Effects of Agrochemicals on the Radiometric Properties of Different anti-UV Stabilized EVA Plastic Films

Most of the agrochemical substances used in protected cultivation, especially those based on sulphur and chlorine, generate by-products that lead to a degradation of the covering materials together with a variation of their mechanical and physical properties. The degradation due to agrochemicals depends on their active principles, method and frequency of application, and ventilation. A research was carried out by means of laboratory and field tests to evaluate how agrochemicals contamination and solar radiation influence the radiometric properties of ethylene-vinyl acetate copolymer (EVA) films used for crop protection. The films were manufactured adding different light stabilizer systems and 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 as covering of two low tunnels: one of the two tunnels was sprayed from inside with the agrochemicals containing iron, chlorine and sulphur while the other one was not sprayed and used as control. 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 PAR wavelength range; within 6 months of experimental field tests the variations of these radiometric characteristics were at most equal of 10%. Significative variations, up to 70% of the initial value, were recorded for the stabilised films in the LWIR wavelength range.