Assertion: hay | /r/HasProperty | sprayed with chemical herbicides
Facets:
value: often
type: TEMPORAL
value: to keep unwanted weeds
type: PURPOSE
Source sentences:
text: Hay that is to be certified as weed-free for use in wilderness areas must often be sprayed with chemical herbicides to keep unwanted weeds from the field, and sometimes even non-certified hayfields are sprayed to limit the production of noxious weeds.