GROWTH OF THREE WHEAT CULTIVARS AND NITROGEN USE EFFICIENCY AS AFFECTED BY NITROGEN FERTILIZER LEVELS AND SEEDING RATES

Two field experiments were carried out during 2014/2015 and 2015/2016 seasons at Agric. Exp. Res. Sta. at Giza, Fac. Agric., Cairo Univ. to study the influence of three nitrogen fertilizer levels (75, 100 and 125 kg N/fad.), three seeding rates (200, 300 and 400 grains/m²), on growth of three wheat cultivars (Sakha-94, Gemmiza-9 and Giza-168). Nitrogen levels had significant effect on heading and plant height in the first season only and on flag leaf area in both seasons. Absolute growth rate (AGR) was significantly affected by N levels at 80 days from sowing. Leaf area index (LAI) was significantly affected by N levels at 80 and 100 days in the second season only. Net assimilation rate (NAR) significantly increased with increasing N levels. In general, all previous characters were increased with increasing N levels up to 125 kg N/fad. Nitrogen use efficiency (NUE) significantly decreased with increasing N levels. Seeding rates had significant effect on LAI at 80 days in the first season and on AGR at 80 in the first season as well as at 80 and 100 days in both seasons, respectively. The highest values for the previous traits were produced with seeding 300 or 400 grains/m². Seeding rates did not affect NAR. Nitrogen use efficiency was not affected by seeding rates. Plant height and heading significantly affected by cultivars. AGR at 80 days in the first season and at 100 days in both seasons significantly affected by cultivars. LAI at 60, 80 and 100 days significantly affected by cultivars. Cultivars significant affected NAR except at 100 days in the first season. Cultivars did not affect NUE. All interactions had a significant effect on growth characters in both seasons, except the effect of N levels × seeding rates on flag leaf area, LAI at 60 days, plant height and number of tillers/ m², N levels × cultivars on LAI at 60 days, plant height and number of tillers/m², seeding rates × cultivars on LAI at 100 days in both seasons, plant height and number of tillers/m² in the first season as well as LAI at 80 days in the second one and N levels × seeding rates × cultivars on flag leaf area, plant height and number of tillers/m² in the first season. The overall findings concluded that seeding Gemmiza-9 or Giza-168 with 300 or 400 grains/m² and application of 125 kg N/fad., could be more beneficial in the study area. Some interactions had significant effect on NAR. Moreover, none of studied interactions significantly affected NUE.