Salt tolerance and canopy reflectance of kentucky bluegrass cultivars

Abstract

Six cultivars or selections of kentucky bluegrass (Poa pratensis L.) were grown outdoors from vegetative clones in a gravelly sand medium from Apr. to Sept. 2005 in Riverside, CA, at soil water salinities ranging from 2 to 22 dS m-1. Cultivars Baron, Brilliant, Cabernet, Eagleton, Midnight, and the selection A01-856, a 'Texas'×kentucky bluegrass hybrid (P. arachnifera×P. pratensis), were evaluated for salt tolerance based on relative and absolute cumulative biomass production, growth rates, leaf chloride concentration, and hyperspectral ground-based remote sensing (RS) canopy reflectance measurements. Remotely sensed indices were linearly correlated with absolute biomass production. Three variations of a Normalized Difference Vegetation Index (NDVIred, NDVIprotein, and NDVIinfra) decreased with increasing salinity-induced changes in grass canopies. An index based on the red-edge inflection point increased (became less negative) with increasing salinity. A Floating Water Band Index decreased with decreased leaf moisture content related to increasing salinity but did not discriminate between cultivars. Shoot spreading rate and NDVIinfra were both related to shoot chloride concentration differences among the kentucky bluegrass (Poa pratensis L) (KBG) cultivars or selections. In theory, non-destructive RS monitoring of above-ground turf development, including NDVIinfra, coupled with measurement of leaf chloride concentrations could be useful in turf salt tolerance breeding programs. Salt tolerance rankings among the KBG cultivars varied depending on the evaluation methods and selection criteria used. Based on absolute and relative biomass, growth rate, and RS, cultivars Baron, Brilliant, and Eagleton were rated as more salt-tolerant than 'Cabernet', 'Midnight', and AO1-856.