Okay... This works best on an ex...and during the middle of summer... but perhaps could be altered to another situation.... like on the carpet under his bed (or on his matress under the sheet, sprinkled with some water from a little sprayer...
While the moon is high above the horizon and the sky is dark (middle of the night),  take a box (or 10) of powdered milk and sprinkle lightly yet liberally all over the grassy parts of the yard.   The dew shall fall and mix with the milk powder and seep into the ground.  When the sun hits high in the sky and the temps rise (best when it hits high 90's/+),  the milk shall sour and the yard shall reek!!!!  Will leave no trace to be tracked as to the source of the smell, yet will take weeks (if done correctly and no heavy rain fall)  for the smell to leave.
My bff told me I was evil back then.  Not evil, just vengeful!!!!