Urea can be broadcast on the soil surface without any nitrogen loss.

The Common Belief Many farmers believe that once urea is scattered across the field, the entire dose feeds the crop. The logic feels sound: the urea is on the soil, the roots are in the soil, so surely the plant gets all of it. Unfortunately, soil chemistry works against you the moment those white granules land on an uncovered surface. A large share of that nitrogen can disappear into the air before your crop ever uses it — and because the loss is invisible, most farmers never realize it is happening. What Actually Happens in the Soil When urea touches moist soil, an enzyme called urease — found everywhere in soil and crop residue — rapidly converts it. The reaction runs in three quick steps: urea combines with water to form ammonium carbonate, which breaks down into ammonium, which finally releases ammonia gas (NH₃). That last product is a gas. If the urea is lying on the surface with nothing to trap it, the ammonia simply floats away into the atmosphere. This process is called volatilization, and it is completely invisible — which is exactly why the myth survives. Worse, urea hydrolysis raises the pH right around each granule, and higher pH pushes even more nitrogen into the escaping gas form. In other words, surface urea creates the very conditions that speed up its own loss. What the Research Shows Field studies across the world confirm these losses are real and often large. A Canadian study by Rochette and colleagues (2013) measured up to 50% ammonia loss from surface-applied urea, but found the loss dropped to nearly zero once the urea was incorporated about 7.5 cm deep. A Wisconsin trial by Oberle and Bundy (1988) recorded 16–19% nitrogen loss from surface urea in corn and pasture. A global meta-analysis by Silva and colleagues (2017) found ammonia losses averaging around 31%, ranging from 3% to 40% depending on conditions. The pattern is consistent: the more the urea stays exposed on the surface, the more nitrogen you lose. Four Conditions That Make Losses Worse Losses are not fixed — they spike under conditions common across Indian fields. First, high temperature: urease works faster in heat, so losses climb steadily through the warm Kharif season. Second, high soil pH: alkaline and sodic soils, widespread across north India, convert far more nitrogen into escaping ammonia gas. Third, crop residue on the surface: straw and stubble carry extra urease and block urea from soaking in, so residue-covered and no-till fields lose more. Fourth, a moist-then-drying surface: a light shower that wets the urea but does not wash it into the soil, followed by sun and wind, is the perfect recipe for loss. How to Protect Your Nitrogen You are not doomed to lose nitrogen — you simply have to stop the urea from sitting exposed. The most reliable practice is incorporation: mix urea into the soil through tillage, or band it at least 5 cm below the surface (and 5 cm away from the seed, since urea placed on the seed can harm germination). Incorporation below about 7.5 cm cuts loss to nearly nothing. The next best option is to time application with water: a rainfall or irrigation of even 5–12 mm within 24 hours washes urea into the soil and largely prevents loss, so apply just before expected rain or irrigation. In India, neem-coated urea slows the conversion process and has been shown to reduce ammonia loss and improve nitrogen use efficiency; urease inhibitors such as NBPT can cut volatilization losses by roughly 40–53% where available. Finally, avoid the worst windows — do not broadcast on hot, windy, bare, or high-pH surfaces and expect no loss. The Bottom Line Broadcasting urea and leaving it on the surface is not a loss-free practice. Depending on heat, soil pH, and residue, you can silently lose a fifth to a half of your nitrogen investment. Getting the urea into the soil — through incorporation, banding, or timely watering — is the single highest-return habit for making every rupee of fertilizer count.