This study was conducted in a pot experiment during 2012-2013 to investigate the
response of four Syrian bread wheat cultivars (Sham 4, Sham 6, Bohouth 4, and Bohouth
6) to increasing levels of nitrogen fertilization (0, 40, 80, 120, 160, and 200 k
g N/h).
Nitrogen was added in two equal split applications, half was added as urea (46% N) at
sowing, and the second half was added as ammonium nitrate (33.5 % N) at tillerring and
stem elongation stage. Some growth and productivity parameters were investigated.
Nitrogen application led in all four cultivars to significant increase in number of
tillers, productive on the expense of non-productive tillers. This was accompanied by a
significant increase in number of spikes on plant and number and weight of grain in the
spike. Sham 6 had a higher number of productive tillers at nitrogen rate of application 200
kg N/h, whereas Bohouth 4 had a greater height for main stems and tillers compared to
other cultivars.
Grain productivity increased with the first level of nitrogen application (40 kg N/h)
by a rate of 53, 57, 55, and 48 % for cultivars Sham 4, Sham 6, Bohouth 4, and Bohouth 6,
respectively. Grain yield reached with nitrogen application of 200 kg N/h to 15.89, 15.96,
13.6, and 15.7 ton/h, respectively. Cultivars differed significantly in grain yield within
each nitrogen application level. Grain yield for Bohouth 6 got closer to Sham 4 and Sham
6 with nitrogen application reaching 160 kg N/h, and after which became not significantly
different, while grain yield of Bohouth 4 remains significantly lower compared to all
cultivars.
