Urea Uses In grain and cotton crops, urea is often applied at the time of the last cultivation before planting.In high rainfall areas and on sandy soils (where nitrogen can be lost through leaching)and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season.Top-dressing is also popular on pasture and forage crops.In cultivating sugarcane, urea is side-dressed after planting, and applied to each ratoon crop.In irrigated crops, urea can be applied dry to the soil, or dissolved and applied through the irrigation water.Dissolving urea in water is endothermic, causing the temperature of the solution to fall when urea dissolves.

When urea is placed on the surface of the soil, a chemical reaction takes place that changes the urea to ammonium bicarbonate. The ammonium will convert into a gas, which is then lost if not protected. This means that urea should be mixed in with the soil for maximum effectiveness. This may be done either by broadcasting the urea then plowing it into the soil immediately or by injecting the urea into the soil. This may also be done by broadcasting urea then irrigating heavily to push dissolved urea into the soil.