IRRIGATION AND DRAINAGE Irrig. and Drain. 59: 547 558 (2010) Published online 13 November 2009 in Wiley Online Library (wileyonlinelibrary.com).520 COMPARISON OF DIFFERENT IRRIGATION METHODS BASED ON THE PARAMETRIC EVALUATION APPROACH IN THE PLAIN WEST OF SHUSH, IRAN y MOHAMMAD ALBAJI, SAEED BOROOMAND NASAB*, HYDAR ALI KASHKOLI AND ABDALI NASERI Department of Irrigation and Drainage, Faculty of Water Science Eng, Shahid Chamran University, Ahwaz, Iran ABSTRACT The main objective of this research was to compare the suitability of land for surface and drip irrigation methods according to a parametric evaluation system in the plains west of the city of Shush, in south-west Iran. After analysing and evaluating soil properties, suitability maps were generated for both methods by means of remote sensing (RS) and a geographic information system (GIS). The results showed that 9031 ha (21.5%) of the studied area was highly suitable for surface irrigation methods, whereas 32 500 ha (77.5%) of the study area was highly suitable for drip irrigation methods. Also some land units covering an area of 2111 ha (5.0%) were not suitable to be used for surface irrigation systems. One land unit with an area of 724 ha (1.7%) was classified as not suitable for drip irrigation systems. Moreover, the results indicated that a larger amount of the land (30 100 ha 71.8%) can be classified as more suitable for drip than surface irrigation. Ultimately, the application of a drip irrigation system was suggested as the best method to be applied to the study area. The main limiting factors in using surface irrigation methods in this area were sandy soil texture and slope; moreover, for drip irrigation methods, the main limiting factor was soil calcium carbonate. Copyright # 2009 John Wiley & Sons, Ltd. key words: surface irrigation; drip irrigation; land suitability evaluation; parametric method; land units Received 10 February 2008; Revised 3 March 2009; Accepted 3 March 2009 RÉSUMÉ L objectif principal de cette recherche était de comparer l aptitude des terres à l irrigation de surface et au goutte-àgoutte, selon un système d évaluation paramétrique, dans la plaine ouest de la ville de Chouch, dans le sud-ouest de l Iran. Après avoir analysé et évalué les propriétés du sol, des cartes d aptitude ont été produites pour les deux méthodes d irrigation grâce à la télédétection (RS) et un système d information géographique (SIG). Les résultats ont montré que 9030 ha (21.5% de la zone étudiée) sont très appropriés pour l irrigation de surface, alors que 32 500 ha (77.5%) sont très convenables pour l irrigation au goutte à goutte. En outre une superficie de 2110 ha (5.0%) n est pas apte à l irrigation de surface. Une superficie de 724 ha (1.7%) a été classée comme ne convenant pas à l irrigation au goutte à goutte. En outre, les résultats ont montré qu une plus grande surface (30 100 ha 71.8%) peut être classée comme plus apte à l irrigation au goutte à goutte qu à l irrigation de surface. En fin de compte il a été suggéré que l irrigation au goutte à goutte est la meilleure méthode à appliquer à la zone d étude. Les principaux facteurs limitant dans l utilisation de l irrigation de surface dans cette zone ont été la texture sableuse du sol et la pente; de plus pour l irrigation au goutte à goutte le principal facteur limitant est le carbonate de calcium dans le sol. Copyright # 2009 John Wiley & Sons, Ltd. mots clés: irrigation de surface; goutte à goutte; évaluation de l aptitude des terres; méthode paramétrique; unités foncières * Correspondence to: Mr. Saeed Boroomand Nasab, Irrigation and Drainage Deapartment, Water Sciences Faculty, Shahid Chamran University, P.O.Box 61357-8-3151, Ahwaz, Iran. (Islamic Republic of Iran). E-mail: boroomandsaeed@yahoo.com y Comparaison des différentes méthodes d irrigation par une approche d évaluation paramétrique dans la plaine ouest de Shush, Iran. Copyright # 2009 John Wiley & Sons, Ltd.
548 M. ALBAJI ET AL. INTRODUCTION Irrigated agriculture makes a major contribution to food security, producing nearly 40% of food and agricultural commodities on 17% of agricultural land. Irrigated areas have almost doubled in recent decades and contributed much to the growth in agricultural productivity over the last 50 years. Irrigated agriculture uses more than 70% of the water withdrawn from the earth s rivers; in developing countries the proportion exceeds 80% (FAO, 2002). Food production via irrigated agriculture, however, does not correspond to the current rapid population growth (Hargreaves and Merkley, 1998). Soil salinity and contamination in addition to excessive urbanization development are among the main factors that affect the state of food production through irrigated agriculture (Conway, 2003). The available water resources may not be able to meet various demands that will inevitably result in the irrigation of additional lands in order to achieve a sustainable global food security. 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 of defined use. According to FAO methodology (1976), this is strongly related to land qualities including erosion resistance, water availability, and flood hazards that are not easily measurable. As these qualities derive from the land characteristics such as slope (angle and length), rainfall and soil texture, which are measurable or estimable, it is beneficial to use the latter indicators in land suitability studies. Thus, land parameters are used to determine 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 the 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. Hired et al. (1996) and Bond (2002) improved the classification methods for evaluating suitability for effluent irrigation and land suitability for irrigation. These factors influencing land suitability in irrigation practice included soil properties and topography. Tesfai (2002) investigated a land suitability method for gravity (surface) irrigation schemes in the Sheeb area of Eritrea. According to the results, 40% of the study area was highly to moderately suitable for surface irrigation, and 57% marginally suitable to unsuitable for surface irrigation. The main limiting factor for surface irrigation was soil salinity. Bienvenue et al. (2003) evaluated the land suitability for surface (gravity) and drip (localized) irrigation in Thies, Senegal, using the parametric evaluation system proposed by Sys et al. (1991). Under surface irrigation, there was no area classified as highly suitable (S 1 ). Only 20.2% of the study area proved suitable (S 2, 7.7%) or slightly suitable (S 3, 12.5%). Most of the study area (57.7%) was classified as unsuitable (N 2 ). The limiting factor to this kind of land use was mainly the soil drainage status and texture that was mostly sandy, whereas surface irrigation generally requires heavier soils. For drip irrigation, a good portion (45.2%) of the area was suitable (S 2 ), while 25.0% was classified as highly suitable (S 1 ) and only a small portion was almost suitable (N 1, 5.8%) or unsuitable (N 2, 5.8%). In the latter cases, the handicap is caused by the shallow soil depth and bad 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 and drip irrigation, in the Tunisian Oued Rmel catchment using the suggested parametric evaluation. According to the results, drip irrigation suitability provided more irrigable areas as compared to surface irrigation practice due to the topographic (slope), soil (depth and texture) and drainage limitations worked out in the surface irrigation suitability evaluation. Rees and Laffan (2004) studied the land suitability for sprinkle irrigation in the Southwood Processing Complex, in southern Tasmania. In this research, soil properties such as depth, texture, structure, hydraulic conductivity, massive hardpan and stone content, and topographic properties such as slope, land form, surface rock, frequent waterlogging and drainage properties, were considered to be central factors in land suitability evaluation for any sprinkle irrigation practice. Barberis and Minelli (2005) provided land suitability classification for both surface and drip irrigation methods in Shouyang county, Shanxi province, China. The study was carried out using a modified parametric system. The
IRRIGATION BASED ON THE PARAMETRIC EVALUATION APPROACH IN IRAN 549 results indicated that due to the unusual morphology, the area suitable for surface irrigation (34%) is smaller than that used for drip irrigation (62%). The major 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 a central research institute, i.e. 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 the 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 Danling county, Sichuan province, China, using Sys s parametric evaluation system. Drip irrigation was more suitable everywhere than surface irrigation due to the minor environmental impact that it caused. Albaji et al. (2008) investigated land suitability evaluation for surface and drip irrigation in the Shavoor Plain, Iran. The results showed that 41% of the area was suitable for surface irrigation, 50% was highly recommended for drip irrigation and the rest of the area due to soil salinity and drainage problems was not deemed suitable for either irrigation method. Since no similar research has been carried out in Iran (excluding the land suitability evaluation for surface and drip irrigation in the Shavoor Plain), the newness and topicality of the research were important for decision makers in Khuzestan province. The main objective of this research is to evaluate and compare land suitability for surface and drip irrigation methods based on a parametric evaluation system for areas in the plains west of the city of Shush, in Khuzestan province, Iran. MATERIALS AND METHODS The present study was conducted in an area of about 42 000 ha in the plain west of the city of Shush in Khuzestan province, south-west Iran, during 2007. The study area is located 5 km west and north-west of Shush (31.63 31.828 N and 48.95 49.128 E). Average annual temperature and precipitation for the period 1966 2000 were 24.4 o C and 295 mm, respectively. Also, the annual reference evapotranspiration (ETo) of the area is over 2000 mm (Khuzestan Water and Power Authority, 2002). The main water supply to this area is the Karkheh 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. plateau and gravelly alluvial fans, where plateau physiographic units are common. Seven different soil series were found in the area. In order to determine the soil characteristics, the semi-detailed soil survey report of western Shush was used (Khuzestan Water and Power Authority, 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. Also, soil properties such as cation exchange capacity (CEC), percentage of basic saturation (PBS), organic matter (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 for the purposes of irrigation. Based upon the profile description and laboratory analysis, the groups of soils that had similar properties and were located in a same physiographic unit were considered as a series of soils and were classified to form a soil family as per the Keys to Soil Taxonomy (USDA, 2000). Ultimately, seven soil series were selected for the surface and drip irrigation land suitability evaluation. In order to obtain the average soil texture, salinity and CaCO 3 for the upper 150 cm of soil surface, the profile was subdivided into six 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). In order to evaluate land suitability for surface and drip irrigation, the parametric evaluation system was used (Sys et al., 1991). This method is based on the morphological, physical and chemical properties of the soil. Six parameters including slope, drainage properties, electrical conductivity of soil solution, calcium carbonates status, soil texture and depth were also considered and values were assigned to each as per the related tables
550 M. ALBAJI ET AL. Table I. Rating of textural classes for Irrigation Textural class Rating for gravity irrigation Rating for drip irrigation Fine gravel (%) Coarse gravel (%) Fine gravel (%) Coarse gravel (%) <15 15 40 40 75 15 40 40 75 <15 15 40 40 75 15 40 40 75 Clay loam (CL) 100 90 80 80 50 100 90 80 80 50 Silty loam (SiL) 100 90 80 80 50 100 90 80 80 50 Sandy clay loam (SCL) 95 85 75 75 45 95 85 75 75 45 Loam (L) 90 80 70 70 45 90 80 70 70 45 Silty loam (SiL) 90 80 70 70 45 90 80 70 70 45 Silty (Si) 90 80 70 70 45 90 80 70 70 45 Silty clay (SiC) 85 95 80 80 40 85 95 80 80 40 Clay (C) 85 95 80 80 40 85 95 80 80 40 Sandy clay (SC) 80 90 75 75 35 95 90 85 80 35 Sandy loam (SL) 75 65 60 60 35 95 85 80 75 35 Loamy sand (LS) 55 50 45 45 25 85 75 55 60 35 Sandy (S) 30 25 25 25 25 70 65 50 35 35 (Tables I VI), thus, a capability index for irrigation (Ci) was developed as shown in the equation below: Ci ¼ A B 100 C 100 D 100 E 100 F 100 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. Suitability classes are defined by considering the value of the capability indices and presented in Table VII. Table II. Rating of soil depth for irrigation Soil depth (cm) Rating for gravity irrigation Rating for drip irrigation <20 30 30 20 50 60 70 50 80 80 90 80 100 90 100 >100 100 100 Table III. Rating of CaCo 3 for irrigation CaCo 3 (%) Rating for gravity irrigation Rating for drip irrigation <0.3 90 90 0.3 10 95 95 10 25 100 95 25 50 90 80 >50 80 70
IRRIGATION BASED ON THE PARAMETRIC EVALUATION APPROACH IN IRAN 551 Table IV. Rating of salinity for irrigation EC (ds m 1 ) Rating for gravity irrigation Rating for drip irrigation C, SiC, S, SC textures Other textures C, SiC, S, SC textures Other textures <4 100 100 100 100 4 8 90 95 95 95 8 16 80 50 85 50 16 30 70 35 75 35 >30 60 20 65 20 C: Clay, SiC: Silty clay, S: Sand, SC: Sandy clay. Table V. Rating of drainage classes for irrigation Drainage classes Rating for gravity irrigation Rating for drip irrigation SiCL, C, SiC, S, SC textures Other textures SiCL, C, SiC, S, SC textures Other textures Well drained 100 100 100 100 Moderately drained 80 90 100 100 Imperfectly drained 70 80 80 90 Poorly drained 60 65 70 80 Very poorly drained 40 65 50 65 Drainage status not known 70 80 70 80 C: Clay, SiC: Silty clay, S: Sand, SC: Sandy clay. Table VI. Rating of slope for irrigation Slope classes (%) Rating for gravity irrigation Rating for drip irrigation Non-terraced Terraced Non-terraced Terraced 0 1 100 100 100 100 1 3 95 95 100 100 3 5 90 95 100 100 5 8 80 95 90 100 8 16 70 85 80 90 16 30 50 70 60 70 >30 30 50 40 50 Table VII. Suitability classes for the irrigation capability indices (Ci) classes Capability index Definition Symbol >80 Highly suitable S 1 60 80 Moderately suitable S 2 45 59 Marginally suitable S 3 30 44 Currently not suitable N 1 <29 Permanently not suitable N 2
552 M. ALBAJI ET AL. RESULTS AND DISCUSSION In much of the plain to the west of the city of Shush, a surface irrigation system has been applied specifically for field crops to meet the water needs of both summer and winter crops. The major irrigated broad-acre crops grown in this area are wheat, barley, maize, sunflower, fruits including melon and watermelon, and vegetables such as tomato and cucumber. There are very few instances of drip irrigation on large farms in the plain west of Shush. Seven soil series and 32 series phases or land units were derived from the soil study of the area. The land units are shown in Figure 1 as the basis for further land evaluation practice. The soils of the area are of the Inceptisol and Entisol orders. Also the soil moisture regime is Ustic while the soil temperature regime is Hyperthermic (Khuzestan Water and Power Authority, 2003). As shown in Tables VIII and IX, for surface irrigation, the land units coded 4.1, 4.2, 5.1, 6.1, 7.1, 7.2 and 7.3 (9031 ha 21.5%) were highly suitable (S 1 ). Land units coded 2.1, 2.3, 2.4, 4.3, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 6.2, 6.3, 6.4, 6.5, 6.6 and 6.7 (23 472 ha 55.9%) were classified as moderately suitable (S 2 ), and land units coded 2.2, 2.5, 3.1, 3.2, 6.8 and 6.9 (7342 ha 17.5%) were found to be marginally suitable (S 3 ). Only land units coded 1.1, 1.2 and 1.3 (2111 ha 5.0%) were classified as not suitable (N 1 ) for any surface irrigation exercises. By analysing the land suitability maps for surface irrigation (Figure 2) it is evident that a highly suitable area can only be observed in some parts of the plain west of Shush which have deep soil, good drainage, texture and proper Figure 1. Soil map of the study area
IRRIGATION BASED ON THE PARAMETRIC EVALUATION APPROACH IN IRAN 553 Table VIII. Ci values and suitability classes of gravity and drip irrigation for each land unit Codes of land units Gravity irrigation Drip irrigation Ci Suitability classes Ci Suitability classes 1.1 43.8 N 1S 57.0 S 3S 1.2 43.5 N 1S 56.3 S 3S 1.3 30.8 N 1S 32.1 N 1S 2.1 69.9 S 2S 87.5 S 1 2.2 48.0 S 3S 76.8 S 2S 2.3 66.1 S 2S 87.3 S 1 2.4 65.9 S 2S 86.9 S 1 2.5 58.1 S 3tS 77.1 S 2S 3.1 54.0 S 3tS 56.4 S 3S 3.2 53.9 S 3tS 56.4 S 3S 4.1 91.7 S 1 90.2 S 1 4.2 80.7 S 1 85.5 S 1 4.3 78.1 S 2S 82.3 S 1 5.1 84.0 S 1 85.5 S 1 5.2 78.0 S 2S 80.4 S 1 5.3 78.6 S 2S 81.4 S 1 5.4 78.5 S 2S 81.6 S 1 5.5 78.6 S 2S 81.5 S 1 5.6 78.2 S 2S 80.9 S 1 5.7 78.7 S 2S 81.7 S 1 6.1 85.8 S 1 82.5 S 1 6.2 78.0 S 2S 80.4 S 1 6.3 78.4 S 2S 81.1 S 1 6.4 78.1 S 2S 80.6 S 1 6.5 78.7 S 2S 81.7 S 1 6.6 65.2 S 2S 85.4 S 1 6.7 78.7 S 2S 81.3 S 1 6.8 55.7 S 3tS 73.7 S 2S 6.9 58.0 S 3tS 76.9 S 2S 7.1 84.0 S 1 85.5 S 1 7.2 81.9 S 1 83.3 S 1 7.3 77.5 S 1 85.5 S 1 Limiting factors for surface irrigation: s (sandy soil texture), t (slope). Limiting factors for drip irrigation: s (calcium carbonate). Table IX. Distribution of gravity and drip irrigation suitability Suitability Gravity irrigation Drip irrigation Land units Area (ha) (%) Ratio Land units Area (ha) Ratio (%) S 1 4.1,4.2,5.1, 6.1, 7.1,7.2,7.3 9 031 21..5 2.1,2.3,2.4,4.1,4.2,4.3,5.1,5.2 32 505 77.5 5.3,5.4,5.5,5.6,5.7,6.1,6.2,6.3,6.4, 6.5,6.6,6.7,7.1,7.2,7.3 S 2 2.1,2.3,2.4,4.3,5.2,5.3,5.4,5.5, 23 474 55.9 2.2,2.5,6.8,6.9 5 267 12.5 5.6,5.7,6.2,6.3,6.4,6.5,6.6,6.7 S 3 2.2,2.5,3.1,3.2,6.8,6.9 7 342 17.5 1.1,1.2,3.1,3.2, 3 462 8.3 N 1 1.1,1.2,1.3, 2 111 5.1 1.3 724 1.7 Total 41 958 100 41 958 100
554 M. ALBAJI ET AL. Figure 2. Land suitability map for surface irrigation slope. The largest part of the cultivated area in this plain was evaluated as moderately suitable because of its loamy sand soil texture. Other factors such as drainage, depth and slope do not influence the suitability of the area. As seen from the map, the marginally suitable area is located only in some parts of this area due to the loamy sand and sandy soil texture and slope.the current non-suitable lands can be observed only in the north-east of the plain because of the physical limitations such as gravelly sandy soil texture. For almost the entire study area, soil depth, drainage, salinity and CaCO 3 were not considered as limiting factors. In order to verify the possible effects of different management practices, the land suitability for drip irrigation was evaluated (Tables VIII and IX). For drip irrigation, land units coded 2.1, 2.3, 2.4, 4.1, 4.2, 4.3, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 7.1, 7.2 and 7.3 (32 506 ha 77.5%) were highly suitable (S 1 ), while land units coded 2.2, 2.5, 6.8 and 6.9 (5267 ha 12.5%) were classified as moderately suitable (S 2 ). Further, land units coded 1.1, 1.2, 3.1 and 3.2 (3462 ha 8.2%) were found to be slightly suitable (S 3 ). Only the land unit coded 1.3 (724 ha 1.7%) was classified as not being currently suitable (N 1 ) for drip irrigation. In this case (Figure 3), the highly suitable lands covered a big portion of the plain (77.5%). The slope, soil texture, depth, calcium carbonate, salinity and drainage were in good condition. The moderately suitable lands could be observed only in some parts of the plain (north and south-east) due to the medium rate of calcium carbonate. The marginally suitable lands were found in the centre and north-east of the area. The limiting factors for this land were
IRRIGATION BASED ON THE PARAMETRIC EVALUATION APPROACH IN IRAN 555 Figure 3. Land suitability map for drip irrigation sandy soil texture and high rate of calcium carbonate. Finally, only a land unit coded 1.3 was classified as not being currently suitable for drip irrigation systems in the north-east of the plain because of the gravelly sandy soil texture and high rate of calcium carbonate. For the entire study area, slope, soil depth, drainage and salinity were not considered as limiting factors. The mean of the capability index (Ci) for surface irrigation was 70.0 (moderately suitable); also, for drip irrigation it was 77.6 (moderately suitable). The comparison of the capability indexes for surface and drip irrigation (Table VIII) indicated that in land units coded 1, 1 2, 1.3, 2.1, 2.2, 2.3, 2.4, 2.5, 3.1, 3.2, 4.2, 4.3, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.1, 7.2 and 7.3, applying drip irrigation systems was the more suitable than surface irrigation systems. Only in land units coded 4.1 and 6.1 were surface irrigation systems much more suitable than drip irrigation systems. Figure 4 shows the most suitable areas for surface and drip irrigation systems in the plain west of Shush by attention to the capability index (Ci) for both irrigation systems. The results in Table X indicates that a larger amount of the west Shush plain s land will be classified as more suitable for drip irrigation than surface irrigation. Moreover, the main limiting factors in using surface irrigation methods in this area were sandy soil texture and slope, and the main limiting factor in using drip irrigation methods in this area was soil calcium carbonate. Briza et al. (2001) applied a parametric system (Sys et al., 1991) to evaluate land suitability for both surface and drip irrigation in Ben Slimane province, Morocco, and no highly suitable areas were found in the area studied. The
556 M. ALBAJI ET AL. Figure 4. The most suitable map for surface and drip irrigation largest part of the agricultural areas were 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 land suitability evaluation for surface and drip irrigation systems in the province of Larche, Morocco, by using the parametric evaluation systems. The results showed a large difference between applying the two different evaluations. The area not suitable for surface irrigation was 29.2% of the total area and it becomes 9% with drip irrigation; the suitable area was 19% versus 70%. Moreover, the highly suitability was extended on an area of 3.29% in the former case and it became 38.96% in the latter. The main limiting factors were physical limitations such as slope and sandy soil texture. Land units coded 2.1, 2.3, 2.4, 4.3, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 6.2, 6.3, 6.4, 6.5, 6.6 and 6.7 (23 472 ha 55.9%) improved from moderately suitable (S 2 ) to highly suitable (S 1 ), and land units Table X. Comparison of the land units for both surface and drip irrigation methods Improvement of suitability classes from gravity to drip irrigation Land units Area (ha) Ratio (%) From S 2 to S 1 2.1,2.3,2.4,4.3,5.2,5.3,5.4,5.5, 23 474 55.9 5.6,5.7,6.2,6.3,6.4,6.5,6.6,6.7 From S 3 to S 2 2.2,2.5,6.8,6.9 5 267 12.5 From N 1 to S 3 1.1,1.2 1 387 3.3 Total 30 128 71.8
IRRIGATION BASED ON THE PARAMETRIC EVALUATION APPROACH IN IRAN 557 coded 2.2, 2.5, 6.8 and 6.9 (5267 ha 12.5%) were developed from marginally suitable (S 3 ) to moderately suitable (S 2 ). In addition, land units coded 1.1 and 1.2 (1387 ha 3.3%) improved from currently not suitable (N 1 )to marginally suitable (S 3 ). The results demonstrate that a large expanse of the plain west of Shush (30 128 ha 71.8%) is classified as being more suitable for drip irrigation than surface irrigation (Tables I VII). CONCLUSIONS Details are given for the analysis of field data to compare the suitability of the land for surface and drip irrigation systems. The analysed parameters included soil and land characteristics. In this research, the land is not being improved. The lands are just being ranked according to defined criteria (Tables I VII) to establish which irrigation method (surface or drip) is best suited to the characteristics of the land. That is, the land suitability for irrigation methods (surface or drip) is being compared while taking into consideration the characteristics of the land. The results obtained showed that drip irrigation is more suitable than surface irrigation for most of the study area. The major limiting factors for the surface irrigation method were sandy soil texture and slope, however for drip irrigation methods soil calcium carbonate was the restricting factor. Comparison of the maps indicates that the highly suitable lands are much wider for drip irrigation and include a large part of the plain west of Shush. Drip irrigation is definitely a means for improving the irrigation practices on sandy soils and steep slopes. Of course, in the application of this sort of irrigation, a change of agricultural management would be necessary. Horticulture and mulched crops should replace extensive crops such as wheat, barley, etc. actually adopted. This is the same strategy that has been followed by large companies currently operating in the area and which can ensure a higher income for the local farmers. Such a management change would require the availability of greater initial investments to farmers (different credit conditions, for example) as well as a different storage and market organization. Due to the scarce water supply in this arid and semi-arid climate, maximizing water use efficiency is critical. A shift from surface irrigation to high-tech irrigation technologies, e.g. drip irrigation systems, may yield significant water savings. ACKNOWLEDGEMENTS The authors would like to thank the Research and Standards Office for Irrigation and Drainage Networks of KWPA for their financial support and assistance (NRP-8615853). REFERENCES Albaji M, Landi A, Brommand Nassab S. 2008. Land suitability evaluation for surface and drip irrigation in Shavoor Plain. Journal of Applied Sciences 8(4): 654 659. Barberis A, Minelli S. 2005. Land evaluation in Shouyang County, Shanxi Province, China. The 25 th Professional Master Course, 8 November 2004-23 June 2005. IAO: Florence, Italy; 49 58. Bazzani F, Incerti F. 2002. Land evaluation in the Province of Larache, Morocco. The 22 nd Professional Msster Course Geomatics and Natural Resources Evaluation. 12 November 2001-21 June 2002. IAO: Florence, Italy; 67 80. Bienvenue JS, Ngardeta M, Mamadou K. 2003. Land evaluation in the Province of Thies, Senegal. The 23 rd Professional Master Course. Geomatics and Natural Resources Evaluation. 8 November 2002-20 June 2003. IAO: Florence, Italy; 65 70. Bond WJ. 2002. Assessing site suitability for an effluent plantation. In Soil Physical Measurement and Interpretation for Land Evaluation, McKenzie NJ, Cressswell H, Coughlan K (eds). CSIRO Publishing: McKenzie Australia; 351 359. Briza Y, Dileonardo F, Spisni A. 2001. Land evaluation in the Province of Ben Slimane, Morocco. The 21 st Professional Master Course. Remote Sensing and Natural Resource Evaluation. 10 November 2000-22 June 2001. IAO: Florence, Italy; 62 67. Conway K. 2003. Local solutions in the global water crisis (http://www.idrc.ca). Dengiz O. 2006. A comparison of different irrigation methods based on the parametric evaluation approach. Turkish Journal of Agriculture and Forestry 30: 21 29.
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