The objective of this study was to characterize the radiometric relationship and changing in three greenhouses covered with transparent low density polyethylene film (PEBD) with a 150µm single layer of low density polyethylene film, treated with compounds that inhibit rapid degradation by ultraviolet radiation, under effects of different environments. The experiments were conducted during hydroponics lettuce production of Vera variety at Campinas region-SP in different periods of the year, aiming the use of experimental data from meteorological stations in substitution of the needs to pursue radiometric equipments for internal measurements. Three identical greenhouses, in shape and volume, with steel metal structure were used. Data of internal and external global solar radiation (RSGI and RSGE, W m²), photosynthetically active radiation (RFA, µmol m-2 s-1), and ultraviolet radiation in 254; 312 e 365 nm (RUV, W m-2) were collected. The results showed that the linear regression equations are acceptable to estimate the photosynthetically active radiation based on the external global solar radiation. Closed acclimatized greenhouses show better statistical correlation between the photosynthetically active radiation and the external global solar radiation. The orientation of non acclimatized greenhouses does not influence the internal scattering of photosynthetically active radiation.
Protected environment; climatization; low density polyethylene; solar radiation
