Evaluation of two transmittance meters in estimating chlorophyll and nitrogen concentrations in grapevine cultivars

Two transmittance-based chlorophyll meters (SPAD-502 and CCM-200) were evaluated in estimating chlorophyll (Chl) and nitrogen (N) levels in grapevine leaves. The study was conducted in a fertilization experiment [0 (N0), 60 (N1) and 120 (N2) kg N/ha] during the summer 2009, in two commercial vineyards located in Northern Greece and planted with cvs Cabernet-Sauvignon and Xinomavro (Vitis vinifera L.). When data were pooled over cultivars and samplings, leaves of N2 vines had the highest N and Chl content, as well as SPAD and CCM readings, followed by the respective values of N1. However, neither of the devices could detect the seasonal decline in leaf N and Chl content. Significant relationships between extracted Chl and measured leaf N were found in both cultivars. A strong linear function related SPAD and CCM readings in both cultivars. Total Chl and N were strongly correlated with SPAD and CCM readings in Cabernet Sauvignon (p<0.001) while relationships were poor for SPAD and not significant for CCM in Xinomavro. The results suggest that non-destructive chlorophyll estimations by transmittance-based meters are not applicable in all situations without specific estimations by transmittance-based meters are not applicable in all situations without specific calibrations necessary to improve their utility and accuracy over grapevine cultivars.