Best Fertilizer for Onions: Top 7 Reviewed

Best Fertilizer for Onions

Onions are a kind of stable vegetable full of vitamins, minerals, and antioxidants. The great news is anyone can grow them in any garden as they’re easy to care for.

Although onions don’t demand any special requirements to grow, they’re called “Heavy Feeders” because they need to be fertilized often for higher production.

In a nutshell, onions need a high source of nitrogen; thus, a nitrogen-based fertilizer is a good choice.

You might end up stretching your head when choosing the best fertilizer for onions. Because there’s a bunch of options on the market.

We’ve enlisted our top 7 picks for fertilizers for your convenience. They can bring you bigger and better green onion bulbs.

Let’s dive in.

Jobe's Organics Blood Meal Jobe’s Organics Blood Meal
  • Fertilizer for nitrogen loving plants
  • Not to burn when used as directed
Check Price
Lilly Miller Fish Emul Fertilizer Lilly Miller Fish Emul Fertilizer
  • Healthy plant growth with 11 vitamins
  • Stimulates microorganisms
Check Price
Fox Farm 6-4-4 Fertilizer Fox Farm 6-4-4 Fertilizer
  • Contains essential trace minerals
  • Environment-friendly
Check Price
Burpee Organic Bone Meal Fertilizer Burpee Organic Bone Meal Fertilizer
  • Provides vital Organic nitrogen, phosphorus and calcium
  • Boosts young plants 
Check Price


7 Best Fertilizer for Onions in 2023

We’ve shortlisted the best choices after considering vital facts like growth capacity, insect restraint, disease control, etc. Hopefully, you can get the suitable one for your garden.

1. Jobe’s Organics Blood Meal

As for onions, a nitrogen-loving tree, Jobe’s Organics Blood Meal can be the best fertilizer with 12% of nitrogen. The granular fertilizer is made with organic blood meal. This can ensure healthier and bigger onion production.

This organic fertilizer is good for soils with poor nitrogen levels and helps to balance nutrients in the compost pile. It not only ensures higher growth of onions, but this 100% natural fertilizer is also safe for kids and pets.

The OMRI-certified fertilizer can meet the nutritional needs of hungry onion plants with a 12-0-0 NPK ratio. It’s not only good for onions but also does the job for ginger, garlic, turmeric, trees, and other shrubs.

It’s a slow-release fertilizer that releases essential nutrients slowly but evenly into the soil. That’s why you can get uniform onion bulbs without applying fertilizer so often. Therefore, this 3-pound package serves for a long time.

Apply 1 cup of fertilizer per foot of plant to get healthier onions. We recommend applying this fertilizer 3-4 weeks after planting onion crops.


  • Good for all bulb-type plants
  • Safe for kids and pets
  • Protects against insects
  • Higher nitrogen content
  • Serves for a long time


  • No source of phosphorus and potassium

2. Lilly Miller Fish Emul Fertilizer

If you aren’t happy with granules and want the concentrate version of fertilizer, Lilly Miller is the right call to make.

This eco-friendly fertilizer can ensure solid growth in onion plants and extensive yields with 11 vitamins. Made of fish-based organic mixtures, it performs well in soils to fulfill the nitrogen requirements.

It’s a complete fertilizer containing 5% nitrogen and 1% phosphorus and potassium, respectively. The natural formula promotes optimal onion growth in most gardens providing a higher level of nitrogen.

This organic fertilizer contains 11 different plant vitamins and can bring you a healthy, strong, and strenuous plant. It increases soil fertility by facilitating soil microbes and prevents the plant from environmental stresses.

Use 1- 4 tablespoons of fertilizer per gallon of water to get optimum results. Ensure enough watering after fertilization.


  • Promotes quick growth of onion plants
  • Eco-Friendly & organic
  • Prevents environmental stress
  • Contain multiple nutrients
  • Produce healthier onions


  • Doesn’t offer much nitrogen

3. Fox Farm 6-4-4 Fertilizer

Do you want your onion plants to grow like crazy? Fox Farm 6-4-4 Fertilizer is the right fertilizer to go for, no wonder. It’s a well-balanced fertilizer containing 6% nitrogen, 4% phosphorus, and 4% potash.

This liquid concentrate fertilizer facilitates extensive growth of onions providing proper amounts of nutrients to the soil. It comes with a strong mixture of nutrients that help to strengthen your onion plants and enhances the overall quality.

Apart from providing major nutrients, this all-around fertilizer also balances the ratio of other vital minerals like copper, iron, zinc, manganese, etc. These trace elements promote the instant prosperity of onions.

This 1-pint of liquid fertilizer is good enough to cover your onion sets and serves a long life. It’s totally free of harmful chemicals, making it safe for plants, pets, and kids.

Use 2-3 tablespoons of liquid fertilizer in a gallon of water during the growing season. Be sure to water the plants after each fertilizing session to get incredible results.


  • Contains essential trace minerals
  • Environment-friendly
  • Safe for kids and pets
  • Free of harmful chemicals


  • Overfeeding impacts the plants

4. Espoma Garden-Tone 3-4-4 Fertilizer

Who doesn’t prefer organic gardening? If you want to taste organic onions, you can go for the Espoma Garden-Tone. This fertilizer is specially made for bulb-type plants like onions.

The garden tone 3-4-4 fertilizer provides 3% nitrogen, 4% phosphorus, and 4% potash to the soil. It comes in 15 different plant nutrients to nourish your onion plants to grow healthier bulbs and lush green foliage.

Being a granular fertilizer, it slowly feeds your onion’s required nutrients. On top of that, the fertilizer contains 0.5% quick-release nitrogen in order to nourish most hungry onion plants.

Preventing harmful insects and pests, the bulb-tone fertilizer takes good care of your onion plants. Accordingly, your onions grow bigger, sweeter, and healthier as well with time.

The well-balanced fertilizer contains many soil microbes and 1% humic acid to enhance soil conditions and protect plants from environmental stress.

Apply 1.5 teaspoons of fertilizer for each onion plant to get amazing results. Mixing the fertilizer into the soil surface is highly recommended. Ensure proper watering after fertilization.


  • Entirely natural & organic
  • Ensures slow-release feeding
  • Promotes bigger and better bulbs
  • Enhance soil conditions
  • Has multiple nutrients


  • Often spreads unbearable scents

5. Burpee Organic Bone Meal Fertilizer

Who doesn’t cherish bigger onions? If that’s what you want, Burpee Organic Bone Meal Fertilizer can exactly do so and might be the right choice for you. It provides a great amount of calcium to the soil that ensures the rapid growth of onion plants.

According to the NPK ratio, Burpee organic fertilizer contains 6% nitrogen, 8% phosphorus, and 0% potash. These two major nutrients help to establish healthy roots, green bulb sets as well as vegetative growth.

The good news is this organic fertilizer contains water-insoluble nitrogen, meaning it works as a slow-release nutrient to meet up the nutritional needs of your onions. 

A fertilizer has to be environment friendly, causing no harm to the environment. This Burpee organic fertilizer meets that requirement, surprisingly.

Use 1 tablespoon of fertilizer for each onion plant to get sudden results. Mix it to the soil surface thoroughly and ensure proper watering.

It’s an OMRI-certified fertilizer that is free of inorganic compounds that could harm your onion plants.


  • Includes no inorganic compounds
  • Totally safe for the environment
  • Comes with all essential nutrients
  • Water-insoluble nitrogen contents


  • Has no potash

6. Ammonium Sulfate Fertilizer

Are your onions not growing properly? If you want abundant, bigger, and lush green onion bulbs, Ammonium Sulfate Fertilizer can make your dream true.

We know onion loves nitrogen and this fertilizer exactly does that by offering high nitrogen content of about 21%. This is a perfect blend of nutrients that can promote onion growth.

Moreover, you’d be happy to know that Ammonium sulfate fertilizer features 24% sulfur. Significant amounts of nitrogen and sulfur promote green bulb growth, accordingly more onions. It nourishes alkaline soils for increasing soil fertility and can be used with other nitrogen fertilizers.

You can apply the fertilizer in two ways, either side dressing or liquid formulation. If you prefer side-dressing, be sure to follow light cultivation and apply the fertilizer to the side of the plants.

You can go for liquid formulation for quick and maximum results. Inject the fertilizer via a drip irrigation system.


  • Higher nitrogen level
  • Increases soil fertility
  • Promotes onion growth
  • Included sulfate ensures taste and flavor


  • Not good for organic gardening

7. Ultimate Veg Garden Fertilizer

Wish to bring some miracle to your onion garden? Get the Ultimate Veg Garden Fertilizer. It’s specially made for vegetable gardens with significant amounts of proper nutrients.

With an NPK ratio of 10-20-10, it comprises 20% nitrogen, 20% phosphorus, and 10% of potassium. The right formulation is good for vegetable gardens and root crops, especially onions.

This ultimate fertilizer not only contains macronutrients but also comprises 17% sulfur and 6% iron. It promotes the root development of onions and bigger onion bulbs.

Containing some soluble sugar elements, it can provide nutrients to the soil microbes. As a result, soil fertility increases and ensures abundant yields of crops.

The peak time of applying this fertilizer is August to September. Sprinkle 1-2 tablespoons of fertilizer per 10 feet of onion beds. After fertilization, make sure proper watering.


  • Great vegetable food
  • Easy to apply
  • Organic and free of harsh chemicals
  • Value for the money
  • A perfect blend of nutrients


  • The built quality could be better

What Type of Fertilizer Do Onions Like

Onions are a popular vegetable that can be used in many dishes. They have a mild flavor and a crunchy texture that makes them an ideal ingredient for salads and other dishes. Onions can be planted in the garden or grown in containers. To ensure your onion plants are healthy and produce a high yield, it is important to use the right fertilizer.

When it comes to fertilizing onions, it is important to understand the specific needs of the plant. Onions require a balanced fertilizer with a high nitrogen content. Nitrogen helps to promote healthy stem, leaf, and root growth. Phosphorus and potassium are also necessary for onions to reach their full potential and to keep them vigorous.

Organic fertilizers, such as compost, manures, and humus can provide a balanced source of nitrogen, phosphorus, and potassium. Organic fertilizers release nutrients slowly, ensuring that they are available to the plant when needed. Additionally, organic fertilizers can help improve the soil structure and promote better drainage.

Inorganic fertilizers, such as ammonium nitrogen, superphosphate, and potassium chloride, can also be used to provide the nutrients needed for healthy onion growth. These fertilizers must be applied at the proper rates, as too much can burn the plants. Additionally, inorganic fertilizers do not improve soil structure and can increase the salt content in the soil.

To ensure the best results, it is important to choose the right fertilizer for the specific needs of your onion plants. A balanced organic fertilizer can provide the necessary nutrients while also improving soil structure and drainage. Inorganic fertilizers can be used to supplement organic fertilizer, but they should be applied at the proper rates to prevent burning the plants. With the right fertilizer, you can ensure your onions reach their full potential and bring delicious flavor to your dishes.

Best Organic Fertilizer for Onions

One of the quickest ways of getting organic onions is to apply a compost pile to the onion plants. Compost enhances beneficial soil microbes, essential nutrients and consequently improves the soil texture.

Some of the best organic fertilizers for onions include:

  • Fish Emulsion

You can find this concentrated fish emulsion at most of the garden centers and hardware stores. It provides a rich boost of nitrogen to your onion plants and brings you bigger and better organic onions.

Make a proper solution with fish emulsion and water. Then, apply to the plants.

  • Manure

Animal manures are being used as an organic matter in most plants. It boosts the drainage and aeration of soil as well as providing significant amounts of nutrients.

  • Compost

Compost is made with decomposed sediments like leaves, tree branches, grass clippings, kitchen scraps, etc. It adds slow-release nutrients to your onion plants and ensures quick and healthy growth.

  • Compost or Manure Tea

Most of the organic gardeners used to make a specialized tea combining compost and manure. This all-natural tea provides a rich boost of nutrients to your onion plants.

When to Fertilize Onions

First of all, you’ve to prepare the soils for your onion plants prior to fertilizing.

Once you’ve prepared soils for onions, plant them. You should apply fertilizer after 20-30 days of planting. We recommend applying fertilizer during the growing season.

This is because, in the growing months, onions start to establish roots. If you fertilize them, the roots can obtain essential nutrients and enough water to ensure quick growth.

Be sure to re-apply fertilizer after every one to two weeks. Keep in mind that the re-applying schedule may carry depending on the type of fertilizer as well as its brand. Make sure to follow the label instructions.

Fertilization Requirements for Onions

As we’ve already said, onions require high nitrogen content for proper growth and abundant yields. They need potassium and phosphorus and other micronutrients as well for root development.

We recommend using a well-balanced fertilizer that contains a significant amount of essential nutrients.


  • Apply fertilizer at the rate of 1 cup for every 20 feet of row. The first application should be made after 3 weeks of planting.
  • Once the roots have established, reapply fertilizer after every 2-3 weeks.
  • In that case, we recommend applying ammonium sulfate fertilizer that contains higher nitrogen content. It helps to make deep foliage green and keep growing.
  • Stop applying any more fertilizer when you notice the neck starts being soft.
  • After that, you’ll see a new leaf emerge every 2-3 weeks. Once the soil starts to crack around, it means the bulb is forming. If so, the thriving process is complete, and no further application of fertilizers.  


Proper watering is highly recommended after fertilization. You need to keep the foliage growing and free of diseases. And you know leaf wetness is the main culprit for most of the diseases.

  • Make sure to water immediately after feeding and retain enough moisture during the growing months.
  • Avoid overhead watering as it causes bacterial spores to the leaves. Drip irrigation does well in onions.
  • If the soils become over wet, onions can rot. Be mindful that the irrigation system should be applied uniformly.
  • Maintain irrigating water 1-2 inches depth until bulbing. During bulbing, water 3-4 inches depth per week.
  • To control excessive moisture and weeds, mulching is necessary.

What Are the Best Fertilizers to Use to Get Large Onions?

When you wish to get larger onions, selecting onion variety, proper fertilizing, and enough watering are essential. The size and number of leaves are the primary indicators of getting larger onions. The more the leaves, the larger the onions.

  • Before Planting

Enhance soil conditions with 3 inches of compost prior to planting. Compost gives some slow-release nutrients to the soil and accordingly improves texture.

As a starter fertilizer, you can use a superphosphate fertilizer instead of balanced fertilizers. It nurtures healthy, strong, and early roots.

  • Growing Season

Onions demand higher nitrogen content during the growing months. A steady supply of nitrogen helps to form larger bulbs.

In early or midsummer, apply 1 cup of nitrogen-based fertilizer. For alkaline soils, ammonium sulfate does well by lowering the pH levels. In the case of acidic soils, you may use ammonium nitrate.

  • Organic Options

If you aim to get organic onions, sprinkle 2-3 shovelfuls of compost into the soil. Avoid spreading compost to the bulbs. You need to use high-quality compost formulated with composted vegetable materials and manure.

  • Considerations

Avoid applying fertilizer after mid-summer. Late application of fertilizers doesn’t work well in onions.

Onions demand adequate fertilizer and evenly moist soil for larger growth. You have to mulch the ground to prevent excessive moisture and weeds.

How to Fertilize Onions

Fertilizing onion plants is an easy process and often varies according to the type of fertilizer. Let us give you a basic outline of fertilizing onion plants:

Step 1: Measure the fertilizer

The first step goes to measuring fertilizer, following the label instructions.

Step 2: Prepare the solution

Remember that this step is only necessary for liquid or water-soluble fertilizers. Measure liquid or water-soluble fertilizer according to the first step. Then make a solution by mixing the fertilizer with water.

Step 3: Apply the fertilizer to onions

If you are using granular fertilizer, sprinkle the fertilizer power throughout the onion plants or beds. In the case of liquid fertilizer, you need to pour the prepared solution into the plants.

Final Words

As you’re here, we believe you’ve read the whole discussion above and found a suitable fertilizer for you.

If you’re still confused about making the right call, we’d recommend Jobe’s Organics Blood Meal as the best fertilizer for onions. Because it contains higher nitrogen content of 12% and onions love so. It comes with a perfect blend of nutrients to ensure the healthier and rapid growth of onions.

If you wish to bring a miracle to your onion garden, the all-in-one fertilizer can meet your expectations.

Anyway, the last call should be yours. All the recommended products are more than just good for fertilizing onion plants. Hopefully, now you understand everything you need regarding the fertilizer for onions.

It’s time to enjoy your garden-full of onions.

2 thoughts on “Best Fertilizer for Onions: Top 7 Reviewed”

  1. Christa Whitaker

    I heard that adding sulphur was a good idea… can you verify that and if so, how often?

    Thank you for a great informative article

  2. shoya izakaya

    I’m not sure where you’re getting your information, but great topic. I needs to spend some time learning much more or understanding more. Thanks for magnificent info I was looking for this info for my mission.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top