Fairway reflectance and clipping yield from: 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 post-application, is lacking. Our objective assessed how petroleum-derived spray oil (PDSO) and synthetic Cu II phthalocyanine colorant (C) combination product influences creeping bentgrass (Agrostis stolonifera L.) reflectance up to 10 d following application. A maintained fairway received semi-monthly 9.76 kg ha–1 soluble N treatments alone or in combination with 27 L PDSO+C ha–1. Treatment by PDSO+C 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+C treated plots artificially deflated mean normalized differential vegetative indices (NDVI). 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).

采用多光谱辐射法（multispectral radiometry）进行重复测量，可精准量化相同养护管理条件下同一草坪草品种的冠层属性。此前学界已证实，在合成酞菁着色剂（synthetic phthalocyanine colorant）施用后24小时内对草坪冠层开展多光谱辐射表征存在偏差，因此当前已规避该时段的相关操作；但针对施用后24小时以上的后续应用场景，仍缺乏明确的操作指南。本研究旨在评估石油基喷雾油（petroleum-derived spray oil, PDSO）与二价铜酞菁着色剂（Cu II phthalocyanine colorant, C）的复配产品，在施用后长达10天内对匍匐翦股颖（Agrostis stolonifera L.）冠层反射特性的影响。
试验地块为一处日常养护的高尔夫球道（fairway），设置两种处理方案：单施每半月9.76 kg·ha⁻¹可溶性氮（soluble N），以及配施27 L·ha⁻¹ PDSO+C复配产品的联合处理。结果表明，PDSO+C复配处理可提升地上部平均生长量（单位：kg·ha⁻¹）以及基于可见光波段反射光谱计算得到的深绿色色度指数（dark green color index, DGCI）。但经PDSO+C处理的样地，其远红光（far red）与近红外（near infrared）波段的反射率出现下降，导致归一化差异植被指数（normalized differential vegetative indices, NDVI）的平均值被人为低估。因此在评估经PDSO与二价铜酞菁复配产品处理的高尔夫球道时，建议对基于710~810 nm冠层反射光谱计算得到的植被指数进行谨慎解读。