If your soil has plenty of nitrogen, but you need to supplement other nutrients, such as phosphorus, potassium, magnesium, calcium, or sulfur, then there are lots of options available. I did some research to find out about some of these fertilizers.
So, which fertilizers are low in nitrogen? Any fertilizer package with a zero as the first number, such as 0-10-10, contains no nitrogen at all. A low first number means the fertilizer has low nitrogen content. Some soil amendments, such as bone meal, have relatively low nitrogen content. It is also possible to add low-nitrogen compost or mulch to your garden.
Let’s start by looking at some common fertilizers that are low in nitrogen. Then we’ll get into the reasons to use low nitrogen fertilizers.
Which Fertilizers Are Low In Nitrogen?
Every package of fertilizer comes with a set of three numbers, which indicate the nutrient content. These three numbers correspond to the three nutrients N-P-K, or nitrogen, phosphorus, and potassium.
For instance, a fertilizer labelled as 5-10-15 contains 5% nitrogen by weight, 10% phosphorus by weight, and 15% potassium by weight. Thus, a 100 pound bag of this fertilizer would contain 5 pounds of nitrogen, 10 pounds of phosphorus, and 15 pounds of potassium.
For more information, check out my article on fertilizer numbers and NPK ratios.
If you want a fertilizer that is low in nitrogen, you want a smaller first number on the bag of fertilizer. You can even find some fertilizers that contain no nitrogen at all (the first number will be a zero in this case).
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 alternatives, 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 can help to control crabgrass, or it can be used to supplement potassium in your soil if the nitrogen and phosphorus levels are acceptable. A 50 pound bag covers up to 12,000 square feet. 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, without adding any nitrogen or phosphorus. It is water-soluble, meaning that it can be easily absorbed by plants 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, but contains no nitrogen or phosphorus at all. Due to the high potassium content, be very careful when applying this to your soil, since 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). 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, with 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 Amazon.
- 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 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, such as when you have already mixed composted 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.
Warnings About Using Fertilizer
There are some considerations before using any type of fertilizer, either low-nitrogen or otherwise.
First of all, you should always do a soil test before adding any amendments to your garden. Knowing the pH and nutrient levels in your soil 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.
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.
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.
Natural Low-Nitrogen Fertilizers
There are also some ways to provide low-nitrogen nutrition for your garden in a more natural way. Some options include compost, mulch, and blood meal.
The nitrogen content of compost will vary depending on what you put into your compost 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 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.
For more information, check out my article on making your own compost.
You can also use low-nitrogen mulch on top of the soil in your garden. In addition to insulating soil and preventing evaporation of water, mulch will eventually decompose and provide organic material for your garden.
Some common low-nitrogen mulches that you can use are wood chips or wood ash from a fire. 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. Bone meal is a good choice when you need to supplement calcium or phosphorus without overloading your plants with nitrogen.
Epsom salts (magnesium sulfate), chelated iron, lime (calcium carbonate), and sulfur are soil additives that contain no nitrogen and are used to address either nutrient deficiencies or pH imbalances.
Other common soil additives, such as blood meal, cottonseed meal, and fish emulsion do contain higher levels of nitrogen. As such, you should avoid 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.
First of all, you may have excessive nitrogen in your soil, due to aggressive application of high-nitrogen fertilizers in the past. Using “fresh” manure in your garden can also raise nitrogen levels in the soil.
You may also have a deficiency of certain other nutrients, such as phosphorus, potassium, calcium, magnesium, or iron, while the nitrogen levels in the soil are fine.
You may also wish to avoid adding excessive nitrogen in order to encourage more flowers and fruit on the plants in your garden. Too much nitrogen can encourage green growth of leaves, branches, and stems at the expense of flowers and fruit.
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.
Any of these are valid reasons to consider using low-nitrogen fertilizers in your garden.
By 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.
I hope you found this article helpful – if so, please share it with someone else who can use the information. If you have any questions or advice about low-nitrogen fertilizers, please leave a comment below.