What are disadvantages of using plastic in farming, especially organic farming?

Question

Toxic chemicals those are released, its effect on the crops and ultimate consumers?

Answer 1

Most plastics are pretty stable, and will release few toxic chemicals.  There are exceptions (polycarbonate has come under scrutiny recently for releasing bisphenol A), but the releases are likely to be small.  The larger problem comes in disposal.  Plastic sheets must be replaced each year/crop, and plastic does not degrade in landfills...