Soil is what makes life possible, says the documentary Symphony of the Soil, playing Saturday at the Roxie. The film explores the science of the precious planetary resource across four different continents, giving audiences an insight into how the soil is being affected by, and effecting, environmental changes. The filmmakers have consulted and interviewed experts from many fields — geologists, farmers, chemists, biologists, and nonprofit leaders — who lend their voices to the film. The filmmaker, Deborah Koons Garcia, won several awards for science and food films for her endeavor, which brings to light the complex relationship we have with the "earth's skin." Soil will never look so beautiful.