Using bone meal for plants has been passed down for generations. It is made from ground animal bones and comes in a granular or powder form.
When I did a lot of landscaping as a teenager and in my early 20s, I was using bone meal for almost all of my plantings, but then I learned about the potential risks and studied organic gardening and learned about a few superior products.
Since the mid-1980s and especially the late-90s, there has been concern as to whether using bone meal for plants might be harmful, as inhaling the dust can cause a form of Mad Cow Disease in humans.
I think there are a lot more important things to worry about, but if you're into the precautionary principle, you might want to use something else.
In the SOUL Organic Land Care Standard, it says using bone meal is “Permitted only if guaranteed free of specific risk materials (e.g. prions associated with Mad Cow Disease). Use is strongly discouraged due to the potential spread of prion diseases.” (Source)
Many certification bodies in Europe and Canada (Source) have prohibited its use due to the risk of BSE contamination. Organic bone meal is often exempt, but almost impossible to find.
It’s fairly difficult to guarantee the bone is free of prions, since the nerves run through the bones, and since it's very difficult to kill them no matter how much heat and toxic chemicals are applied, so most of us organic gardeners just don’t use it.
Many scientists claim there is little risk to humans from using bone meal for plants, but there are some who are seeing disturbing trends (here are some articles).
I won’t get into the science here and I don’t pretend to understand it all, but I've decided to follow the precautionary principle and stay away from using bone meal in my organic garden.
My goal is not to scare you away from using it, but just to let you know about this Mad Cow thing, and to let you know about some other great products you might want to look at instead.
Bone meal supplies phosphorus and a few other elements, but conventional and organic gardeners mainly use it for the phosphorus because it is supposedly important for root development, which is kind of true.
The other things is, how do you know you need phosphorus? Maybe your soil has enough or too much already, and adding more might just throw the nutrient balance in the soil more out of whack.
Adding any concentrated minerals just for "good measure" is inappropriate, as it can set off a string of unintended reactions in the soil. Good organic gardening practice is to add specific minerals only when you know you need them, generally based on an organic soil test, and using bone meal for plants is no different.
What you use instead of bone meal for plants depends on how much effort you want to put into this, but the cost isn’t much and neither is the time. There are the 3 products I generally use when planting in my organic garden.
I talk about them in my next article: Bone Meal Alternatives
Update: Some people say I'm scare-mongering with this post. I actually thought I was pretty laid back about the whole thing. It's important for me to note that this is just a blog post. It's not meant to be an authoritative dissertation with all kinds of sources. Indeed, a lot of the chatter about using bone meal and Mad Cow Disease is over 10 years old (like this website) and I don't know much about the research going on now - it's just that when I was studying organic gardening, I was taught to avoid using it because my national organic standard didn't allow it, and still does't allow it. You're certainly welcome to use it. I'm not trying to offend or scare anyone. Have a nice day!