Two field experiments were conducted in a sandy soil in the extension field in El–Salhia region, Sharkia Governorate during 2004/2005 and 2005/2006 seasons to study the effect of three levels of nitrogen (45, 65 and 85 kg N/fad) and three glycinebetaine rates (0, 8 and 12mM/fad) on the growth and yield of barley (Giza 124 cv.) under two irrigation intervals (weekly irrigated and di-weekly irrigated). The most important findings could be summarized as follows:
Irrigation every two weeks instead of one week reduced significantly all growth attributes. The relative decrease percentages were 25.41 and 22.93%, 22.63 and 19.98%, and 25.11 and 26.19% for flag leaf blade area, total chlorophyll and relative water content in both seasons, respectively.
Addition of 85 kg N/fad increased these traits by 12.80 and 13.63%, 1.88 and 3.50%, and 3.28 and 4.59% in the first and second seasons, respectively compared with the addition of 45 kg N/fad. Meanwhile, using 12 mM glycinebetaine (GB) increased these traits by 20.63 and 23.06%, 32.30 and 35.80%, and 22.57 and 30.40% in the first and second seasons, respectively compared with untreated plants. Under stress or non stress condition, increasing N level from 45 to 85 kg/fad without GB did not increase total chlorophyll. Meanwhile, this trait was increased significantly with increasing GB from zero to 12 mM.
Prolonging the period of irrigation from 7 to 14 day reduced significantly the yield and its attributes. The relative reduction percentages for grain and straw yields were 22.73 and 26.02% and 26.73 and 24.79% in both seasons, respectively.
Increasing N-level from 45 kg to 85 kg N/fad increased grain yield, straw yield and mean productivity by 12.84 and 12.78%, 16.43 and 14.7%, and 12.88 and 12.85% in both seasons, respectively. Meanwhile, the relative increase percentages due to application of 12mM GB/fad compared with zero GB were 21.27 and 24.77%, 24.82 and 26.83%, and 21.30 and 24.73% for these traits in both seasons, respectively.
The interaction between frequent irrigation, zero GB and 45 kg N/fad gave 11.38 ardab/fad compared with 15.34 ardab/fad which was obtained from frequent irrigation, 8mM GB/fad and 85 kg N/fad. Meanwhile, the interaction between drought condition, zero GB and 45 kg N/fad gave 8.66 ardab/fad compared with 11.69 ardab/fad which was obtained from drought condition, 8mM GB/fad and 85 kg N/fad treatments.