If your soil already has plenty of nitrogen, you might not want to use a high-nitrogen fertilizer. Luckily, there are some options that avoid high nitrogen levels.
So, which fertilizers are low in nitrogen? Low nitrogen fertilizers include any package with a zero as the first number. For example, 0-10-10 fertilizer contains no nitrogen at all. A low first number on a package means the fertilizer is low in nitrogen. For example, 3-1-2 fertilizer contains only 3% nitrogen by weight. Some soil amendments (such as bone meal) are natural low nitrogen fertilizers. It is also possible to add low-nitrogen compost or mulch to your garden.
Of course, there are lots of low-nitrogen fertilizers that add other nutrients, including phosphorus, potassium, calcium, and sulfur.
In this article, we’ll start off by looking at some common low-nitrogen fertilizers. Then we’ll get into the reasons to use low nitrogen fertilizers.
Let’s get started.
Which Fertilizers Are Low In Nitrogen?
Fertilizers that have a low first number are low in nitrogen. For example:
- A package of 0-10-10 contains no nitrogen at all (it contains 0% nitrogen by weight).
- A package of 3-1-2 is low in nitrogen (it contains 3% nitrogen by weight).
Every package of fertilizer comes with a set of three numbers, which indicate the nutrient content. These three numbers correspond to the “big three nutrients” N-P-K:
- N = nitrogen
- P = phosphorus
- K = potassium
For example, a fertilizer labelled as 5-10-15 contains:
- 5% nitrogen by weight
- 10% phosphorus by weight
- 15% potassium by weight
- 70% filler
Thus, a 100 pound bag of this fertilizer would contain 5 pounds of nitrogen, 10 pounds of phosphorus, and 15 pounds of potassium, along with 70 pounds of filler.
For more information, check out my article on fertilizer numbers and NPK ratios. Remember that the NPK nutrients are 3 important ones for plant growth, but there are others.
If you want a fertilizer that is low in nitrogen, seek out a bag of fertilizer with a smaller first number on the label. You can even find some fertilizers that contain no nitrogen at all (for those, the first number will be a zero).
Remember that any complete fertilizer contains all three of the nutrients nitrogen, phosphorus, and potassium. So, if you want a fertilizer with no nitrogen, don’t use a complete fertilizer.
Instead, seek out one of the nitrogen-free or low-nitrogen alternative fertilizers, such as those listed below.
Here are a few fertilizers that contain either phosphorus, potassium, or both, but no nitrogen at all.
Lesco Crabgrass Control: 0-0-7
This fertilizer contains only potassium (7% by weight). There is no nitrogen or phosphorus in it.
It can help to control crabgrass. It can also supplement potassium in your soil if the nitrogen and phosphorus levels are acceptable.
A 50 pound bag covers up to 12,000 square feet (240 square feet per pound). You need a rotary spreader to apply it, and you should wear gloves to avoid staining your skin.
For more information, check out Lesco Crabgrass Control Fertilizer on Home Depot’s website.
K-Mag Fertilizer (or Sul-Po-Mag): 0-0-22
This fertilizer provides potassium, magnesium, and sulfur to your soil. However, it contains no nitrogen or phosphorus.
It is water-soluble, meaning that plants can easily absorb it if you water it in after application. It will dissolve gradually so that your plants will receive a dose of these three nutrients throughout the season.
For more information, check out K-Mag Fertilizer (Sul-Po-Mag) on Amazon.
SOP (Sulfate of Potash): 0-0-50
Sulfate of potash, or potassium sulfate, is very high in potassium (50% by weight). However, it contains no nitrogen or phosphorus at all.
Due to the high potassium content, be very careful when applying this to your soil. Remember: a little bit goes a long way.
For comparison: this formula contains 5 times as much potassium per pound as a complete fertilizer such as 10-10-10. This makes it easy to burn your plants by over fertilizing.
For more information, check out Sulfate of Potash on Amazon.
Muriate of Potash (Potassium Chloride): 0-0-62
Muriate of Potash, or Potassium Chloride, has extremely high potassium content, at 62% potassium by weight. It has no nitrogen or phosphorus.
As with sulfate of potash, you need to be careful when applying this to your garden.
For more information, check out Muriate of Potash on Greenway Biotech.
Hi-Yield Bone Meal: 0-10-0
Bone meal is a common way to recycle waste products (bones) from slaughterhouses. Bone meal is high in phosphorus, but contains no nitrogen or potassium.
This makes it ideal as a supplement when your soil shows a phosphorus deficiency, but nitrogen and potassium levels are acceptable.
Bone meal contains 10% phosphorus by weight, which is good but not too high. It also provides a slow-release of phosphorus, meaning you won’t need to worry as much about harming your plants with a high concentration.
For more information, check out Hi-Yield Bone Meal on the Seed Ranch website.
Alaska Morbloom: 0-10-10
This fertilizer contains no nitrogen, but provides a good dose of both phosphorus and potassium.
This is ideal for a garden that already has plenty of nitrogen. For example, after you have already mixed compost or aged manure into your garden.
For more information, check out Alaska Morbloom fertilizer on the Home Depot website.
Grow More 5088 Water Soluble Fertilizer: 0-50-30
This fertilizer has high levels of both phosphorus and potassium, but no nitrogen at all. You need to be careful when applying this fertilizer to your garden, since a little will go a very long way.
For comparison, you would only need 1/5 to 1/3 as much of this fertilizer as you would need of Alaska Morbloom to get the same effect.
Remember that this fertilizer is water soluble, meaning that the nutrients will quickly become available to your plants if you water it in after application.
For more information, check out Grow More 5088 on Amazon.
Fertilizer Use Warnings
There are some considerations before using any type of fertilizer, either low-nitrogen or otherwise.
Do A Soil Test
First of all, you should get a soil test before adding any amendments to your garden. Knowing the pH and nutrient levels is important to making good decisions about what to use to improve your soil.
You can buy a do-it-yourself soil test kit online or at a garden center. You can also send a soil sample to the lab at your local agricultural extension office to get a more detailed analysis.
If you tell them what you are growing, the lab will also provide recommendations on how to treat your soil.
For more information, check out my article on how to do a soil test.
Follow Fertilizer Label Instructions
Also, make sure to follow instructions when adding fertilizer to your garden. Adding too much fertilizer too quickly can result in fertilizer burn, which can damage or kill your plants.
Remember that you can always add more fertilizer later, but it is difficult to remove it after the fact. This is especially true if you use fast-release fertilizers, which tend to be water-soluble and can easily burn your plants.
For more information, check out my article on over fertilizing plants.
Pay Attention To Overall Soil Health
Finally, remember that your best bet is to look after soil health first, and use fertilizer as a supplement to compost, manure, mulch, and other more natural methods.
Things like soil texture, soil organisms, and water retention are all important. These things cannot be fixed by any fertilizer.
Luckily, adding compost or aged manure can help with all of these factors:
- Compost can make clay soil drain better, and it can make sandy soil retain a little more water.
- Organic material in compost or manure attracts beneficial soil organisms (such as earthworms and nitrogen-fixing bacteria), which make nutrients available and improve soil quality.
Natural Low-Nitrogen Fertilizers
There are also some ways to provide low-nitrogen nutrition for your garden in a more natural way.
Low Nitrogen Compost
The nitrogen content of compost will vary depending on what you put into the pile:
- Any “greens”, such as grass clippings or cuttings from pruned plants, will be high in nitrogen.
- Any “browns”, such as straw and sawdust, will be high in carbon.
As mentioned before, it is a good idea to use compost in your soil first, to provide nutrients and organic material to your garden. This material slowly decomposes over time, due to bacteria and worms in the soil.
As such, it provides a small dose of slow-release nutrients to your garden. The best part about compost is that you can make it from kitchen scraps and yard waste.
For more information, check out my article on making your own compost.
A low-nitrogen manure will add organic material to soil, along with other nutrients – all without burning your plants. However, not all manure is created equal.
Chicken manure is much “hotter” than cow manure, since it contains a lot more nitrogen. In fact, chicken manure contains up to 6% nitrogen by weight, depending on the water content.
You can also use low-nitrogen mulch on top of the soil in your garden. A layer of mulch has many benefits, including:
- Insulating soil against temperature fluctuations
- Retaining water by preventing evaporation
- Providing organic material for your garden (after it decomposes).
Some common low-nitrogen mulches that you can use are wood chips or wood ash from a fire. According to the Oregon State University Extension, wood ash contains 0% nitrogen, 5% phosphorus, and 3% to 7% potassium by weight.
For more information, check out my article on using wood ash in your garden.
Bone meal is another soil additive that contains a high amount of both calcium and phosphorus, but low amounts of nitrogen.
It is possible to find bone meal (steamed) with only 0.7% nitrogen by weight, but with a whopping 18% to 24% phosphorus by weight (there is no potassium in bone meal).
Bone meal is a good choice when you need to supplement calcium or phosphorus without overloading your plants with nitrogen.
There are several other soil additives that contain no nitrogen at all, but work to supplement important plant nutrients including:
- Epsom salt (magnesium sulfate) – adds magnesium and sulfur to soil. You can learn more about Epsom salt here.
- Chelated iron – adds iron in a form that plants can absorb. You can learn about other iron supplements for soil here.
- Lime (calcium carbonate) – adds calcium to soil. Also used to raisesoil pH.
- Sulfur – adds sulfur to soil. Also used to lower soil pH.
Some of these additives (such as Epsom salt and chelated iron) can be dissolved in water and sprayed on the leaves of plants. This is known as foliar feeding, where the plants absorb the water and nutrients through their leaves.
Other common soil additives, such as blood meal, cottonseed meal, and fish emulsion do contain higher levels of nitrogen. As such, you should avoid using them if a soil test reveals too much nitrogen in your soil.
If your soil is still short on nutrients after adding compost, low-nitrogen fertilizers can be a good supplement to add what is missing.
Why Use A Low Nitrogen Fertilizer?
There are several reasons to use a low-nitrogen fertilizer, one or more of which may apply to your garden.
Excessive Nitrogen In Soil
First of all, you may have excessive nitrogen in your soil. This could be due to aggressive or improper application of high-nitrogen fertilizers in the past.
For example, using “fresh” manure in your garden or high-nitrogen fertilizers will raise nitrogen levels in the soil.
According to the Colorado State University Extension, too much nitrogen in your soil can cause lower yields, resulting in fewer vegetables of poor quality. They also give guidelines for calculating the nitrogen needed for various garden vegetables.
Nutrient Deficiency In Soil
You may also have a deficiency of certain other nutrients, such as:
At the same time, there might already be plenty of nitrogen in your soil. In that case, a low-nitrogen fertilizer would make sense.
Lack Of Flowers Or Fruit On Plants
You may also wish to avoid adding excessive nitrogen in order to encourage more flowers and fruit on the plants in your garden.
It is true that nitrogen is important for plant growth (after all, it is a part of chlorophyll!) However, too much nitrogen encourages green growth of plants (leaves, branches, and stems) at the expense of flowers and fruit.
If you notice this problem on your plants, it might be a good idea to try a low-nitrogen fertilizer for a while.
Fertilizer Burn Of Plants
Finally, the salts found in fertilizers can acidify soil or cause fertilizer burn in plants, which can harm or kill them.
This is especially true of ammonium based fertilizers (such as those containing ammonium nitrate), which are high in nitrogen.
Now you have a much better idea of which fertilizers are low in nitrogen and where to find them. You also know how to provide organic material to your garden without adding too much nitrogen.
You might also be interested to read my article on low phosphorus fertilizers.
I hope you found this article helpful – if so, please share it with someone else who can use the information.