Nitrogen and Tillage Interactions for Wheat in Alabama.

Alabama wheat (Triticum aestivum L.) farmers are changing management practices to maximize yields and reduce trips across their fields, which include adopting no-till or reduced tillage practices.  The use of different tillage practices has prompted questions about nitrogen (N) fertilizer rates and application timings.  Four locations [Tennessee Valley Research and Extension Center (TVS) in Northern AL, E.V. Smith Research Center (EVS) in Central AL, Wiregrass Research and Extension Center (WGS) in Southeast AL and Gulf Coast Research and Extension Center (GCS) in Southwest AL] were used to examine tillage practices and N rates during the 2008 - 2011 wheat growing seasons resulting in nine site-year comparisons. Each location followed cotton (Gossypium hirsutum L.) and consisted of a split plot design with tillage (conventional or non-inversion; no-till at TVS) as the main plot and twelve N fertilizer treatments that included fall applications as subplots replicated four times.  At TVS, early season tiller counts and tiller biomass were not affected by fall tillage or fall N.  On the Coastal Plain soils (EVS, GCS, and WGS), fall N consistently improved tiller counts and tiller biomass.  No-tillage (TVS) produced equivalent yields to conventional tillage, while non-inversion tillage (EVS, GCS, and WGS) produced 13% greater yields over conventional tillage across all site-years.  Wheat yields at TVS were not influenced by fall N and total N required to maximize yields was inconsistent.  However, fall N (22 kg ha^-1) was essential on the Coastal Plain soils (EVS, GCS, and WGS) followed by 78 kg N ha^-1applied early in the spring (mid-February).  These findings validate existing wheat recommendations, while improving knowledge about tillage systems for wheat production in Alabama.