Made popular by Jean-Martin Fortier, silage tarps are used to kill weeds by occultation, whereby the plastic maintains a warm, moist environment that stimulates weed germination, blocks out light, and subsequently kills the weeds. Used in fallow fields to prevent weed growth, or placed on freshly prepared beds a few weeks prior to seeding or transplanting for a virtually weed-free environment for crop growth. For best results, orient black side up and secure well with sandbags, tires, etc. 5 mil black/white polyethylene. UV resistant. Approximately 120 lbs.