UPTAKE AND AGRONOMIC EFFICIENCY OF NITROGEN IN WINTER BARLEY AND WINTER-WHEAT

Nitrogen (N) uptake and utilization efficiency (N,,,) of the high-yiel ding cultivars 'Gemini' of wheat and 'Jaidor' of barley were tested wi th N rates of 0, 140 and 210 kg ha(-1) and 0, 80 and 140 kg ha(-1), re spectively. The different grain yield response was linked to their dif ference in nitrogen uptake and utilization efficiency. The highest yie ld in barley was recorded with 80 kg N ha(-1) and in wheat with 210 kg N ha(-1). Nitrogen application affected the accumulation of biomass u p to heading in wheat and barley. While N uptake during grain filling did not show any correlation to N applied in barley, it was markedly c orrelated in wheat. At N-0 and N-140 N applied, barley exhibited a 32 and 8% higher N-Ute than wheat. N agronomic efficiency, a parameter re presenting the ability of the plant to increase yield in response to N applied, was similar in barley and wheat (8.7 and 9.2 kg kg(-1) of N applied, respectively), suggesting that both species respond equally t o nitrogen fertilization. Nevertheless, due to its lower N-Ute, wheat requires high N fertilization to optimize yields; by contrast, in barl ey the lower N rate needed to achieve highest yields enables this crop to perform better in low-input conditions. As a results, the reduced N requirements for barley highest yield associated with a better R-F v alue (apparent N fertilizer recovery of 63% in barley and 49% in wheat at N-140) makes barley crop a better choice to reduce ground-water po llution due to nitrate leaching in winter and early spring. (C) 1998 E lsevier Science B.V.