Effect of different solarizing materials on weed suppression and lettuce response

The effect of four solarizing plastic materials on weed suppression and yield response of two lettuce cultivars ('Bacio' and 'Moringa') grown during two consecutive seasons was investigated at Metaponto (40 degrees 23'N; 16 degrees 47'E; 10 ma.s.l.), southern Italy. All solarization treatments suppressed winter and summer weeds with no significant difference among the plastic materials, although biodegradable film was less efficient in controlling common purslane and common amaranth. Weed infestation at the harvest of both lettuce cultivars was not affected by the solarizing material, whereas fewer weeds were found in the plots grown with 'Bacio' than with 'Moringa'. Lettuce yield in two successive growing seasons was always significantly higher in solarized plots than in nontreated control, without any statistical difference among the plastic materials. Yield and head quality of cv. 'Bacio' were higher than 'Moringa' in the first growing season, but the opposite occurred in the second crop. Soil solarization was confirmed to be effective for weed management in field lettuce crops in the Mediterranean areas, although weed suppression may be affected also by the lettuce cultivar. Choice of solarizing materials, when similarly effective on weeds and crop yield, should take into account also their cost. Low density polyethylene plastics emerged as the best choice in conventional lettuce crops as highly effective as, and less expensive than the other materials, whereas the use of biodegradable films should be limited to organic lettuce systems.