The best thing you can do is dig up and remove the poison Ivy plants with a shovel however it poses the risk of getting the Poison Ivy rash if you come into Contact with the Poison Ivy plants.
So to kill off the Poison Ivy Plants before digging them up you can mix salt dish soap and water together and spray the Poison ivy Plants with the mixture.
Mix 1 Cup of Salt to One gallon of water and then add 1 tablespoon of dish soap and mix it up.
Then use a sprayer and spray the poison Ivy plants directly with the mixture.
Eventually the Poison Ivy Plants will start to wilt and die off.
After the Poison Ivy Plants die out then you should dig the plants out to their roots and then dispose of them and then spray the area every few months with this mixture to keep more Poison Ivy plants from sprouting.