What will the temperature of dry ice make soil?

For a science project we are wrapping dry ice in 2 sheets os newspaper. We are also using the blocks of dry ice not the little cubes but the purpose of it is we are surrounding a beaker with a growing plant inside of it. We know that dry ice itself is a ridiculously low temperature but does anyone know at least around how cold it could make soil in a beaker? the environment that its in would be wrapped in the newspaper surrounding the beaker in an insulated cooler. thank you!