A material in the form of a sheet for enveloping a bale of agricultural material is coated with or contains a preservative in order to prevent spoilage of wrapped bales of agricultural material by aerobic organisms. A second interlayer insulating film provided with a bonding pad on an upper surface has a three-layered structure including an F doped silicon oxide film, a TEOS based silicon oxide film and an SiH4 based silicon oxide film. The valve characteristic variable mechanism includes electrically operated motors for changing operational timings and lift quantities of the above-mentioned engine valves. A control system sends a control signal for setting each said individually controllable elements to a desired state.