Components of the solar radiation in tomato cultivated under greenhouse conditions

The objective of this paper was to evaluate of net radiation, photosynthetic and solar irradiation in greenhouse conditions cultivated with tomato crop and its relationship with the global solar irradiation of the external environment. The tomato was cultivated in greenhouse (not acclimatized), with covering of polyethylene 0.12 mm of thickness. The global solar irradiation (Rgi), the net radiation (Rni) and the flux density of photosynthetic photons were obtained by radiometers connected to a datalogger installed into the protected environment. The external data (global solar irradiation, Rg) were collected in the Agrometeorological Station of the Agricultural Science Center of Federal University of Alagoas. The protecting environment promoted reduction in the solar irradiation, expressed as the transmittance of the polyethylene in 62%. The relationships between the components of radiation from internal and external environment were expressed satisfactorily by linear regressions, with coefficients of determination (R-2) greater than 0.88, while for the photosynthetic irradiation (PARi) the R-2 were higher than 0.52. The obtained relationships showed that Rni is 0.60 of the Rgi and the PARi is proportional to 0.28 of the Rg and 0.44 of the Rgi. The mean albedo of crop over the cycle was 0.15.