Two field experiments were carried out with corn, using no-tillage system (NTS) over oat residues, in a clay dark-red latosol at the Centro de Pesquisa Novartis - Seeds, in Uberlândia, State of Minas Gerais, Brazil, and conventional tillage system over soybean residues (CTS), in a sandy red-yellow latosol at the Santa Terezinha farm, Uberlândia. The objective of this study was to evaluate the NH3-N volatilized from nitrogen sources, side-dressed applications, of approximately 100 kg ha-1, applied in the middle of the rows. Five nitrogen sources [urea, ammonium nitrate, ammonium sulphate, urea + ammonium nitrate solution (uran) and urea + ammonium nitrate + ammonium sulphate solution (sulphuran)] and two forms of application: surface and incorporated (5-7 cm) were used in both crop systems. After the nitrogen side-dressing application, three semi-open static collectors of NH3-N were installed by treatment. Six samples were taken at intervals of four to five days. In the NTS, the accumulative NH3-N losses from urea, uran and sulphuran were, respectively, 75.5, 39.2 and 25.5% of the surface applied N. The most significant losses in the CTS occurred with urea (30.7%) and uran (9.7%). Ammonium sulphate and ammonium nitrate showed NH3-N losses lower than 15.0%. A negative linear regression was found between relative corn yield and NH3-N losses. The data showed that 7.9 kg ha-1 of grains were lost per kilogram of volatilized nitrogen.
no-tillage system; conventional system; NH3-N volatilization; nitrogen fertilizers; fluid fertilizers; corn