Sunlight can have a stronger influence than air temperature on soil solarisation: observational evidence from Australia

Soil solarisation is a method for pest and weed control pioneered in agriculture, and it is increasingly being adopted by restoration practitioners. Solarisation works by covering moist soil during hot periods with a sheet of clear plastic. The success of soil solarisation depends in large part on increasing the temperature of the topsoil. Topsoil temperature depends on several physical variables, including soil moisture content, ambient temperature, and sunlight intensity. In restoration scenarios, solarisation can be used to reduce weed and pathogen loads prior to planting target plants. It is rarely possible to have tight control over all the variables that are important for solarisation; however, practitioners can time interventions to maximise seasonal temperature and sunlight intensity. In this study, we investigated how these two key physical variables - temperature and sunlight - contributed to the success of soil solarisation. We found that while both ambient temperature and sunlight contributed to soil temperature, the data suggests that sunlight was the more influential driver of soil temperature. These results show that, when planning for soil solarisation during ecological restoration, land managers can benefit by considering sunlight as well as air temperature. The result that sunlight may be the more influential driver of soil temperature empowers land managers to better plan solarisation using sunlight projections, even when temperature is not optimal or is unpredictable. Our short article reports an original dataset on soil solarisation from a grassland restoration project in Australia. Using this dataset, we demonstrate that sunlight may be a more influential driver of soil solarisation than previously thought. This result empowers land managers to better plan soil solarisation for restoration projects.