Whether it's your own cat or the neighborhood stray doing the dirty deed, it only takes one hot summer day to realize you've got a problem with cat urine odor in your yard. Finding a cat urine stain in dirt can be a challenge, but once you do, the tried-and-true methods for removing cat urine odors indoors can be adapted for use outside as well.
Locate the spot
Wait until it gets dark. Follow your nose, and bring a black light with you (you can find one at your area home goods or hardware store). Shine the black light around where you think the odor is. The spot will glow yellowish green. Mark all spots with chalk so you can find them in daylight.
Use a shovel or rake to loosen the earth at the offending spot, if possible. This will allow the cleaning mixture to penetrate better.
Mix 2 cups water with 1/2 cup apple cider vinegar, and pour over spot. Let sit overnight. Turn the earth again in the morning.
Mix 2 Tbsp. dish liquid detergent with 1 bottle hydrogen peroxide. Pour over spot. Let sit 10 minutes.
Cover spot completely with baking soda. Turn the earth again.