What does it mean to dream about dog poo?

A meaningful interpretation is not possible without further information. For instance, what was happening with the cat soil? With whom? Where? A dream of a toddler playing in a cat litter box would be very different from, for example, a dream of flying poo at work. Very generally, excrement of any kind would symbolize the dreamer's feelings of disgust and/or the need to cleanse oneself.