ARS | Publication request: Cotton NDVI response to applied N at different soil EC levels

Submitted to: Proceedings of the Annual Precision Ag Conference
Publication Type: Proceedings
Publication Acceptance Date: May 4, 2010
Publication Date: July 18, 2010
Citation: Bauer, P.J., Evans, D.E., Strickland Jr, E.E. 2010. Cotton NDVI response to applied N at different soil EC levels. In: Proceedings of the International Conference on Precision Agriculture, July 18-21, 2010, Denver, Colorado. 2010 CDROM.

Technical Abstract: Many fields in the southeastern Coastal Plain are highly variable in soil physical properties and are irregular in shape. These two conditions may make it difficult to determine the ‘best’ area in the field to place nitrogen (N) -rich strips for normalized difference vegetative index (NDVI) -based spatial N fertilizer application. This field study was conducted to determine if soil electrical conductivity (EC) could be used to delineate N-rich areas for spatial N application. Cotton was grown on a field that contained five different soil map units with soil surface EC ranging from 0.4 to 10 mS/m. Treatments in the study were three N rates (0, 34, and 112 kg N/ha). Mid-season NDVI increased with soil EC up to approximately 5 mS/m. Greatest differences among the N rates for NDVI were at soil EC levels between 2 and 5 mS/m. Cotton yields differed among the N rates, but there was no interaction between N rate and soil EC for yield. Predicted N fertilizer recommendations for the 0 and 34 kg N/ha plots using the Oklahoma State algorithm were low. These preliminary results suggests that there is potential for using soil EC for delineating N-rich areas on highly variable fields in the southeastern Coastal Plain.