This work was performed to study the effect of different types of covering material on the air temperature inside the cultivation channel and on the growth of lettuce (Lactuca sativa L.), plants cv. Verônica using closed NFT-hydroponics system. Two types of cover material were used: black and white double-faced plastic sheet and Tetra-Pak™. Uncovered polypropylene tubes were used as control. The experiment was carried out at Campinas Agronomic Experimental Station, São Paulo State, Brazil (22°54'S, 47°05'W, 674 m of altitude), using workbenches of 24 m long, divided in four symmetric blocks with treatments distributed at random. Sixty thermocouples were installed inside the tubes to measure the air temperature, being the signals collected by a datalogger. Air temperatures inside the cultivation channel were always higher than the outside. However, on the Tetra-Pak™ covered benches the values of temperature were lower and the fresh weight of the plants were higher in comparison to the double-faced plastic sheet and control treatments. These differences were statistically significant at P > 0.05 level. During the nighttime, the covering materials did not have any influence on the inside channel temperatures.
Lactuca sativa L.; protected environment; hydroponics
