The study aimed to evaluate interception patterns of photosynthetically active radiation (PAR) in vineyards (Vitis vinifera cv. 'Moscato Giallo'), with and without plastic covering over the vegetative canopy. An experiment was carried out in Flores da Cunha, Rio Grande do Sul state, Brazil (29°06'S, 51°20'W, 541 m) during the 2005/2006 growing season. It comprised uncovered and covered rows of plants by using a transparent 160µm thick plastic film (low density polyethylene). Continuing measurements of PAR were taken at different levels of the canopy in both treatments. The leaf area index (LAI) was determined by a non-destructive method along the crop cycle, and regression models relating LAI to the accumulated degree-days were adjusted. Regression models were also adjusted in order to estimate the intercepted PAR as function of LAI by covered and uncovered vineyards. The plastic covering over the vineyard promoted an increment of 12% for the interception efficiency of PAR. The covered vineyard showed a lower extinction coefficient for PAR than in open sky.
grapes; plasticulture; photosynthetically active radiation; microclimate
