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LIGHT ENVIRONMENT AND CANOPY ASSESSMENT PARAMETERS WITHIN TABLEGRAPE VINEYARDS TRAINED TO THE OVERHEAD TRELLIS IN THE SOUTH-CENTRAL REGION OF CHILE
These factors when combined with canopy management practices define canopy assessment parameters that have important implications on yield and quality of the crop.
Until now, no comprehensive quantitative study about light environment and leaf area relations in commercial vineyards trained to the overhead trellis has been published.
The purpose of this study was to provide such a description for table grape vineyards cv.
Thompson Seedless.
Eight sites were selected on the basis of their varying degrees of growth allowing a wide range of canopy situations to be evaluated.
Photosynthetic active radiation (PAR), leaf area index (LAI), leaf layer number (LLN) and percent canopy gaps (through a point quadrant analysis) were measured.
LAI ranged from 1.8 to 8.06 for all sites under study.
Leaf area density increased less than 20% between fruit set and harvest in sites having LAI<2,8 (low vigor) and between 90 and 200% in sites having LAI >5.0. Light distribution was not uniform within the canopy as PAR levels decreased from 40 down to 5% of ambient values when measured from the periphery to center of the plant.
This differences increased as season progressed reaching levels of 1.5% ambient values during the period of veraison – harvest.
In all sites LLN was higher that reported literature levels averaging 4.4. Leaf area per gram of fruit was higher than reported literature values for grapes in 60% of the sites reaching average levels of 16.7 cm2/g.
Fruit overall quality and postharvest disorder (waterberry and weak berries) incidence was positively correlated to those sites having high LLN, low canopy gaps and excessive growth during the veraison-harvest period.