Automated Calibration Stamp Technology for Improved In-Season Nitrogen

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

Review o Pre-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). o Predicting N mineralized from soil organic matter could lead to improved N fertilizer recommendations (Cabrera and Kissel, 1988). o Mulvaney et al. (2001) found that the concentration of amino sugar N was highly correlated with check-plot yields and fertilizer N response. o Temporal variability strongly influences N supplied by soil organic matter and the demand for in-season N

Review (cont) o 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) o This strategy explicitly places the risk of predicting the environment (good or bad year) on the farmer o Varvel 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%. o Sufficiency index < 90% at the V 8 growth stage in corn, maximum yields could not be achieved with in-season N fertilizer applications (Varvel, 1997).

Review o Normalized difference vegetation index (NDVI) divided by the number of days from planting to sensing used to predict mid-season winter wheat yield potential (OSU) o Response Index: N Rich Strip (sufficient nitrogen but not excess) strip and the adjacent area with the field rate of preplant applied N. o 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.

Response Index variable from year to year in the same field 2004 RI = 1. 7 1995 Long term N-P-K Experiments (1969 -2004) Dr. Billy Tucker RI = 1. 2

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

14 Response to Fertilizer N Long-Term Corn Experiment Mead, NE, 1969 -1983 12 Grain Yield, Mg/ha 10 0 -N kg/ha UAN-180 kg N/ha 8 6 4 2 0 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 4 Response Index 3. 5 3 2. 5 2 1. 5 1 Prof. R. A. Olson

Materials and Methods o 2003 Honda Four. Trax Foreman ES 4 -wheeler (433 -cc, o o 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 -m 2 grid. 9 separate 1 -m 2 areas Four corners receive no fertilizer N. Rates of 22, 45, 67, 90, and 112 kg N ha-1 occupy the other 5

Calibration Stamp

lb N / acre 80 0 20 0 Blue Dye, 30 ml L-1 100 40 0 60 0

Pumpless pressurized spray system 19 L auxiliary air tank 11. 3 L Spartanburg stainless steel tank Programmable logic controller Remcor solenoid valves Automated Calibration Stamp

Winter Wheat Calibration Stamp applied in December Visual Interpretation in March

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

December Calibration Stamp March

Results o Field-specific topdress N rate prescribed by choosing the lowest N rate where no visual differences were observed between it and the highest rate. o o o o N Rate 100 0. 80 80 0. 79 60 0. 78 40 0. 65 20 0. 55 0 0. 51 NDVI 100 80 60 40 20 0 N Rate 0. 76 0. 74 0. 68 0. 55 0. 41 NDVI 100 80 60 40 20 0 N Rate NDVI 0. 69 0. 68 0. 69 0. 67 0. 68 0. 54

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

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

Summary o Calibration 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. o Cost: Honda 4 X = $5000 Tanks, Controller, Nozzles, Valves, Boom, Programming, Labor = $800 o Can be used with on-line Sensor Based N Rate Calculator to improve mid-season N management

Green. Seeker-Red Average NDVI = 0. 816, standard deviation in NDVI = 0. 0056 Distance to target: 0. 8 -1. 2 m

>15 readings 0. 4 m 2 +/- 0. 005