Calculating the pounds of nitrogen in a gallon of 32% fertilizer requires understanding the specific composition and density of the liquid product. This liquid fertilizer is formally known as Urea Ammonium Nitrate solution, or UAN-32, a widely used nitrogen source in agriculture. Determining the precise amount of actual nitrogen (N) contained in a volumetric measurement like a gallon is a fundamental step for farmers and growers. This calculation ensures accurate application rates and allows for efficient nutrient management.
Understanding the 32 Percent Nitrogen
The number “32” in UAN-32 refers to the guaranteed analysis, indicating that the solution contains 32% nitrogen by weight. This percentage measures the total elemental nitrogen present within the liquid fertilizer solution. For example, 100 pounds of UAN-32 solution will contain 32 pounds of actual nitrogen.
The nitrogen in UAN-32 exists in three distinct forms, providing a phased release for the crop. These forms are urea, ammonium, and nitrate nitrogen, typically blended in an approximately 50%, 25%, and 25% ratio, respectively. The nitrate form is immediately available for plant uptake, while the ammonium form is slower-acting. The urea form must be converted by soil microbes before becoming available, making UAN-32 a versatile fertilizer choice.
How Much a Gallon of UAN-32 Weighs
To determine the actual pounds of nitrogen in a gallon, the weight of the liquid fertilizer must first be established. The weight of any liquid fertilizer is primarily determined by its specific gravity, which measures its density compared to water. A standard gallon of UAN-32 solution is significantly heavier than a gallon of water, which weighs about 8.34 pounds.
The standard industry weight for UAN-32 is approximately 11.06 pounds per gallon. This weight is measured at a standard temperature, typically 68 degrees Fahrenheit (20 degrees Celsius). While temperature can slightly affect the density, the 11.06 pounds per gallon figure is the accepted standard used for practical application and calculation purposes.
The Final Calculation for Nitrogen Pounds
With the two necessary figures established—the nitrogen percentage and the weight per gallon—the final calculation is a straightforward multiplication. The weight of the gallon (11.06 pounds) is multiplied by the percentage of nitrogen contained within it (32%, or 0.32). The calculation is 11.06 lbs/gallon x 0.32.
Performing this calculation yields 3.5392 pounds of actual nitrogen per gallon of UAN-32. When rounded, one gallon of 32% Urea Ammonium Nitrate solution contains approximately 3.54 pounds of nitrogen. This final figure represents the amount of the nutrient available for plant use.
Farmers use this specific weight to accurately calculate application rates based on crop needs. For example, if a field requires 100 pounds of nitrogen per acre, the grower divides the total required nitrogen by the amount in a single gallon (100 lbs N / 3.54 lbs N per gallon). This calculation shows the grower needs to apply about 28.25 gallons of UAN-32 per acre. This is a fundamental step in precision agriculture, ensuring the right amount of nutrient is delivered efficiently.