Just not clear as to when and where I would use either of these products?
Thank you for contacting the Toronto Master Gardeners. Blood meal, bone meal, and wood ash have been used for many decades by organic gardeners and farmers as soil amendments (supplements) to add Nitrogen, Phosphorus, and Potassium (respectively) to the soil.
Blood meal is dried and powdered animal blood. Bone meal comes from the ground bones of animals.
Blood meal increases soil nitrogen levels, and is especially useful to add to leafy vegetables (but not cabbages). The nitrogen is released into the soil relatively quickly so do not use it around seedlings, and place it so that it does not touch the plant stems. You can do this at any time during the growing season. Gently dig it into the topsoil. Follow the direction on the packet for quantity. Blood meal keeps squirrels and other rodents away so it is also useful to add a bit of blood meal around your bulbs when you plant them in the fall.
There is emerging research against using bonemeal in the garden. There are a number of articles from Washington State University by Linda Chalker-Scott on the use of soil amendments such as bone meal. She states that bone meal should no longer be utilized as a supplement when planting trees and shrubs as it inhibits mycorrhizal fungi growth. See Linda Chalker-Scott on the Myth of Bonemeal. https://s3.wp.wsu.edu/uploads/sites/403/2015/03/bonemeal.pdf
Until we know more, perhaps it would be a good idea not to add bonemeal to your garden.
I hope this is helpful. Happy gardening.
June 12,2021