Generations of farmers and gardeners have used bone meal as a fertilizer for trees, shrubs, perennials, bulbs and vegetables. Although organic bone meal can be a reliable and effective fertilizer, it's important to understand how it is used and also be mindful of potential concerns.
Bone Meal at a Glance
Bone meal is a type of fertilizer made from the steamed, sterilized, crushed, and ground bones of animals. The end product is available in different grades from course to fine. It is a slow release fertilizer so benefits may not be noticed immediately, but because bone meal breaks down slowly, it does not need to be applied as often as other fertilizers.
Bone meal is an excellent source of calcium and phosphorus in the garden, but also contains trace amounts of nitrogen and potassium. Store-purchased bone meal products may contain other additives. The average NPK ratio for bone meal is 1-11-0 with 20% total phosphate and 24% calcium.
Bone meal is a good source of phosphorus, which helps primarily with root growth in plants. Root vegetables such as carrots and onions benefit from bone meal. Similarly, flowers grown from bulbs, corms and tubers will also benefit.
The calcium boost from bone meal helps with cell and seed formation, strengthens stems, and encourages new shoots in perennials and shrubs. It can also help prevent blossom end rot in tomatoes and other vegetables.
Do not look for immediate results after applying as it takes time for bone meal to be converted into a form that plants can use. Bone meal should be mixed well into the soil to help disperse nutrients. It has an alkaline reaction with soil, so avoid applying around acid-loving plants such as azaleas and rhododendrons. Bone meal may need to be used with other amendments to create the right balance of nutrients.
With certain soils, bone meal may not be the best fertilizer to choose. In soils with very high pH, phosphorus can be present in the soil, but not in a form that can be readily used. In this case, adding bone meal will not be helpful. When in doubt, a soil test done by your Cooperative Extension can tell you exactly how to amend and balance your soil.
Bone Meal and Pets
Because bone meal is made from crushed animal bone, it can entice dogs and other animals to lick or scratch at the soil. It is important to work bone meal into the soil, rather than simply adding it on top. Store bone meal out of the reach of pets.
Potential Risks to Humans
There has been speculation about whether inhaling bone meal dust could cause bovine spongiform encephalopathy (BSE), known commonly as Mad Cow Disease. Numerous independent studies have shown that there is little risk. As Lori Bushway of Cornell Cooperative Extension explains, bone meal fertilizer sold in the U.S. should be free of the agent that causes BSE because domestic manufacturers use a method in the rendering process that destroys the BSE agent. In addition, bone meal can no longer be imported from England, where BSE had infected cows.
The U.S. Department of Agriculture has an active program of testing for BSE. The likelihood of being infected with BSE from using bone meal fertilizer is extremely remote.