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REMOTE SENSING

Developing Nitrogen Fertilizer Recommendations for Corn Using an Active Sensor

^a USDA-NRCS, 1383 Arcadia Rd, Room 200, Lancaster, PA 17601
^b USDA-ARS, Building 3702, Curtin Rd., University Park, PA 16802
^c Dep. of Crop and Soil Sci., The Pennsylvania State Univ., 116 ASI Building, University Park, PA 16802

^* Corresponding author (adam.dellinger{at}pa.usda.gov).

Producers often overapply N fertilizer to corn (Zea mays L.) because of the uncertainty in predicting the economic optimum nitrogen rate (EONR). Remote sensing represents a potential opportunity to reduce this uncertainty with an in-season assessment of crop N status. This study examines the relationship between EONR and reflectance from a ground-based sensor, and considers its potential for developing sidedress N recommendations for corn. Four fields with unique cropping histories were planted to corn during each of 2 yr. Three preplant whole plot treatments (control, 56 kg N ha^–1 as NH₄NO₃, and manure) were used to create a range of N availability. Split plot treatments included seven sidedress rates (0, 22, 45, 90, 135, 180, and 280 kg N ha^–1) and one preplant rate (280 kg N ha^–1) as NH₄NO₃. The EONR for the sidedress N rates was determined for each whole plot treatment at each site. A ground-based active sensor was used at the sixth- to seventh-leaf growth stage (V6–V7) to collect reflectance data at 590 and 880 nm, which were then used to calculate the Green Normalized Difference Vegetation Index (GNDVI). The EONRs for sidedress N application for the 24 preplant treatment–site combinations ranged from 0 to 202 kg N ha^–1. The EONR was strongly related to relative GNDVI (r² = 0.84) for the control and manure preplant treatments; but unrelated when NH₄NO₃ was applied at planting (r² = 0.20). Developing sidedress N recommendations for corn using an active sensor could be an effective N management tool in Pennsylvania.

Abbreviations: AIR, Penn State farms located near the University Park Airport • EONR, economic optimum nitrogen rate • GNDVI, Green Normalized Difference Vegetation Index • NDVI, Normalized Difference Vegetation Index • RS, Rock Springs

¹ Trade or manufacturers' names mentioned in the paper are for information only and do not constitute endorsement, recommendation, or exclusion by the USDA-NRCS or USDA-ARS.

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Received for publication December 3, 2007.

This article has been cited by other articles:

				R. P. Sripada, J. P. Schmidt, A. E. Dellinger, and D. B. Beegle Evaluating Multiple Indices from a Canopy Reflectance Sensor to Estimate Corn N Requirements Agron. J., October 21, 2008; 100(6): 1553 - 1561. [Abstract] [Full Text] [PDF]