Blood meal is a popular natural amendment for gardeners seeking an organic boost for their plants. This dried, granular material is used primarily to supply a concentrated source of nitrogen to the soil. Its use is favored in organic gardening practices for promoting vigorous, green growth, especially when soil tests indicate a nitrogen deficiency.
Composition and Sourcing
Blood meal is a byproduct of the meat processing industry, typically sourced from the blood of cattle or hogs collected at slaughterhouses. The collected material is dried and processed into an inert, dark-colored powder or pellet form.
The primary nutritional profile is its high nitrogen content, often represented by an NPK ratio around 12-0-0 or 13-0-0. It contains approximately 12 to 13 percent nitrogen by weight, with only trace amounts of phosphorus and potassium. The nitrogen is present as protein, which is quickly broken down by soil microorganisms into forms plants can absorb, making blood meal a fast-acting organic fertilizer.
Practical Application Guidelines
When applying blood meal, it is important to mix it directly into the top few inches of soil before planting or use it as a side-dressing for established plants. This ensures the nitrogen is readily available to the roots and minimizes the attraction of unwanted animals to the surface of the soil. For existing plants, a common guideline is to apply about one teaspoon per plant, or one to two pounds per 100 square feet of garden space.
Blood meal is highly concentrated, so gardeners must use caution to avoid over-application, which can result in nitrogen toxicity, commonly known as “burning” the plant. Because of its effect on vegetative growth, it is particularly beneficial for heavy nitrogen feeders like leafy greens, brassicas, and corn. Plants showing signs of nitrogen deficiency, such as yellowing of older leaves, are good candidates for a light application.
The concentrated nitrogen can also be dissolved in water to create a liquid feed. Conversely, plants that require low nitrogen levels or those grown for root development, like carrots or potatoes, may not benefit from a high-nitrogen amendment. Excessive nitrogen can promote too much leafy growth at the expense of flower or fruit production, so it should be used strategically.
Key Advantages and Potential Drawbacks
A primary advantage of blood meal is its ability to accelerate vegetative growth and help plants achieve a deep green color. As an organic source, it supports the soil food web and can be used to balance the carbon-to-nitrogen ratio in a compost pile, speeding up decomposition. The strong odor of blood meal may also help to deter certain garden pests, such as rabbits and deer, when lightly sprinkled around the area.
The high concentration of nitrogen presents a risk of damaging plant roots and foliage if the recommended application rates are exceeded. This potential for nitrogen burn is a major drawback of using this amendment. Another concern is that the scent of the product can attract domestic dogs and some wildlife, such as raccoons, who may dig up the treated garden beds in search of the source. Blood meal can also function as a mild acidifier, temporarily lowering the soil’s pH, which should be considered when applying it to already acidic soils.