1 urea/urea phosphate, produced greater ear‐leaf at silking N concentrations than did surface‐banded urea. Amending urea with KCI, or UAN with ammonium thiosulfate, did not result in yields, ear‐leaf N concentrations, or N uptakes significantly different from those obtained with their unamended surface‐applied counterparts in the one year that each was tested.