Issue: April 7, 1997

Bone meal and mad cow disease

I saw a television program about Mad Cow disease and on in the program they warned us that it was dangerous to use bone meal in the garden. Most of the books I read recommend bone meal, especially for bulbs. What can I do? Is it really dangerous? What else can I use?

I didn't see that program, but I did find an article written by a medical doctor about this topic. If you have a computer and access to CompuServe and want to read the article I found, it is in the Garden Forum with the title "bonemeal.txt". It also referenced a USDA website for those who have access to the World Wide Web (http://www.aphis.usda.gov). The website has excellent and detailed information about bovine spongiform encephalopathy (BSE), the Mad Cow disease that has been in the news and is the cause of concern over the use of bone meal.

There were apparently four deaths of gardeners in Great Britain attributed to use of bone meal from cattle which may have had this disease. It is believed that they inhaled bone meal dust as they were applying bone meal to their garden. The first point made by the doctor who wrote the article was that the rendering process which generates bone meal used in Great Britain in the 1970's and 1980's was a part of the problem. The process used in the United States is different and appears to produce a safe bone meal. The second, and a very important consideration, is that BSE has not been detected in cattle in the U.S. The U.S. Department of Agriculture has an active program of testing for BSE and veterinarians across the country are involved. Any cattle suspected of exhibiting BSE symptoms are tested. None have been shown to be infected in the U.S. No cattle or meat from British cattle have been imported into the U.S. since 1989, so the chance of coming into contact with contaminated bone meal is extremely remote. Nevertheless, if you wish to be absolutely certain to avoid infection, you can wear a dust mask when handling bone meal or you can switch to another source of phosphorus in your garden.

In New Mexico, bone meal is not the gardener's best source of phosphorus. In most New Mexico soils, the phosphorus is not available to the plants. Our calcareous soils with their high pH keeps the phosphorus insoluble and therefore unavailable to plants. This is why, while there is often phosphorus in the soil, we must add soluble, available, phosphorus. Phosphorus is present in most fertilizers, in super phosphate, triple super phosphate, colloidal phosphate and other forms. You may choose to use one of these. The commercial phosphate fertilizers have been treated to make them more soluble, but that is a temporary situation in our New Mexico soils. Colloidal phosphate must be added in much higher concentrations than the others to provide sufficient phosphate to the plants. In any case, the soil eventually binds the phosphate as it reacts with the calcium and forms insoluble calcium phosphates. Addition of organic matter, sulfates, sulfur, or other acidifying materials will help prolong the availability of phosphate, but this is an ongoing process. At least there is no concern that a gardener will get sick from properly using these sources of phosphorus.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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