Eric Miller August 3rd, 2010 Dr. Camberato & Dr. Nielsen Variability of Maize Canopy Reflectance within Field-Length Strips Fertilized With Low to High Rates of Nitrogen Eric Miller August 3rd, 2010 Dr. Camberato & Dr. Nielsen http://www.agry.purdue.edu/intranet/images/logos/Grey-logo.jpg http://www.agry.purdue.edu/intranet/images/logos/Purdue-logo.jpg

Research objective Do “Virtual Reference Strips” occur in under-fertilized corn?

Virtual Reference Strip OptRx calibration process 1/3 – 1/2 estimated total N consumed Suggested pre-plant N rates: 67 - 90 kg N ha-1 Corn following Soybean 90 - 112 kg N ha-1 Corn following Corn

Virtual Reference scan consists of driving for five minutes over the tallest, greenest plants in the field Vegetative Index Reference Value

Project Description 2006 - 2009 6 Purdue Agricultural Centers 32 site years 2006, 2007, 2008 and 2009: 19 CS and 13 CC Plots range in size from 120 m – 550 m in length Starter + sidedress with 28% UAN at six rates from 0 – 286 kg N ha-1 Crop Circle ACS-210 were run 14 – 25 days after N application Single hybrid/near-isoline was planted 2006 - 2008

Relative CI well correlated with rel. yield over 23 site-years 2006: ACRE, DPAC, NEPAC, PPAC, SEPAC (all C/S) 2007: ACRE, DPAC, NEPAC (C/S and C/C) 2008: ACRE, DPAC, NEPAC, PPAC, SEPAC, TPAC (C/S and C/C) * Normalized to values of highest N rate in each rep

Sensor Measurements 2 ACS-210 sensors 4 mph, 40,000 hz, 38,400 baud rate Recording data every 18 cm Partitioned data into 30 and 60 sec runs Approx. 3,500 30-sec runs/305 m

Few 30 sec. runs of CI equal to RefCI C/S rotation, sidedressed with 90 kg N/ha, V9-V10 sensor readings Optimum N rate, kg/ha 167 169 190 204 225 232

Throckmorton Purdue Ag Center 305 m long plots, 12 rows, 76 cm wide V-stage: V10 Sensor Data Collected: July 8th Hybrid: Pioneer Brand ‘33F88’ Population Density: 81,500 plants ha-1 Dominant Soil: Throckmorton- Fine-silty, mixed, superactive, mesic Mollic Oxyaquic Hapludalfs Precipitation during growing season: 25 cm Planted: May 24th Previous Crop: Soybean Fertilized: June 24th

Yield Response

30 second runs = 53 meters of row Avg. CI = 4.77 Frequency, % Avg. CI = 4.77 30 second runs = 53 meters of row With 114 kg N ha-1 (68% of optimum N rate) 17% ≥ CI 4.77 Starter only (14% of optimum N rate) 2% ≥ CI 4.77

Location of CI = RefCI 114 kg N ha-1 24 kg N ha-1 77 131 130 77 84 67

Davis Purdue Ag Center 365 m long plots, 12 rows, 76 cm wide V-stage: V10 Sensor Data Collected: July 9th Hybrid: Pioneer Brand ‘33F88’ Population Density: 81,500 plants/ha Dominant Soils: Blount- Fine, illitic, mesic Aeric Epiaqualfs Pewamo- Fine, mixed, active, mesic Typic Argiaquolls Precipitation during growing season: 37 cm Planted: May 26th Previous Crop: Soybean Fertilized: June 15th

Yield Response

30 second runs = 53 meters of row Avg. CI = 4.00 54% of optimum N rate Frequency, % 54% of optimum N rate 38% ≥ CI 4.00 34 % of optimum N rate 16% ≥ CI 4.00

Conclusions Few areas of a field fertilized with 50-70% of the optimum N requirement had CI equal to or greater than the reference CI. Areas with CI ≥ ref. CI were small, generally less than 200 m and 2 minutes in length. Could we have found these areas without previously running the sensors? Would these areas identified in 2009 continue to be ≥ ref. CI?

Questions?