Use of Urea Fertilizer

Urea's promotion of green growth makes it ideal for lawn care.

Urea fertilizer has become more popular than its cousin ammonium nitrate, according to the University of Minnesota Extension. It contains 46 percent nitrogen and involves almost no explosive hazard, making it easier to handle and transport. It is the most inexpensive form of nitrogen per pound, and it lends itself to a variety of applications and blending. Urea is volatile and failure to use it properly can result in your garden getting much less nitrogen than you think.

Purpose

Urea fertilizer provides nitrogen, which promotes green leafy growth that not only makes your garden look lush, but is also important for photosynthesis. The key is that urea provides only nitrogen -- no phosphorus or potassium -- so it is primarily used where the features of other fertilizers, such as bloom growth and vertical height may not be desired.

Application

Urea is most commonly broadcast into the soil in solid form, but care must be taken to keep it at least 2 inches from seedlings to protect them from the initial alkaline reaction. Utah State University Cooperative Extension recommends turning the urea into the soil rather than just placing it on top to minimize the loss of nitrogen to the atmosphere as the fertilizer breaks down. Urea can also be dissolved in water as a 50/50 mix to use as a foliar spray. It should be applied according to the nitrogen fertilizer recommendations for the crop.

Timing

Urea is best applied in the spring, but can be applied in fall if subsequently plowed down. Although cooler temperatures reduce volatility and nitrogen losses in the fall, spring applications generally bring better results. High soil pH and high temperatures maximize the loss of nitrogen, so the more alkaline your soil, the more beneficial it is to fertilize in either early spring or late fall. The exception is pastures, in which case the urea should be applied in the summer when there is a chance of rain.

Blending

Urea blends freely with solid mono- and diammonium phosphates, but not superphosphates. The reaction creates a damp mixture that creates problems with accurate spreading. Even if the mixture is dry, urea has a different weight than other granular fertilizers, so the mixture may throw unevenly. Liquid formulas of urea and ammonium nitrate are frequently used for better uniformity, but have different properties than a simply liquid urea mixture and should be studied carefully before use.

References

• University of Minnesota Extension; "Fertilizer Urea"; Curtis J. Overdahl, et al.; 1991
• Utah State University Cooperative Extension; "Urea: A Low Cost Nitrogen Fertilizer with Special Management Requirements"; D.W. James; December 2010
• Ohio State University Extension; "Selecting Forms of Nitrogen Fertilizer"; Jay W. Johnson