Microclimatic conditions and gas exchange in a vineyard under plastic cover

Abstract

Plastic covers are being used in an increasing number of vineyards to avoid problems derived from high radiation and rainfall levels. The effects of this new management system on microclimatic, gas exchange and crop water demand are not well known. In this context, the objective of this study was to analyse possible changes in soil moisture, microclimatic variables and gas exchange in a vineyard (cv. Niágara Rosada, for table consumption) under transparent plastic cover. The experiments were performed in São Fidelis, Rio de Janeiro State, Brazil, on a growing cycle (March to June 2013). The crop was covered at the top with a 160 μm thick low density polyethylene film. Within a commercial vineyard (1 ha) we had two plots (covered and uncovered, 0.035 ha each), each one instrumented with a meteorological station. Soil humidity was determined by gravimetry. Stomatal conductance (gs) and net photosynthesis (AN) measurements were made at 08.00-10.00 am, in 5 plants of each treatment and on days 42, 56, 68, 91 and 106 after pruning. The plastic cover permitted greater soil humidity, reduced the photosynthetic active radiation, and increased the maximum and medium temperature and the vapor pressure deficit. The greater soil water availability, however, may not lead to greater plant water use efficiency