INTRODUCTION
Food security and stability in the world greatly depends on the management
of the natural resources. Due to depletion of water resources and an increase
in population, irrigated area per capita is declining and irrigated lands
now produce 40% of the food supply (Hargreaves and Mekley, 1998). Consequently,
the available water resources may not be able to meet various demands
in near future that will inevitably result in the irrigation of additional
lands in order to achieve a sustainable global food security. The suitability,
by definition, is the natural capability of a given land to support a
defined use. The process of land suitability classification is the appraisal
and grouping of specific areas of land in terms of their suitability for
a defined use.
According to the FAO methodology (1976), this is strongly related to
the land qualities including erosion resistance, water availability and
flood hazards that are not measurable qualities. As these qualities are
derived from the land characteristics, such as slope angle and length,
rainfall and soil texture which are measurable or estimable, it is advantageous
to use the latter indicators in the land suitability studies. Thus, the
land parameters are used to obtain land suitability for irrigation purposes.
Sys et al. (1991) suggested a parametric evaluation system for
irrigation methods which was primarily based upon physical and chemical
soil properties. In their proposed system, the factors affecting the soil
suitability for irrigation purposes can be subdivided into four groups:
| • |
Physical properties determining the soil-water relationship
in the soil such as permeability and available water content |
| • |
Chemical properties interfering with the salinity/ alkalinity
status such as soluble salts and exchangeable Na |
| • |
Drainage properties |
| • |
Environmental factors such as slope |
Briza et al. (2001) applied a parametric system (Sys et al.,
1991) to evaluate land suitability for both surface and drip irrigation
in the Ben Slimane Province, Morocco, while no highly suitable areas were
found in the studied area. The largest part of the agricultural areas
was classified as marginally suitable the most limiting factors being
physical parameters such as slope, soil calcium carbonate, sandy soil
texture and soil depth.
Bazzani and Incerti (2002) also provided a land suitability evaluation
for surface and drip irrigation systems in the province of Larche, Morocco,
by using parametric evaluation systems. The results showed a large difference
between applying the two different evaluations. The area not suitable
for surface irrigation was 29.22% of total surface and 9% with the drip
irrigation while the suitable area was 19 versus 70%. Moreover, the highly
suitability was extended on a surface of 3.29% in the former case and
it became 38.96% in the latter. The main limiting factors were physical
limitations such as the slope and sandy soil texture.
Bienvenue et al. (2003) evaluated the land suitability for surface
(gravity) and drip (localized) irrigation in the Thies, Senegal, using
the parametric evaluation system proposed by Sys et al. (1991).
Under surface irrigation, there was no area classified as highly suitable
(S1). Only 20.24% of the study area proved suitable (S2,
7.73%) or slightly suitable (S3, 12. 51%). Most of the study
area (57.66%) was classified as unsuitable (N2). The limiting
factor to this kind of land use was mainly the soil drainage status and
texture that was mostly sandy while surface irrigation generally requires
heavier soils. For drip (localized) irrigation, a good portion (45.25%)
of the area was suitable (S2) while 25.03% was classified as
highly suitable (S1) and only a small portion was almost suitable
(N1, 5 .83%) or unsuitable (N2, 5.83%). In the latter
cases, the handicap is given by the shallow soil depth and incompatible
texture due to a large amount of coarse gravel and/or poor drainage.
Mbodj et al. (2004) performed a land suitability evaluation for
two types of irrigation i.e., surface irrigation and drip irrigation,
in Tunisian Oued Rmel Catchment using the suggested parametric evaluation.
According to the results, the drip irrigation suitability gave more irrigable
areas compared to the surface irrigation practice due to the topographic
(slope), soil (depth and texture) and drainage limitations encountered
with in the surface irrigation suitability evaluation.
Barberis and Minelli (2005) provided land suitability classification
for both surface and drip irrigation methods in Shouyang county, Shanxi
province, China where the study was carried out by a modified parametric
system. The results indicated that due to the unusual morphology, the
area suitability for the surface irrigation (34%) is smaller than the
surface used for the drip irrigation (62%). The most limiting factors
were physical parameters including slope and soil depth.
Dengiz (2006) also compared different irrigation methods including surface
and drip irrigation in the pilot fields of central research institute,
lkizce research farm located in southern Ankara. He concluded that the
drip irrigation method increased the land suitability by 38% compared
to the surface irrigation method. The most important limiting factors
for surface irrigation in study area were soil salinity, drainage and
soil texture, respectively whereas, the major limiting factors for drip
or localized irrigation were soil salinity and drainage.
Liu et al. (2006) evaluated the land suitability for surface and
drip irrigation in the Danling county, Sichuan province, China, using
the Sys`s parametric evaluation system. For surface irrigation the most
suitable areas (S1) represented about (24%) of Danling County,
(33%) was moderately suitable (S2), (9%) was classified as
marginally suitable (S3), (7%) of the area was founded currently
not suitable (N1) and (25%) was very unsuitable for surface
irrigation due to their high slope gradient. Drip irrigation was everywhere
more suitable than surface irrigation due to the minor environmental impact
that it caused. Areas highly suitable for this practice covered 38% of
Danling County, about 10% was marginally suitable (the steep dip slope
and the structural rolling rises of Jurassic). Only the steeper relieves
of the study area (23%) were almost or very unsuitable for such a practice.
Albaji et al. (2007) investigated land suitability evaluation
for surface and drip Irrigation in Shavoor Plain, Iran. The results showed
that 41% of the area were suitable for surface irrigation, 50% of the
area were highly recommend for drip irrigation and the rest of area were
not suitable for the both irrigation method due to soil salinity and drainage
problem.
Albaji et al. (2007) compared different irrigation methods based
on the parametric evaluation approach in west Shoush Plain, Iran. The
results showed that 9031 ha (21.52%) of the studied area were highly suitable
for surface irrigation method whereas 32505 ha (77.47%) of the study area
were highly suitable for drip irrigation method. Moreover, by applying
drip irrigation method instead of surface irrigation method, land suitability
classes of 30128 ha (71.81%) of west Shoush Plain will improve. Ultimately,
drip irrigation system was suggested as the best method to be applied
to the study area. The main limiting factors in using surface irrigation
method in this area were sandy soil texture and slope, also for drip irrigation
methods the main limiting factor was soil calcium carbonate.
The main objective of this research is to evaluate and compare land suitability
for surface, sprinkle and drip irrigation methods based on the parametric
evaluation systems for Fakkeh Plain, Elam Province, Iran.
MATERIALS AND METHODS
The present study was conducted in an area about 43700 ha in Fakkeh Plain,
Elam Province, west of Iran during 2007. The study area is located 80
km southwest the city of Andimeshk, 32° 01´ to 32°
13´ N and 47° 32´ to 47° 57´ E. Average annual temperature and
precipitation for the period of 1965-2004 were 24.1°C and 230 mm,
respectively. Also, the annual evaporation of the area is 1950 mm (KWPA,
2005). The main water supply to this area is Dowayrej River. The study
area has been commonly used for irrigated agriculture. Presently, the
irrigation systems used by farmlands are furrow irrigation, basin irrigation
and border irrigation schemes.
The area is composed of two distinct physiographic features i.e. Plateaux
and Flood Plains, where Plateaux physiographic units are the dominating
features. Also, seven different soil series were found in the area. The
semi-detailed soil survey report of Fakkeh Plain was used in order to
determine the soil characteristics (KWPA, 2003). The land evaluation was
determined based upon topography and soil characteristics of the region.
The topographic characteristics included slope while soil properties included
soil texture, depth, salinity, drainage and calcium carbonate content.
Soil properties such as cation exchange capacity (CEC), percentage of
basic saturation (PBC), organic mater (OM) and pH were considered in terms
of soil fertility. Sys et al. (1991) suggested that soil characteristics
such as OM and PBS do not require any evaluation in the arid regions while
clay CEC rate usually exceeds the plant requirement without further limitation,
thus, fertility properties can be excluded from land evaluation with the
purpose of irrigation.
| Table 1: |
Suitability classes for the irrigation capability indices
(Ci) classes |
|
Based upon the profile description and laboratory analysis, the group
of soils that had similar properties and located in a same physiographic
unit were considered as a series of soils and were taxonomied to form
a soil family as per the Keys to Soil Taxonomy (2000). Ultimately, seven
soil series were selected for the surface, sprinkle and drip irrigation
land suitability.
In order to obtain the average soil texture, salinity and CaCO3
for the upper 150 cm of soil surface, the profile was subdivided into
6 equal sections and weighting factors of 2, 1.5, 1, 0.75, 0.50 and 0.25
were used for each section, respectively (Sys et al., 1991).
For the evaluation of land suitability to surface and drip irrigation,
the parametric evaluation system was used (Sys et al., 1991). This
method is based on morphology, physical and chemical properties of soil.
Six parameters including slope, drainage properties, electrical conductivity
of soil solution, calcium carbonates status, soil texture and soil depth
were also considered and rates were assigned to each as per the related
tables, thus, the capability index for irrigation (Ci) was developed as
shown in the equation below:
where A, B, C, D, E and F are soil texture rating, soil depth rating,
calcium carbonate content rating, electrical conductivity rating, drainage
rating and slope rating, respectively.
In Table 1, the ranges of capability index and the
corresponding suitability classes are shown.
RESULTS AND DISCUSSION
In much of the Fakkeh Plain, the surface irrigation system has been applied
specifically for field crops to meet water needs of both summer and winter
crops .The major irrigated broad-acre crops grown in this area are wheat,
barley, fruits including melon, watermelon and vegetables, such as tomato
and cucumber. There are very few instances of sprinkle and drip irrigation
on large area farms in the Fakkeh Plain.
|
| Fig. 1: |
Soil map of the study area |
| Table 2: |
Suitability index (Ci) values and suitability classes of surface,
sprinkle and drip irrigation systems for each land units |
|
| *Limiting factors for surface irrigation: s (Soil
texture); **Limiting factors for sprinkle irrigation: s (Soil texture);
***Limiting factors for drip irrigation: s (Calcium carbonate and
Soil texture) |
Seven soil series and fifteen series phases or land units were derived
from the semi-detailed soil study of the area. The land units are shown
in Fig. 1 as the basis for further land evaluation practice.
The soils of the area are of Aridisols and Entisols orders. Also, the
soil moisture regime is Aridic while the soil temperature regime is Hyperthermic
(KWPA, 2003).
As shown in the Table 2 and 3, for
surface irrigation, the land units coded 3.2 (1715 ha, 3.93%) were highly
suitable (S1); land units coded 2.1, 3.1, 5.1, 5.2, 6.1 and
6.2 (5650 ha, 12.93%) were classified as moderately suitable (S2)
and land units coded 1.2, 1.3, 1.4, 1.5 and 2.2 (25320 ha, 57.94%) were
found to be marginally suitable (S3). Also, land units coded
1.1 and 7.1 (7665 ha, 17.54%) were classified as currently not-suitable
(N1). Only land unit coded 4.1 (1670 ha, 3.82%) was classified
as permanently not-suitable (N2) for any surface irrigation
exercises.
By analyzing the suitability irrigation maps for surface irrigation (Fig.
2), it is evident that the highly suitability area can be observed
just in one land unit (3.2) of the Fakkeh Plain due to deep soil, good
drainage, texture and proper slope of the area. The moderately suitable
area is located only in some part of this area due to sandy loam soil
texture. The others factor such as drainage, depth, salinity and slope
never influence the suitability of the area. As seen from the map, the
largest part of cultivated area in this plain was evaluated as marginally
suitable because of the loamy sand soil texture. The currently not-suitable
lands and permanently not-suitable lands can be observed only in the center
and east of the plain because of the physical limitations such as sandy
soil texture. For almost the entire study area slope, soil depth, salinity,
drainage and CaCO3 were never taken as limiting factors.
| Table 3: |
Distribution of surface, sprinkle and drip irrigation
suitability |
|
| *Miscellaneous Lands: (Hill, Sand Dune and River Bed) |
|
| Fig. 2: |
Land suitability map for surface irrigation |
In order to verify the possible effects of different management practices,
the land suitability for sprinkle and drip irrigation was evaluated (Table
2, 3).
For sprinkle irrigation, land units coded 2.1, 3.1, 3.2, 5.1, 5.2, 6.1
and 6.2 (7365 ha, 16.86%) were highly suitable (S1) while land
units coded 1.2, 1.3, 1.4, 1.5 and 2.2 (25320 ha-57.94%) were classified
as moderately suitable (S2). Further, land units coded 1.1
and 4.1 (8600 ha, 19.68%) were found to be slightly suitable (S3).
Only land unit coded 7.1 (735 ha, 1.68%) was classified as currently not-suitable
(N1) for sprinkle irrigation.
In this case (Fig. 3), the highly suitability area
can be observed just in some part (west and east) of the Fakke Plain due
to proper slope, deep soil, good texture and drainage of the area. As
seen from Fig. 3, the largest part of cultivated area
in this plain was evaluated as moderately suitable for sprinkle irrigation
because of the loamy sand soil texture. The others factor such as drainage,
depth, salinity and slope never influence the suitability of the area.
The marginally suitable area is located only in two land units coded 1.1
and 4.1 located in east and center of this plain due to sandy soil texture.
The currently not-suitable lands can be observed only in one land unit
coded 7.1 located in the southwest of the plain because of the salinity
and drainage limitation. The permanently not-suitable land did not exist
in this plain. For almost the entire study area slope, soil depth, salinity,
drainage and CaCO3 were never taken as limiting factors.
For drip irrigation, land units coded 1.2, 1.3, 1.4, 1.5, 2.1, 2.2, 3.1
and 3.2 (28190 ha, 64.51%) were highly suitable (S1) while
land units coded 1.1, 5.1, 5.2, 6.1 and 6.2 (11425 ha, 26.15%) were classified
as moderately suitable (S2). Further, the land unit coded 4.1
(1670 ha, 3.82%) were found to be slightly suitable (S3). Only
land unit coded 7.1 (735 ha, 1.68%) was classified as currently not-suitable
(N1) for drip irrigation.
In this case, (Fig. 4) the highly suitable lands covered
nearly a big portion of the plain (64.51%). The slope, soil texture, soil
depth, calcium carbonate, salinity and drainage were in good conditions.
|
| Fig. 3: |
Land suitability map for sprinkle irrigation |
The moderately suitable lands could be observed in some part of the plain
(east, center and wet parts) due to medium content of calcium carbonate.
The marginally suitable lands were founded only in one land unit coded
4.1 located in the east of the area. The limiting factors for this land
unit were sandy soil texture and medium content of calcium carbonate.
Finally, only a land unit coded 7.1 was classified currently not-suitable
for drip irrigation systems in southeast of the plain because of salinity
and drainage limitations and also medium content of calcium carbonate.
For the entire study area, slope, soil texture, soil depth, drainage and
salinity were never considered as limiting factors.
The mean capability index (Ci) for surface irrigation was 56.65 (slightly
suitable) while for sprinkle irrigation was 71.97 (moderately suitable).
Also, for drip irrigation it was 76.17 (moderately suitable). For the
comparison of the capability indices for surface, sprinkle and drip irrigation.
Table 2 and 4 indicated that in land
units coded 1.1, 1.2, 1.3, 1.4, 1.5, 2.1, 2.2, 3.1 and 4.1 applying drip
irrigation systems was the most suitable than surface and sprinkle irrigation systems.
In land units coded 5.1, 5.2, 6.1, 6.2 and 7.1 applying sprinkle irrigation
systems was the most suitable compared with surface and drip irrigation
systems. Only in the land unit coded 3.2 applying drip or sprinkle irrigation
systems were the most suitable than surface irrigation systems. Figure
5 shows the most suitable map for surface, sprinkle and drip irrigation
systems in the Fakkeh plain by notation to capability index (Ci) for different
irrigation systems. As seen from this map, the largest part of this plain
was suitable for drip irrigation systems and some part of this area was
suitable for sprinkle irrigation systems, also, there was not founded
area that was suitable for surface irrigation systems.
The results of Table 4 indicate that by applying drip
irrigation instead of surface and sprinkle irrigation methods, suitability
classes of land units coded 1.2, 1.3, 1.4, 1.5, 2.1, 2.2 and 3.1 (26475
ha, 60.58%) improved to highly suitable (S1) and land unit
coded 1.1 (6930 ha, 15.87%) was developed to moderately suitable (S2).
In addition, the land unit coded 4.1 (1670 ha, 3.82%) improved to marginally
suitable (S3).
| Table 4: |
The most suitable land units for surface, sprinkle and
drip irrigation systems by notation to capability index (Ci) for different
irrigation systems |
|
|
| Fig. 5: |
The most suitable map for different irrigation systems |
The results demonstrate that by applying sprinkle
Irrigation instead of surface and drip irrigation methods, suitability
classes of land units coded 5.1, 5.2, 6.1 and 6.2 (4495 ha, 10.29%) developed
to highly suitable (S1) and land unit coded 7.1 (735 ha, 1.68%)
was developed to currently not-suitable (N1). Also, for the
land unit coded 3.2 (1715 ha, 3.92%) applying drip or sprinkle irrigation
systems were improved to highly suitable (S1). The results
demonstrate that by applying drip Irrigation instead of surface and sprinkle
irrigation methods, suitability classes of 36790 ha (84.19%) of Fakkeh
Plain`s land will improved. Also by applying sprinkle Irrigation instead
of surface and drip irrigation methods, suitability classes of 6945 ha
(15.89%) of this Plain`s land will improved The comparison of the different
types of irrigation revealed that the drip irrigation was more effective
and efficient then the surface and sprinkle irrigation methods improved
the suitability to the irrigation purposes. After that, the sprinkle irrigation
was more useful than surface irrigation method. Therefore, The most suitable
irrigation systems in Fakkeh Plain`s land were drip irrigation and sprinkle
irrigation respectively. There were not highly suitable lands for surface
irrigation system in the studied area (instead of land unit coded 3.2).
So that, the surface irrigation system was not suitable for Fakkeh Plain`s
land. Moreover, the main limiting factor in using surface and sprinkle
irrigation methods in this area was soil texture and the main limiting
factor in using drip irrigation methods was soil calcium carbonate content.
CONCLUSION
Details are given for the analysis of the field data to compare the suitability
of different irrigation systems. The analyzed parameters included soil and land
characteristics. The results obtained showed that drip irrigation is more suitable
than sprinkle and surface irrigation methods for most of the study area. The
major limiting factor for the drip irrigation methods was soil calcium carbonate
content, however for sprinkle and surface irrigation methods soil texture was
the restricted factor. As seen in the results of the comparison between the
maps, introduction of a different irrigation management policy could be an important
improvement. The highly suitable area is very wider for drip irrigation and
it includes a large part of the Fakkeh Plain. The drip irrigation can obviously
be a way to improve the practice on light soil textures. Of course in the application
of this sort of irrigation, an agricultural management change would be necessary:
horticulture and mulched crops should replace extensive crops such as wheat,
barley, etc actually adopted. This is the same strategy adopted by large companies
currently practicing in the area and that can ensure the highest incomes to
the farmers.
Such a management change would imply the availability of larger initial
capitals to farmers (different credit conditions, for example) as well
as a different storage and market organization. On the other hand, because
of insufficiency of water in arid and semi arid climate, maximizing water
use efficiency is necessary to produce more crops per drop and to help
for solving the water shortage crisis in the agricultural sector. The
shift from surface irrigation to high-tech irrigation technologies, e.g.
drip and sprinkle irrigation systems, therefore, offers significant water-saving
potentials. Finally, since drip irrigation system typically applies small
amount of water on a frequent basis to maintain soil water near field
capacity, it would be more beneficial to use drip irrigation method in
this plain.
ACKNOWLEDGMENTS
The authors should acknowledge their indebtedness to the Research and
Standards Office for Irrigation and Drainage Networks of Khuzestan Water
and Power Authority (KWPA) for their financial support and assistance
(NRP-8615860).
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