Recovery of fertiliser nitrogen in wheat grain and its implications for economic fertiliser use

Abstract

Grain yield, protein, and nitrogen uptake responses are reported for 6 wheat fertiliser experiments in northern New South Wales which were representative of sites that were highly responsive, moderately responsive, and non-responsive to nitrogen (N) fertiliser applied at sowing. Apparent recoveries of applied N of 33-57% in the grain were recorded where grain yield was steeply increasing in response to additional applied N. Where yield increases were smaller in response to increments of N fertiliser, N recovery was 22-3096, but where further N application increased grain protein content but not grain yield, apparent recovery of additional fertiliser N fell below 20%. Apparent recovery was less than 10% in experiments where there was no yield response to N fertiliser. The implications for fertiliser recommendations are discussed relative to potential premium payment for wheat protein levels. It was concluded that established premium payments are too low to make N application an economic proposition to increase grain protein levels in the absence of grain yield responses.