Knowing the precise weight of a liquid fertilizer, such as UAN 32, is essential for accurate application and inventory control in agriculture. UAN 32 is a common liquid nitrogen solution used extensively in modern farming practices. Understanding its density, or weight per gallon, ensures farmers deliver the correct amount of nitrogen to their crops. This information also helps calculate tank capacity and confirm the volume of product received from a supplier.
Understanding UAN 32
UAN 32 stands for Urea Ammonium Nitrate solution, a liquid fertilizer containing 32% nitrogen by weight. It is a blend of three nitrogen sources—urea, ammonium nitrate, and water—which acts as a solvent to maintain a stable solution. The 32% concentration makes it one of the most concentrated liquid nitrogen fertilizers available.
The three forms of nitrogen provide a phased release of nutrients to the plant. Nitrate nitrogen is immediately available for uptake, ammoniacal nitrogen is absorbed quickly or converted by soil microbes, and the urea component offers a slower, sustained feeding source. Because UAN 32 is a dissolved liquid solution, its density is significantly greater than that of pure water.
Determining the Weight of a Gallon
The standard density of UAN 32 is a well-established figure in agriculture. This measurement is typically based on 60°F (15.5°C), the industry standard for measuring liquid fertilizer density. At this temperature, one gallon of UAN 32 weighs approximately 11.08 pounds.
Manufacturer specifications may list a slightly different weight, such as 11.05 or 11.06 pounds per gallon, often measured at 68°F (20°C). The solution’s specific gravity is around 1.32 to 1.33, meaning the fertilizer is about 1.33 times heavier than the same volume of water.
The weight per gallon is crucial because it allows for the precise calculation of the actual nitrogen content being applied. Using the 11.08 pounds per gallon weight, a gallon of UAN 32 contains about 3.5 pounds of actual nitrogen (11.08 lbs 0.32). This calculation is necessary for accurately meeting crop nutrient requirements.
The Role of Temperature in Density
The weight of a UAN 32 gallon is not constant and changes significantly with temperature. Like most liquids, UAN 32 experiences thermal expansion and contraction. As the temperature increases, the liquid expands, increasing its volume. Since the mass remains the same, this expansion causes the density, or weight per gallon, to decrease.
Conversely, when the temperature drops, the liquid contracts, and the weight per gallon increases. This variability impacts application accuracy if not accounted for; for instance, a gallon at 30°F will weigh more than the same gallon at 80°F.
Industry data shows UAN 32 density can range from approximately 11.18 pounds per gallon at cold temperatures to about 10.98 pounds per gallon at warmer temperatures. This fluctuation is a consideration for storage and application, especially since the product’s salting-out temperature, where crystals begin to form, is around 32°F (0°C).
Using Weight for Accurate Application and Calibration
Knowing the precise density of UAN 32 is essential for volumetric measurement and equipment calibration.
When purchasing or receiving the product, the weight per gallon helps verify the quantity delivered, ensuring the correct amount of product is in the tank. Since the product is often sold by volume but its concentration is by weight, this conversion is necessary for business transactions.
The density is used to accurately calibrate application equipment, such as sprayers and liquid applicators. Liquid fertilizer flows through nozzles differently than water due to its greater density. If a sprayer is calibrated using water, which is lighter, it will apply a lower rate of the heavier UAN 32 solution than intended.
To correct for this density difference, an adjustment factor must be used when calibrating a sprayer with water. For UAN 32, this factor is typically around 1.15. This factor is multiplied by the target fertilizer application rate to determine the higher water-only rate needed for calibration, ensuring the desired amount of actual nitrogen is applied per acre.