Urea fertilizer is a highly concentrated source of nitrogen, typically labeled as 46-0-0, meaning it contains 46% nitrogen by weight. This high concentration makes it one of the most cost-effective nitrogen options for plant nutrition. Mixing urea with water to create a liquid solution is the preferred method for many applications, allowing for quick nutrient delivery and precise control over the application rate. This dissolved form ensures the nitrogen is immediately available for uptake, either through the leaves in a foliar spray or through the roots via soil drenching or irrigation systems.
Safety Requirements and Equipment Preparation
Working with concentrated fertilizer requires protecting your skin and eyes from irritation. You must wear personal protective equipment, starting with chemical-resistant gloves and protective eyewear or a face shield. Wear long-sleeved shirts and trousers to minimize skin exposure when handling the dry granular material or the liquid solution.
Before mixing, gather all necessary equipment. The mixing vessel should be a clean, non-reactive container, such as a sturdy plastic bucket or a stainless steel tank, to prevent chemical reactions. You will need a reliable measuring device, such as a calibrated scale for weighing the urea and a liquid measuring container for the water. A long-handled, non-metallic stirring implement is necessary for continuous agitation during dissolution.
Calculating the Correct Dilution Rate
Determining the dilution rate is the most important step in creating a safe and effective solution. The primary goal is to deliver the target amount of nitrogen while keeping the concentration low enough to prevent phytotoxicity, or “fertilizer burn,” on plant tissues. Since urea is 46% nitrogen, find the weight of the product needed by dividing your target nitrogen rate by 0.46.
A common application for turfgrass targets 0.10 to 0.25 pounds of actual nitrogen (N) per 1,000 square feet. If you aim for 0.20 pounds of N, you need approximately 0.43 pounds of urea product (0.20 รท 0.46 = 0.43 pounds) to cover that area. The volume of water used, known as the carrier volume, is determined by the capacity of your sprayer and must ensure even coverage across the target area.
For foliar applications, the solution concentration is often a greater concern than the nitrogen rate per area, since high concentrations cause leaf burn. The urea concentration in the final solution should not exceed 2% by weight for most plants to avoid damage. A 2% solution is equivalent to dissolving about 0.2 pounds of urea product in one gallon of water. Always begin with the lowest recommended concentration for your plant type and only increase it if the plants show no signs of stress.
Step-by-Step Mixing Procedure
Dissolving urea must be managed carefully due to the chemical reaction involved. The dissolution of urea in water is an endothermic process; it absorbs heat from the surrounding liquid, causing the water temperature to drop. This cooling can significantly slow the dissolving rate and lead to clumping or crystallization.
Start with lukewarm water, as this temperature accelerates the process. Begin by adding the calculated amount of water to the mixing container first, never the other way around. Next, introduce the measured urea granules to the water slowly and steadily rather than dumping the entire amount in at once.
Agitation is required as the urea is added to prevent it from settling and forming a cake. Use your stirring implement to mix until the solution is completely clear and no visible granules or crystals remain. Thorough mixing ensures a uniform concentration throughout the solution, which is necessary for consistent application and accurate nitrogen delivery.
Application Methods and Timing Considerations
Once the urea is fully dissolved, the solution is ready for application through foliar spraying or soil drenching. Foliar application delivers nitrogen directly to the leaves for rapid uptake, while a soil drench allows the solution to move into the root zone. The timing of the application is a major factor in efficiency and plant health.
Apply the solution during the cooler parts of the day, in the early morning or late afternoon, to minimize the risk of foliar burn. Applying in high heat or during peak sunlight can cause the water to evaporate too quickly, leaving a concentrated salt residue on the leaf surfaces. Avoid application when plants are already stressed from drought or heat, as this increases their susceptibility to damage.
For applications where the solution lands on plant leaves, follow immediately with a light watering or rinsing. This washes the concentrated urea solution off the leaf blades and moves it into the soil, preventing tip burn and reducing nitrogen loss. If the liquid sits on the soil surface, especially in warm conditions, volatilization can occur, where up to 30% of the nitrogen is lost to the atmosphere as ammonia gas.