A NOTE ON UREA VERSUS CALCIUM AMMONIUM-NITRATE FOR WINTER-WHEAT

Urea and calcium ammonium nitrate (CAN; 275 g N/kg) were compared as sources of N for winter wheat in field experiments at a total of nine sites over a 3-year period. The rates of N used were 0, 50, 100, 150, 200 kg/ha and it was applied in two splits. The mean yield was 4.04 t/ha for the ON treatment. Mean yields (t/ha) for the CAN treatments were 5.92, 7.22, 7.83 and 8.16 following 50, 100, 150 and 200 kg N/ha, respectively. The corresponding yields with urea were 5.28, 6.71, 7.52 and 7.92 t/ha. The yield reductions (%) with urea compared to CAN were 10.8, 7.1, 4.0 and 2.9 at 50, 100, 150 and 200 kg N/ha, respectively. The drier the weather and the soil around the time of N application, the poorer was the performance of the urea relative to CAN. Grain protein content (at a moisture content of 150 g/kg) ranged from 79 to 100 g/kg and was significantly lower following urea than following CAN. It is concluded that, for winter cereals, CAN is a better source of N than urea.