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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #211208

Title: Developing Sidedress Nitrogen Recommendations for Corn using an Active Sensor

Author
item Schmidt, John
item DELLINGER, ADAM - USDA-NRCS
item BEEGLE, DOUGLAS - PENN STATE UNIV

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2007
Publication Date: 11/4/2007
Citation: Schmidt, J.P., Dellinger, A., Beegle, D. 2007. Developing Sidedress Nitrogen Recommendations for Corn using an Active Sensor. ASA-CSSA-SSSA Annual Meeting Abstracts. Paper No. 51-7.

Interpretive Summary: An interpretive summary is not required.

Technical Abstract: Active crop canopy reflectance sensors can be used during a sidedress N application to modify on-the-go fertilizer rates; but will this method be an improvement to current approaches to developing N recommendations? Our objective was to compare the potential for developing N recommendations for corn (Zea mays L.) based on an active sensor with those developed from more traditional approaches. Corn was grown at four sites in each of two years. Pre-plant whole-plot treatments included a control, 56 kg per ha N as ammonium nitrate, and 129-185 kg per ha total N as manure. Split-plot treatments included six N rates applied at the 8-leaf growth stage (0, 22, 45, 90, 135, and 180 kg per ha) and one pre-plant N rate (280 kg per ha) as ammonium nitrate. Canopy reflectance in the 590nm and 880nm wavelengths and SPAD measurements were collected at the 8-leaf growth stage. Relative Green Normalized Difference Vegetation Index (RGNDVI) was determined for each whole plot, as GNDVI(0) / GNDVI(280). Economic Optimum N Rate (EONR) was determined using a quadratic-plateau yield response function. When 56 kg per ha N was applied at planting EONR was not related to RGNDVI; however, when N fertilizer was not applied or when manure was applied at planting, EONR was strongly related (r2=0.79) to RGNDVI in a linear-floor type relationship. Nitrogen recommendations for each whole plot treatment deviated from EONR by: i) -68 to 126 kg per ha N when determined from a soil testing lab; ii) -49 to 162 kg per ha N when based on the Pre-Sidedress N test; and iii) -139 to 115 kg per ha N when based on a SPAD meter. Economic optimum N rate was strongly related to RGNDVI, when commercial fertilizer was not applied at planting, and offers the potential to improve N recommendations for corn.