Ambiência no crescimento e produção de alface, em ambiente protegido, com e sem tela termorrefletora

Abstract

The reflective screen is an option to promote the shading, to reduce the air temperature in greenhouse, and to allow a better growth and developments of the plants. This way, the present work had as objective evaluates the effect of the air temperature, evaporation and the air s evaporative power on the acting of four cultivate of curly lettuce (Itapuã, Paola, Vera and Veronica) under greenhouse with and without reflective screen, in the conditions of summer at west of Paraná. The experiment was carried at Assis Chateaubriand/PR, in a private property in a greenhouse with organic cultivation system. The greenhouse had the following dimensions 4.5m height, 3m pier, 60m length, and 5m wide. The greenhouse was divided into two equal parts, forming two atmospheres with 30m length each. One of the rooms was covered with polyethylene with low density, 100 micras of denseness and the other room, under this covering, it was installed to the height of the foot-righ, the reflective screen 50%. Inside each room three small evaporimeter were established to 0.4m height, and a meteorological protection at 1.5m height, containing Piche evaporimeter, maximum and minimum thermometer and Dattalogger. In order to evaluate the productive characteristics of the cultivate, treatments distributions followed the randomized design (DCA), with 6 replications. The evaluations were done at 0, 7, 14, 21 and 28 days after the transplantation (DAT). The, minimum, medium and maximum air temperatures observed in the room without term reflective screen were respectively 16,3; 25,1 and 38,4 °C; and 16,7; 24,6 and 36,2 °C in the room with reflective screen. The reflective screen reduced significantly the air temperature and it was influenced by the weather conditions, mainly on cloudy or rainy days. The amount of evaporated water in the atmosphere without reflective screen was 26% upper than the other one. The air s evaporative power was 4,16mm in the atmosphere without reflective screen and 3,82mm in the atmosphere with it. However it was not observed a significant statistical difference between those numbers. The cultivates of Itapuã, Vera and Verônica lettuce demonstrated better results in productivity in relation to Paola in both evaluated atmosphere. However, when it compares the atmospheres, the one without reflective screen presented productivity of 14.97 t ha against 12.61 t ha to the atmosphere with reflective screen