Two field trials were conducted at Ihe extension field in Shieba viltage, Zagazig. Destrict (Sharkia Governorate) during 2001/2002 and 2002/2003 growing seasons to
study the eHect of nitrogen levels (zero, 40 and 80 kg Ntfed ) and timing of application
(once full, two and tree equal doses) on yield and its attributes and quality of hull-
less barley cultivars (Giza 129, Giza 130 and Giza 131). The results show that, barley cultivars diHered significantly regarding their plant
height, flag leaf area, spike length, number of grains/spike, protein %, biological yield
(ton Ifed) and harvest index. The increase of nitrogen level up to 80 kg N/ fed produced significant increases
in grain yield (ton/fed.), protein content % and almost of all yield attributes. Also, the
application of nitrogen in three equal doses (at sowing, at tiUering and jointing stages)
recorded the highest average values of yield and its attributes. The interaction between barley cultivars and nitrogen levels was significant and
showed that grain yield of Giza 131 CV. exhibit in the highest response grain yield/ ed
to the Increase of N level and splitting of N doses compared to the other cultivars The results indicated that grain yield/fed was positively and highly significantly
correlated with almost studied traits including number of grains/spike, weight of
grains/plant, number of spikes/m", 1 OOO-grain weight and protein content %. Path analysis revealed that (he main sources of grain Yield variation
according to their relative importance were number of grains/spike, number of spikes
/m" and WOO-grain weight, since the direct and indirect eHects. of these characters
contributed more than 64.21 % from the variation of grain yield.