Automated Calibration Stamp Technology for Improved In-Season Nitrogen FertilizationK. Freeman, R. Teal, C. Mack, K. Martin, B. Arnall, K. Desta, J. Solie, M. Stone, H. Zhang, B. Raun

ReviewPre-sidedress nitrate test (PSNT) was an extension of preplant nitrate tests, in-season soil nitrate analysis was used to refine topdress rates (Bundy and Andraski, 1995). Predicting N mineralized from soil organic matter could lead to improved N fertilizer recommendations (Cabrera and Kissel, 1988). Mulvaney et al. (2001) found that the concentration of amino sugar N was highly correlated with check-plot yields and fertilizer N response. Temporal variability strongly influences N supplied by soil organic matter and the demand for in-season N

Review (cont)In many states, 33 kg N ha-1 is recommended for every 1 Mg of anticipated wheat yield (2 lb N ac-1 for every bushel of expected wheat grain yield)This strategy explicitly places the risk of predicting the environment (good or bad year) on the farmerVarvel et al. (1997) employed chlorophyll meter readings to calculate a sufficiency index: in-season N fertilizer applications were made when index values were below 95%. Sufficiency index < 90% at the V8 growth stage in corn, maximum yields could not be achieved with in-season N fertilizer applications (Varvel, 1997).

ReviewNormalized difference vegetation index (NDVI) divided by the number of days from planting to sensing used to predict mid-season winter wheat yield potential (OSU)Response Index: N Rich Strip (sufficient nitrogen but not excess) strip and the adjacent area with the field rate of preplant applied N. Although systems have been developed to determine midseason N fertilizer topdress recommendations, the need exists for a simple system that cereal grain producers can use to quickly estimate required N topdress rates.

Long term N-P-K Experiments (1969-2004)Dr. Billy TuckerResponse Index variable from year to year in the same field

1995RI = 1.22004RI = 1.7

Response to Fertilizer N Long-Term Wheat Experiment Lahoma, OK 1970-2003

Response to Fertilizer NMead, NE, 1969-1983Response to Fertilizer NLong-Term Corn ExperimentMead, NE, 1969-1983Prof. R.A. OlsonProf. R.A. Olson

Materials and Methods2003 Honda FourTrax Foreman ES 4-wheeler (433-cc, 127-cm wheel base, 116-cm wide) with a 3-m wide spray boom and a 1-m spacing between nozzles Modified to deliver a range of fixed N rates as urea ammonium nitrate (28 %N) within a 9-m2 grid. 9 separate 1-m2 areasFour corners receive no fertilizer N.Rates of 22, 45, 67, 90, and 112 kg N ha-1 occupy the other 5

Calibration Stamp

80 1004006000200lb N / acreBlue Dye, 30 ml L-1

Automated Calibration StampPumpless pressurized spray system 19L auxiliary air tank 11.3L Spartanburg stainless steel tank Programmable logic controller Remcor solenoid valves

Winter Wheat Calibration Stamp applied in December Visual Interpretation in March

Topdress N rate prescribed by choosing the lowest N rate where no visual differences were observed between it and the highest rate.

DecemberMarchCalibration Stamp

ResultsField-specific topdress N rate prescribed by choosing the lowest N rate where no visual differences were observed between it and the highest rate.

N RateNDVIN RateNDVIN RateNDVI1000.801000.761000.69800.79800.74800.68600.78600.68600.69400.65400.55400.67200.55200.45200.6800.5100.4100.54

http://www.soiltesting.okstate.edu/SBNRC/SBNRC.php

www.nue.okstate.edu

N Rich Strip (J. Lawles, S. Reed)NTech Industrieswww.ntechindustries.com

SummaryCalibration stamps applied preplant or soon after planting assist in providing visual interpretation of N mineralization + atmospheric N deposition from planting to the time mid-season N is applied, and improved determination of topdress N rates.Cost: Honda 4X = $5000 Tanks, Controller, Nozzles, Valves, Boom, Programming, Labor = $800Can be used with on-line Sensor Based N Rate Calculator to improve mid-season N management

GreenSeeker-RedAverage NDVI = 0.816, standard deviation in NDVI = 0.0056Distance to target: 0.8-1.2m

>15 readings 0.4m2+/- 0.005