Abstract
Three experiments were conducted in greenhouse under hydroponic conditions to study the response of wheat to: i) different ammonium/nitrate (NH4/NO3) ratios, ii) the application of NH4 during different phenological states, and iii) the addition of calcium carbonate (CaCO3) for maximum replacement of NO3 by NH4. Small amounts of NH4 considerably increased yield and grain quality. The best response was observed with a 2/5 ratio NH4/NO3 (meq/L). The application of small fractions of NH4 during grain fill increased production. Dry matter (DM) production decreased when large quantities of NH4 were applied. However, when CaCO3 was used in amounts similar to those of NH4, it was possible to neutralize the acidifing effect of reduced nitrogen (N) and to recuperate DM and grain production, thus increasing the harvest index.