Influence of solar heating on herbicide dissipation in polluted soils

Solar heating techniques were tested to enhance the dissipation of eight herbicides belonging to four different chemical families (phenylurea, triazine, dinitroaniline and diphenylether derivatives). Guano, vermicompost, green manure, and goat manure were used as biofumigants for biosolarization. In all experiments, the soil was covered with high-density polyethylene (HDPE) film along 60 d after treatment and the results were compared with control plots. A significant increase in the soil temperature from 2 to 6 degrees C was detected in solarized soils as compared to control plots being probably the direct hydrothermal effect the most important factor on herbicide degradation. The behaviour of herbicides in mulched soils presents a faster phase of disappearance (15 d) followed by a slower phase (15-60 d). The mean half-lives ranged from 98 d in control plots to 17 d in the solarized soil amended with goat excrements manure being isoproturon and trifluralin the more and the less persistent herbicides, respectively. In all cases, significant differences (p < 0.05) in the persistence were observed between control soil and solarized soils for all herbicides. Therefore, the use of solar heating techniques, especially biosolarization can be considered as an environmentally friendly tool to enhance herbicide disappearance from the soil.