Effect of Nitrogen Levels on Barley (Hordeum vulgare L.) Crop Yield and Its Components at Mrawa and El-Wasiata, El-Jabal Al-Akhdar Libya

Two field experiments were conducted in the two locations (Marawaa and in El-wasiata) situated at 21° 24´ and 21° 39´ N ;32° 20`and 32° 47´ E and 508, 185m over sea altitude for the 2 situates, respectively, during 2014/2015 season to study the response of the six rows barley variety rehan sown by the rate 70 kgha^-1 in lines 15cm apart to the nitrogen levels (0,50,100 150Kg N/ha^-1) in the form of urea 46%. The experiments were carried out in RCBD with 4 replicates, plat area was (25m^2). The Results revealed significant (P 0.01) effect on plant height in El-wasiata ,number of economic tillers and spike traits in both locations ,where the greatest incase resulted from 150Kg N/ha^-1 compared to the control. Biological yield was significantly (P 0.01) affected by N-levels, the least yield (3.65, 3.76 t/ha) due to control however the highest (4.11, 4.63 t/ha) resulted from 150Kg N/ha^-1 application in the first and second locations, respectively. Although there were increases in grain yield from 1.46, 1.51 t/ha due to non fertilization to 1.87, 1.96 t/ha due to 150Kg N/ ha application, but these differences did not reach the significance level in both location, .Straw yield exhibited significant (P 0.01) increases from ( 2.11, 2.24 t/ha) in control treatment to (2.4, 2.5 t/ha) at 150KgN/ha application . Harvest index was not significantly affected by N-levels in both sites, while 1000 – grain weight affected significantly (P 0.01)where the least values (35.86, 35.20g) due to 50Kg N/ha^-1 and zero comparing to the highest (39.20, 37.40g) resulted from 150Kg N/ha in both Marawaa and El-wasiata, respectively.