When the meat from the Thanksgiving turkey is all eaten, making the leftover bones into broth is one way to stretch the bird’s value, but you can easily take it even further.
Boiling the bones to make broth cleans and softens them, which prepares them to be turned into powerful soil amendments: bone meal and bone char.
Both are simple to make, have numerous benefits for your soil health and can save you money. Once you get the hang of it, you can use this process for other leftover bones.
Bone meal is basically cleaned, powdered bones, commonly used in gardening to provide calcium and phosphorus. When burned, it becomes bone char, also a great source of phosphorus second only to fresh manure. Both options are best for somewhat acidic soils with a pH level less than seven.
Phosphorus helps plants develop strong root systems and produce good yields. Calcium also helps develop strong plants and leaves, and too little of it can lead to diseases such as blossom end rot in tomatoes.
Some people bury whole bones in the garden to let them decompose and slowly release nutrients, though this might be safest if your garden is securely fenced to keep critters out.
After making broth with the bones and cooking them until soft, allow them to dry out.
For bone meal, put the bones in a bag and crush them with a hammer, then grind them into a powder with a mortar and pestle. Or, instead of drying first, cook them until they are soft and grind the wet bones in a food processor, old coffee grinder or other grinding machine. Use a dehydrator to turn the paste into powder.
That second step is optional. Larger pieces will still break down over time. When it’s ready, the meal can be added directly to the soil, incorporated into your compost pile or added to compost tea at a rate of one tablespoon per gallon.
Making bone char is a bit more labor-intensive, but it can also improve the soil’s structure and ability to retain water, in addition to providing phosphorus and calcium and increasing crop yields. Recent research has also shown it can bind heavy metals such as lead and zinc in soil, reducing the amount that is taken up by the plants you eat.
To make it at home, burn bone meal or whole, cooked bones on a hot grill, in a wood stove or in an outdoor fire until charred. You may also have success roasting bones in the oven at 400 degrees for three to four hours.
Don’t worry about wood ash from the fire getting mixed in with the char — it’s a lime product that raises the soil pH. Maine farmers have been doing it this way for a long time: in an 1882 edition of this newspaper, members of the Penobscot Farmers Club recommended mixing wood ash and bone char with water as a low-cost and effective way to help “worn out” soil.
If you’re burning outside, check the fire danger in your municipality and make sure open burning is allowed in Maine’s current dry conditions.
Bone char and bone meal both store well, so you can keep it until spring. The application rate will vary based on your soil conditions. Typically, recommendations range from 1 to 15 pounds per 100 square feet.
If a test shows you have enough phosphorus in your soil, you might not need much, but the meal can also be used for animal feed.
