Best Onion Fertilizers

Best Onion Fertilizers 2020: Reviews & Buyer’s Guide

Can you imagine the taste of food without onions? This is the crucial vegetable used in preparing various recipes. Growing onions in a healthy way would need the help of fertilizers apart from watering. It can grow in different soils and is easy to care for.

Though there is no particular condition required growing this crop, these are heavy feeders that depend on fertilizers to yield a good harvest. The nutritional requirements of onions would depend on the soil, so you must choose the right fertilizer.

We have compiled the best fertilizer list for onions that you can use to yield the harvest and the factors to consider to buy the best one.

Top 10 Best Onion Fertilizers 2020

1. Osmocote Smart-Release Plant Food Plus

If you are looking for the best fertilizer for onions, then you can choose this fertilizer. There are 11 nutrients that you can find in this fertilizer to supply essential nutrients for the onion crop. The no-burn formula in the fertilizer would let you use the solution for the plants that you would cultivate in summer months without any issues.

If you feed the onion crops when they are new or when onion bulbs are forming, you will get a perfect harvest. You can use this fertilizer in all types of soils and in indoor as well as outdoors.


  • Comprise of 11 nutrients
  • Can be used up to 6 months
  • Use to the plants that are grown outdoors and indoors
  • No crop would burn when you use it directly
  • Work with all kinds of plants that are grown in different conditions


  • Release some sort of white plastic balls when the fertilizer is completely dissolved.

2. Espoma Triple Phosphate Fertilizer

If you want to grow onions in your field and boost their growth, you must use the best fertilizer for onions. It is the best in the market that comprises of all essential things for its healthy growth such as phosphorous, nitrogen and potassium.

You can use this fertilizer individually or mix it with other fertilizers. It is designed especially for the people who are cultivating onions and want to reap the best yield.

The product is synthetic but does not have anything that could pose a severe threat to the environment or the crop. It helps the plants to grow stronger from its roots and has an enriched source of phosphorous. It feeds the plants at a brisk pace.


  • Consist of phosphorous that promotes quick growth
  • Easy to apply to plants
  • Safe and reap best results


  • Hard to determine its effectiveness
  • Not for all types of soils

3. Osmocote Smart-Release Plant Food

If you want to receive the best yield for your onion crop, then you must use this fertilizer that promotes the best growth and yield. It makes the onion to grow stronger from the roots. However, you can also use this fertilizer for a vegetable garden and perfect for perennials. It is the formula that is used to grow colorful blooms for up to four months.

You must take a cup of the fertilizer and sprinkle on the area where you are growing onion. The nutrients present in the fertilizer would dissolve and promote the healthy growth of onions.


  • Can feed up to four months
  • Strong development of roots
  • Easy to use
  • Spread with ease
  • Promote growth


  • No proper directions on how to use the product

4. Lilly Miller All Purpose Planting and Growing Food

If you are looking for a fertilizer that promotes slow yet effective growth of onions, then this is the best fertilizer for onions for you to buy.

It makes sure that onions crop would receive the essential nutrients required for its healthy growth for a long time. The formula used in the fertilizer would comprise potassium, phosphorous, and nitrogen to deliver the nutrients for the healthy growth of plants while keeping the pH levels optimum.

It is perfect for growing different kinds of crops. The gardeners who use this fertilizer for growing different kinds of plants would appreciate its effectiveness and feel happy with the healthy and strong growth of onion. It can be used on all plants without worrying about them getting burnt. It is the best one to use on the young plants.

The mix of nitrogen would make it unique to use for the growth of plants. The phosphate and potash would supply the essential nutrients and promote the quick growth of onion bulbs. You must apply it once; it would supply the nutrients up to 6 weeks continuously.


  • Natural ingredients
  • Can be used for growing different plants
  • Comprise of plant minerals
  • NPK formula is rich
  • Supply nutrients up to 6 weeks
  • Low release of nutrients for the continuous growth of plants


  • Pricey

5. Ultimate Fertilizer The Veg Garden Fertilizer

If you are looking for the best vegetable fertilizer that can promote healthy growth of onions in your land, you must use it. The NPK ratio of the compost is 10-20-10. You can use this in the vegetable garden, root crop, where there is a high requirement for phosphorous. It supplies 17% of sulfur and 6% of iron. It is perfect for growing onions.


  • Perfect vegetable garden fertilizer
  • Promote the healthy growth of onions


  • Running off phosphorous would pose some threat to the quality of water

6. Earthworm Technologies TeaDrops Plant Fertilizer

If you want the fertilizer that is easier for you to grow onion crop, then this is the best fertilizer for you to use. The liquid organic fertilizer can be used for growing different varieties of plants and flowers. There are 16 tea drop packets that you get in one package, and it can produce up to 32 gallons of fertilizer.

You do not have to get your hands dirty to use this fertilizer. You can spray it on the shrubs or perennial plants to reap the best yield. It just takes a couple of seconds for you to prepare the mixture. You must pick the tea package, dip it into 1 to 2 gallons of water, and let it steep for a couple of hours.

You can use this even for the indoor plants. It promotes the natural growth of plants. It is 100% organic and is child friendly.


  • Organic
  • No harm to the environment or pets
  • The perfect formula to promote healthy growth of plants
  • Easy to use


  • You must use it carefully without which it burns the plants

7. EarthPods Best Root Starter Fertilizer

If you want to feed the plants with the organic fertilizer, then there is no other better fertilizer then this. The safe pods would supply the essential nutrients for the plants and promote healthy growth without any fuss.

There is some quantity of dosage available in each capsule. All you have to do is to put the capsule in the soil that is closer to the roots of the plants and water there to see miraculous results in a short time. Once it vanishes, you can recycle the container.


  • Organic
  • Does not cause any harm to the environment
  • Use the fertilizers without any kind of measuring cup or stink
  • Supply nutrients that promote the plant growth
  • Easy to use


  • It is not suitable for transplants and cutting

8. Espoma BT4 3-5-3 Plant Food

If you want a safe yet eco-friendly fertilizer, then this is an excellent option for you to buy. It is the best fertilizer for onions that you can ever give to the plant as it comprises 15 nutrients. It is perfect for growing bulbs such as onions, tulips, daffodils, crocus, and hyacinths.

It is a blend of organic and other nutrients that feed the plants and make them grow stronger. It is entirely safe for the environment when you use this fertilizer. There are no toxic ingredients that you find in this fertilizer.


  • Easy to use
  • Eco-friendly
  • No toxins
  • Perfect for plant bulbs


  • Pricey

9. Espoma GT4 3-4-4 Plant Food

If you want to buy an organic yet natural fertilizer for the healthy growth of onions, this one is the right choice. It is developed for both professional gardeners and home gardeners who are growing different types of vegetables.

Fifteen different types of ingredients are present in this package, including calcium and magnesium. A healthy mix of NKP ratio is 3-4-4, i.e., nitrogen, phosphate, and soluble potash.

It is the secret to the promotion of healthy plant growth. It is the combination of thousand microbes that are highly beneficial for plant growth and reap good yield. There are no toxic ingredients that you find in this type of fertilizer.

It is eco-friendly, so there is no risk of any chemical getting into the soil and contaminating it. It has low salts, so it does not burn the plants.

The slow-release formula would continuously feed the vegetables and herbs up to a month. It is suitable for transplants and for the plants that are established. You can use this for indoor and outdoor plant growth. There is a strong odor, so there should be proper ventilation to let the smell go out without getting accumulated inside when using indoors.


  • Superior quality
  • The best formula to grow herbs and vegetables in the garden
  • Promote the healthy growth of plants
  • Produce a bigger harvest
  • Perfect for organic gardening
  • Eco-friendly
  • Safe for pets
  • Use natural ingredients
  • 3-4-4 fertilizer mix
  • Comprise of 15 different nutrients
  • Do not burn
  • Perfect for outdoor and indoor plants


  • Produces a strong odor
  • Comprise of bone meal
  • It is not certified as organic

10. Jobe’s Organics Tomato Plant Food

If you want to promote the healthy growth of vegetables, you must use this fertilizer. The NPK ratio of this fertilizer is 2-3-4 and is perfect for the growth of vegetables, fruits, shrubs, and trees. It is used for organic gardening.

When you spray this fertilizer, it can feed the crop up to 3 months continuously. It also increases the growth of root mass and foliage. There are no harmful chemicals that are used in the growth of the onion heavy feeder fertilizer.

It does not burn the plants, so it is safe to use in the places where there are kids and pets. It also boosts the soil’s condition, promotes growth, and increases the crop resistance to resist crop diseases.


  • Superior quality
  • Affordable
  • Quick results
  • Last up to 3 months
  • No synthetic chemicals are used
  • Promote the healthy growth of roots and absorb nutrients
  • Safe to use


  • Strong odor
  • Need some preparation to mix with the soil


1. What Are The Fertilizers That Are Best For The Growth Of Onion Bulbs?

Onions would need the fertilizers that are rich in nitrogen. There is another ingredient that onions would love to have in fertilizers, i.e., ammonium sulfate, and it reduces the soil’s pH level. The pH level of the soil where you are growing onions must be 6.5 to 8.0. It is best to supply the essential nutrients required for its growth.

2. Is Potash Perfect For Onion Growth?

Yes, potash is very good for onion plants. There are a few gardeners who add potash to the onion yield to improve its taste and potency. You must only add up to 4.8 ounces of potash for 100 square feet. The natural source to get potash is through wood ashes.

3. What Is NPK Ratio?

When you plan to buy the fertilizer for onions, the first thing you must check is the NPK ration, i.e., the nitrogen, phosphorous, and potassium levels in the fertilizers.

It is best to choose the fertilizer with higher nitrogen levels as it boosts the onion and improves the quality of the bulb. It makes an onion crop to resist the pests and improve its longevity. You need to buy the fertilizer with the NPK ration of 16-6-4.


If you want healthy growth of onion and yield best harvest, then you must use the fertilizers. We have listed the top 10 fertilizers with its pros and cons. You can go through each fertilizer’s pros and cons and choose the one that best fits your gardening needs.