Why is the plastic bags harmfull to the soil?

plastic bags are harmful to the because they release chemicals which remove the nitrogen content  of the soil and they make the soil infertile.

because they are non- biodegradable i.e., they cannot be broken down into simpler substances by microbes present in the soil. Hence, they remain persistent and cause blockage to the passage of air in the soil and also lead to the loss of fertility of the soil.