Abstract
Field experiments were carried out at the University of Sydney Farm, to examine nitrogen fertilizer application strategies for increasing N uptake and productivity of wheat (Triticum aestivum L.) grown on a red-brown earth (Natrixeralf) in Australia, under dryland and supplementary irrigation. Increasing N rate increased shoot dry matter and N uptake consistently but grain yield response was greatly dependent on soil moisture or rainfall in the post-heading period. Water availability at this time determined kernel weight and hence grain yield, even when sufficient grain number had been established. Split application of N increased N uptake most, when the second dose was applied at tillering. On the other hand, delayed applications to the time of heading or anthesis resulted in a relatively lower uptake of N even with supplementary irrigation. The effect of a single pre-sowing application was similar to that applied at sowing or early tillering. We conclude that a split application of N is important for increasing N uptake when the second dose is applied during tillering rather than at heading or anthesis.