Monday, November 5, 2007 - 2:30 PM
101-6

Extension and Analysis of the Ramp Calibration Strip Fertilization Strategy.

D.E. Edmonds, Brian D. Arnall, B. Chung, M.C. Daft, Kefyalew Desta, C.R. Dotson, B.B. England, S.L. Holtz, Clinton Mack, William Raun, John B. Solie, Randal Taylor, B.S. Tubana, P.L. Turner, O.S. Walsh, and D.L. Zavodny. Oklahoma State University, 051 Ag Hall, Stillwater, OK 74078

The nitrogen (N) ramp calibration strip (RCS) strategy has been established for winter wheat (Triticum aestivum), but implementation into other crops has yet to be developed. The RCS is an innovative method used to determine mid-season, top-dress N application rates. Visual and/or sensor based (i.e. GreenSeeker™) analysis of the RCS can be used to determine the appropriate mid-season, top-dress N rate. This study is being conducted to implement the RCS strategy into alfalfa (Medicago sativa), bermudagrass (Cynodon dactylon), corn (Zea mays), cotton (Gossypium spp.), and grain sorghum (Sorghum bicolor), in addition to continue to refine the strategy in winter wheat production systems. RCS applicators for winter wheat systems have been developed to apply N rates at a minimum of 0 kg ha-1 stepping up by 14 kg ha-1 through 16 steps to a maximum 224 kg ha-1. Nitrogen rates for the RCS for each crop are based upon the N requirements of the crop and therefore are adjusted from the applicators rate used in winter wheat. Multiple locations in Oklahoma were used for this trial. The implementation of the RCS for mid-season N recommendations for alfalfa, bermudagrass, corn, cotton, grain sorghum, and wheat is a viable tool for applying sufficient mid-season N needs of the crop to produce maximum yields, improving the nitrogen use efficiency (NUE), lowering the environmental impact of N pollution, and reducing economic inputs.