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.
A pot experiment was conducted in a green house at Tishreen University in which bread
wheat (cv. Sham 6) was grown at different levels of potassium nutrition (K0=0, K1=25,
K2=50, K3=75, K4=100, K5=150) mg k/kg soil. The increase in potassium fertil
ization
rates led to a significant increase in the number of total tillers and fertile tillers on the
expense of non-fertile tillers. This was accompanied with no significant increase in
number of main stems spikes grains, while the tillers spikes of the first level of potassium
application (K1) was higher significantly compared to control treatment (K0). The same
treatment (K1) gave the best weight of grain on the main stems spikes and tillers. The
productivity of grain yield increased (but non-significantly) with increasing the level of
potassium fertilization. The highest yield value was obtained in K5 treatment which was
13933 kg /ha. This productivity constitutes a rate of increase 18% compared to the control
treatment (K0). The calculation of Agronomic Efficiency (AE) showed a high value of
(about 13 kg seeds/kg of K fertilizer added) in the K1 treatment, and thereafter, AE
gradually decreased with potassium fertilization to reach about 6 kg grain/kg K fertilizer
for K4 and K5 treatments (100 and 150 mg K/kg).