Bison and cow composts have different microbial populations due to the different diets and digestive systems of the animals. Bison are herbivores, while cows are omnivores, and this difference in diet can result in variations in the types and amounts of microbes present in their manure.
Bison manure typically has a higher proportion of microbes that are beneficial for plant growth, such as nitrogen-fixing bacteria, as well as a more diverse microbial population overall. This is due in part to the bison's diet, which consists mostly of grasses and other plants.
In contrast, cow manure may have a higher proportion of pathogens and potentially harmful bacteria due to their diet which may include a mix of grass and grains. However, cow manure also has a good amount of beneficial microbes for plant growth too.
Both bison and cow composts can be effective soil amendments, but the specific microbial population and nutrient content will depend on the specific materials used to make the compost and the composting method used.