Preventing post-poop kicking?

I don't know, and I don't think anyone has studied this subject, but my guess is that scent travels better when attached to particulate in the air, so kicking up some dust helps spread the scent.

The good news is that, even if you don't know why your dog is doing this, you can make a difference in when, where, and how much your dog kicks. The post-poop dirt scratch is part of a pattern (like circling is part of the pre-poop pattern) so your timing needs to be spot on and you will need to be patient as you work with your dog. If you have a puppy, a habit of not kicking will be easier to install than if you have an older dog who has had this habit for a while.

Step one: Observe

Your dog is likely repeating the same pattern each time he goes. Learn your dog's pattern--really watch how your dog moves. Does he take three steps then kick? Or is it one step?

Step two: Plan

Part A: Take what you learned about your dog's pattern of behavior and form a plan to interrupt it. Have an exact plan of action and a back-up plan. I was working with a very feisty kicker the other afternoon. Her owner and I used a squeaker toy right after she pooped to get her attention. She ran right to the squeaker (about 6 steps), sniffed it, and finished her kicking. If I had planned better I would have also had a treat ready to lure her into a sit.

Part B: Be reasonable. Interrupting patterns is hard work; don't make it harder for yourself. I have a medium-sized hound dog who loves to kick after peeing and pooping. There are a lot of wood chips on the paths where we walk and he prefers to pee and poop over the chips. Because the paths are paved, all I have to do is interrupt the kick and get him onto the cement. Once he's on the cement I let him kick away (and I've never have to trim his back nails).

Step three: Practice & Reward

Your dog may not learn to do this right away. You will need to be a willing and enthusiastic coach and you will need to remind him all the time in the beginning. Be nice. When you first start this, just focus on the interruption. If you can interrupt your dog, reward him well. Don't be mad at yourself or your dog if he finishes kicking after the reward.

Hints

Know what your dog wants! If your dog likes food, use it. If your dog is mad for squeaky tennis balls, use those.

Interrupt your dog BEFORE he kicks--this is where knowing the pattern helps.

Try replacing the kicking with another behavior, like spin, jump, give-five, or tug.

Once you get 95% success, start paying your dog for performance. If he does the work, he gets a big reward. If you do the work (heavy encouragement needed to interrupt the kicking), he gets a reward, but not as much.