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varies from 2.0 to 8.2 g/l. Sodium and magnesium are the dominating cations. It
was also found that the organic matter in these soils ranges from 0.7 to 1.5 g
1
,
while the cation exchange capacity varies between 5 and 10 cmol(
)kg
1
.Total
nitrogen (N) and phosphorus (P) contents in salt affected soils are low, usually
ranging between 0.07-0.15 % and 0.10-0.18 %, respectively. Available potassium
(K) content is classified as low or moderate. Consequently, the natural fertility of
the saline soils, especially in the of main rivers deltas is characterized as rather
low, and cultivation of most agricultural crops requires high inputs of chemical
fertilizers or applying of costly leaching practice. This strategy, however, increases
the risk of re-salinization in the root zone and leaching process has to be repeated
every cropping season in order to avoid build-up of high salt concentration. In this
respect the appropriate practices for salinity control should be selected based on the
quantification of water and salt movement in the soil, crops response and adaptation
to water and salinity stress and how environmental conditions and management
influence these interactions. In this regard, efficient water use for irrigation coupled
with introduction of modern bio-remediation technologies can help to integrate
all interactions and define the best management for crop production under saline
environments.
Access to irrigation water in this region has drastically decreased in the last
years, which caused additional obstacles to rangelands productivity and agricultural
production (Lamers et al.
2005
; Toderich et al.
2010
). Replacement of deep-
rooted, perennial native vegetation with shallow-rooted, annual agricultural crops
and halophytic pastures has resulted in increased recharge causing shallow saline
water tables leading to dryland salinity and loss of plant diversity. This results in
greater amounts of water entering a groundwater system, water table rise and the
concentration of naturally occurring salts near the soil surface. Slight changes in
temperature or soil moisture and dissolved salts regime could therefore substantially
alter the composition, distribution and abundance of species. Increased frequency
of climatic extremes and changes in soil salinity induce changes in plant functional
group composition with invasion of non-native annual plant, which significantly
reduce productivity in arid ecosystems. Therefore, functioning of these arid systems
depends to a high degree on plant diversity.
C
4
Role of Biosaline Agriculture Technologies to Improve
the Productivity of the Degraded Rangelands
4.1
Floristic Composition of Vegetation of Salt Affected Lands,
Mineral Content and Evaluation of Halophytic Germplasm
The inland Irano-Touranian desert ecosystem including plant communities is con-
sidered one of the most fragile under currently ongoing climate changes. It is
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