Fertilizing your Bermuda grass lawn requires a nuanced understanding of its nutrient needs. This comprehensive guide will help you determine the right amount of fertilizer, understand fertilizer labels, and explore the types of nitrogen available. By mastering these elements, you can ensure your Bermuda grass thrives, delivering a lush, green lawn.
Nitrogen, Phosphorus and Potassium
These are commonly sold together, so we will take about them together. A good fertilizer will show clearly it’s N-P-K ratio. Examples: 15-5-10 or 6-4-0.
Nitrogen (N):
- Primary Function: Promotes lush, green growth and increases the density of the grass.
- Benefits: Encourages rapid growth and improves the overall health and color of Bermuda grass. It is vital for the synthesis of chlorophyll, which is essential for photosynthesis.
Phosphorus (P):
- Primary Function: Supports strong root development and energy transfer within the plant.
- Benefits: Essential for establishing new Bermuda grass and enhancing root growth. It helps in the formation of seeds, flowers, and fruits, and is crucial during the early stages of growth.
Potassium (K):
- Primary Function: Enhances overall plant health and stress tolerance.
- Benefits: Improves the resilience of Bermuda grass to diseases, drought, and extreme temperatures. It strengthens cell walls, aids in water regulation, and helps in the synthesis of proteins and starches.
Nitrogen Requirements: How Much is Enough?
Nitrogen depletes faster than other nutrients, so most of your fertilizer applications will focus on it. While phosphorus and potassium are also important, they don’t deplete as quickly, especially in clay soil. High phosphorus levels can cause problems, whereas potassium is generally safe even in high amounts. Although excessive nitrogen can cause burn, Bermuda grass recovers quickly. Since nitrogen is key to maintaining a green lawn, here’s how to approach your fertilizer applications.
For Thin Lawns
If your Bermuda grass lawn is thin and needs filling in, aim for 1.0-1.5 lbs of Nitrogen per thousand square feet of lawn per month. This will encourage faster growth and help your lawn become denser.
For Mature Lawns
For lawns that are already mature and reasonably thick, a lower amount of 0.5 lbs of Nitrogen per thousand square feet per month should suffice. This will maintain your lawn without causing excessive growth.
Understanding NPK Ratios
While nitrogen is crucial, it’s not the only nutrient your lawn needs. Phosphorus (P) and Potassium (K) are also essential but are best determined through a soil sample test from your local extension office. As a rule of thumb, a 2:1 Nitrogen to Potassium ratio is generally safe, as Potassium tends to leach from the soil regularly. Phosphorus is rarely needed.
Reading Fertilizer Labels
The values of N-P-K are the percentage, by weight, of each of the 3 macronutrients in fertilizer: nitrogen, phosphorus and potassium. Let’s consider a Scotts Turf Builder with a 32-0-4 analysis. Here’s how to interpret it:
- 32% Nitrogen: To get 1 lb of Nitrogen on your lawn, you would need to apply about 3 lbs of this product per thousand square feet.
- 0% Phosphorus: This product contains no phosphorus which is great as too much phosphorus causes problems. However, not great if your soil test says your lawn needs it.
- 4% Potassium: This means 4% of the fertilizer is potassium. It’s a low amount but you don’t it as much as nitrogen. To put down 0.5 pounds of potassium per 1000 sqft, you’d have to put down 12.5 pounds of fertilizer because 12.5 pounds x 0.04 = 0.5 pounds. However, 12.5 pounds of fertilizer would include too much nitrogen, so you can’t do 0.5 pounds at once.
Types of Nitrogen: Slow vs. Fast Release
Slow Release Nitrogen
Usually coated Urea, slow-release nitrogen provides a steady supply of nutrients over 4-8 weeks. This is ideal for sustained, even growth.
Fast Release Nitrogen
Commonly found as Urea (46-0-0) or Ammonium Sulfate (21-0-0), fast-release nitrogen is quickly used up by the grass or lost through volatilization or leaching within 2-3 weeks. It’s generally cheaper but needs to be applied more frequently. It is ideal for pushing growth, and particularly used by those who don’t mind more maintenance in exchange for better results.
Nitrogen Frequency
For fast-release nitrogen like urea or ammonium sulfate, one might apply every 2-3 weeks to maintain grass vigor without leaching or volatilization losses. For slow-release forms such as polymer-coated urea, monthly applications are sufficient. The path you choose is based on your goals.
Spoon Feeding and Liquid Fertilization Techniques
Spoon feeding involves applying small amounts of nitrogen weekly, keeping your lawn consistently green and growing without peaks and troughs in nutrient availability. For liquid fertilization, dissolve urea or ammonium sulfate in water and apply no more than 0.25-0.5 lbs of nitrogen per 1000 sq ft. Water the lawn immediately post-application to enhance nutrient uptake and prevent burn. The more nitrogen you use, the quicker you need to water in. The application limits for liquid fertilizer are lower than if applied in granular form. The results are quicker and uptake is better via this foliar application. Granular applications rely on correct pH and other properties of the soil for efficient uptake, whereas foliar bypasses any soil inefficiencies.
Example Nitrogen Fertilizer Schedules
As you increase your frequency, you decrease the amount of nitrogen you apply per application. Here are some example schedules you might follow throughout the growing season. The examples use urea and ammonium sulfate, choose one based on your needs. You don’t have to use them, but they’re popular.
Goal: Maintain lawn
| Week Number | Option 1 Urea Amount (lbs per 1000 sq ft) | Option 2 Ammonium Sulfate Amount (lbs per 1000 sq ft) |
|---|---|---|
| Week 1 | 1.09 lbs | 2.38 lbs |
| Week 2 | 0 lbs | 0 lbs |
| Week 3 | 0 lbs | 0 lbs |
| Week 4 | 0 lbs | 0 lbs |
| Week 5 | 0 lbs | 0 lbs |
| Week 6 | 0 lbs | 0 lbs |
| Week 7 | 1.09 lbs | 2.38 lbs |
| Week 8 | 0 lbs | 0 lbs |
| Week 9 | 0 lbs | 0 lbs |
| Week 10 | 0 lbs | 0 lbs |
| Week 11 | 0 lbs | 0 lbs |
| Week 12 | 0 lbs | 0 lbs |
Goal: Push growth via granular application
| Week Number | Option 1 Urea Amount (lbs per 1000 sq ft) | Option 2 Ammonium Sulfate Amount (lbs per 1000 sq ft) |
|---|---|---|
| Week 1 | 1.08 lbs | 2.14 lbs |
| Week 2 | 0 lbs | 0 lbs |
| Week 3 | 1.08 lbs | 2.14 lbs |
| Week 4 | 0 lbs | 0 lbs |
Goal: Push maximum growth via liquid application
| Week Number | Option 1 Urea Amount (lbs per 1000 sq ft) | Option 2 Ammonium Sulfate Amount (lbs per 1000 sq ft) |
|---|---|---|
| Week 1 | 0.82 lbs | 1.79 lbs |
| Week 2 | 0.82 lbs | 1.79 lbs |
| Week 3 | 0.82 lbs | 1.79 lbs |
| Week 4 | 0.82 lbs | 1.79 lbs |
Micronutrients
Micronutrients are predominantly sold as a liquid meant as a foliar spray. This is because mixing is crucial with micronutrients. Some micronutrients (like boron and copper) are toxic if a granular product were not to be thoroughly mixed.
Soils with high pH tend to have uptake issues. While we’re on the topic: if you don’t know your soil pH, you can get the most accurate test money can buy from mailing a soil sample to Clemson and paying $3. If you have high pH, it is recommended to apply your micros via a foliar spray and let them dry on the leaf. This can bypass pH and other tie-up issues in the soil if the selected micronutrient has proper sized molecules to be absorb by the leaf (for example, iron sulfate cannot be absorbed by the leaf). That doesn’t mean you should avoid correcting your soil, but you have great options in the meantime.
Primary Cations: Calcium, Magnesium, Potassium, and Sodium
Cations balance soil structure, control pH, and compete for space on soil particles. Balance the ratio between one another is important. This is where a plan that only applies magnesium foliarly becomes a bit tricky. A lack of magnesium in the soil with a reliance on micros (like magnesium) only applied foliarly can mean a higher percent of the other 3 cations. This is why it’s important to amend these 4 with a granular option. They can still be applied regularly by liquid but you should look to amend the soil to balance these out. Do a soil test once to understand where you’re at and then apply those recommendations once a year.
Calcium – Apply gypsum or lime. Commonly low in sandy Southeast soils.
Potassium – Apply potash (KCl). Often low in heavy rain areas like Florida.
Magnesium – Apply dolomitic lime or Epsom salt. Low in acidic soils like parts of the Northeast.
Sodium – Rare to need adding, but can rise near coasts or with poor irrigation water.
In my case, in Texas I’ve always had high calcium so I apply K-Mag once a year to get both potassium and magnesium to keep the calcium and sodium in range. Another option is a high potassium fertilizer like a 0-0-50 and epsom salt for the magnesium. Epsom salt, contrary to it’s name, does not contain salt.
Conclusion
Fertilizing your Bermuda grass lawn is not a one-size-fits-all endeavor. The amount of nitrogen you need depends on the current state of your lawn and your goals for its appearance and health. By understanding how to read fertilizer labels and the differences between slow and fast-release nitrogen, you can make informed decisions that will help your Bermuda grass thrive. So grab that fertilizer bag, do some quick math, and get ready to give your lawn the nutrients it craves.
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