1. Developing Sidedress N Recommendations for Corn in Central PA
using a Crop Circle ACS-210
John Schmidt
Adam Dellinger
Doug Beegle
ARS and Penn State

2. Background Improving N recommendations for corn
Sidedressing N is common in PA
Many fields with a manure history
Spatial variability in relief, aspect, soil water content

3. Field selection – 2005 State College area, four fields Previous crop
Corn, Soybean, Soybean with manure history, Alfalfa
Soil pH: 5.5 – 6.2
Soil P (M3): 17 – 101 mg kg-1
Soil K (M3): 93 – 160 mg kg-1

4. Treatment design Whole plot, 30 x 105 ft Control
50 lb acre-1 N as NH4NO3
Manure, 115 – 165 lb acre-1 total N
Split-plot, 30 x 15 ft
250 lb acre-1 N as NH4NO3 at planting
20, 40, 80, 120, and 160 lb acre-1 N as NH4NO3 at sidedress
Four Blocks

5. Sensor Sensor Crop Circle ACS-210 Plant Canopy Reflectance
Emission Bands: 590 and 880 nm
Two detectors: 400 – 680 nm, 800 – 1100 nm
Sensor
Crop Circle ACS-210 Plant Canopy Reflectance
Emission Bands: 590 and 880 nm
Two detectors: 400 – 680 nm, 800 – 1100 nm

6. Data collection 8 samples per second Simultaneously georeferenced
Trimble Pro XRS GPS and TSCe Field Device
24 – 32 inch sensor height
Weekly, June 8 – July 12
Data collection

7. Data collection Grain yield PSNT from the control
SPAD readings at sidedress
Leaf tissue at silking
Stalk nitrate test, selected trts
Data collection

8. Grain yield response – Corn after corn
EONR = 94
EONR = 73
EONR = 124
$0.30 / lb N
$2 / bu corn

9. Grain yield response – Corn after soybean
EONR = 43
EONR = 0
EONR = 54

10. Grain yield response – Corn after alfalfa

11. Grain yield response – Corn after soybean
(manure history)

12. EONR (Economic Optimum N Rate)
Previous crop
Whole plot trt
EONR (lb N / acre)
Corn
Control 94
50 lb N / acre 73
Manure
124
Soybean 43 54
Alfalfa
Soybean (manure history)

13. NDVI, Corn after corn, Control (whole plot)
June 24
N applied

14. NDVI, Corn after corn, Control (whole plot)

15. NDVI, NDVIratio and SPADratio

16. EONR as a function of NDVI ratio

17. NDVIratio compared to SPAD ratio, June 21

18. EONR as a function of NDVIratio or SPAD ratio
June 21

19. Summary First year of results in PA
Sensor was effective at those sites requiring N fertilizer
NDVI ratio was correlated to SPAD ratio
NDVI ratio was better correlated to EONR than SPAD ratio