Know a Humane Way to Get Rid of Voles in the Garden?

Do you have any suggestions for a humane way to get rid of voles in the garden? Have tried the environmentally friendly Swedish remedy deer repellent, Plantskydd, which did nothing except make the treated areas smell like a rendering plant when it rained. Voles excavated right next to treated areas overnight. They are eating the roots of wanted plants, but I don’t want to poison them.