Back 2 Basics: Fertilizer Math

Understanding Fertilizer Analysis: How to Read Fertilizer Numbers and Apply the Right Nutrient Rates

Every fertilizer product has a basic analysis listed on the label. After evaluating your soil’s nutrient inventory and capacity through a soil test, the next step is determining what nutrient source and application rates will best help you reach your yield goals. Understanding fertilizer analysis is the foundation of any effective crop nutrition program.

What Do Fertilizer Numbers Mean?

While it is common knowledge in the field what what these numbers represent, how to interpret them correctly is another matter. Those numbers tell you the percentage of nutrients contained in the product and help you understand exactly what you’re applying to your field.

Before choosing a fertilizer, it’s important to know whether you’re working with dry fertilizer or liquid fertilizer, since the calculations differ slightly between the two.

Breaking Down Dry Fertilizer Analysis

Dry fertilizer analysis is fairly straightforward because the numbers represent percentages of nutrients by weight.

For example, in an 11-52-0 fertilizer:

• 11% is nitrogen
• 52% is phosphate (P₂O₅)
• 0% is potash (K₂O)

If you apply 100 pounds of that product, you’re applying:

• 11 pounds of nitrogen
• 52 pounds of phosphate
• 0 pounds of potassium

If potassium is needed, a product like 0-0-60can be added. Applying 100 pounds of 0-0-60 supplies 60 pounds of potassium. When combined with the original fertilizer, you now have a blended nutrient program and know exactly how much nitrogen, phosphorus, and potassium you’re applying per acre.

How to Calculate Nutrients in Liquid Fertilizer

Liquid fertilizer requires an extra step because you must account for pounds per gallon, which is listed on the product label.

For a 9-24-3 liquid fertilizer:

• The product weighs about 11.21 pounds per gallon
• Applying 5 gallons per acre equals roughly 56 pounds of total product

From there, nutrient calculations follow the same percentage method:

• 9% of 56 pounds = just over 5 pounds of nitrogen
• 24% of 56 pounds = just over 13 pounds of phosphate
• 3% of 56 pounds = just over 1 pound of potassium

This calculation allows you to understand how much nutrition you’re delivering with each liquid application. The other consideration when developing a crop nutrition plan is the availability of the nutrients to the plant.

Why Fertilizer Analysis Matters for Crop Nutrition

Understanding fertilizer analysis ensures you know exactly what nutrients are being applied and at what rates. This clarity helps you:

• Match fertilizer applications to soil test results
• Build balanced fertility programs
• Avoid under- or over-applying nutrients
• Maximize efficiency and return on investment

Once you understand how to read fertilizer labels, you can confidently adjust your program to meet crop needs and yield goals.

Get Help Understanding Fertilizer Numbers

Fertilizer analysis doesn’t have to be complicated, but getting it right matters. If you have questions about fertilizer numbers, nutrient rates, or product selection you can ask an AgroLiquid Agronomist. Submit our online form and one of our professional agronomists will reach out to help you make sense of your fertilizer program.