There are some major benefits to using organic fertilizers, namely that they work slowly as they need to be broken down by soil organisms for their nutrients to be released, and this takes time.
However, because they work slower than inorganic or chemical fertilizers, nothing is wasted, as everything is consumed as it is released.
Soil containing organic fertilizers tend to be easier to work with as the organic material contributes to the structure of the soil, allowing more air to get to the roots of the plant which permits the soil to hold water longer.
Due to the extra organic substances in the fertilizer, fungal and bacterial activity are also increased. Overall, organic garden fertilizers improve the soil, allowing your plants to flourish.
While you still need to be careful with natural fertilizers, they are less likely to burn the roots of your plants (especially delicate seedling roots) or create a toxic concentration of salts when over-applied.
Below are some of the most widely-used types of organic fertilizers for plants.
1. Manure (Animal Dung)
Most manure used for your farm comes from cows, rabbit, chicken, sheep, and horses. Rabbit manure is especially used on tomato plants because of its rich nitrogen-boosting qualities.
Manures have a lot of organic matter, but it is lower in nutrients than other organic fertilizers. They are best used as organic soil amendments and mulches.
Soil amendments have a number of uses such as improving your soil’s drainage and density as well as adjusting the pH balance. Be careful when using fresh manure as a fertilizer as it is known to burn plants.
2. Earthworm Castings
All three of the nutrients you’re going to want for your garden can be found in earthworm castings.
Because of this high content, this organic fertilizer is highly recommended for gardens specializing in flowers and vegetable patches.
3. Kelp Fertilizer
Cold processing is what creates this unusual fertilizer, which is somewhat scant in the three main components, but thriving in trace elements.
Filled with natural growth hormones, and easy to apply, kelp meal is bound to give any crop a much needed helping hand.
You simply mix it with water and spray or pour around the plants.
Extremely common, this is a versatile organic fertilizer for vegetables and plants that can contain almost any natural plant source.
Bark, pine needles, or even grass mixed together to create a healthy batch of effective glop that helps water and air more easily get into the soil.
Arguably an easy homemade organic fertilizer to make, compost is composed of whatever is put into it.
It’s one of the most versatile, able to be used as both a mulch or as a conditioner for garden soil. You can even use it as a foliar feed.
You can make it yourself by just filling a bucket with non-meat based products and mixing it up. It has a tendency to become alkaline, however, so use with caution.
6. Shellfish Fertilizer/Shell Meal
Shellfish fertilizer is made from the crushed bones or shells of crabs, shrimp, and/or other shellfish.
It contains a great deal of calcium (it is made up of 12% of calcium) as well as phosphorus, nitrogen and a number of trace minerals.
Another advantage of using shellfish fertilizer is that it contains chitin which boosts the growth of beneficial organisms that destroy harmful pest nematodes.
7. Bat Guano
The caves where bat guano is found protect the substance from leaching, so the nutrients found in the guano are conserved. For this reason, it is high in soluble nitrogen, phosphorus, and trace elements.
Bat guano can be used any time of the year as a top dressing, or try diluting it in a tea and using it as a foliar spray.
If you can get hold of it, South American seabird guano is the best. It is rich in nitrogen, phosphorus and a number of other nutrients.
8. Fish Emulsion
Fish emulsion is partially decomposed, finely ground fish, so it can smell, but there are deodorized versions on the market. Use it sparingly as it is known to burn plant roots.
There is also fish bone meal that has more calcium and phosphorus.
9. Egg Shells
Eggshells are made up of 96% calcium carbonate crystal, bound together by proteins, so they can be used as a fertilizer to strengthen the cellular structure and the transport of nutrients in your plants.
Eggshells decompose very quickly, so there is no need to sterilize them or grind them up.
Tomatoes and peppers will enjoy some eggshells mixed in with their organic fertilizer as they are easily affected by calcium deficiency.
10. White Vinegar
Plants that crave an acidic environment, such as roses, hydrangeas, and berries will love you for dowsing them with a vinegar mixture once every three months.
Simply mix a tablespoon of vinegar with a gallon of water. A low pH can be harmful to plants that thrive in a highly acidic environment. Just be sure to test your soil before you alter the pH levels.
11. Epsom Salt
Epsom salts (hydrated magnesium sulfate) contain both sulfur and magnesium, which plays an important role in the photosynthesis process.
This assists plants with a number of functions, such as root growth, amino acid production and the formation of chlorophyll.
Onions, broccoli, and cabbages will all benefit from the use of Epsom salts as a fertilizer, which will, in turn, sweeten the produce.
Peppers, all types of tomatoes, and roses will blossom and grow stronger when fertilized with Epsom salts. Use Epsom salts in a solution to replace depleted levels of magnesium and sulfur in potting soil.
Epsom Salts, like other foliar applications or liquid fertilizers, have the added benefit that their nutrients are absorbed into the soil more quickly than other organic fertilizers.
12. Bone Meal
As the name implies, bone meal is finely ground bone that comes from slaughterhouses. It’s an amazing form of raw calcium with a whopping 15% phosphate.
Because of this, it’s very highly recommended for bulbs, flowers, and fruiting trees since it helps establish a strong root system.
13. Rock Phosphate
This calcium/lime-based phosphate rock is a great source of nutrients for plants and is a fertilizer commonly used in organic farming practices.
Rock phosphate is made by grinding down the rock into a fine powder or crumbs for easy application and distribution.
Its phosphate level reaches well over 30% complete with generous amounts of trace elements. It also remains largely unchanged after application.
Greensand is a popular type of iron potassium silicate which causes any mineral it appears in to have a slight greenish tint.
It can be found in an ancient seabed in New Jersey and is heavily rich in many minerals that add dozens of micronutrients into the soil.
15. Alfalfa Meal
Alfalfa meal is normally a major part of livestock diets, but grinding it up for faster breakdown gives the resulting fertilizer low amounts of nitrogen, potassium, and phosphorus.
This makes it a slower acting variety best used as a soil conditioner in early spring.
16. Cottonseed Meal
Cottonseed meal is stuffed with nitrogen, phosphorus, and potassium and it’s great for conditioning gardens.
The earlier it’s used, the more it breaks down into the soil for better distribution of its elements. The only problem is that it’s a slow-acting variety.
17. Soybean Meal
High in nitrogen, low in phosphorus and calcium, soybean meal works depending on local growing conditions. These factors determine how quickly it’ll be absorbed by the soil.
It can be anywhere from slow to moderate speed, but it’s great for use as a long term soil conditioner.
18. Feather Meal
Very high in nitrogen, but contains no calcium or phosphorus, with a moderate speed of absorption.
For best results, if you plan to use it, apply feather meal to the soil well in advance. The earlier you mix it in, the better conditioned the soil will be when it’s time to plant.
19. Seabird Guano
This is a unique one gathered from islands that are privy to low rainfall with hot, arid climates.
This type of environment helps the resulting seabird guano retain a high level of nutrients with trace elements mixed in.
You’ll find a lot of calcium, phosphorus, and nitrogen in it and it’s actually considered to be one of the world’s most elite fertilizers in the organic category.
This is one of the best ones because if you live near the coast, you can go and pick it up for free. It just washes ashore.
You’ll find small amounts of the three main nutrients mixed in, coupled with tons of zinc and iron.
These factors make seaweed highly sought after as a grain crop fertilizer, or anything requiring higher potassium.
21. Grass Clippings
Another one you can get for free as long as you or someone you know owns a lawnmower, this one helps curb weed growth.
It’s difficult to calculate the amount of nitrogen in each batch, so spread it liberally across the soil for the best effect.
A layer of 1-2 inches should do the trick. Avoid cuttings from herbicide treated lawns, however. You’ll poison your garden.
Depending on where you get it will determine what benefits you’ll reap from it.
Limestone is highly effective in balancing PH levels in the garden, especially highly acidic soil.
It also encourages the addition of magnesium, which assists in stronger, hardier plant growth.
Just test your soil first before adding this potent fertilizer.
23. Wood Ash
You might not think of this one, but you should. Ash discarded after a wood fire in the hearth is a great natural fertilizer.
It’s a great choice for any low acidic gardens and it even helps to keep pests away like slugs and snails.
24. Green Teas
Everyone knows the benefits of green tea, and soon your garden will, too.
Just mix any trimmed weeds to a bucket of water with green tea and let sit for three days before applying.
People have been using this one in organic gardening practices for years. Different molasses types are created in different ways.
Blackstrap molasses has the most sulfur, magnesium, iron, calcium, and potassium and gives plants a power boost when applies.
Add 2-3 tablespoons of dry molasses to 1 gallon of warm water and spray on leaves or pour around roots.
Unsulphered blackstrap molasses can also be added to other natural fertilizer mixes.
You read that right. It’s been proven that urine from a healthy person is actually a highly clean and beneficial fertilizer for plants.
It’s 95% water composed of vitamins and minerals that passed through naturally, as well as a metabolic waste named urea, which is extremely beneficial to growing plants.
If you’re a little squeamish, it’s okay. There are plenty of varieties of organic fertilizers and this is just one of them.
Gypsum is a naturally occurring mineral found concentrated in various places underground.
It is an excellent source of calcium and sulfur — important elements for improving crop yield and plant nutrition.
It also keeps the soil hydrated and helps prevent soil erosion.
Azomite is a complex of naturally occurring micro-nutrients that are essential for plant growth. It is naturally derived from volcanic mineral deposits.
It improves the vigor and root system of a variety of plants.
Make sure that any ingredients you add to your natural fertilizers don’t contain other harmful chemicals, such as herbicides, as these will defeat the purpose.
As most organic fertilizers for plants are slow-release, the timing of when you use them is not as important as it is with inorganic or chemical fertilizers.
As with all the foods we eat, organic is best, so work hard to nourish your plants as you would nourish your body.