Optimizing Nitrogen Application Timing in No‐Till Soft Red Winter Wheat

As no‐till acreage increases, N management guidelines need re‐examination due to the potential effects of surface residue on N transformations and crop development. Our objectives were to determine: (i) if N applied at Zadok's Growth Stage (GS) 25 improves grain yield of no‐till winter wheat ( Triticum aestivum L.), (ii) if any yield increase was the result of increased spring tillering, and (iii) if there is a critical tiller density above which N application at GS‐25 in no‐till wheat was not required. Research was conducted at three sites in North Carolina with seven site‐years between fall 1996 and spring 1999. A continuum of GS‐25 tiller densities was generated (161‐1774 tillers m −2 ) by planting at different seeding rates and dates in a randomized complete block design. Five N treatments were applied at GS‐25, and three were applied at GS‐30. Tillering response to early spring N, yield, and yield components were measured. increasing early spring N rates resulted in higher tiller densities at GS‐30, and GS‐25 tiller density was a significant covariate. With GS‐25 tiller densities >550 tillers m −2 , yields were higher when all N was applied at GS‐30. In years without spring freezes, wheat with <550 tillers m −2 achieved optimum yields when spring N was applied at GS‐25. Manipulating the timing of spring N application can optimize early spring tillering and yield component formation.