Making Bone Meal. 31 Mar 24.

 I made another batch of bone meal.  It's easy but takes a little effort.  And some bones.

Even though I am vegetarian, I make all of Rufus's dog food.  The main source of meat is chicken thigh or legs, both of which are high-taurine which some dogs require to prevent heart disease.

I slow cook the thighs and legs overnight.  The meat just slips off the bones easily.  This is probably easier than other bones.

Bird bones are light and more fragile than mammal bones.  This would not work for cow or pig or sheep.

The bones need to be thoroughly dry.  During the summer, I dry them in the sun room, which becomes very hot.  Sometimes I use the oven after baking something, and it is cooling off.  The temp doesn't matter.  I don't leave them sit around damp.  They would become moldy or attract creatures.  If it's a while before they can be dried, they can be frozen in a freezer bag. This time, I was also making chicken heart jerky.  I cut the hearts lengthwise, and dry in food dehydrator 145 F for 12-hours.  Rufus likes them and they are 100% meat.  At the same time, I spread the chicken bones on one of the trays and they dried just fine.

Then I pick a nice afternoon to sit on the deck with an audiobook and a granite mortar and pestle to smash and grind the bones into bone meal.

It's difficult to find a good analysis of trace chemical composition specifically of chicken bone, on line.  Also, analyses may be for bone without marrow.  Bone meal in general is an excellent source of calcium and phosphorus.  I saw some suggestions they also contain magnesium in trace amounts.  The brown color is from the marrow, which I imagine contains iron and protein (nitrogen) and some fat.   The N-P-K is about 3-15-0 (Wikipedia) and calcium is about 12%.   

As for use, bone meal needs to be mixed with soil, not on top.  It breaks down over about four months, so now is a good time.   It's best used in acid soil (Pacific NW, west of the Cascades for example).  In Steve Solomon's book about gardening in the NW, he states the rains leach calcium from the soil, so soils here benefit from nitrogen supplement (no reference, just my memory).  

Various sources recommend about a quarter cup of bone meal mixed with the soil when planting rose bushes.  I did that.  Also in garden bed preparation, I add about a cup per bed (40 square feet) or 1/4 cup per 4 foot row then mix in before planting.