Ants have a certain kind of food that they prefer. Fire ants collect animal protein and and fats. Many ants bring the food home and, rather than eating it, they farm that food until the right fungus or bacterium grows on it. Then they eat the microbes. Knowing that ants are farmers helps to understand what causes them to vacate an area. If you can disrupt their farming activities, they will go away (in theory). Two things come to mind as biologically offensive to farming proteins. Those are the addition of sugars and yeasts. Spraying the yard with molasses at 3 ounces per gallon is easy enough. If you could infuse the molasses with something like bread yeast, that might enhance the damage done to the underground farms. I don't know enough about yeast to know if it completely dissolves so as to flow through a hose end sprayer. You would have to spray the entire yard if you don't want them to just move around within it.