Page 8 - Molecular Soil Biology

Molecular Soil Biology (online), 2011, Vol. 2 No.1, 1-8
ISSN1925-2005 http://msb.sophiapublisher.com
- 5 -
possible that classification criteria for NO3
- type SSS
can be performed based on the height and yield of
harvested fruits per plant.
We can sum up that increasing salinity will
significantly affect cucumber fruit quality including
fruit total soluble sugar, total soluble protein and
crude fiber contents, whereas the superfluous nitrate
will decrease fruit VC contents. The conclusion in the
present study has been consistent with that of other
reported studies (Elates et al., 2002). The increasing of
TSC and TSP could indicate the improvement in
quality, whereas the increasing CF and the decreasing
VC indicate the deterioration of fruit quality. However,
the improvement in quality was unable to economically
compensate for the reduction in fruit yield (Magán et
al., 2008).
Plants exposing to saline environments are subjected
to several adverse conditions, which can be
categorized as shown in Table 5 (Abrol et al., 1988).
Similarly, based on the results of the relationships and
analyses mentioned above, the classification of NO3
-
type SSS in greenhouse should be proposed according
to the parameters of height and yield of cucumber. It
is then suggested that the NO 3
- type SSS in this study
was classified into five catalogues from level Ⅰ (light
salinity) to level Ⅴ (heavy salinity). When the height
and yield are not affected by the salinity in soils, the
NO3
- type SSS classification is defined as level Ⅰ.
When the height and yield reduced by 0%~15%
caused by salinity in soils, the NO 3
- type SSS
classification is defined as level Ⅱ. When the height
and yield reduced by 15%~30% caused by salinity in
soils, the NO3
- type SSS classification is defined as
level Ⅲ . When the height and yield reduced by
30%~60% caused by salinity in soils, the NO 3
- type
SSS classification is defined as level Ⅳ . As long as
the height and yield reduced more than 60% caused by
salinity in soils, the NO3
- type SSS classification is
defined as level Ⅴ. Correspondingly, level Ⅰ means
no secondary salinization; level Ⅱ stands for a slight
salinization; level Ⅲ indicates moderate salinization;
level Ⅳ presents severe salinization, and level V
refers to heavy salinization.
Table 5 General guidelines for plant response to salinity (adapted from Abrol et al., 1988)
Soil salinity class Conductivity of the saturation
extract (EC, ds/m)
Effects on crops
Non saline 0~2 Salinity effects negligible
Slightly saline 2~4 Growth of sensitive plants may be restricted
Moderately saline 4~8 Growth of many plants are restricted
Strongly saline 8~16 Only tolerant plants grow satisfactorily
Very strongly saline > 16 Only a few very tolerant plants grow satisfactorily
The EC-threshold of Y/P in the present work was at
2.03 ds/m, which is lower than the tomato threshold
EC of 3.2 ds/m (Magán et al., 2008). Because the
cucumber is more sensitive to the SSS than that of
tomato. When Y/P decreased by 10%, 30%, 50% and
70%, the soil EC was 2.03 ds/m, 3.67 ds/m, 5.32 ds/m
and 6.97 ds/m, respectively. But when the soil EC
reached the 6.15 ds/m (T4), the seedlings completely
died. When the plant height decreased by 15%, 30%
and 60%, the corresponding soil EC were 2.33 ds/m,
3.69 ds/m, 6.39 ds/m, respectively. Then, it is likely
that the secondary salinization could be classified as
follows, level Ⅰ: 0.89 ds/m < EC < 2.03 ds/m, level
Ⅱ: 2.03 ds/m < EC < 3.67 ds/m, level Ⅲ: 3.67 ds/m <
EC < 5.32 ds/m, level Ⅳ : 5.32 ds/m < EC < 6.15 ds/m,
level Ⅴ : EC > 6.15 ds/m.
There are no criteria of salinity where plants fail to
grow. As the salinity increases, growth decreases until
plants become chlorotic and die. Plants differ widely
in their ability to tolerate salts in the soil. Salt
tolerance ratings of plants are based on yield reduction
on salt-affected soils when compared with yields on
similar non-saline soils.
The classification for NO3
- type SSS might be similar
to the salt tolerance ratings of plants. Therefore, the
classification criteria of NO3
- type SSS in
cucumber-based greenhouse in China’s Yangtze River