Let’s face it – a natural garden is much better than one that uses artificial chemicals. In addition to providing nutrients, natural fertilizers also add organic material, improve soil structure, and attract beneficial organisms (earthworms and bacteria).
So, how do you add nutrients to soil without fertilizer – naturally? Compost and manure are natural ways to add nutrients to soil. Add feather meal, blood meal, or fish meal to provide nitrogen. Add hair, bone meal, and worm castings to provide phosphorus. Add burned cucumber skins, kelp, and wood ash to provide potassium. Add crushed egg shells to provide calcium.
Of course, the ingredients you use in your compost will depend on what nutrients you want to add the most of. A soil test can help you to determine which (if any) nutrients are lacking in the soil.
In this article, we’ll talk about the many ways you can add nutrients to your soil – without artificial fertilizers made from harsh chemicals.
Let’s get going.
How To Add Nutrients To Soil Without Fertilizer (Naturally)
On a commercial farm, chemical fertilizers are common and difficult to avoid. However, it doesn’t need to be that way in your home garden.
Whether you need a boost of one specific nutrient or a balanced supplement, there is bound to be something you can use on this list. Let’s start with balanced sources of nutrients: compost and manure.
Natural Fertilizers for Plants
Compost and manure serve several purposes in a home garden, such as:
- Adding nutrients to soil (including NPK, or nitrogen, phosphorus, and potassium)
- Adding organic material to soil (attracts beneficial organisms, like earthworms and bacteria)
- Improving soil structure (making clay soil drain better, and making sandy soil retain water)
The key is to make sure that they are properly aged and to use them correctly.
Compost
Compost is made from kitchen scraps and garden waste. Given enough time, bacteria and earthworms will break down this material and convert it into a form that plants can use.
Compost is made from a mix of “green” (nitrogen rich) and “brown” (carbon rich) materials.
Some common green materials for compost include:
- Grass clippings
- Leaves
- Weeds
- Fruit and vegetable scraps
Some common brown materials for compost include:
- Pine needles
- Sawdust
- Wood ash
- Cardboard
There are certain materials that you should avoid composting, including:
- Meat and fish
- Bone
- Dairy Products
It is necessary to keep compost wet enough so that decomposition will occur. However, the compost should not be soggy.
Compost is a slow-release fertilizer. This means the nutrients in compost become available to plants gradually over time, rather than all at once.
Compost provides a good mix of nitrogen, phosphorus, and potassium, along with other nutrients.
You can learn more about how to make compost in my article here.
Manure
Manure is animal waste and bedding, which provides a good source of nutrients for plants. As with compost, manure should be aged properly before using.
If you apply manure to your garden before it ages, the salt content could burn your plants. A better option is to add aged manure to your compost and mix the combination into your soil.
Manure is a medium to fast-release fertilizer. This means the nutrients in manure become available to plants faster than those in compost.
Manure provides a good mix of nitrogen, phosphorus, and potassium, along with other nutrients. Manure can have a much higher nutrient content than compost.
Natural Sources of Nitrogen for Plants
Sometimes, a soil test will reveal a nitrogen deficiency in your soil. This can happen if you plant vegetables that use up nitrogen without using crop rotation or cover crops (green manure).
Using chemical fertilizers with too much nitrogen can cause algae on water or in wet areas of your garden or greenhouse.
If you need to add a dose of nitrogen to your soil, the following natural materials will help. You can learn more about them in my article here.
Feather Meal
Feather meal comes from poultry feathers. The process involves heating the feathers under pressure and grinding them into powder.
Feather meal does not dissolve in water. It is a slow-release fertilizer, and it is effective for 4 to 6 months.
Feather meal contains 15% nitrogen by weight – much more than compost or manure. This makes it an excellent natural source of nitrogen for your soil.
If you raise poultry, you can also add feathers to a compost pile to get a nitrogen boost. The only drawback is that feather meal does not have any phosphorus or potassium.
For more information, check out this article on feather meal from Wikipedia.
Blood Meal
Blood meal is made by grinding dried blood (from cattle, hogs, or chickens) into powder.
Blood meal contains 12.5% nitrogen by weight – not as much as feather meal, but still much more than compost and manure.
Blood meal has a medium-release speed, and it is effective for 6 to 8 weeks. As an added benefit, blood meal has 1.5% phosphorus and 0.6% potassium by weight.
For more information, check out this article on blood meal from Wikipedia.
Hoof and Horn Meal
Hoof and horn meal is made by grinding up the hooves and horns of animals into powder.
Hoof and horn meal contains 9% to 14% nitrogen by weight, making it a great natural source of nitrogen for your garden.
In addition, hoof and horn meal has 1.5% to 2% phosphorus. However, it does not contain any potassium.
For more information, check out this article on hoof and horn meal from Feedipedia.
Fish Meal
Fish meal is a powder made from grinding up fish remains, including bones.
Fish meal contains 10% nitrogen by weight, making it a good natural source of extra nitrogen for plants.
Fish meal has a medium-release speed, and is effective for 4 to 6 months.
In addition, fish meal contains 4% to 6% phosphorus by weight. It does not contain any potassium, though.
For more information, check out this article on fish meal from Wikipedia.
Crab Meal
Crab meal is made by grinding up the remains of crabs, including the shell. The shell contains chitin, which helps plants to protect themselves from diseases.
For more information, check out this article on chitin from Wikipedia.
Crab meal has 10% nitrogen by weight, making it equal to fish meal as a natural source of nitrogen for plants.
Crab meal has a slow-release speed, and is effective for 4 to 6 months.
Crab meal also contains tiny amounts of both phosphorus (0.25%) and potassium (0.05%).
Bat Guano
Guano is waste from seabirds and bats. Bat guano contains 5.5% to 8% nitrogen by weight, making it a better natural source of nitrogen than compost or manure.
Image from: https://commons.wikimedia.org/wiki/File:Fulvous_leaf_nosed_bat.jpg
It will be a challenge to find bat guano yourself, so you will need to buy it from a store or online.
Bat guano has a medium-release speed, and is effective for 1-2 months.
Remember that bat guano is very acidic (it has a low pH). As such, use it with caution to avoid burning your plants with a sudden change in pH.
You can also add bat guano to a compost pile to dilute its acidity before mixing the combination into your soil.
As an added benefit, bat guano contains quite a bit of other nutrients: 4% to 8.6% phosphorus and 1.5% potassium by weight. This makes it a good balanced fertilizer that provides plenty of each nutrient.
For more information, check out this article on guano from Wikipedia.
Soybean Meal
Soybean meal provides protein and energy for both people and animals. Soybean meal is produced by extracting soybean oil from the beans. Soybean meal might also contain ground up soybean husks.
Image courtesey of the United Soybean Board from: https://commons.wikimedia.org/wiki/File:Soybean_Meal_(10059014026).jpg
Soybean meal has 6.5% nitrogen by weight, making it a fairly good natural source of nitrogen.
As a bonus, soybean meal also has 1.5% phosphorus and 2.4% potassium by weight.
Soybean meal has a slow to medium-release speed.
For more information, check out this article on soybean meal from Wikipedia.
Cottonseed Meal
Cottonseed meal is made by extracting cottonseed oil from cotton seeds. Cottonseed meal has 4% to 6% nitrogen by weight, which means it is better than manure and compost.
Cottonseed meal has a slow to medium-release speed, and is effective for 4 to 6 weeks.
Cottonseed oil is somewhat acidic, so mix it into compost instead of directly into soil.
Cottonseed oil also contains 2.5% to 3% phosphorus by weight and 1.6% potassium by weight, giving it a good balance of nutrients.
For more information, check out this article on cottonseed meal from Wikipedia.
Fish Emulsion
Fish emulsion is made from what remains after fish is processed for fish oil or fish meal.
Fish emulsion has 5% nitrogen by weight, meaning it is still a better natural source of nitrogen than most compost or manure.
Fish emulsion also has 1% phosphorus and 1% potassium by weight, rounding out the nutrient profile of this natural fertilizer.
Fish emulsion has a fast-release speed, and is effective for 2 weeks.
You can either spray the foliage of plants with fish emulsion (for foliar feeding) or apply a diluted solution to the soil.
For more information, check out this article on fish emulsion from Wikipedia.
Natural Sources of Phosphorus for Plants
If a soil test reveals a phosphorus deficiency in your soil, there are a few materials that can replace it naturally. You can learn more about them in my article here.
Hair
Hair is a completely natural source of phosphorus for your garden. However, it might be the first thing that comes to mind when you think about fertilizer for a garden.
Still, hair has 26% phosphorus by weight. This makes it one of the best natural sources of phosphorus that you can find.
The trouble is that it can be difficult to find enough hair, since it takes a lot of hair to make up a pound. If you know a barber, you might be in luck!
The only problem is that hair from barbershops will often contain chemicals, such as hair spray or gel, which you may not want to mix into your garden soil.
Hair has a very slow-release speed, and it is effective for 4 to 12 months.
Mix hair into a compost pile instead of applying it directly to your soil.
As if the high phosphorus content weren’t enough, hair also contains 12% nitrogen by weight. However, it does not contain any potassium.
Bone Meal
Bone meal is made by grinding bones into powder. Bone meal has 15% to 27% phosphorus by weight – not as high as hair, but still a great natural source of phosphorus for plants.
Bone meal has a medium-release speed, and is effective for about 6 weeks.
As a caution, remember that bone meal may burn plants if used in high amounts.
As with many other supplements, mix bone meal into your compost pile instead of adding it directly to your soil. After a few months to a year, you will have a balanced compost mix with plenty of nutrients for your plants.
Keep in mind that plants can only absorb phosphorus from bone meal if the soil pH is below 7.0 (acidic). The only way to tell for sure is to do a soil test.
Bone meal also contains plenty of calcium, along with 2% to 6% nitrogen by weight. However, it contains no potassium.
For more information, check out this article on bone meal from Wikipedia.
Worm Castings
Worm castings come from vermicomposting, where worms are used to help decompose vegetables and food waste and turn it into fertilizer. Worm castings contain nutrients and organic material.
Worm castings have 2.5% phosphorus by weight, meaning that they contain higher amounts than compost. Worm castings also have 1.5% nitrogen and 1.3% potassium by weight, making it a balanced source of nutrients that will not burn plants.
For more information, check out this article on vermicompost from Wikipedia.
Natural Sources of Potassium for Plants
There are also some natural options for adding potassium to your soil. You can learn more about them in my article here.
Burned Cucumber Skins
As surprising as it is, burned cucumber skins are a great source of potassium for plants. They contain 27% potassium by weight.
The only difficulty is finding enough cucumber skins to make this a feasible source of potassium. A local restaurant might have some if they serve salads.
Burned cucumber skins have fast-release speed.
Burned cucumber skins also have 11% phosphorus by weight. However, they do not contain any nitrogen.
Kelp
Kelp is a large seaweed that grows underwater in clusters called “forests”. Kelp is brown and grows in nutrient-rich water.
Kelp has 4% to 13% potassium by weight, which makes it a good source for this nutrient.
Kelp has a slow-release speed, and is effective for 4 to 6 months.
As another benefit, kelp contains 1% nitrogen and 0.5% phosphorus by weight.
For more information, check out this article on kelp from Wikipedia.
Wood Ash
Wood ash what remains after you burn wood. The nutrient content of wood ash varies, depending on the type of wood that was burned.
Most wood ash has 3% to 7% potassium by weight, making it another good source of this nutrient.
Wood ash also contains 5% phosphorus by weight, but it does not contain any nitrogen (since nitrogen is burned off into the air when the wood combusts).
Wood ash has a fast-release speed, and is effective for 1 to 4 months. It is alkaline (basic), so be careful about adding wood ash to soil with high pH.
Also, don’t use ash from wood that was treated with chemicals – you don’t want to put toxins into your garden.
For more information, check out my article on wood ash.
You can also check out this article on wood ash from Wikipedia.
Sawdust
Sawdust is what remains after trees are processed into boards, or after boards are cut for carpentry projects. However, it should not be treated as waste!
In addition to its use as mulch or in particle board, sawdust can act as a fertilizer. When used as fertilizer, sawdust contains 2% to 4% potassium by weight.
Sawdust also has very small amounts of nitrogen and phosphorus by weight (less than 0.1%).
Sawdust has a very slow-release speed, and is effective for 2 to 4 years.
One caution about using sawdust is that it can cause nitrogen deficiency, due to the high carbon content. You can learn more in my article on how to compost sawdust.
For more information, check out this article on sawdust from Wikipedia.
Natural Sources of Calcium for Plants
You may also find that your soil has a calcium deficiency. In that case, some of the natural fertilizers mentioned earlier (wood ash and bone meal) will provide some calcium.
However, there is an even better natural source of calcium for plants.
Shells (Egg, Oyster, or Clam)
Shells from eggs, clams, and oysters contain lots of calcium, in the form of calcium carbonate. According to Scientific American, the shells are mostly calcium carbonate (about 98%), with the remaining 2% made up of protein and other trace minerals.
(Calcium carbonate is the same compound that makes up agricultural lime).
Just like other fertilizers, shells are act faster when you crush them into smaller pieces. If you can grind the shells into powder, the calcium will be released even faster for your plants.
To break eggshells into smaller pieces, put them in a blender or coffee grinder. After they are crushed, you can mix the pieces into water and pour the mixture into your compost pile.
For more information, check out my article on composting eggshells.
For clam shells and oyster shells, you are better off breaking them into small chunks with a hammer first (wear goggles if you do this!). Then, use a mortar and pestle to break the chunks of shell into smaller pieces.
Conclusion
Now you know about lots of different ways to add nutrients to soil – naturally, without artificial chemicals.
If you are interested in being even more eco-friendly, check out my article on ways to use recycled materials in your garden.
You can also learn more about low-nitrogen fertilizers in my article here.
I hope you found this article helpful. If so, please share it with someone who can use the information.
If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. Enjoy!
~Jonathon