Effects of agrochemicals, ultra violet stabilisers and solar radiation on the radiometric properties of greenhouse films

Agrochemicals, based on iron, sulphur and chlorine, generate by-products that lead to a degradation of the covering greenhouse films together with a decreasing of their mechanical and physical properties. The degradation due to agrochemicals depends on their active principles, method and frequency of application, and greenhouse ventilation. Aim of the research was to evaluate how agrochemicals contamination and solar radiation influence the radiometric properties of ethylene-vinyl acetate copolymer greenhouse films by means of laboratory and field tests. The films, manufactured on purpose with the addition of different light stabilizer systems, were exposed to natural outdoor weathering at the experimental farm of the University of Bari (Italy; 41° 05' N) in the period from 2006 to 2008. Each film was tested for two low tunnels: one low tunnel was sprayed from inside with the agrochemicals containing iron, chlorine and sulphur while the other one was not sprayed and used as control. Radiometric laboratory tests were carried out on the new films and on samples taken at the end of the trials. The experimental tests showed that both the natural weathering together with the agrochemicals did not modify significantly the radiometric properties of the films in the solar and in the photosynthetically active radiation wavelength range; within 6 months of experimental field tests the variations of these radiometric characteristics were at most equal of 10%. Significant variations, up to 70% of the initial value, were recorded for the stabilised films in the long wave infrared radiation wavelength range