Epoca de aplicación y tipo de fertilizante nitrogenado sobre el patrón de acumulación de materia seca y nitrógeno del maíz en un Ultisol y un Mollisol de Venezuela1

types of n sources, and time of n-fertilizer application could affect n use and yield production of maize, zea mays l. in this experiment, maize response to application of 120 kg n ha-1 applied as urea, ammonium nitrate (an), and an ammonium source (10-26-26), and time of application of the sidedress was evaluated in an ultisol and in a mollisol of venezuela. normally there were more dry matter production, and n uptake under na. in the mollisol, early application of the n dose (the whole n at sowing or side dressing at 15 days) allowed more n uptake by the crop than late application of the element (sidedressing at 25 and 35 days).