Influence of greenhouse volume/area ratio on soil solarization efficiency.

Soil temperature under plastic cover is function of incoming radiation and thermal characteristics of the mulching material and the soil, but it could be also affected by greenhouse characteristics (structure, cover, Volume/Area ratio). The aim of this research was to evaluate the effects of different greenhouse unitary volumes and different plastic mulching on soil temperature and soil solarization efficiency. The experiment was carried out in nonheated greenhouses covered with low density transparent polyethilene (PE), located at the experimental field of AAT Department of Palermo University, Italy (138° 7' N, 13° 22' E). Four Volume/Area (V/A) ratios were tested: 1.5 - 2.0 - 2.5 - 3.0. Individual plots were covered with transparent or black PE film from the end of July till the end of August (30 days) in 2003, 2004 and 2005. Results showed a good efficiency of soil solarizzation under closed greenhouses and confirmed other studies. Maximum soil temperatures were increased solarizing under greenhouse with V/A 2.5 ratio. Plots mulched with transparent PE film reached higher soil temperatures than those mulched with black PE. Nevertheless black PE mulching under high V/A ratio greenhouses allowed to keep soil temperature over threshold values lethal for soilborne pathogens and seeds. Black PE film could be used and left on the soil even after solarization as crop mulching, saving money for mulching replacement and reducing plastic waste.