Effect of different greenhouse covering photoselective films on yield and quality of tomato

Ultraviolet (UV)-absorbing plastic films are being used as a photoselective barrier to control insect vectors and associated virus diseases in different horticultural crops. An experiment was carried out in Murcia (south-eastern Spain) in 4 tunnel greenhouses to evaluate the effects of ultraviolet (UV)-blocking films on tomato yield and quality. Each greenhouse had a floor area of 50 m(2). The orientation was N-S. Four covering films were tested: T1 co-extruded three layer 200 mu, T2 thermal PE 200 mu, T3 long life PE 180 mu and T4 UV-absorbing PE 200 mu. Fruits were harvested twice a week at turning ripening stage. Radiation outside and inside of each greenhouse were measured with a photo-radiometer. The following parameters were determined: number of fruits per plant, fruit weight, early and total yield, colour, fruit firmness, juiciness, dry matter, pH, electrical conductivity (EC), titratable acidity (TA) and soluble solids (TSS). At the beginning of the experiment plastic films had a 30 (T1), 55 (T2), 95 (T3) and 99 (T4) % of reduction in incoming UV-A, respectively. Covering films had worse radiation properties after 158 days, especially those with UV-blocking characteristics. The agronomical results showed T4 had the highest early production and the lowest final production. Covering materials hardly affected tomato quality, only T3 and T4 types influenced fruit quality, promoting EC and TSS values, respectively.