Reduced creeping bentgrass fairway reflectance following synthetic colorant application

Repeated measures using multispectral radiometry resolutely quantify canopy attributes of identical turfgrass cultivars under similar management. Concern regarding multispectral radiometric characterization of turfgrass canopies <24 h following synthetic phthalocyanine colorant application has been affirmed and is accordingly now avoided; yet explicit guidance on subsequent employ, at time(s) > 24-h postapplication, is lacking. Our objective assessed how petroleum-derived spray oil (PDSO) and synthetic Cu II phthalocyanine colorant (CPC) combination product influences creeping bentgrass (Agrostis stolonifera L.) reflectance up to 10 d following application. A maintained fairway received semimonthly 9.76 kg ha^–1 soluble N treatments alone or in combination with 27 L PDSO+CPC ha^–1. Treatment by PDSO+CPC increased mean shoot growth (kg ha^–1) and dark green color index (DGCI) calculated by visible waveband reflectance. Yet reduced far red and near infrared reflectance from PDSO+CPC treated plots artificially deflated mean normalized differential vegetative indices. Cautious interpretation of vegetative indices relying on 710-to-810-nm canopy reflectance is encouraged when evaluating fairways treated by PDSO and Cu II phthalocyanine combination product(s).