Plants, fruits and vegetables always need a good amount of phosphorus and calcium to grow properly, and bone meal can be a good source of these nutrients. however; there is an average amount of bone meal that you need add.
The gold standard here is three cups per 100 square feet or about 10% to 15% of the garden bed’s area.
Of course for some plants the exact amount of bone meal needed may vary depending on the plant and the composition of the soil.
Let’s delve deeper into the topic.
About Bone Meal: What It Is & What It Does
Bone meal is a common gardening soil enhancer and organic fertilizer made from ground animal bones.
This chocks full of minerals, nutrients and other benefits that help flowers bloom, fruits develop and overall plant growth.
The main desirable minerals and nutrients of bone meal are calcium and phosphorus.
The following table compares the benefits versus some of the downsides ( pros and cons ) of using this powerful, slow-releasing amendment.
| Pros | Cons |
| Calcium-rich | Attracts animals, especially cats, dogs and other meat-eating predators |
| Phosphorus-rich | Soil must be acidic; a pH balance of 7 or lower |
| One-time application | It will not work in alkaline soil; pH of 7 or higher |
| Organic, safe and natural |
Deciding if Bone Meal is Right to Use
Just because bone meal is good for one soil doesn’t mean it’s appropriate for every situation.
So, it’s imperative to get a soil test done on your planting area to get an understanding of what your soil needs, what it has an overabundance of and what you should leave alone.
Once you understand what your soil needs, then you can determine how much bone meal to add.
For instance, if you use a test device to test the N-P-K ( Nitrogen , Phosphorus and Potassium ).
Your test will come back and there will be a letter “P” and a number following it.
The “P” means phosphorus and the number tells you how high or low those levels are in your soil.
The same can be applied with Nitrogen and Potassium ( N, and K ).
Understanding Your Soil Test
If the number is below 50, it’s low and if it’s below 25, it’s far too low. Should the number read higher than 75, the soil has too much phosphorus.
In other words, if you get a reading between 40 and 75, you shouldn’t add any bone meal to your soil at all.
Anything less than 40 should benefit from bone meal amendment.
However, even this will impinge on how acidic the soil is. Bone meal will not improve phosphorous levels if the pH balance is higher than 7.0.
This means you have to amend the soil with something else like rock phosphate, fresh manure or a plant fertilizer with a high amount of phosphorus.
Bone Meal to Soil Ratio
When you’re certain bone meal will be the perfect fix for your soil, consider the level of phosphorus from the soil test.
While 3 cups per 100 square feet is the standard, this isn’t a catchall measurement.
You should gauge by eye and use your soil test as a guide to tell you how much bone meal to add.
To illustrate, if you have a 40, then sprinkle 5% of the total planting area and gently mix it into the top part of the soil.
But, if you have a 20, then you may need to use 4 cups per 100 square feet and mix it down into the soil by as much as six inches.
How Much Bone Meal To Add To Soil?
Contrary to popular belief, you don’t need to dump an entire bag over the surface of your gardening plot and dig it in deep to mix with the soil.
If you had a large farming area or your soil is really depleted of things like calcium and phosphorus, then yes, you will do this.
But, for the typical garden bed, a simple shaker or sprinkle of the desired amount with a light mix into the upper portion of the soil will be sufficient.
You should add this two weeks to one month before you begin planting.
This will allow the bone meal to gently work its way into the soil in layers while evenly distributing nutrients.
Final overview on how much bone meal per gallon of soil.
If you’re looking to make the soil rich with bone meal, it’s not about weight.
The general rule is that you will add three cups of bone meal for every 100 square feet of soil.
But, this is not always going to be the case for every garden.
Using soil test results in relationship to the space will tell you how much bone meal to add or if you even need to add it in the first place.
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Nadine is a passionate gardening writer sharing practical tips, innovative ideas, and valuable insights on plant and soil care, In her spare time, she tries to convince her plants to grow by singing them catchy tunes.