SUMMARY Micrometeorological afterations caused by low tunnels of black plastic screen with 18, 30, and 50% of solar radiation reduction in central region of the Rio Grande do Sul state, Brazil, was investigated during the summer. The experiment was carried out in the Federal University of Santa Maria, where four plots were cultivated with lettuce. Three plots were covered by low tunnels of black plastic screen and one was left uncovered as a control. The study was conducted in 3 periods: 11/30/90 to 01/17/91, 02/06/91 to 03/25/91, and 12/10/91 to 03/01/92. Soil and air temperature, and soil water consumption decreased with solar radiation reduction. However, air minimum temperature and relative humidity were similar inside and outside, and aiso among different leveis of reduction caused by plastic screen.
solar radiation; soil and air temperature; plastic screen; shading
