The results of four field experiments conducted for 2 or 3 years on two soils, loamy sand (Typic Ustipsamments) and silty clay loam (Natric Ustochrept) showed that in rice, application of N in three equal amounts was more efficient than one or two applications, irrespective of source of N and type of soil. The results further showed that application of the first dose of N 7 days after transplanting rice was more beneficial than its application at transplanting. Calcium ammonium nitrate was significantly inferior to urea and/or ammonium sulphate for rice in both soils. There were no significant differences in wheat yield, N concentration or uptake due to time and source of N application.