VARIATION IN THE RESPONSE OF BARLEY CULTIVARS TO NITROGEN FERTILIZER

Field experiments were conducted in South Australia in 2 years (1991 and 1993) to compare the response to nitrogen (N) fertilizer among 78 cultivars of 2row barley (Hordeum vulgare) differing in height and yield potential. The aim of the study was to quantify the genotypic variation of responsiveness in grain yield and grain protein concentration (GPC) and to assess the practicability of screening for N responses in the field. There was a difference in the responses to N between the 2 years and the correlation between responsiveness of the cultivars in the 2 years was small. The grain yield responses and GPC responses to N within each year were not correlated, suggesting it may be possible to select for yield and GPC responsiveness .independently. Despite the variability between seasons, principal component analysis indicated that short cultivars were more responsive in both years. Late-flowering cultivars tended to have lower yields, but in terms of the response to N, late ear emergence contributed to a higher yield response. At a site where symptoms of boron toxicity were evident, sensitivity to boron toxicity also contributed to yield responsiveness to N. The study indicated that there is considerable genotypic variations in responses to N and that it is possible to screen a large number of cultivars for response to N but such screening needs to be conducted over a large number of sites and years because of the inherent variability of the target environment.