Fall‐ Versus spring‐applied urea for spring‐sown barley: Influence of nitrogen rate

Field experiments with barley were conducted on stubble of cereal grains in northcentral and central Alberta to determine the effect of N rate (25, 50, and 100 kg N/ha) on yield, N recovery and the relative efficiency (RE) of fall versus spring application of incorporated urea to barley. In most instances fall‐applied N was inferior to spring‐applied N and there were large differences in yield and N uptake of barley grain between fall‐ and spring‐applied N. The differences generally increased with increasing N rate for yield and N uptake, but decreased substantially for N use efficiency and % N recovery. As the N rate increased from 25 to 100 kg N/ha average RE of fall‐ versus spring‐applied N increased from 47 to 73% for yield increase and from 42 to 69% for N recovery. The increased RE with increasing N rate did not imply that the greatest level of N reduced the quantity of over‐winter N loss. Instead the results indicated that a lower proportion of the yield or N uptake was lost from fall application when the greatest rate of N was applied.