18-18-18 fertilizer is a balanced fertilizer with equal amounts of nitrogen, potassium, and phosphorus. This makes 18-18-18 fertilizer good for gardens, especially if you are growing vegetables. However, 18-18-18 fertilizer is a very poor choice for lawns, since it contains too much phosphorus and not enough nitrogen to produce healthy grass. If you can’t find 18-18-18 fertilizer you can replace it with any fertilizer where all three NPK numbers are the same. This includes 10-10-10 and 5-5-5 fertilizers. You will just have to change the application rates since these other balanced fertilizers contain less nutrients per pound.
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What Do the Numbers on 18-18-18 Fertilizer Mean?
The 3 numbers in 18-18-18 fertilizer tell you how much nitrogen, phosphorus, and potassium are in the fertilizer. The first number on any bag of fertilizer refers to the percentage of nitrogen in the fertilizer, by weight. So, the first 18 in 18-18-18 fertilizer means that 18% of the fertilizer’s content is nitrogen.
- The three numbers on fertilizer packaging always signifies the amount of nitrogen, phosphorus, and potassium in the fertilizer.
- The first 18 means that the fertilizer contains 18% nitrogen.
- The second 18 means that the fertilizer contains 18% phosphorus.
- The third 18 means that 18-18-18 fertilizer has 18% potassium.
- The remaining 46% of the fertilizer is made up of micronutrients and additives that improve fertilizer absorption.
The second 18 in 18-18-18 fertilizer means that the fertilizer contains 18% phosphorus. Since the final 18 in 18-18-18 fertilizer means that it contains 18% potassium. This three-number sequence is the same for all fertilizers. So, you can use your knowledge of fertilizer numbers to find the nitrogen, phosphorus, and potassium content for any fertilizer.
What is 18-18-18 Fertilizer Good For?
18-18-18 fertilizer is best used for growing vegetables. If you are growing tomatoes, peppers, squash, or other garden veggies, 18-18-18 provides a balance of primary nutrients required for these plants. So, it’s best to use it in the vegetable garden only. This nutrient balance isn’t good for all plants.
- Vegetables thrive when fed with 18-18-18 fertilizer.
- Farmers use 18-18-18 fertilizer for vegetable crops.
- 18-18-18 fertilizer is not a good choice for every plant.
Whether it is a liquid fertilizer or granular fertilizer, 18-18-18 is always best used to fuel the growth of vegetables. In commercial use, it is used for growing large vegetable crops. In fact, 18-18-18 fertilizer can be a difficult type of fertilizer to find in home and garden stores.
Is 18-18-18 Fertilizer Good for Lawns?
Do not use 18-18-18 fertilizer for the grass growing in your lawn. It contains much higher phosphorus and potassium levels than grass needs. Your lawn will do much better when it is grown using a fertilizer that is high in nitrogen, contains almost no phosphorus, and has very little potassium. The best lawn fertilizers often have fertilizer ratios such as 32-0-4. Using 18-18-18 fertilizer will not provide your lawn with the nutrition it needs.
- 18-18-18 is a very poor lawn fertilizer.
- Lawns require fertilizers with high nitrogen content, low phosphorus, and less potassium than nitrogen.
- In many areas, it is illegal to use a high-nitrogen fertilizer like 18-18-18 on your lawn.
Another reason not to use 18-18-18 fertilizer on your lawn is that it may be illegal. Many US states have banned the use of phosphorus fertilizer on lawns. Fertilizers with high phosphorus content can pollute waterways and result in harmful algal blooms. To grow the greenest lawn and protect the environment, do not use 18-18-18 fertilizer for grass.
Is 18-18-18 Fertilizer Good for Flowers?
While 18-18-18 isn’t a terrible flower fertilizer, it is far from the best choice. It contains far more phosphorus than is necessary and more potassium than your flowers need. This results in a lot of phosphorus being lost to soil leaching, which pollutes the environment.
- 18-18-18 fertilizer is not an ideal flower bed fertilizer.
- Phosphorus and potassium levels in 18-18-18 are too high for healthy flower growth.
- Look for a 3-1-2 fertilizer to grow the healthiest flowers.
Flowers do best when grown using a fertilizer with a 3-1-2 ratio. That means the largest number on the bag should be the first number, which represents nitrogen. The second number (representing phosphorus) should be the lowest. Finally, the third number (representing potassium) should be the second-largest.
How Much 18-18-18 Fertilizer Should You Use?
Use 1 pound of 18-18-18 fertilizer per 300 square feet in your vegetable garden. This will provide adequate nutrition without overloading the soil and harming your plants. You can fertilize the soil with 18-18-18 just before planting. Then, you can repeat this application every month until 2 to 4 weeks before you start harvesting.
- 1 pound of 18-18-18 fertilizer can adequately fertilize 300 square feet of your garden.
- You can use 18-18-18 on your vegetable garden up to once per month during the growing season.
- Too much fertilizer can dry out your plants, so monitor your garden after each application.
Monitor your garden after you apply 18-18-18 fertilizer. It is a powerful fertilizer with high nitrogen content. This means using too much 18-18-18 can actually “burn” your plants. You will know if your plants are suffering from fertilizer burn if their leaves begin to turn brown and dry in the 2 weeks after fertilizing. If this happens, pause fertilizer use and make sure to give your vegetables plenty of water.
What Can You Use Instead of 18-18-18 Fertilizer?
You can use any balanced fertilizer in place of 18-18-18 fertilizer. This means any fertilizer where all three numbers on the bag are the same is a good substitute. The reason is that they have the same balance of ingredients, just in different concentrations. For instance, 6-6-6 fertilizer contains equal amounts of nitrogen, phosphorus, and potassium, but is less concentrated than 18-18-18. 3 pounds of 6-6-6 fertilizer contains as much nutrition as 1 pound of 18-18-18 fertilizer.
- This 6-6-6 fertilizer is a great substitute for 18-18-18. You will just have to use more fertilizer to equal the same amount of nutrients in 18-18-18.
- All fertilizers where all 3 numbers are the same work just as effectively as 18-18-18.
- Look for balanced fertilizers such as 5-5-5 as a replacement for 18-18-18
Since 18-18-18 fertilizer is not commonly found in retail stores, you can use a different balanced fertilizer for your vegetable garden. 5-5-5 and 10-10-10 fertilizers are both rather common. Since they have the same ratio of ingredients, they are just as good for vegetable gardens. Just follow the application rates on the bag to apply the right amount of fertilizer to your garden.
Is 18-18-18 Fertilizer Good?
Before you use 18-18-18 fertilizer, review these facts:
- 18-18-18 fertilizer is a “balanced” fertilizer since all 3 numbers on the bag are the same.
- The 18-18-18 numbers means the fertilizer contains equal parts nitrogen, phosphorus, and potassium.
- 18-18-18 and other balanced fertilizers are great for growing vegetables.
- Never use 18-18-18 on your yard—it’s very poor for fueling grass growth.
- 18-18-18 is not the best fertilizer for flowers.
- You can use any balanced fertilizer—such as 5-5-5—as a replacement for 18-18-18.
- If you replace 18-18-18 with a different balanced fertilizer, the application rates will be different.
18-18-18 is a perfect fertilizer if you are growing vegetables, but so are other balanced fertilizers. If you have a bag of 18-18-18 in your shed, use it to grow some incredible veggies this year.