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Range Mgmt. & Agroforestry 35 (2) : 182-187, 2014
ISSN 0971-2070
Direct seeding of Salsola vermiculata for rehabilitation of degraded arid and semi-arid
rangelands
M. Louhaichi*, K. Clifton and S. Hassan
International Center for Agricultural Research in the Dry Areas, Amman 11195, Jordan
*Corresponding author e-mail: m.Louhaichi@cgiar.org
Received: 1st October, 2014 Accepted: 15th December, 2014
Abstract
Proper soil preparation provides the basis for good seed
germination and establishment of steppe vegetation in
the arid and semi-arid areas of West Asia and North
Africa. Salsola vermiculata is a key shrub species of the
region and contributes to rangeland and livestock
productivity. The aim of this study was to evaluate the
establishment of S. vermiculata using three different soil
preparation techniques since transplanting is often cost
prohibitive. This study also aims to assess the
establishment in different gradients of gentle landscape
depressions for scarification and furrowing; at the top,
on slope and at the core. The experiment was conducted
in the semi-arid steppe of the Hama District in Syria with
three establishment treatments viz., scarification (SC),
pitting machine (PM) and furrowing (FR). Our results
indicated that the density of S. vermiculata under
scarification treatment is 10 folds higher (P < 0.05) than
the other two techniques. The results suggest that direct
seeding with superficial soil surface scarification may
provide a significant remedy for the rehabilitation of
degraded arid rangelands. Seeding densities tested on
different gradients of landscape depressions were
highest on the top, followed by on slope for both furrowing
and scarification.
Keywords: Arid environment, Plant density, Seed
germination, Soil moisture, Transplanting seedlings,
Water infiltration
Introduction
Arid and semi-arid rangelands correspond to fragile
zones, typically dominated by harsh environmental
conditions in terms of low and erratic rainfall, shallow
and poor soils, extreme temperatures, and high
evaporation rates (Allison, 1998). The Syrian rangeland
locally referred as badia, covers more than 10 million
hectares, i.e., approximately 55% of the country’s
landmass (Louhaichi and Tastad, 2010). These lands
have been extensively used over time to support livestock
production, in particular small ruminants (Lewis, 1987).
However, these rangelands are suffering from
anthropogenic and environmental disturbances
(Louhaichi et al., 2012; Ouled Belgacem and Louhaichi,
2013) and are gradually losing their inherent soil fertility
and are subject to erosion due to over-exploitation and
inappropriate management practices. As a result, the
grazing area is shrinking, available biomass is reduced
and species biodiversity is being eroded (Enne et al.,
2004). There is an urgent need to reverse the trend of
rangeland degradation through appropriate rehabilitation
techniques.
The most common and often most reliable method of
rehabilitating arid and semi-arid rangelands are to
transplant native plants to a variety of sites (Akroush et
al., 2011). However, direct seeding is an alternative to
transplanting and its cost is one-tenth that of shrub
transplanting (Osman and Shalla, 1994). Given the vast
areas, large scale range improvement will require the
development of more cost effective approaches.
The main advantage of direct seeding is the ability to
sow large areas rapidly at a lower cost compared to
transplanting (Douglas et al., 2007). Furthermore, direct
seeding is considered to produce a more natural
appearance and improved successional pathway
compared to spaced-planting (Douglas et al., 2007).
However, direct seeding also has a number of potential
disadvantages, including; difficulty in sourcing large
quantities of viable seed, lack of information on optimum
sowing times for many species, variability in
commencement and duration of germination, less
flexibility to control conditions for seed germination and
early seedling growth, predation of seed and seedlings,
and the need to control intense competition from existing
vegetation, particularly grasses (Douglas et al., 2007).
One of the principal ways to improve the success of any
direct seeding operation is thorough soil surface prepa-
Louhaichi et al.
183
-aration. In arid and semi-arid pastoral ecosystems of
West Asia and North Africa (WANA), lack of soil moisture
is probably the greatest limitation for satisfactory
establishment of sown species (Karrou and Oweis,
2011). Historically, brittle rangelands, such as those in
WANA, rely on soil and plant disturbance by hooved wild
animals for presentation of water and seeds into the soil
(Savory, 1988). Soil surface scarification and furrowing
with direct seeding attempts mimic these natural
processes. In arid and semi-arid regions of WANA, where
water availability is the critical limiting factor, techniques
which involve the scarification and ripping of substantial
amounts of soil to maximize rainfall catchment and
improve the infiltration of water have proven to be the
most effective (Louhaichi, 2011).
Direct seeding of native Mediterranean shrub species is
rarely successful in rangelands of the WANA region,
except for S. vermiculata (Gintzburger et al., 2006).
Although Salsola vermiculata is successful in direct
seeding, seeds have a short storage life compared to
other range species (Kay et al., 1988). The seed of S.
vermiculata loses its viability within 6-9 months under
ambient storage conditions (Tadros et al., 2000). Even
though the storatolity can be extended by reducing storage
temperature (Zaman et al., 2010). It is not always
available in many developing countries. Thus,
investigating the best direct seeding soil preparation
methods is important to improve the success rate and
establishment for restoration projects.
Salsola vermiculata L. is a member of the
Chenopodiaceae family and is perhaps the most
valuable browse species in arid rangelands of WANA.
This plant provides a drought reserve for livestock and
provides green feed with protein and other nutrients at a
time of low nutritional value of other grasses and forbs
(Pengelly et al., 2003). It is grazing resistant, self-
reseeding and as a result used in many rangeland
rehabilitation projects in Jordan and Syria (Gintzburger
et al., 2006).The aim of this study was to evaluate the
establishment of S. vermiculata using direct seeding in
different gradients (at top, on slope and at the core) of
gentle landscape depressions using scarification and
furrowing soil preparation techniques, as well as
evaluate the use of pitting machines on flat land in the
semi-arid steppe of the Hama district in Northern Syria.
The focus is on denuded rangelands, which avoids the
more complex biological interactions that occur adjacent
to and within shrub ruminants.
Materials and Methods
Study area
The study was conducted in the semi-arid steppe of the
Hama district in Northern Syria. The climate in this area
is Mediterranean arid, exhibiting highly variable and
extreme precipitation and temperature patterns. The
average annual precipitation (1996-2010) was 187.22
mm at the nearest weather station in Maragha, with the
highest amounts occurring between December and
March (Fig. 1). The average annual temperature is 17.6°C,
with a range of 2.4°C in January to 39°C in August. During
the study period the annual rainfall was 124.8mm and
the average temperature was 13.8°C. Gentle landscape
depressions are characteristic of the area. The study site
areas were historically degraded from long-term barley
encroachment until ban on its cultivation in 1995. Soils
are derived from gypsiferous deposits and calcareous
gypsic materials that accumulate in topographic
depressions throughout the region.
0
50
100
150
200
250
300
350
199 6 199 7 199 8 199 9 200 0 200 1 200 2 2003 2 004 2 005 2 006 2 007 2 008 20 09 20 10
Total annual precipitation (mm)
Year
Fig 1. Annual precipitation (1996 to 2010) at Maragha in
Northern Syria
Soil preparation and direct seeding
Seeds of Salsola vermiculata were collected from the
Syrian rangelands in autumn of 2010. Before seed
broadcasting the soil was prepared using three
establishment techniques: 1) scarification (SC) using
shallow cultivation of the whole surface area; 2) furrowing
(FR) by opening 15 furrows per ha spaced 6 m apart and
having 30 cm width each and 3) pitting (PM) using a
pitting machine generated approximately 1,000 pits per
ha. The seeding rate was set at 8 kg/ha for each
technique. Seeds were sown in three landscape
depressions (top, slope, and the core) for scarification
and furrowing. The landscape depressions had a slope
less than 10% and a maximum depth around 1 meter
(Fig. 2). The pitting machine was tested on relatively flat
surfaces only, as it was pulled by a pickup.
Rangeland rehabilitation through direct seeding
Fig 2. Landscape depression gradient locations and
maximum depth
The soil preparation including scarification, furrowing,
and pitting occurred in September/October, just prior to
the rainy season. Assaeed (2001) reported that late
autumn and early winter sowings should be
recommended, when salinity and temperature stresses
are reduced after the first rains of the season. Therefore,
seeds were broadcasted in November taking advantage
of the fall rain in order to improve the germination rate.
Plant density
In order to estimate the density of Salsola seedlings, ten
randomized quadrats of 1m x 1m were chosen during
the spring season. Quadrats were placed at the top, on
the slope, and at the core of each landscape depression.
Plant density was expressed as the number of individuals
that occurred within a designated surface unit (m2). The
average density was calculated for each treatment at the
different gradient positions.
Statistical analysis
The experiment design consisted of a randomized block
design based on three blocks (sites) and eight
replications per treatment. Treatments consisted of a
factorial combination of three establishment methods
and three landscape depressions features. ANOVA with
the general linear model procedure was performed (SAS,
2009). If differences were significant, the separation of
means was done with Duncan’s Multiple Range Test,
and a probability level < 0.05 was considered significant.
Results and Discussion
The WANA rangelands are deteriorating as a result of
mismanagement and climate change resulting in
recurrent droughts and increased temperatures. Direct
seeding is considered to be one of the most economical
and effective methods for restoring degraded rangelands,
particularly where the seed bank is depleted (Porto,
2001). Our results indicated that the density of S.
vermiculata under scarification treatment was 10 fold
higher (P<0.05) than the other two techniques (Fig. 3).
There was no significant difference between furrowing
and pitting machine.
0
4
8
12
16
20
Direct seeding
Furrowing
Pitting machine
Density (plants/m
2
)
a
b
b
Fig 3. Density (number of Salsola plants/m2) in all sites
(bars that have different letters are significantly P < 0.05
different from one another).
When applying the soil scarification technique, the density
of S. vermiculata was higher at the top and on the slope
compared to the core of the landscape depressions (p =
0.039) for all sites (Fig. 4). However when comparing
within individual sites; sites 1 and 2 did not record any
significant differences in density, site 3 had higher density
at the top of the landscape depressions compared to the
slope and the core (P = 0.004) (Fig. 5). The reason for
the lower density at the core of the landscape
depressions than the top could be attributed to water
that is collected at the core (bottom). The persistence of
such a ponded area would limit the germination of the
seed because of asphyxia (anaerobic conditions).
0
4
8
12
16
20
Top
Slope
Core
Density (plants/m
2
)
aa
b
Fig 4. Density (number of Salsola plants/m2) when using
soil surface scarification for all sites (bars that have dif-
ferent letters are significantly P < 0.05 different from one
another).
184
0
4
8
12
16
20
24
Site1
Site2
Site3
Density (plants/m
2
)
Top
Slope
Core
a
a
a
a
a
a
a
b
b
Fig 5. Density (number of Salsola plants/m2) in each site
when using soil surface scarification (In each site, bars
that have different letters are significantly P < 0.05 differ-
ent from one another).
0
1
2
3
Top
Slope
Core
Density (plants/m
2
)
a
b
b
0
1
2
3
4
5
Site1
Site2
Site3
Density (plants/m
2
)
Top Slope Core
b
ab
a
a
a
a
a
a
a
Fig 6. Density (number of Salsola plants/m2) in all sites
when using soil surface furrowing (bars that have differ-
ent letters are significantly P < 0.05 different from one
another).
core (P = 0.011) (Fig. 6). However, when comparing the
densities within the individual sites, no significant differ-
ences were observed among the 3 landscape depres-
sion positions (Fig. 7).
Understanding the best soil preparation techniques and
the best gradient for Salsola vermiculata is important
since it is a key native forage species for restoring
degraded rangeland in the WANA region. Temperature,
soil moisture status and salinity are some of the most
important environmental conditions that affect seed
germination, seedling establishment and survival in arid
areas. Episodic rather than average environmental
conditions control the successful plant recruitments in
arid and semi-arid regions (Call and Roundy 1991).
Research is needed to improve the success rate of
rehabilitation projects that plant S. vermiculata.
Based on climatic models, several studies show
relationships between climate change and drought in
the region which predict that the impacts of climate
change will result in more frequent and harsher droughts,
higher temperatures and lower and more unpredictable
precipitation levels. The situation becomes more severe
due to a steady population increase coupled with
groundwater depletion. Similar to other arid ecosystems
in the region, the Syrian Badia has a high resilience. Its
natural vegetation is well adapted to frequent droughts
and wet periods. If managed well, the system can recover
after prolonged droughts.
In this study, direct seeding of S. vermiculata following
soil surface scarification gave the best results based on
the number of seedlings established in one year. This is
likely due to climatic condition during the establishment
phase. The precipitation was lower than the long-term
average which is key for seed germination and
establishment. The small pits created by the pitting
machine gave a uniform seed bed and most of the seed
germinated at once. When the soil moisture dropped
because of prolonged drought, most of the seeds died.
Though in principle the furrowing seems to mimic soil
scarification, the depth at which the seeds were sown
was too deep for the small seeds to germinate and rise
above the soil surface. Soil surface scarification (top 5
cm) presented a more ideal situation for S. vermiculata
to germinate and succeed. The micro topography
generated by the soil surface scarification gave a mosaic
of small scale niches that allowed seeds positioned at
certain topographic facets to succeed fully. This
assessment coincides with the view that rangeland
185
Louhaichi et al.
Fig 7. Density (number of Salsola plants/m2) in each site
when using soil surface furrowing (In each site, bars that
have different letters are significantly P < 0.05 different
from one another).
For the furrowing technique, density for all sites was
higher at the top of the LD compared to the slope and
productivity is governed by climate (temperature and
precipitation), disturbance (grazing), topography, and the
interaction of these (Gibson, 2009).
Conclusion
The results suggest that the superficial soil surface
scarification is the best soil preparation technique for
direct seeding for S. vermiculata when compared to
furrowing or pitting machine. Direct seeding in soil
scarifications may provide a significant remedy for the
rehabilitation of degraded arid rangelands in WANA. Such
a technique is not suggested for the core of landscape
depressions as water logging may reduce plant density.
While shrub transplanting makes it possible to establish
plants that are not easily started from seed in the field, it
is expensive and can be cost prohibitive in many contexts.
Further experimentation of different methods for direct
seeding soil preparation is recommended as well as
the inclusion of other species.
Acknowledgements
This research was supported by the International Center
for Agricultural Research in the Dry Areas (ICARDA), the
CGIAR Research Program on Climate Change,
Agriculture and Food Security (CCAFS) and the CGIAR
Research Program on Dryland Agricultural Production
Systems (CRPDS). The authors appreciate the logistical
support of the Badia development project (Aleppo
steppes, Syria) in making this study possible. The helpful
comments of anonymous reviewers are also
appreciated.
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