Microclimate of vineyards under protected cultivation/Microclima de vinhedos sob cultivo protegido

Microclimate alterations promoted by plastic covering over vineyards interfere in the plant physiology and fungal diseases incidence on grapevines. The aim of this research was to evaluate the influence of the plastic covering on the microclimate of vineyards, in particular on the quality of the incoming solar radiation. The experiment was carried out in 2005/06 and 2006/07 seasons in Flores da Cunha-RS, in a vineyard of Moscato Giallo cultivar shaped in Y, with impermeable plastic (160 µm) over 12 rows of 35m length and five rows without covering (control). In both treatments the air temperature and humidity, incoming photosynthetically radiation and wind speed were measured at the level of the canopy and clusters. Continuing measurements were taken through sensors and automatic acquisition systems (datalogger). Influences of the covering on quality of the incoming solar radiation, from 300 to 750nm, were evaluated through a spectroradiometer. The impermeable plastic covering above the plant rows increased the air temperature and decreased the photosynthetically radiation and wind speed. The covering interfered on the quality of the incoming solar radiation, by reducing mainly the irradiance in the ultraviolet band and reducing also the ratio between the irradiance in the red and far-red bands. Key words: Vitis vinifera, plasticulture, micrometeorology, protected cultivation. Alteracoes microclimaticas em vinhedos, provocadas pelo uso de cobertura plastica, interferem na fisiologia das plantas e na incidencia de doencas fungicas em videiras. Assim, o objetivo deste trabalho foi avaliar a influencia da cobertura plastica no microclima de vinhedos, em particular na qualidade da radiacao solar. O experimento foi conduzido nos ciclos 2005/06 e 2006/07, em Flores da Cunha, Rio Grande do Sul (RS), em um vinhedo de 'Moscato Giallo' conduzido em "Y", com cobertura plastica impermeavel (160 ?m) sobre 12 fileiras com 35m, deixando-se cinco fileiras sem cobertura (controle). Em ambas as areas, avaliou-se o microclima quanto a temperatura do ar, umidade relativa do ar, radiacao fotossinteticamente ativa e velocidade do vento, proximo ao dossel vegetativo e aos cachos. Medicoes continuas foram efetuadas utilizando sensores e sistemas automaticos de aquisicao de dados. Alteracoes na qualidade da radiacao solar incidente sobre o dossel vegetativo, no espectro de 300 a 750nm, foram avaliadas por meio de medicoes durante cinco dias, com espectroradiometro. A cobertura pla