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

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

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

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

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

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

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

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

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

Grain yield response – Corn after alfalfa

Grain yield response – Corn after soybean (manure history)

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)

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

NDVI, Corn after corn, Control (whole plot)

NDVI, NDVIratio and SPADratio

EONR as a function of NDVI ratio

NDVIratio compared to SPAD ratio, June 21

EONR as a function of NDVIratio or SPAD ratio June 21

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