Strategic applications of nitrogen fertiliser to increase the yield and nitrogen use efficiency of wheat.

In southern Australia a large proportion of crop nitrogen requirements are usually applied early in the season, either just before or at sowing, or during the first 6-8 weeks after sowing. However, the time of greatest demand for nitrogen by wheat crops is during the stem-elongation phase when the crop is growing fastest, while early demand for nitrogen is small. The study utilised two field sites in South Australia (Hart and Mintaro) over two seasons (2003-04) to examine the effect of delayed applications of nitrogen fertiliser on nitrogen use efficiency (NUE) to dryland wheat. Treatments were applied to manipulate the crop canopy and to measure the balance between canopy size and structure and crop nitrogen uptake. In both seasons and sites significant (P