Nitrogen Use Efficiency, Nitrogen Fertilizers, NUE, Nitrogen and the Environment Calibration Stamp Technology
Farmer Experiences with Calibration Stamps and the N Rich Strip
Video Link Coming Soon
Calibration Stamps for Improved Mid-Season Fertilizer N Recommendations in Corn and Wheat Production SystemsResearch Article Documenting the Application of the Calibration Stamp:
Automated Calibration Stamp Technology for Improved In-Season Nitrogen Fertilization Agronomy Journal (in press)

Calibration Strip Sprayer (David Zavodny)

Precision Ag Update, CCA 2005 (J. Solie)

 New Approach to Determing RI

Sensor Based Nitrogen Rate Calculator, Topdress and Sidedress N rates for Corn and Wheat, Nitrogen management




Calibration Stamp Technology for improving in-season fertilizer N applicationsOklahoma State University recently released the first automated calibration stamp applicator for improving in-season fertilizer N rates and ultimate Nitrogen Use Efficiency.

Accurate determination of mid-season fertilizer N rates for cereal production is complicated.  Mid-season fertilizer N is currently recommended using a wide range of soil-test and soil-N mineralization procedures, with no fundamental scientific agreement anywhere in the world on the methodology.  A conventional 2003 Honda FourTrax Foreman ES 4-wheeler (433cc, 127cm wheel base, 116cm wide) with a 3 m wide spray boom and a 1 m spacing between nozzles was modified to deliver a range of fixed N rates as urea ammonium nitrate (28%N) within a 9m2 grid.  Within each grid, 9 separate 1m2 areas exist, whereby each of the 4 corners receive no fertilizer N.  Rates of 22, 45, 67, 90, and 112 kg N ha-1 occupy the other 5, 1m2 areas within the 9m2 grid (termed as an N rate calibration stamp).   Traveling at 5 mph, consecutive 9m2 grids can be applied continuously.  The calibration stamps should be applied preplant and superimposed on top of the farmer practice.  By mid-season, differences between the 1m2 N rate areas can be visualized and a field-specific topdress N rate can be prescribed by choosing the lowest N rate where no visual differences were observed between it and the next highest rate.  Using preplant or early-season applied calibration stamps, topdress N rates can be determined that precisely account for N mineralization, and atmospheric N deposition from planting to the time mid-season N is applied.

Click here for VIDEO of the Calibration Stamp!

Clint Mack prepares to apply calibration stamps in Western Oklahoma

Calibration Stamp in Western Oklahoma showing the 3 strips with decreasing N rates.

Calibration Strips applied just north of Experiment #222, fall 2004, read on March 18, 2005

Dr. Marvin Stone, Dr. John Solie, David Zavodny, and Kyle Freeman stand in front of the very first CST applicator.

Jerrel Powell and Tom Denker discuss the N Rich Strip Program

Figures (above and below).  Calibration stamps applied soon after planting (left) and visual stamp differences mid-season (right) that are used to prescribe accurate mid-season N fertilizer rates.


Continuous calibration stamps (9m2) applied at Perkins, OK on top of winter wheat at Feekes growth stage 4, and superimposed schematic of actual N rates in kg N/ha using urea ammonium nitrate applied as a foliar spray.

UAN with Blue Dye applied soon after wheat planting such that calibration stamps can be visualized by cooperators/farmers.

Kyle Freeman and Brian Arnall adjust the air pressure for the spraying system that requires 30 PSI.  Next to his left hand is the controller which can be operated with 3 switches (power, purge, and spray).  The controller automatically cycles if the spray button is held down.  Each cycle includes a stamp with 9 squares (4 checks of 0, and one each of 20, 40, 60, 80, and 100 lbs N/ac).  Each square measures 1 x 1 m, while the entire stamp measures 3 x 3 m. 

Prior to putting out the calibration stamps, Kyle Freeman purges the system with UAN.

Comprehensive information on Nitrogen Use Efficiency for cereal crop production