Testing soil solarization as an alternative method for weed suppression at archaeological sites

Abstract

Archaeological sites around Greece are usually large scale open spaces that are colonized by dense populations of various weed species soon after the excavations. This causes severe problems to both the monument and the functionality of the site that includes mechanical damages to the architectural parts, obstruction of restoration and excavation works, obstruction of visitor access, visual exclusion of the monument, threat of fire during the dry summer period and chemical corrosion. The national law for the protection of man and the environment prohibits the spraying of pesticides in archaeological sites. Soil solarization is a non-chemical method of weed suppression that could be applied as an alternative method in archaeological sites. The aim of the study was to determine the most effective combination of plastic mulch type, application period and soil pretreatment in weed suppression. An experimental field was set up in the Agricultural University of Athens in July 2014. Soil solarization treatments included two types of plastic mulch (opaque and clear), two application periods (July to August and August to September) and two types of soil pretreatments (no tillage, with tillage). Weed species growth was significantly affected by soil solarization treatments. Visual ratings of weed control revealed that clear plastic mulching during July-August provided close to 100% control for six months after treatments, even without soil pretreatment. Clear plastic mulching during August-September provided four months of around 100% residual control, while opaque mulching provided only one to two months of above 90% control for both application periods and soil pretreatments. Lowest fresh and dry biomass weight was measured under clear plastic mulching applied July-August with no differences between soil pretreatments. Second best results concerning biomass weight were obtained by clear plastic mulching applied August-September, with no differences between soil pretreatments. In conclusion, it was shown that soil solarization can be utilized effectively as an alternative tool for weed control in archaeological sites.