Date of this Version
BULLETIN OF THE AGRICULTURAL EXPERIMENT STATION OF NEBRASKA
Station Bulletin SB 479 (Revised), 1964 
Fertilizer nitrogen is necessary for the efficient production of grain crops throughout the midwest. Farmers have recognized this need by tremendous increases in nitrogen consumption duhng the past decade.
Fertilizer nitrogen where needed for optimum yield usually increases slightly the total water used by the crop. The water required in making this optimum yield, however, is used a good deal more efficiently than where nitrogen is omitted. Nebraska studies on fertilizer economy have demonstrated nitrate leaching losses in some cases, especially serious on sandy soils of low water holding capacity and with irrigation. Strong circumstantial evidence also suggests denitrification of nitrate leached into the subsoil of some fine-textured subsoil types and resultant escape of elemental nitrogen gas.
In other cases, ammonia volatilization losses have proved serious, particularly with surface broadcasting of products containing or producing ammonium ion on neutral to alkaline soils. Magnitude of ammonia evolution is accentuated by drying conditions and by surface residue where nitrogen carriers are applied in solution form. Loss by volatilization is reduced greatly as the fertilizer is mixed immediately with the soil.
Summer sidedressing of fertilizer nitrogen for row crops, regardless of chemical form, has usually proved superior to fall or spring applications. This superiority has been especially apparent at the lower application rates. Not only has this been noticeable in the year of application, but the carryover nitrogen effect has been greater than with earlier application times. Thus, losses are minimized by delaying application to a time when crop roots are actively absorbing nitrogen from the soil.
In getting the most out of fertilizer nitrogen in grain crops, soil incorporation of the fertilizer and delayed application time seem in order.