Bone Meal - Background

Background

Legally, for something to be classified as a fertilizer, it has to be a soil amendment that guarantees the minimum percentages of nutrients, primarily nitrogen, phosphorus, and potash. For a fertilizer to be considered "organic," it has to be derived from natural sources.

Bone meal once was often used as a human dietary calcium supplement. Research in the 1980's found that many bone meal preparations were contaminated with lead and other toxic metals, and is no longer recommended as a calcium source.

Bone meal, along with a variety of other meals, especially meat meal, is used as a dietary/mineral supplement for livestock. It is used to feed monogastric animals with bone meal from ruminants, and vice versa, to prevent the spread of Bovine Spongiform Encephalopathy (BSE) or "mad cow disease". Proper heat control can reduce BSE and salmonella contaminants.

As a fertilizer, the N-P-K (Nitrogen-Phosphorus-Potassium) ratio of bone meal is generally 4-12-0, though some steamed bone meals have N-P-Ks of 1-13-0. Bone meal is also an excellent source of calcium, but does not provide enough nitrogen to be beneficial to plants. Plants can only get phosphorus from bone meal if the soil pH is 7.0, according to recent Colorado State University research.

Organic fertilizers usually require the use of a variety of fungi in the soil to make the nutrients in the fertilizer bioavailable to the plant. For plants needing phosphorus, the fungi Mycorrhizae, penetrate the root break down the compounds containing the phosphorus for easier absorption and utilization, and in turn the plants supply the mycorrhizae with amino acids and sugars. In sterile potting soil, these fungi may not exist. Without these necessary fungi, which have a mutualistic relationship with the plants, plants could not utilize the needed nutrients in a high enough quantity for growth. Phosphorus, in particular, is needed for cell growth, as well as many other important functions.

While it has been long-believed that adding phosphorus to soils, as an amendment, "stimulates" root growth, in actuality it does not. If phosphorus levels are too high, the plant will not excrete the necessary organic acids that are needed to attract and feed the mycorrhizae. As a result, the plant will increase its root mass in an effort to compensate for the lack mycorrhizae at the expense of other plant tissues. The calcium in bone meal can wreak havoc on plants if too much exists in the soil. Phosphorus can be toxic to some plants, especially those of the Protea family of plants. It can also be toxic to those plants that have adapted to nutrient-poor soils.

Bone meal is frequently used, for the phosphorus, in preparing planting holes for blooming bulbs. The calcium in bone meal may help tomato plants prevent blossom-end rot. However, blossom-end rot can happen even with sufficient calcium present if watering is irregular.

Bone meal may also reduce the bioavailability of lead in soils contaminated with lead. Although, bone meal itself may contain lead (and mercury) in amounts that may be harmful to plants.