Among essential mineral nutrients, nitrogen is the one plants need in the largest quantity. It's the backbone of chlorophyll, the green pigment that drives photosynthesis. Without enough of it, leaves yellow, growth stalls, and yields drop. With too much in the wrong window, plants grow lush foliage at the expense of fruit and become more susceptible to environmental stress.
Urea (CO(NH₂)₂) is a synthetic compound first produced in 1828 — a milestone in chemistry as the first organic compound made from purely inorganic precursors. Once applied to moist soil, the enzyme urease converts it to ammonium (NH₄⁺) within 24-72 hours, which soil microbes then nitrify into nitrate (NO₃⁻). Both forms are plant-available; nitrate is more mobile in the soil profile, ammonium binds to soil particles and resists leaching.
The 46% concentration is what makes urea the workhorse of global nitrogen agriculture. Compared to ammonium sulfate (21% N) or calcium nitrate (15.5% N), every pound of urea delivers more than double the actual nitrogen — meaning less product to spread, less weight to ship, and lower cost per unit of N delivered to the plant.
For deeper coverage of how plants use nitrogen, see our guide on What's the Function of Nitrogen in Plants? and our comparison of the seven best nitrogen fertilizers compared.