Putting green clipping yield, canopy reflectance, and vegetative indices by time from colorant and spray oil combination product application

Multispectral radiometry resolutely quantifies canopy attributes of
similarly managed monocultures over wide and varied temporal arrays.
Likewise, liquid phthalocyanine-containing products are commonly applied
to turfgrass as a spray pattern indicator, dormancy colorant, and/or
product synergist. While perturbed multispectral radiometric
characterization of putting greens within 24 h of treatment by synthetic
phthalocyanine colorant has been reported, explicit guidance on subsequent
use is absent from the literature. Our objective was to assess creeping
bentgrass (Agrostis stolonifera L. ‘Penn G2’) putting green reflectance
and growth one to 14 d following semi-monthly treatment by synthetic Cu II
phthalocyanine colorant (Col) and petroleum-derived spray oil (PDSO)
combination product at a 27 L ha–1 rate and/or 7.32 hg ha–1 soluble N
treatment by one of two commercial liquid fertilizers. As observed in a
bentgrass fairway companion study, mean daily shoot growth and canopy dark
green color index (DGCI) increased with Col+PDSO complimented N treatment.
Yet contrary to the fairway study results, deflated mean normalized
differential red edge (NDRE) or vegetative index (NDVI) resulted from an
associated Col+PDSO artifact that severely impeded near infrared (810-nm)
putting green canopy reflectance. Regardless of time from Col+PDSO
combination product treatment, the authors strongly discourage turfgrass
scientists from employing vegetative indices that rely on 760- or 810-nm
canopy reflectance when evaluating such putting green systems.