
%0 Journal Article
%A Strong, WM 
%A Dalal, RC 
%A Weston, EJ 
%A Cooper, JE 
%A Lehane, KJ 
%A King, AJ 
%T Nitrogen fertiliser residues for wheat cropping in subtropical Australia
%J Australian Journal of Agricultural Research
%D 1996/08/01
%V 47
%N 5
%P 695-703
%K Vertisol;15N-depleted fertiliser;monoculture;no till
%R https://doi.org/10.1071/AR9960695
%U https://www.publish.csiro.au/paper/AR9960695 
%X Applied nitrogen (N) recovered by fertilised wheat and by successive wheat crops in a 4-crop sequence (1987-90) was studied by applying 15N-depleted ammonium nitrate (0, 2.5, and 7.5 g/m2) to a Vertisol in the summer-dominant rainfall region of northern Australia. Recoveries of applied N by each of the 4 crops in order of cropping sequence were 60.3¦ 4.2, 4.4 ¦ 2.3, 1 . 3 ¦ 0.49, and 0- 8 ¦ 0.56%, there being no effect of 2 tillage treatments, conventional tillage (CT) and no till (NT), on uptake of applied N. There was very low recovery of residual fertiliser N after the first wheat crop was harvested; usually <lo% of the applied N was recovered. There was evidence of a substantial N carryover benefit where fertiliser N (7.5 g/m2) was applied in 1987, but not when applied at the same rate in 1988 or 1989. Carryover effect was shown only when fertiliser N was applied after a long fallow when antecedent NOT-N was already high (100-150 v. 30-55 kg/ha with a normal summer fallow). Carryover of subsoil NO3 -N from a single N fertiliser application to the crop, as occurred with application in 1987, will provide useful buffer for declining N supplies of soil N in seasons of good crop response. Routine application of N at moderate rates (<75 kg/ha) provides an effective means of supplementing declining soil N reserves for winter cereals in this region of unreliable rainfall. 
