Blood meal fertilizer is a type of plant fertilizer best used on vegetable gardens that require a lot of nitrogen to grow. Made of dried, powdered animal blood, blood meal fertilizer is created as a byproduct at slaughter houses. In addition to its use as a nitrogen fertilizer, blood meal can also be used as a pest deterrent for small mammals and as an decomposition aid in compost piles.
An organic fertilizer, blood meal contains no artificial materials. It is considered a nitrogen fertilizer, which means it replaces the nitrogen in the soil that plants use to grow. Bacteria in the soil, which eat organic material, break the protein which is plentiful in blood down into ammonia and other substances. The nitrogen in the ammonia is then processed by the plants and used to create plant protein, which allows the plant to produce green leaves.
The need for nitrogen in leaf production is why this type of fertilizer is best for leafy seasonal plants that grow quickly, such as many vegetables. It should not be used for beans, however, since these plants have bacteria in their roots that fix nitrogen from the air and do not obtain that nutrient from the soil. Additionally, care should be taken in humid conditions since humidity can cause decomposition to accelerate, possibly harming plant roots. Blood meal fertilizer is also less desirable for use on any cabbage family plant because the addition of large amounts of ammonia to the soil raises the pH to undesirable levels.
When applied, blood meal fertilizer should be blended into the soil. Though it is always applied once the plants are growing, blood meal should not be placed on seedlings. Once applied, the fertilizer should last about four months.
Blood meal fertilizer can also be used as a pest deterrent. Scattering the fertilizer around the area rather than blending it into the soil is particularly effective to keep away deer, rabbits, or other mammals which are likely to find the garden a handy food source. Although the fertilizer's smell deters many herbivorous animals, it may attract carnivorous ones, such as dogs and raccoons.
Since blood meal fertilizer adds nitrogen to soil, it works to maintain the balance of carbon and nitrogen in compost heaps as well. This balance is necessary for compost to decompose effectively. If a compost heap contains high amounts of carbon, it made be necessary to aid blood meal fertilizer, or another nitrogen fertilizer, to help increase the rate of decomposition.