Repeated solarization and long-term effects on soil microbiological parameters and agronomic traits

Innovative methods less invasive for man and environment are needed to solve the problem of weeds, pests and diseases in cropping systems. Soil solarization is one practice that involves passively heating soil covered by a thin clear plastic film for several weeks during the periods of high solar radiation before the crop is planted. Soil solarization treatments were repeated to verify their long-term effectiveness on soil microbial biomass and its respiration activities, in addition to yield response and root-knot nematodes control in tomato and melon crops following soil heating. Experiments in greenhouse were carried out in Southern Italy (40 24 0 N, 16 28 E) during the summer of 1998, 1999 and 2000 on soil infested by the root-knot nematode Meloidogyne javanica. Crop yields and fruit quality of all vegetable crops were positively affected by repeating solarization for two and three years, compared to an untreated soil and soil treated once in 1998. Solarization was effective in controlling root-knot nematode damage, but solarization affected the soil biota populations and their activities as a consequence of repeated treatments.