It's applied directly to soil that grows food — which makes it a different kind of risk than packaging waste.
Plastic film mulch — thin polyethylene sheeting spread over rows to suppress weeds and retain soil moisture — is the largest single source of agricultural plastic pollution, and field surveys have found that farms with more visible macroplastic debris also show correlated increases in microplastic soil contamination [1].
That correlation matters for audit design: it means visible plastic debris on a farm is a legitimate, checkable proxy signal during a facility audit, not just an aesthetic issue. It's also why the MPFREE supply-chain scope specifically prohibits polyethylene agricultural mulch film rather than treating farm-level material choices as outside a product certification's scope — the plastic doesn't stay in the field; it fragments into the soil that grows the crop.