Bone meal is a byproduct of animal rendering, a mixture of finely-crushed bones that is a slow-release organic fertiliser. It does not pollute the environment like many chemical fertilisers. It is high in phosphorus with an NPK ratio of 4-12-0. Phophorus helps support health root development. Bone meal is generally placed into the hole where new plants are being set. Other fertilisers also provide high amounts of phosphorus that can substitute for bone meal.
Rock phosphate is a byproduct of rock mining. It has a high phosphorus content and is used to increase the fertility of soils and as a substitute for bone meal. It is particularly good for planting bulbs and other flowering plants. Rock phosphate has an NPK ratio of 0-3-0, according to OrganicGardenInfo. It releases phosphorus very slowly into the soil.
Soybean meal can also be used as a substitute for bone meal because the NPK ratio is 7-2-1, supplying sufficient phosphorus for root growth. However, according to the a North Carolina State University examination of the effects of soybean meal on young plants, the high nitrogen level in soybean can burn the tender roots. The university suggests working the soybean meal into the soil at least two weeks before planting to allow the soybean meal to break down.
Crab meal is produced from the shells of crab and has an NPK ratio of 5-2-0.5, according to BasicInfo4OrganicFertilizers. One of the benefits of using crab meal is a substance in it called "chitin." Chitin releases enzymes that help to control nematodes in the soil. Crab meal is a slow-release fertiliser. Using mulch in combination with crab meal will help to retain moisture and sustain the time release features of the fertiliser.
Poultry manure is an organic fertiliser that is naturally high in phosphorus and can be used as a substitute for bone meal. All types of poultry manure exhibit this high phosphorus content though there are variations in the percentages, according to North Carolina State University. Poultry manure should be applied as uniformly as possible. The manure can cause leaf burn when in contact with foliage.
With an NPK ratio of 4-13-1, bat guano has all the high phosphorus advantages as bone meal. It also adds microorganisms and trace elements that help detoxify soil, according to BetterOrganicGardening. It can also be soaked in water and made into a tea that is then applied to the soil around plants.