Urea fertilizer, commonly identified by its nitrogen-phosphorus-potassium (NPK) ratio of 46-0-0, is the most concentrated solid nitrogen source available for agricultural and gardening use. This synthetic organic compound is synthesized from anhydrous ammonia and carbon dioxide, making it a globally utilized product for boosting plant growth and yields. Purchasing this high-concentration fertilizer requires an understanding of its physical forms, the correct quantity needed, and the logistical differences between various vendors.
Properties of Urea Fertilizer
Urea is chemically known as carbamide, and its high-concentration rating of 46% nitrogen makes it an efficient source of this plant nutrient. The product is highly water-soluble, dissolving readily in water at a rate of approximately 108 grams per 100 milliliters. This rapid solubility allows for easy application through irrigation systems, providing a quick nitrogen boost to plants.
Once applied, the nitrogen in urea is not immediately available for plant uptake; it must first be converted into ammonium and then nitrate by soil microbes. A potential issue with surface application is volatility, where a significant portion of nitrogen can be lost as ammonia gas. This loss is accelerated if the fertilizer remains on the soil surface, particularly in high-temperature environments. To prevent this, urea should be incorporated into the soil or watered in shortly after application.
Selecting the Correct Formulation and Quantity
Buyers must choose between the two primary physical forms of urea: prilled and granular, as well as considering specialty coatings.
Physical Forms
Prilled urea consists of smaller, uniform, spherical pellets that dissolve quickly, making the nitrogen rapidly available. Granular urea has larger, irregularly shaped particles, which leads to a slower dissolution rate and a more gradual release of nitrogen.
Specialty Coatings
Coated or stabilized urea formulations are specialty products designed to manage the nitrogen release rate. Polymer-coated or sulfur-coated urea slows the conversion process, which improves efficiency by reducing the risk of nitrogen loss through volatilization or leaching. While coated options come at a higher price, they can reduce the frequency of application compared to standard prilled or granular urea.
Quantity Considerations
Purchasing quantities start with small bags (5 or 10 pounds), suitable for small-scale home gardening or lawn spot treatments. Mid-sized applications, like those for serious gardeners or small farms, typically utilize 50-pound bags. Larger operations often buy in bulk, involving super sacks (totes) holding around one ton, or bulk tonnage delivered directly. Calculating the quantity needed requires determining the total square footage to be treated and the recommended nitrogen application rate for the specific crop or lawn type.
Where to Purchase Urea Fertilizer
The source for purchasing urea depends largely on the volume required, with different vendors catering to distinct customer needs.
Small Volume Purchases
Home gardeners needing small quantities can easily find 5 to 50-pound bags at local hardware stores, big-box retailers, and online garden supply websites. These sources offer convenience but may feature a higher cost per pound compared to agricultural suppliers.
Medium Volume Purchases
For medium-volume users, dedicated farm and feed supply stores are a better option. These retailers, which include regional co-ops and national chains, stock 50-pound bags in greater volume and at more competitive prices. They sometimes also offer access to less common formulations, such as those with slow-release coatings.
Bulk Volume Purchases
Commercial agriculture and large-scale turf management operations purchase urea in bulk, often by the ton. This volume is best sourced from agricultural elevators, chemical distributors, or direct sales from fertilizer manufacturers. Bulk purchasing requires logistical considerations, such as having the necessary equipment for pickup and storage space for a large volume of material.
Storage and Safety Guidelines
Proper storage of urea is necessary to maintain its quality and prevent safety hazards. Urea is highly hygroscopic, meaning it readily absorbs moisture from the air, which leads to the material caking or hardening into solid clumps. To prevent this, it must be stored in a cool, dry location with a relative humidity below 60%.
The product should be kept in its original sealed containers or bags, and placed on pallets to avoid contact with damp floors. Urea is non-flammable but can decompose when exposed to high heat, releasing toxic gases like ammonia. It must be stored away from open flames and heat sources. During handling, wearing protective equipment like gloves and safety glasses is advised to prevent skin and eye irritation.