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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #136810
Title: AERIAL PHOTOGRAPHY USED TO ASSESS SPATIALLY VARIABLE CORN NITROGEN NEED

Author
item WILLIAMS, JARED - UNIV OF MISSOURI
item Kitchen, Newell
item SCHARF, PETER - UNIV OF MISSOURI
item STEVENS, WILLIAM - UNIV OF MISSOURI

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/17/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Rising fertilizer costs, environmental concerns, and a desire for higher yields are reasons for corn [Zea mays L.] producers to improve their nitrogen (N) management strategies. Remote sensing of crop color has been proposed as an information source to guide N fertilizer inputs. Our objective was to evaluate, at a field scale, the relationship between crop color in aerial photographs and yield response to N. Six experiments were conducted in production corn fields in 2000 and 2001. Three soil types were represented each year: alluvial, claypan, and deep loess. Nitrogen was applied at rates of 0, 56, 112, 168, 224, and 280 kg N/ha in field-length (> 400 m) strips. Photographs were taken using 35 mm film at early (V6) and late (V11) vegetative growth stages and images processed to determine color digital counts (DC). Relative color (DC(no N)/DC(high N)and optimum N rate were calculated for each 20 m section of each replication. Analyzed by location, red (R) and green (G) DC ratios were generally poorly related to optimum N rate (r**2 < 0.40) for the six site years. Crop reflectance variation from N rate and the resultant impact on yield was verified with chlorophyll meter measurements taken at the same time as aerial photos. Therefore, the poor relationship between DC and optimal N was attributed to coarse photo resolution. Other concerns identified were unreplicated N rates for each optimal economic N calculation, weed infestation, stand, and atmospheric effects. Further research will be needed to refine N fertilizer rates for corn that rely on inexpensive aerial photographs. These results will be used to further explore the potential for aerial images to detect corn N status, explain soil type and crop color interactions, and develop in-season variable N fertilizer maps for producers.