ENVIRONMENTAL MODIFICATION CAUSED BY PERFORATED TRANSPARENT POLYETHYLENE LOW TUNNELS CULTIVATED WITH LETTUCE

Environmental modifications caused by low tunnels made of perforated transparent polyethylene were determineted in an area alocated at the Federal University of Santa Maria, RS. The perforation densities were 100, 200, 300 and 400 perforations per square meter, corresponding respectively to 0.78% (T1), 1.57% CT2), 2.35% (T3) and 3.14% (T4) of area perforated. The results indicated that perforation density did not significantly affected solar energy availability. As perforation density increased there was a decrease on the average diurnal air temperature which demonstrated the viability of ventilating low tunnels with perforated plastic. It was also observed that inside the perforated tunnels the averages values for soil, air minimun and diurnal temperatures and air relative humidity were higher than on the external environment.