Nitrogen uptake and utilisation efficiency of two-row and six-row winter barley cultivars grown at two N levels

In order to limit overproduction and pollution risks, low N fertiliser agricultural systems are likely to be advocated in Europe. An experiment was carried out in 1994 and 1995 to compare N uptake and N utilisation of two-rowed and six-rowed winter barley (Hordeum vulgare L.). Two sets of two-rows and six-rows, composed of 12 varieties each, were cultivated in northern France on a haplic luvisol without (N1) and with 100-110 kg/ha (N2) N fertiliser. Mean grain yield was 596 g/m(2) at N1 and 779 g/m(2) at N2. On average six-rows outyielded two-rows by 4% (34 g/m(2)) at N2 and 11% at N1 (70 g/m(2)). Ears/m(2) was the yield component which fell most sharply between N2 and N1 (718 and 510 ears/m(2) on average). Six-rows had fewer ears/m(2) at both N levels but they lost more ears than two-rows (-33% and -26%, respectively). While the number of grains/ear was approximately the same for two-rows at both N levels (21.9 grains/ear on average) in 1995, it was significantly higher at N1 than at N2 for six-rows (44.7 and 38.5, respectively). Thousand kernel weight was higher at N1 than at N2, the difference being higher for six-rows (+7%) than for two-rows (+4%). N uptake efficiency (total plant N/soil N supply) was identical at N2 and higher for six-rows at N1 in 1995. Total N utilisation efficiency (total above-ground dry weight/total plant N) was equal at both N levels. HI (grain yield/total above-ground dry weight) was higher at N1 in both years and at N2 in 1994 for six-rows. Six-rows outyielded two-rows at high and low N levels. This was therefore associated mainly with higher HT and not with better N uptake or utilisation efficiency. (C) 1999 Elsevier Science B.V. All rights reserved.