Abstract:
In most semiarid and arid areas, fresh water shortage compels managers to use low
quality
water sources w
ith high salinity to irrigate turf and landscape. Recent research
has noticed that management of nitrogen fertilization can alleviate salinity effects on
plants. This greenhouse sand culture experiment was conducted in order to investigate
morphological an
d physiological responses to salinity stress in Kentucky bluegrass (
Poa
pratensis
L.) grown
using
different
nitrogen sources. Three salinity
levels (0, 40 and 80
mM NaCl) and three NO
3
-
/NH
4
+
ratios (6/0.5, 6/1 and 6/2) were applied in nutrient
solutions. U
nder non saline conditions,
higher
ammonium concentration increased
T
urf
Q
uality (TQ), leaf NO
3
-
, proline content,
N
itrate
R
eductase
A
ctivity (NRA), shoot and
root growth. On the other hand, leaf potassium (K
+
) sodium (Na
+
) and
M
alon
DiA
ldehyde
(MDA) conten
t were not affected. During the first week
,
the 40 mM NaCl treatment
showed that the positive effects of NH
4
+
on salinity tolerance were stil
l
perceptible
.
However, the 80 mM NaCl treatment showed that the adverse effects of high salinities
were more prono
unced when turf
received
high ammonium rate nutrient solution, as
manifested by the decrease of TQ, NO
3
-
, NRA, K
+
/Na
+
ratio, shoot and root growth and
by the increase of leaf MDA content
.
T
his suggests that effects of NO
3
-
/NH
4
+
ratio on salt
tolerance vari
es with salinity levels.
Keywords
:
M
orphologi
cal and physiological responses,
NO
3
-
/NH
4
+
ratio,
Salt tolerance.