Understanding Fertilizer Calculations for the Lawn and Garden
Fertilizing your lawn or garden may seem like a daunting task, especially when the math involved is brought up. Fertilizer calculations are simpler than they seem, and understanding them can lead to better results for your plants while avoiding excess costs.
The first step before fertilizing is always to perform a soil test. This will tell you exactly what your soil needs and prevent you from over-fertilizing. The primary macronutrients to focus on are nitrogen, phosphorus, and potassium. Nitrogen promotes healthy leaf growth, while phosphorus helps with root development, and potassium improves overall plant health. While nitrogen is often not included in soil tests due to its rapid fluctuation in the soil, phosphorus and potassium are much more stable and important for long-term fertilizer decisions.
Types of Fertilizers
Fertilizers are labeled with a series of numbers representing their nitrogen (N), phosphorus (P), and potassium (K) content in that order. Common examples include 13-13-13 (balanced fertilizer with equal parts of N, P, and K), 34-0-0 (high nitrogen content), and organic options like blood meal (13-1-0) or bone meal (3-15-0).
Fertilizer recommendations can often be different from fertilizers you have on hand or those you want to use. For instance, if your soil test suggests applying one pound of 10-10-10 fertilizer per 100 square feet, but you only have 13-13-13 fertilizer in your garage, there's a simple way to adjust. You can divide the recommendation (10) by the fertilizer you have (13). (10 ÷ 13 = 0.77) Applying 0.77 pounds of the 13-13-13 fertilizer will give you the same nutrient amounts as the one pound of 10-10-10.
Incomplete or Organic Fertilizer Conversions
The math becomes slightly more complex when dealing with incomplete or organic fertilizers. For example, if the recommendation calls for one pound of nitrogen and you have blood meal (13-1-0), you would need to apply 0.77 pounds of blood meal (10 ÷ 13 = 0.77). However, since blood meal provides nitrogen, you would also need to add a source of phosphorus, like bone meal (3-15-0), applying 0.66 pounds (10 ÷ 15 = 0.66). Finally, you could add potassium sulfate (0-0-50) for potassium, applying 0.2 pounds (10 ÷ 50 = 0.2).
The mix is not quite a perfect 10-10-10, but it is more than close enough.
While these conversions may take a little extra effort, they offer a great way to apply organic fertilizers.
Potassium in Fertilizer
It’s important to note that potassium tends to stay in the soil for a long time. Over-fertilizing with potassium can be harmful, so always conduct a soil test before adding more. Too much potassium can lead to plant issues, and once it's in the soil, it is impossible to remove.
Conclusion
By performing a soil test and understanding the conversions between different types of fertilizers, you can make sure your garden or lawn gets exactly what it needs without wasting money on unnecessary products. Whether using a balanced fertilizer, an incomplete fertilizer or an organic mix, the process is as simple as dividing the recommended amount by what you already have.
Related Videos:
Fertilizer Blends
Fertilizer Basics
Garden Fertilizer Math
Kinds of Fertilizer
How to Calibrate Your Fertilizer Spreader
Related Resources:
Perennials with Winter Interest
Plants can add winter interest to your landscape
The first step before fertilizing is always to perform a soil test. This will tell you exactly what your soil needs and prevent you from over-fertilizing. The primary macronutrients to focus on are nitrogen, phosphorus, and potassium. Nitrogen promotes healthy leaf growth, while phosphorus helps with root development, and potassium improves overall plant health. While nitrogen is often not included in soil tests due to its rapid fluctuation in the soil, phosphorus and potassium are much more stable and important for long-term fertilizer decisions.
Types of Fertilizers
Fertilizers are labeled with a series of numbers representing their nitrogen (N), phosphorus (P), and potassium (K) content in that order. Common examples include 13-13-13 (balanced fertilizer with equal parts of N, P, and K), 34-0-0 (high nitrogen content), and organic options like blood meal (13-1-0) or bone meal (3-15-0).
Fertilizer recommendations can often be different from fertilizers you have on hand or those you want to use. For instance, if your soil test suggests applying one pound of 10-10-10 fertilizer per 100 square feet, but you only have 13-13-13 fertilizer in your garage, there's a simple way to adjust. You can divide the recommendation (10) by the fertilizer you have (13). (10 ÷ 13 = 0.77) Applying 0.77 pounds of the 13-13-13 fertilizer will give you the same nutrient amounts as the one pound of 10-10-10.
Incomplete or Organic Fertilizer Conversions
The math becomes slightly more complex when dealing with incomplete or organic fertilizers. For example, if the recommendation calls for one pound of nitrogen and you have blood meal (13-1-0), you would need to apply 0.77 pounds of blood meal (10 ÷ 13 = 0.77). However, since blood meal provides nitrogen, you would also need to add a source of phosphorus, like bone meal (3-15-0), applying 0.66 pounds (10 ÷ 15 = 0.66). Finally, you could add potassium sulfate (0-0-50) for potassium, applying 0.2 pounds (10 ÷ 50 = 0.2).
The mix is not quite a perfect 10-10-10, but it is more than close enough.
While these conversions may take a little extra effort, they offer a great way to apply organic fertilizers.
Potassium in Fertilizer
It’s important to note that potassium tends to stay in the soil for a long time. Over-fertilizing with potassium can be harmful, so always conduct a soil test before adding more. Too much potassium can lead to plant issues, and once it's in the soil, it is impossible to remove.
Conclusion
By performing a soil test and understanding the conversions between different types of fertilizers, you can make sure your garden or lawn gets exactly what it needs without wasting money on unnecessary products. Whether using a balanced fertilizer, an incomplete fertilizer or an organic mix, the process is as simple as dividing the recommended amount by what you already have.
Related Videos:
Fertilizer Blends
Fertilizer Basics
Garden Fertilizer Math
Kinds of Fertilizer
How to Calibrate Your Fertilizer Spreader
Related Resources:
Perennials with Winter Interest
Plants can add winter interest to your landscape