If you are interested in organic gardening, you may be wondering exactly what it is that makes a fertilizer organic. Do we define organic fertilizer by the ingredients, by the production process used to make it, or maybe both?
So, what is organic fertilizer? Organic fertilizer is made from natural sources, such as animal remains, waste, and bedding or plant remains. Organic fertilizer contains nutrients that are released slowly into the soil. Organic fertilizers are not chemically processed as other fertilizers are.
Of course, there are many different types of organic fertilizer. Depending on your needs, you can find organic fertilizers that are high in nitrogen, phosphorus, or potassium.
Let’s start off by taking a closer look at what makes a fertilizer organic. Then we’ll get into the different types of organic fertilizers.
What is Organic Fertilizer?
Organic fertilizer is made from natural sources, such as:
- animal waste, bedding and remains (such as manure, bone meal, blood meal, etc.)
- plant remains (such as grass clippings, fallen leaves, fruit and vegetable scraps, etc.)
Organic fertilizer serves the dual purpose of building soil and feeding plants at the same time. The nutrients from organic fertilizers are slowly released into the soil. On the other hand, artificial fertilizers do not build the soil, and they release their nutrients quickly.
Organic fertilizers avoid the use of pesticides and artificial fertilizers. They also add structure to the soil and encourage the healthy growth of beneficial bacteria and fungi in your soil.
For more information, check out this article on organic fertilizer from Wikipedia.
One downside is that organic fertilizers often have a lower nutrient content than artificial fertilizers. However, this means that plants are less likely to get burned by excess salts when you apply organic fertilizers to your garden.
For more information, check out my article on over fertilizing your plants.
Soil without excess salt is also a more hospitable home for earthworms and other beneficial soil organisms.
What Are Some Examples of Organic Fertilizer?
Some of the most common organic fertilizers in use today are compost, manure, and green manure. Animal products such as bone meal, blood meal, and feather meal are also commonly used as organic fertilizers.
Let’s start by taking a closer look at compost, including how to make this organic fertilizer.
Compost as an Organic Fertilizer
Compost is made from ordinary yard waste and kitchen scraps. Some common ingredients in a compost pile include:
- grass clippings
- fallen leaves
- dead plants from last year’s garden
- kitchen scraps (banana peels, orange rinds, coffee grounds)
Compost provides nutrients to plants by slowly releasing the nutrients in the soil over time. Compare this to other fertilizers that release nutrients quickly, which can burn plants due to excess salts.
An added benefit of compost is that it can be used to improve the structure of soil. Compost can help to improve drainage of clay soils, which prevents flooding and makes it less likely that you will over water.
Compost also helps to improve water retention of dry (sandy) soils.
Compost is a great way to provide nutrients to your garden while recycling some of the waste and scraps your household produces at the same time.
If you want to learn more, I have a few articles that will help you to get started with composting.
Manure as an Organic Fertilizer
Manure is defined as waste and bedding of animals such as chickens, turkeys, cows, horses, pigs, and so forth. The bedding itself often consists of wood shavings, sawdust, straw, or hay.
Remember that manure should always be allowed to decompose completely before using it in your garden. This decreases the chances of burning your plants with “fresh” manure. It also allows time for harmful microbes to be killed by the heat in a decomposing pile.
For more information, check out my article about how too much manure can kill plants.
Like compost, manure adds nutrients to the soil, slowly releasing them over time. Manure also helps to add structure to the soil. Manure can even be added to a compost pile to get the best of both worlds.
For more information, check out my article on where to get manure for your garden.
Green Manure as an Organic Fertilizer
Green manure refers to the remains of plants. When you use green manure, you plant certain crops in your garden in the fall, only to let them die, till them underground, and let their remains restore nutrients to the soil.
As an example, alfalfa is a legume that is often used as a green manure crop. Its deep roots can reach down into the soil and pull up nutrients that are unavailable to other plants.
When the alfalfa dies and is tilled into the soil, these nutrients become available for whatever is planted next in the same area.
Another benefit of green manure is that it can also be used as animal feed. In that case, it will be turned into actual manure, which you can also use in your garden as described above.
Other green manure crops include:
Green manure crops should be sown in the fall and tilled into the earth in early spring. This allows plenty of time for the nutrients in the plant matter to start being released into the soil.
For more information, check out my article on the benefits of green manure.
Animal Products as an Organic Fertilizer
There are other animal products that can also be used as organic fertilizer. These include:
- earthworm castings – when worms come to your garden and help to process plant matter, they leave behind waste that is rich in nutrients and good for building soil structure.
- blood meal – blood meal is a powder made from slaughterhouse leftovers. It is high in nitrogen.
- bone meal – bone meal is a powder made from slaughterhouse leftovers. It is high in phosphorus.
- fish meal – fish meal is made from ground up fish remains. It is high in nitrogen and phosphorus.
What Organic Fertilizer is High in Nitrogen?
Sometimes, you are looking to add lots of nitrogen to your organic gardening, to give a boost to the green growth of plants.
There are several organic fertilizers with high nitrogen content. These include:
- Feather meal – feather meal contains 15% nitrogen by weight.
- Blood meal – blood meal contains 12.5% nitrogen by weight.
- Hoof and horn meal – hoof and horn meal contains 9% to 14% nitrogen by weight.
- Hair – hair contains 12% nitrogen by weight.
- Fish meal – fish meal contains 10% nitrogen by weight.
- Crab meal – crab meal contains 10% nitrogen by weight.
- Bat guano – bat guano contains 5.5% to 8% nitrogen by weight.
- Manure – manure contains 0.5% to 6.5% nitrogen by weight (largely depends on animal that waste came from)
For more information about nutrient content of these soil additives, check out my article on what fertilizer is high in nitrogen.
As mentioned earlier, you can also try planting “green manure” crops that fix nitrogen in the soil, such as legumes (peas, beans, peanuts, etc.) and other cover crops.
For more information, check out my article on plants that add nitrogen to soil.
What Organic Fertilizer is High in Phosphorus?
If you want to provide a phosphorus boost to your plants with organic fertilizers, then give some of these a try:
- Hair – hair contains 26% phosphorus by weight.
- Burned cucumber skins – burned cucumber skins contain 11% phosphorus by weight.
- Bat guano – bat guano contains 4% to 8.6% phosphorus by weight.
- Fish meal – fish meal contains 4% to 6% phosphorus by weight.
- Bone meal – bone meal contains 1.5% phosphorus by weight.
- Blood meal – blood meal contains 1.5% phosphorus by weight.
For more information about nutrient content of these soil additives, check out my article on what fertilizer is high in phosphorus.
What Organic Fertilizer is High in Potassium?
If you need to supplement potassium in your organic gardening, then check out these rich sources of potassium that are organic fertilizers:
- Burned cucumber skins – burned cucumber skins contain 27% potassium by weight.
- Kelp – kelp contains 4% to 13% potassium by weight.
- Wood ash – wood ash contains 3% to 7% potassium by weight.
- Sawdust – sawdust contains 2% to 4% potassium by weight.
- Bat guano – bat guano contains 1.5% potassium by weight.
For more information about nutrient content of these soil additives, check out my article on what fertilizer is high in potassium.
Now you have a much better idea of what organic fertilizer is, and what it is not. You also know which organic fertilizers will supply nitrogen, phosphorus, or potassium for your plants, and in what amounts.
You might also want to read my article on whether you need fertilizer for your garden (and when to use them).
I hope you found this article helpful – if so, please share it with someone who can use the information. If you have any questions about organic fertilizer, please leave a comment below.