Nondestructive measurement of grapevine leaf area by ground normalized difference vegetation index
Vine leaf area index has a great impact on berry quality. This study was conducted to determine whether vine leaf area index could be estimated, and mapped through normalized difference vegetation index (NDVI) ground-based measurements. The NDVI measurements were performed using a Greenseeker (N-Tech Industires, Ukiah, CA and Oklahoma State Univ., Stillwater), pointed sideways at the vertical shoot positioned vines [Vitis vinifera (L.)] at Bordeaux, France. Canopy gap fraction and vertical leaf area index (VLAI) measurements were also performed. Plot NDVI maps were obtained by linking the GreenSeeker to a GPS during measurements. The NDVI delivered by the sensor was sensitive to the variations of vertical leaf area index and gap fraction of the canopy, that is, vine vigor. The GreenSeeker was successfully used to carry out a follow-up of the foliar growth of the vine, but with many precautions. The maps obtained showed relative variations of vigor at an intraplot level, enabling access to relevant information for better vineyard management.