COMMERCIAL DIGITAL CAMERA TO ESTIMATE POSTHARVEST LEAF AREA INDEX IN Vitis vinifera L. cv. CABERNET SAUVIGNON ON A VERTICAL TRELLIS

The leaf area index (LAI) of a vineyard (Vitis vinifera L.) cv. Cabernet Sauvignon located in the commune of Cauquenes, Maule Region in Chile, was estimated from digital images obtained with a commercial camera using two indirect methods: Leaf Area Gap and Brightness (LAGB) and Photogrammetric Leaf Area Quantification System (PLAQS). The latter requires deleafing of the grapevine. In a normalized difference vegetation index (NDVI) map, three points of vine vigor were selected: high, medium, and low for which horizontal and vertical images were obtained. Images were filtered with the Arc View GIS 3.1 program to provide only leaf images and corresponding pixel numbers. Image area and square meters per linear meter were calculated. The best models were selected from three linear regression adjustments: i) LAI of LAGB vertical images of with LAI of PLAQS, ii) LAI of PLAQS horizontal images with and, iii) LAI of both types of images with PLAQS. The parameters in all models were significant. Adjustment between the LAGB and PLAQS vertical images provides greater simplicity and easy calculation since it requires only a vertical image to estimate LAI. Images thus obtained can accurately estimate LAI in this type of cultivar.