Urea Fertilizer Analysis

Urea

• Urea is a chemical compound with the formula (NH2)2 CO. As you can tell from the formula, it includes neither phosphorus nor potassium, so it's a nitrogen-only fertilizer unless blended with other fertilizers. For a nitrogen fertilizer, urea has excellent nitrogen content -- 46 percent nitrogen by weight, which is printed on the bag as 46-0-0. This high analysis makes urea especially attractive when compared with other nitrogen fertilizers. Ammonium nitrate has an analysis of 34-0-0, while ammonium sulfate has 21-0-0.

Blending

• Farmers need to apply not just nitrogen but potassium and phosphate as well, so urea is often blended with monoammonium phosphate, which has an analysis of 11-52-0, or diammonium phosphate, which has an analysis of 18-46-0. The analysis of the resulting blend will depend on the amount of urea and potassium or phosphorus fertilizer. It's unwise to blend urea with superphosphates because urea will react with them to release water. Urea can also be blended with ammonium nitrate, although this will not contribute any potassium or phosphorus.

Buying Blends

• If you're buying a commercial product, it will often contain other ingredients besides the urea fertilizer as part of the blend. It may, for example, contain nutrients that plants only need in very small quantities, together with fillers that give the fertilizer the desired consistency and make it easier to spread. The analysis of a blended fertilizer of this kind will be very different from the analysis of the urea by itself, because the urea is now only a fraction of the total contents.

Considerations

• Urea is less dense than other fertilizer ingredients like monoammonium phosphate, so if the fertilizer is applied with a spinner or other similar equipment, the ingredients may be spread unevenly, resulting in a streaky growth pattern. In the past, liquid urea was often applied to fields from a prilling tower, causing the product to congeal as it fell. Today if you buy pure urea, you'll find it's generally sold in granulated form. Urea dissolves readily in water, of course, since it's also found in human urine.