Potatoes originated in Central and South America in the Andes. They come in a variety of colors and sizes. Potatoes are easily grown in the home garden from pieces of seed potatoes. If you are considering growing potatoes, you may be wondering, “What is the best fertilizer for potatoes?”
With so many fertilizers out there, it can be hard to know which one to pick. I have found the best fertilizers for potatoes for you, so you know just what to use.
Here are my picks for the best potato fertilizers.
- Triple 10 All Purpose Liquid Fertilizer 10-10-10 – best liquid fertilizer
- Jobe’s Organics, 06028, Fertilizer Spikes – best spike fertilizer
- Dr. Earth Organic Tomato, Vegetable & Herb Fertilizer – best organic fertilizer
- Miracle-Gro Water Soluble Plant Food – best water-soluble fertilizer
- Espoma Organic Bone Meal Fertilizer 4-12-0 – best bone meal fertilizer
- Espoma Organic Garden-Tone 3-4-4 – best budget fertilizer
- Southern Ag All Purpose Granular Fertilizer – best overall fertilizer
Fertilizing Sweet Potatoes Versus Irish Potatoes
The Irish potato (Solanum tuberosum) and sweet potatoes (Ipomoea batatas) are completely different vegetables and need different amounts of fertilizer. This guide talks about the best fertilizers for Irish potatoes.
Why Fertilize Potatoes?
Potatoes require more fertilizer than other vegetables. I have had gardens in several places and have not found soil that has enough nutrients to support potatoes all season. Container potatoes need fertilizer because the nutrients in the soil in a container are quickly exhausted. If you want a good crop of potatoes, you will have to fertilize them.
How Do I Know If My Potato Needs Fertilizer?
If your potato plants are not growing well or have yellow leaves, you probably need to fertilize them.
What Nutrients Do Potatoes Need?
Potatoes need twelve nutrients in varying quantities. Here are the nutrients and what they do.
The major nutrients are nitrogen, phosphorous, and potassium. These nutrients are the ones listed in the numbers on the front of the fertilizer package. Potatoes use large amounts of these nutrients.
Nitrogen is in every part of the plant. It forms part of the cell walls, plant hormones, and chlorophyll. Without enough nitrogen, plants are stunted, and the potato plants do not have as many potatoes. Too much nitrogen can cause burned leaves and roots. In some cases, the burns kill the potato plant.
Phosphorous is necessary for plants to transfer energy from sunlight to the rest of the potato plant, form strong roots, and help plants mature. Low phosphorous causes stunted plants and a poor potato crop. Too much phosphorous causes burns to the leaves and roots and can kill the potato plant.
Potassium helps potato plants form and move sugars, starches, and oils in the plant. Potassium also helps the plants be vigorous and healthy, resisting diseases. Too little potassium causes poor growth and a poor potato crop. Too much potassium can make it hard for the potato plant to use the phosphorous and nitrogen in the soil.
These nutrients are necessary for potato plants but not in as large a quantity as the major nutrients.
Magnesium is part of chlorophyll, so a deficiency means the potato cannot turn the sunlight into energy.
Sulfur is involved in producing energy for the plant and is a part of the amino acids forming plant proteins.
Calcium is important in the formation of new leaves, new roots, and new root hairs.
These elements are important but are only needed in very small quantities.
Manganese is involved in photosynthesis.
Iron is a part of plant hormones that regulate and promote growth.
Copper makes up plant enzymes.
Zinc is part of a plant hormone regulating leaf and stem growth.
Boron helps form cell walls in parts of the plant that grow rapidly.
Molybdenum helps form proteins from nitrogen and helps soil microbes turn nitrogen from the air into a form potato plants can use.
Things to Consider When Buying Potato Fertilizers
Buying fertilizer is not as easy as buying a fertilizer with the right nutrients. Here are some things to consider.
The most important thing you can do to grow good potatoes is to perform a soil test a month or so before you plant your potatoes. I find a soil test tells me what nutrients to add to my soil to start my potatoes off right. I fill in vegetables in the line that asks what you are going to grow in the soil because recommendations vary by the type of plant you are growing. After I get the soil test results, I fertilize my vegetable garden by following the recommendations. After that, I just have to fertilize to replenish the nutrients my plants use during the season.
Buy Good Fertilizer
Many people try to save money by buying cheap fertilizer. I believe this is a mistake. Cheap fertilizers use cheap ingredients. Sometimes, this includes sewage sludge as a nitrogen source. I don’t want sewage sludge on my food plants. It may contain heavy metals or toxic chemicals. Even if the fertilizer does not have sewage sludge in it, the ingredients are mostly fillers. This means you have to spread more fertilizer to get the required nutrients, so the fertilizer ends up costing you just as much as a premium fertilizer. I buy the best fertilizer I can afford because the ingredients are better quality and purer.
Buy Enough Fertilizer
Fertilizers are not just nutrients. They contain ingredients to keep the fertilizer from spoiling, propriety ingredients to make the fertilizer more available to your plants, and fillers so you can more easily spread the fertilizer. The numbers on the front of the fertilizer bag give the percentage of the fertilizer that is nitrogen, phosphorous, and potassium, in that order.
If you need to put down a pound of potassium, and the fertilizer is a 20-20-20, you can’t just put down a pound of fertilizer. To figure out how much fertilizer to put down to get a pound of potassium, divide one by the percentage of potassium in the fertilizer (expressed as a decimal). The equation looks like this: 1÷0.20=5. You would need to put five pounds of fertilizer out in this example. The same equation works for nitrogen and phosphorous.
Best Fertilizers for Potatoes
Here are my picks for the best potato fertilizers.
1. Triple 10 All Purpose Liquid Fertilizer – Best Liquid Fertilizer for Potatoes
Triple 10 All Purpose Liquid Fertilizer 10-10-10 with Amino Acids (5.5%) & Seaweed Extract is my pick for the best liquid fertilizer for potatoes. This fertilizer contains amino acids your potatoes need and seaweed extract for trace minerals. The label says to mix one to two ounces of Triple 10 All Purpose Liquid Fertilizer 10-10-10 with Amino Acids (5.5%) & Seaweed Extract with a gallon of water. The bottle is a measure-and-pour bottle, so I just squeeze the amount I want out into the water.
I use it to water my container potatoes. I water with the fertilizer once every two weeks. This fertilizer does not have fish in it. I was unable to find a fish fertilizer I liked for potatoes. Because of the nitrogen in this fertilizer, I would not use it after the potato plant starts blooming, or it could cause an overgrowth of the plant with few potatoes.
Read my article if you are looking for triple 10 fertilizers.
- Balanced fertilizer
- Measure and pour bottle
- Contains amino acids and trace minerals
- Not organic
- Does not contain fish
- Must fertilize every two weeks
2. Jobe’s Organics – Best Spike Fertilizer for Potatoes
Jobe’s Organics, 06028, Fertilizer Spikes, Vegetable and Tomato also works great for containers. I like being able to go eight weeks without worrying about fertilizing my container plants. While you can use these spikes for in-ground plants, you have to use a lot of spikes. This fertilizer is better for a container potato plant. In addition to an NPK ratio of 2-7-4, these spikes contain Mycorrhizal, Archaea, and healthy bacteria to improve the soil and help your potato plant use the nutrients it needs. Jobe’s Organics, 06028, Fertilizer Spikes, Vegetable and Tomato are specially formulated to have a low odor and are allowed in organic gardening.
The number of spikes I use depends on how large the potato plant is. I use four spikes placed on the edges of the pot for an eight-inch diameter plant. I push the spikes in and cover them with a little soil. The nutrients are released every time I water the container.
- Lasts for eight weeks
- It can be used on other vegetables
- Low odor
- Need several spikes per plant
3. Dr. Earth Home Grown – Best Organic Fertilizer for Potatoes
Dr. Earth Organic Tomato, Vegetable & Herb Fertilizer has an NPK ratio of 4-6-3. In addition, this fertilizer contains probiotics, seven strains of soil microbes, and ecto and endo mycorrhizae. These ingredients help the soil microbes and help the potato plant use the nutrients in the fertilizer. The fertilizer is organic and is the only Non-GMO Project verified fertilizer in the United States, according to the label. I like that Dr. Earth Organic Tomato, Vegetable & Herb Fertilizer is made in the USA from sustainably sourced ingredients. The ingredients are food grade and non-toxic, so the fertilizer is safe to use around pets and children.
I add 1 ½ cups of Dr. Earth Organic Tomato, Vegetable & Herb Fertilizer per ten feet of row before I plant my potatoes. I till the fertilizer in before planting, then water the ground well. After the plants emerge, I use ¾ cup per ten feet of row. I water it in well.
- Safe for pets and children
- Verified by the Non-GMO Project
- Contains extras to help the soil
- Low NPK ratio
4. Miracle-Gro Water Soluble – Best Water-Soluble Fertilizer for Potatoes
Miracle-Gro Water Soluble Plant Food mixes easily with water to give my potato plants a quick boost. It has an NPK ratio of 18-18-21. This fertilizer can be used throughout the time life of the potato plant. The higher potassium content is good for the last part of the potato plant’s life when it needs lots of potassium. Miracle-Gro Water Soluble Plant Food is also economical. One bag feeds about 800 square feet. This fertilizer is guaranteed not to burn your plants if mixed as directed. I like that I can use Miracle-Gro Water Soluble Plant Food with my other vegetables if I want to.
You can apply this with a hose sprayer or from a bucket. I prefer mixing the fertilizer in a bucket and using it to water my potatoes. I mix 1 ½ tablespoons of Miracle-Gro Water Soluble Plant Food into one and a half gallons of water. Every two weeks, I soak the ground around my potatoes with this mixture.
- Good balanced fertilizer
- Immediately available to my plants
- Easy to mix
- Not organic
5. Espoma Organic Bone Meal Fertilizer 4-12-0 – Best Bone Meal Fertilizer for Potatoes
Espoma Organic Bone Meal Fertilizer 4-12-0 is a great fertilizer to add extra phosphorous and calcium to your soil. Espoma has been producing quality organic fertilizers since 1929, and this fertilizer is made in the USA. Potato plants need lots of phosphorous to produce lots of potatoes. Phosphorus also helps develop strong root systems. Since the bones in bone meal come from slaughtered cattle, I feel good using something that would otherwise go to waste.
Espoma Organic Bone Meal Fertilizer 4-12-0 is a slow-release formula that I work into the soil before planting my potatoes. I use ten pounds per hundred square feet and mix it into the soil in the trench I dig before covering it with some soil and putting my potatoes in.
- Lots of phosphorous and calcium
- Made in the USA
- Slow-release formula
- No potassium
6. Espoma Organic Garden-Tone 3-4-4 – Best Budget Fertilizer for Potatoes
Espoma Organic Garden-Tone 3-4-4 is another great Espoma product made in the USA. The NPK ratio of 3-4-4-can be used to fertilize my potato plants all season long. As a bonus, I can use it on the other vegetables in my garden. I think both things make Espoma Organic Garden-Tone 3-4-4 a good budget fertilizer. This fertilizer has the proprietary Bio-tone formula in it, with beneficial soil microbes that help my potato plants use the nutrients in the fertilizer and improve the soil for future gardens.
Before I plant my potatoes, I work three pounds per fifty square feet into the soil. After the potato plants come up, and every month thereafter, I band 1 1/3 cups per five feet of row about six inches from my potato plants. The Espoma Organic Garden-Tone 3-4-4 does have an unpleasant odor, and I use gloves to handle it.
- Good for all growth stages
- Contains beneficial soil microbes
- Contains micronutrients
- Safe around kids and pets
- Unpleasant odor
7. Southern Ag All Purpose Granular Fertilizer 10-10-10 – Best Overall Fertilizer
Southern Ag All Purpose Granular Fertilizer has an NPK ratio of 10-10-10. In addition, this fertilizer has some minor nutrients and trace elements. It doesn’t have all of them, however. The balanced formula makes the fertilizer good for the initial planting and until the potato plant starts drying out. Southern Ag All Purpose Granular Fertilizer is affordable and can be used on other vegetables. This fertilizer is slow-release, so I do not have to fertilize with it as often as some fertilizers.
I use one cup of Southern Ag All Purpose Granular Fertilizer per 25 feet of row. I repeat the fertilization monthly as long as I am fertilizing my potato plants.
- Well balanced
- Contains some minor nutrients and trace elements
- Not organic
- Does not contain all minor nutrients and trace elements
When and How to Fertilize Potatoes?
Potatoes need fertilizer at least three times when they are growing. Do not use manure within a year of growing potatoes in that spot because it may promote scab, a disease potatoes get.
When planting potatoes, I dig a trench that is 6 inches deep. I put the fertilizer recommended by the soil test in two bands inside the edges of the trench. I cover the fertilizer with an inch of soil and water the fertilizer in. I then put the seed potato pieces, cut side down, in a row in the center of the trench. I cover the potato pieces with four inches of soil. If you do not have a soil test, use a balanced fertilizer like a 10-10-10 and put one pound of fertilizer per ten feet of row.
One week after my potato plants emerge from the soil, I spread half a pound of 10-10-10 per ten feet of row in a band about two inches from the potato plants. Water after fertilizing.
Four to Six Weeks After Emergence
Four to six weeks after the potato plants emerge from the soil, I spread another half a pound of 10-10-10 per ten feet of row in a band two inches from the potato plants. Water the fertilizer in after spreading it.
Organic Versus Synthetic Fertilizers
Both organic and synthetic fertilizers have the same nutrients. However, organic fertilizers only have natural ingredients allowed in organic gardening. Further, these fertilizers have been submitted to a certifying agency such as the USDA and have been certified organic. Synthetic fertilizers have components that are made in a laboratory. They may have natural ingredients, too. Fertilizers that say they are “natural fertilizers” may have synthetic ingredients because “natural” as a term is not regulated in the United States.
Dry versus Liquid Fertilizers
Dry fertilizers are granules or powders that are spread around the potato plant. Most granular fertilizers are slow-release. They release their nutrients slowly, over time, so you do not need to fertilize the plants as often. However, slow-release fertilizers may take up to seven days for plants to start showing any effects from the fertilizer.
Liquid fertilizers may be concentrates or ready to use. I buy concentrates because although they cost more initially, they mix into more fertilizer applications than ready-to-use liquids. The nutrients in liquid fertilizers are taken up with the water in the liquids and are immediately available to my plants. However, all the nutrients are available at the same time, so the liquids have to be applied more often.
Homemade Versus Commercial Fertilizers
Commercial fertilizers are purchased. These fertilizers have the major nutrients my potatoes need, and some have minor nutrients and trace elements, too. All I have to do is spread the fertilizer at the recommended times and in the quantity recommended.
Some people like to make their own fertilizer, so they know exactly what is in it. Homemade fertilizer can have the wrong mix of nutrients for potatoes unless you are very careful. Many recipes on the internet may look good but have too much of one nutrient or another.
Here is one recipe for homemade potato fertilizer and how to use it.
- 8 pounds of cottonseed meal (make sure it is organic cottonseed meal because conventional cotton is sprayed with many chemicals you do not want in your garden)
- 2 pounds of bone meal
- 3 pounds of greensand
- ¾ pound kelp meal
Mix the ingredients in an airtight container. This mix makes enough to fertilize forty feet of row once.
To use this mix:
- Spread the fertilizer evenly in the trench you dig for your potatoes
- Mix the fertilizer into the soil with a garden fork or pitchfork.
- Cover the soil with two inches of compost or mulch. Do not use manure because it will spread scab to your potatoes.
- Mix the compost or mulch into the soil with the fertilizer.
- Plant your potatoes
Once the potatoes come up, water with one tablespoon of fish emulsion in one gallon of water every two weeks.
When to Stop Fertilizing Potatoes?
I stop fertilizing potatoes when the plants start dying. Fertilizing too close to harvest can damage the potatoes, and they will not keep as long.
Signs of Overfertilization
I have found that fertilizing potato plants too much can be as bad as not fertilizing them at all. Here are some things I have observed that mean you are fertilizing too much.
Potato plants grow and grow but do not bloom. I have found this overgrowth is caused by excess nitrogen fertilizer. Switch to low-nitrogen fertilizer.
The lower leaves of the potato plant turn yellow. Many things can cause this, but I have observed it when there is excess nitrogen. The excess nitrogen makes it hard for the plant to take up enough water, and the lower leaves dehydrate. Switch to low-nitrogen fertilizer and flush the potato plants with water to dilute the excess nitrogen. Note that the plant will turn brown and fall over when the potatoes are ready to harvest, so don’t water then.
If the leaves on the potato get brown on the edges shortly after you have fertilized, you have put out too much fertilizer. I would flush the potato plants with water unless it is within four weeks of harvest. In that case, watering will cause more problems than the fertilizer.
Fertilizing Potatoes in Different Locations
Some people grow potatoes in containers. These potatoes will need more frequent fertilization because the nutrients in the container’s soil are quickly exhausted. I would use a liquid fertilizer every two weeks to fertilize container plants after the plant emerges from the soil. Stop when the potato plants start to dry out.
Fertilize potatoes in raised beds the same as you would fertilize potatoes in the ground if the raised bed has regular soil under it. If it is on cement or some other non-soil base, fertilize it like a container.
Fertilizing Different Colors of Potatoes
All Irish potatoes, whether they are white, yellow, purple, or red potatoes, need the same type of fertilizer.
Caring For Your Potatoes Throughout Their Lifecycle
Potatoes need more than fertilizer to thrive. Here are some tips to get the best harvest possible.
- Plant potatoes in a place where they will get at least six hours of direct sunlight a day.
- Potatoes need a soil pH of 6.0-6.5 but will tolerate a soil as acid as 5.0.
- Use only certified disease-free seed potatoes. You do not want to introduce potato blight into your garden. Not only will it rot your potatoes, but it will attack any plants in the same family, including tomatoes.
- Grocery store potatoes may be sprayed to keep them from sprouting and may carry diseases. Buy your seed potatoes at a nursery.
- Plant your potatoes eight to twelve inches apart. Twelve inches will give you more large potatoes. If you just want new potatoes, you can plant your potatoes nine inches apart.
- Water the potato plants to keep the soil evenly moist once the plant has emerged from the dirt. Too much or too little water will cause the potatoes to have problems and not store well. An inch a week is good unless you have very sandy soil. In that case, you will need to water more often to keep the soil evenly moist.
- I bought an inexpensive moisture meter and use it to tell if the soil is moist and water when it starts to dry out.
- When the potato plants are six to eight inches tall, hill soil over the plants and the surrounding area. Repeat this twice, then let the plants grow. This is because if the potatoes are exposed to the sun, they make a poisonous compound that turns them green.
- Keep weeds from growing near your potato plants. Weeds steal water, nutrients, and sunlight and can out-compete your potato plants.
- Seven to eight weeks after the plants emerge, you can harvest “new” potatoes, which have a thin skin. You can pull up the plant and harvest all the potatoes or just take a few from each plant and leave the rest to continue to grow.
- When the potato plant dries out, it is time to harvest your potatoes. Use a pitchfork or spade instead of a shovel. Be careful not to stick the fork or spade into the potatoes. It is best to start beside the plant and about six to eight inches away, and gradually work closer to the plant.
- Use any potatoes with bruises or cuts immediately.
- Brush the dirt off potatoes before storing them but wait to wash them until just before you use them.
- Store potatoes at 33-40 degrees and with high humidity. A running refrigerator will store potatoes well. Keep the potatoes in the dark.
- Remove any sprouts from the potatoes before eating the potatoes. Potato sprouts can be poisonous.
Frequently Asked Questions
Is 10-10-10 fertilizer good for potatoes?
If you do not have a soil test, using a 10-10-10 fertilizer is a good choice.
Are Epsom salts good for potatoes?
If you have a deficiency of magnesium, then Epsom salts are one way to add magnesium to your soil. Too much Epsom salts will poison your plant, so only use it when you have a magnesium deficiency.
Is chicken manure good for potatoes?
No, manure can cause potato scab. Do not use manure on potatoes.
In conclusion, potatoes need a lot of fertilizer. I think Southern Ag All Purpose Granular Fertilizer is the best fertilizer for potatoes. I like that I can use it on my other vegetables as well as my potatoes. That way, I only have to buy one fertilizer for my vegetable garden.