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Development of a land use suitability model for saffron (Crocus sativus L.) cultivation by multi-criteria evaluation and spatial analysis
Ecological Engineering 106 (2017) 140–153
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Development of a land use suitability model for saffron (Crocus sativus L.) cultivation by multi-criteria evaluation and spatial analysis Fahimeh Maleki, Hossein Kazemi ∗ , Asieh Siahmarguee, Behnam Kamkar Department of Agronomy, Faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural Resources (GUASNR), PO Box 49138-15739, Gorgan, Iran
a r t i c l e
i n f o
Article history: Received 4 February 2017 Received in revised form 6 May 2017 Accepted 29 May 2017 Keywords: GIS Land use suitability MCA Saffron
a b s t r a c t The principle purpose of agriculture land use feasibility is to predict the potentials and limitations of land for plant production. The present study provides a model to assess land suitability for cultivation of saffron (Crocus sativus L.) in Azadshahr Township, located in the north of Iran. The goal is to provide a special methodological approach to assess land use suitability for saffron cultivation in Iran and other similar regions. This suitability model integrated the perspectives of local saffron experts using an analytic hierarchy process (AHP) from Multi-Criteria Analysis (MCA) to determine the criteria weights such as climate, soil, and topographic used in land use suitability analysis. In the present model, 21 ecological variables were selected for saffron land suitability analysis and thematic maps were developed for each of the parameters in Geographic Information System (GIS).The results showed that the soil and climatic variables have a major role in the development of saffron cultivation. The final land suitability map indicated that the most suitable areas (1743.25 ha) for growing saffron were located in the south and east of Azadshahr township. Also, the largest parts of this region were classified as currently unsuitable (8543.72 ha) and permanently unsuitable (12,450.64 ha) zones. These classes were located in the northern, central and northeastern parts of Azadshahr. The results highlighted that these areas face with limitations for development of saffron cultivation. According to this result, the main limiting features in these classes were high rainfall in the reproductive stage of saffron (25–0 mm), inappropriate slope (12%<), high relative humidity, low annual rainfall, high elevation in north (2700 m<), and unsuitable classes of soil texture. These results can be useful for decision makers and farmers as a planning support tool in saffron cultivation. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Saffron (Crocus sativus L.) is a flowering plant belonging to the Iridaceae family(Gresta et al., 2016). It is the world’s most expensive crop among aromatic and medicinal plants (Turhan et al., 2007) and the most strategic crops in Iran. Saffron cultivation dates back to ancient times (2500–1500 BCE) and probably has originated from Iran and Greece, then became prevalent in India, China, the Mediterranean region, eastern Europe and other regions (Grilli Caiola et al., 2004; Negbi, 1999). In Iran, saffron is one of the most important cash crops and the main crop of smallholders who are farming in water-deficient regions (Mashayekhi et al., 2006; Mollafilabi, 2006). Generally, Iran is the’ world’s biggest producer of saffron. Iran’s share of global production is 90%, while the total
∗ Corresponding author. E-mail addresses: [email protected] (F. Maleki), [email protected] (H. Kazemi), [email protected] (A. Siahmarguee), [email protected] (B. Kamkar). http://dx.doi.org/10.1016/j.ecoleng.2017.05.050 0925-8574/© 2017 Elsevier B.V. All rights reserved.
cultivation area of saffron in Iran is 60 percent of the entire world. Other countries such as Greece, Spain, Morocco, India, Switzerland, Italy, Argentina, Azerbaijan, and Turkey are next in line (Fernandez Pérez and Escribano Martinez, 2000). Saffron has long been cultivated as a medicinal and spice plant. It has been also used for food (natural dye, flavor and aroma) since ancient times (Rios et al., 1996; Basker and Negbi, 1983; Rios et al., 1996; Gresta et al., 2009). Recently, its biological roles (especially those based on cytotoxic, anti-carcinogenic and antitumor properties) in medicine has been highlighted (Abdullaev and Frenkel, 1999; Fernandez Pérez and Escribano Martinez, 2000). Today, saffron is widely used as a condiment for different foods such as rice dishes, pastas, soups, cakes, saffron bread and numerous sweets. Also, it can be used as a refreshing drink. The plant is further used for the production of natural food colors, flavor enhancers, as well as pharmaceutical products (Pérez, 1995; De Juan et al., 2009). Reproductive, vegetative, and dormancy are the main typical phenological stages of saffron (De Juan et al., 2009). In Iran, saffron flowering occurs during the autumn followed by a vegetative stage
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throughout the winter and formation of replacement corms at the base of shoots. At the beginning of dry season, the leaves senesce and wither, and the bulbs go into dormancy (Wilkins, 1985; Botella et al., 2002). Flowering and yield of this plant are directly related to ecological conditions and field management (Yarami et al., 2011). Although this plant is grown in environments with diverse climatic conditions, few landscape-scale studies have been conducted to determine suitable areas for its cultivation. Precise and comprehensive evaluation of suitability based on climatic, soil, topography, and landforms suitability for a given land use is referred as land use suitability assessment. The Food and Agricultural Organization (FAO, 1976) proposed a framework for evaluating the suitability of lands for crops in terms of a suitability rating ranging from highly suitable to unsuitable. This framework is based on soil, topography, features, and crop characteristics. Wang (1997) developed a model for land suitability evaluation of tropical crops in three Asian cities through the Geographic Information System (GIS) media. In another study, Chen et al. (2010) investigated tobacco ecological suitability in Henan Province of China based upon an integrated GIS-hierarchy analysis method. Their results showed that highly suitable regions for tobacco cultivation were located in the western and southern parts of this province. Many works have been also established on GIS-Multi-Criteria Analysis (MCA). These integrated GIS-MCA techniques have been considered within a large number of disciplines using the suitable ˜ et al., 2013). Using MCA, alternative options and criteria (Perpina preferences of land use could be determined. For this goal, suitable objectives and related attributes and criteria should be identified ˜ et al. (Liu et al., 2007). Through the MCA-GIS analysis, Perpina (2013) showed that the most suitable areas for biomass production in Valencia (Spain) were located in the vicinity of residential zones. In this study, physiographic characteristics, involved crops, vegetation state, potential demand, and transport-related cost were the most important factors determining the biomass production. Chen et al. (2001) integrated GIS and MCE in order to assess natural risks in China. They presented three different evaluation methods for the same analysis and compared the results for the purpose of decisionmaking. In another research, Collins et al. (2001) reviewed the application of GIS-based methods for land use suitability analysis in the US. These methods were classified as follows: computerassisted overlay mapping, MCA, and artificial intelligence method. Furthermore, Yalew et al. (2016) developed a web-based GIS-MCDA framework for agricultural land suitability assessment (AgriSuit), based on remote sensing, GIS techniques, and Google Earth Engine (GEE). Based on a fuzzy logic based land suitability evaluation procedure, Feng et al. (2017) assessed the suitability of marginal lands in Upper Mississippi River Basin (UMRB) for three promising biofeedstock crops, i.e. switchgrass, Miscanthus and hybrid poplar. The results showed that 60% of marginal lands in UMRB were moderately to highly suitable for growth of the targeted biofeedstock crops. Moreover, Rhebergena et al. (2016) evaluated land suitability for oil palm production in Ghana and found that the major climatic factor limiting suitability for oil palm production is the annual water deficit. In Iran, Kazemi et al. (2016) developed a land evaluation model for faba bean cultivation using geographic information system and multi-criteria analysis in Gonbad-Kavous region (Golestan Province). Their results revealed that the share of highly suitable, moderately suitable, and marginally suitable lands for faba bean cropping were 23.48% (48,354.5 ha), 25.38% (52,237.37 ha) and 25.03% (51,522.85 ha) of the study area, respectively; in addition, the share of unsuitable lands was just 26.11% of total agricultural lands. Nasrollahi et al. (2017) also demonstrated that high EC, low organic matter, and low annual rainfall are the key limiting vari-
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ables to perform ley-farming systems in the Aq-Qala township, in the north of Iran. Saffron cultivation has been extensively favored in the past few years. The high tendency to develop the culture of this plant is due to its high economic value, low input requirement, and its conformity to small size arable lands. For these reasons, cultivation of this plant is developed in different provinces of Iran such as Golestan, Isfahan, Kurdistan, among others. Most of the information available about this plant in Iran is restricted to farm management methods and their related effects on the qualitative and quantitative traits and little is known about the land suitability for cultivation of saffron in Iran. Therefore, this study aimed to investigate the feasibility of saffron cultivation in Azadshahr Township, Golestan province (north of Iran) using an integrated GIS-MCA framework. 2. Material and method 2.1. Study area The study was carried out in Azadshahr township of Golestan Province, Iran, with a warm, temperate and mountainous climate during 2014–2015 (Fig. 1). The total study area covers approximately 872 km2 . The area coordinate ranges from 36◦ 48.2 to 37◦ 11.5 N latitudes and 55◦ 3.7 to 55◦ 38.3 E longitudes with an altitude range of 92 m to 2800 m a.s.l, respectively. The average annual temperature and precipitation in the region are 378 mm and 17.7 ◦ C, respectively (Golestan Province Government, 2009). 2.2. Parameters used in the suitability analysis 2.2.1. Climatic data Annual rainfall, average temperature, rainfall, maximum and minimum temperature for reproductive, dormancy, and growth stages, sunshine hours, relative humidity, and number of frost days were considered as climatic factors affecting saffron-land suitability. For this purpose, thematic maps for all aforementioned factors were provided in GIS (ArcGIS 10.0 software). The recorded climatic data from 36 weather stations within the target study area and the surrounding areas were used. All data from 1995 to 2014 were averaged. Some interpolation methods, e.g. Local Polynomial Interpolation (LPI), Ordinary Kriging (OK), and Inverse Distance Weighted (IDW), were selected to provide a raster-based spatial distribution of climatic parameters (Table 1). Interpolated or reclassified layers of these parameters are presented in Figs. 2–4. 2.2.2. Soil data Soil data (i.e. pH, EC, and texture classes) were sampled from 200 profiles in Azadshahr Township and adjacent regions. Soil samples were randomly taken on Oct 2015. Samples were taken at depths of 0–30 cm and air-dried to remove stones and coarse plant residues. Three samples from each sampling site were collected from the surface soil layer and were thoroughly mixed; one sample was ground to pass a sieve and subsequently stored in plastic bags prior to analysis. The spatial distribution of soil characteristics on studied lands was mapped in ArcGIS using aforementioned interpolation methods for climatic factors (Table 1). Soil-related maps of the study area are shown in Fig. 5. 2.2.3. Topographic data A 40 × 40 m resolution Digital Elevation Model (DEM), along with required updated political boundaries, were obtained from the Natural Resources Organization of Golestan province and used to provide topographic data. For this, some topographic characteristics such as slope, aspect, and elevation were mapped using surface analysis functions in GIS (Fig. 6).
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Fig. 1. Location of the study area in Azadshahr township, Golestan province, Iran.
Table 1 The best-fitted method/models for interpolation of some variables in agricultural lands of Azadshahr township, Iran. Variable
Method/model
RMSE
Variable
Method/model
RMSE
Annual rainfall Rainfall of reproductive stage Rainfall of growth stage Annual average temperature Maximum temperature of reproductive stage Maximum temperature of growth stage Maximum temperature of dormancy stage
OK − Exponential OK − Circular OK − Circular LPI − 3 OK − Stable
108.38 14.08 106.65 0.325 1.37
Minimum temperature of reproductive stage Minimum temperature of growth stage Minimum temperature of dormancy stage Sunshine hours Relative humidity
LPI − 1 LPI − 1 LPI − 2 LPI − 1 LPI − 1
0.82 0.77 0.70 349 5.74
OK − Spherical
0.57
Number of frost days
LPI − 1
5.79
OK − Stable
1.33
pH
IDW − 1
0.163
EC
OK − Exponential
0.474
OK: Ordinary Kriging, LPI: Local Polynomial Interpolation, IDW; Inverse Distance Weighted, RMSE; Root Mean Square Error.
2.3. Model description 2.3.1. Analytical hierarchy process (AHP) A nine-point scale-based AHP hierarchical model (Saaty, 1980; Table 2) including objectives, criteria, sub-criteria, and alternatives
was constructed to weight affecting factors. The objective was set as the land use suitability analysis for saffron cropping in Azadshahr Township, and the criteria included soil, climatic, and topographic traits. Twenty saffron experts were invited to fill a pairwise comparison table of the mentioned factors to determine the relative
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Fig. 2. Rainfall (mm) maps in Azadshahr township, Iran; a: Annual rainfall, b: Rainfall in reproductive stage, c: Rainfall in growth stage.
importance of the criteria (raw data for AHP model). The final step of AHP, the weight of factors for land use suitability, was obtained from local experts through a pairwise comparisons statistical analysis in Expert Choice Software (version 2001).The obtained weights made it possible to allocate a suitable value for each land mapping
unit. The parameter that is used to check accuracy of comparisons is called the Inconsistency Ratio (IR).This ratio is a measure of low variation allowed and must be less than 10% (Saaty, 2000; Trong Due, 2006).
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Fig. 3. The maps of, a: Relative humidity, b: Sunshine hours, c: Number of frost days in Azadshahr township, Iran.
2.3.2. Land suitability analysis performance For all raster layers (with 100 × 100 m resolution), spatial references were selected as UTM (WGS1984-Zone 40 N). Query analysis was used to extract agricultural lands from all other land uses
(i.e. bare lands, industrial and residential areas, forests, rangelands, water bodies, and impervious lands). In order to follow the main goal, i.e. land suitability assessment for saffron cultivation in Azadshahr Township, the reclassified lay-
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ers (based on 4 categorized classes) were overlaid. The base raster layers were reclassified according to the compliance of all involved layers of different factors with the ecological requirements of saffron; the requirements had been determined via a comprehensive literature review and asking local experts’ opinions. Graphical representation of the land suitability evaluation process is presented in Fig. 7.
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A crucial step of land suitability assessment for crop production is weighting all the parameters affecting the land suitability (Zhang et al., 2015). For this purpose, AHP-acquired weights were assigned to the criteria. Then, land suitability was carried out by the Weighted Overlay Technique (WOT) in GIS. Finally, the land suitability map for this plant was classified into five categories, including highly suitable (S1, the land unit is very favorable for saf-
Fig. 4. The temperature maps (◦ C) in Azadshahr township, Iran; a: Minimum temperature of dormancy stage, b: Maximum temperature of dormancy stage, c: Minimum temperature of growth stage, d: Maximum temperature of growth stage, e: Minimum temperature of reproductive stage, f: Maximum temperature of reproductive stage, g: Annual average temperature.
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Fig. 4. (Continued)
fron production with no limitations), moderately suitable (S2, the land unit is almost favorable with some limitations), marginally suitable (S3, the land unit is marginally desirable with severe limitations), currently unsuitable (N1) and permanently unsuitable (N2). Unsuitable land (N1 and N2) was supposed to have severe limitations, which could rarely or never be overcome by economic use of inputs or management practices (Zhang et al., 2015; Ghafari et al., 2000; Nasrollahi et al., 2017).
3. Results and discussion 3.1. Results of AHP analysis The AHP results based on experts’ pairwise comparisons indicated that the most important criteria, according to their specific weighting, were climate (0.696), soil (0.215) and topography (0.089). Also, among the climate criteria, temperature and rela-
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Fig. 5. The soil properties maps of Azadshahr township, Iran; a: EC, b: pH, and c: Texture.
tive humidity had the highest and lowest weights, respectively. It should be noted that among the temperature sub-criteria, minimum and maximum temperatures of reproductive period had major roles in describing the suitable areas for saffron cultivation (Table 3). In a similar study, AHP was introduced as the best method for land suitability analysis of tobacco production in Shan-
dong province of China (Zhang et al., 2015). Besides, the results of Nasrollahi et al. (2017) demonstrated that climate, soil, and topography were the most important criteria based upon AHP weights for ley-farming performance. Also, among the climate criteria, rain and minimum temperature had the highest and lowest weights, respectively. Based on the results of the experts’ opinions, final weights
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Fig. 6. Topographic maps of Azadshahr township, Iran; a: Slope, b: Elevation and c: Aspect slope.
of 0.150 and 0.131 were assigned to sunshine hours and number of frost days in relation to saffron crop production, respectively (Table 3).
The MCA has been used effectively for the development of decision support systems which are able to rank decision options by simultaneously considering multiple criteria relating to range of
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Table 2 Criteria for delineating land suitability of saffron in Azadshahr region, Iran. Highly suitable (S1)
Moderately suitable (S2)
Marginally suitable (S3)
Currently unsuitable (N1)
Permanently unsuitable (N2)
Climatic factors Annual rainfall (mm)
300–400
180–240
120–180
<120
Rainfall of reproductive period (mm) Rainfall of growth period (mm) Annual average temperature (◦ c) Maximum temperature of reproductive period (◦ c) Maximum temperature of growth period (◦ c) Maximum temperature of dormancy (◦ c) Minimum temperature of reproductive period (◦ c) Minimum temperature of growth period (◦ c) Minimum temperature of dormancy (◦ c) Sunshine hours Number of frost days Relative humidity (%)
17–20 >58 >14.5 >23 23.5 35–40 >9 >−14 >12 >3100 <20 40–50
240–300 and >400 14–17 46–58 11.5–14.5 18.5–23 19–23.5 28–35 7–9 (−18) to (−14) 9.5–12 2480–3100 20–30 50–60
20–25 37–46 9.5–11.5 14.5–18.5 15–19 >40 5–7 (−22) to (−18) 7.5–9.5 1984–2480 30–40 60–70
25–30 30–37 7.5–9.5 11.5–14.5 12–15 22–28 5 (−26) to (−22) 6–7.5 1587–1984 40–50 70–80
>30 <30 >7.5 <11.5 <12 <22 <5 <−26 <6 <1587 >50 >80
2–5 East and northeast 1200–1400
5–12 Southwest and northwest 900–1200
12–17 West and south
>17 –
Elevation (m)
0–2 South, southeast and no direction 1400–2300
700–900 2300–2700
<700 >2700
Soil factors EC (dS m−1 ) pH
<2 7–8
2–4 6.5–7
4–8 8–8.5
8–12 6–6.5
Soil texture
Sandy loam, loam
Clay loam, silty loam, silty clay loam
Clay, clay sandy
Silty clay
>12 <6 >8.5 Other classes
Feature
Topography factors Slope (%) Slope aspects
Fig. 7. Schematic diagram of land use suitability for saffron in Azadshahr region, Iran.
planning and natural resource management issues (Graymore et al., 2015). The superiority of AHP in group decision-making was compared to other techniques proposed by Lai et al. (2002). In another
study, Mbugwa et al. (2015) highlighted that using GIS along with spatial decision support systems (SDSS) procedures can be beneficial in land use suitability.
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Table 3 The weights of criteria and sub-criteria in land suitability analysis of saffron in Azadshahr region, Iran. Criteria
Weight
Rank
Sub- criteria 1
Weight
Sub- criteria 2
Weight
Climate
0.696
1
Temperature
0.434
Annual average temperature Minimum temperature
0.516 0.288
Maximum temperature
Soil
0.215
2
Topography
0.089
3
Rainfall
0.199
Sunshine hours Number of frost days Relative humidity EC Texture pH Elevation Slope aspects Slope
0.150 0.131 0.086 0.441 0.323 0.236 0.510 0.252 0.238
Rainfall of growth stage Rainfall of reproductive stage Annual rainfall
0.197
Sub-criteria 3
Weight
Minimum temperature of reproductive stage Minimum temperature of growth stage Minimum temperature of dormancy Maximum temperature of reproductive stage Maximum temperature of dormancy Maximum temperature of growth stage
0.538 0.286 0.176 0.448 0.304 0.248
0.415 0.328 0.248
Inconsistency 0.03 Ratio (IR)
3.2.1. Highly suitable zone The area with highly suitable degree was identified as the zone that has highly valuable for saffron production. This zone covered an area of 1743.25 ha (5.48% of total arable area) (Table 4). Highly suitable class was characterized by annual rainfall of 300–400 mm during the crop growth cycle, elevation range of 1400–2300 m, slope of 0–2%, soil pH level range of 7–8, EC < 2 dS m−1 , reproductive stage rainfall of 17–20 mm, number of frost days <20, relative humidity of 40–50%, annual average temperature >14.5 ◦ C, and soil texture classes of sandy loam and loam. Based on optimal environmental conditions, it was found that some of lands situated in the south of Azadshahr are in the highly suitable state (Fig. 9). From a climatic viewpoint, some authors reported that the optimal climatic conditions for saffron species are rainy autumns, mild winters, and warm summers (Mollafilabi, 2006). Temperature and soil water content certainly play a vital role in saffron flowering induction and flower appearance (Molina et al., 2005; Yarami and Sepaskhah, 2015). Moreover, saffron has low water requirements and is typically cultivated under rain-fed conditions because it is well adapted to the rainfall pattern of diverse Mediterranean regions (Alizadeh, 2006).
Fig. 8. Land suitability map for saffron cultivation in Azadshahr township, Iran.
3.2. Land suitability Fig. 8 presents the final map of land suitability for saffron cultivation in Azadshahr Township. The comparison of intentions and possible achievement indicated that the study area can be divided into different classes with diverse capacities for saffron cultivation, which includes highly suitable potential, moderately suitable, marginally suitable, and unsuitable. The last class was further divided into two zones, i.e. currently unsuitable and permanently unsuitable.
3.2.2. Moderately suitable (S2) zone The final map of land suitability showed that less than 10.5% of agricultural lands for saffron production are situated in moderately suitable class (Table 4). These regions are in parts of the south and east of the township (Fig. 10). In general, climatic factors have an important role in the saffron cultivation expansion. For example, a frost occurrence in the range of sowing and rosette development months can be very harmful to saffron and cause production losses (Gasolet al., 2011). In this regard, Benschop (1993) concluded that temperature is the most important ecological variable controlling growth and flowering of Crocus species. This is done by affecting enzyme activity in plant metabolism. Principally, moderately suitable class was characterized by annual rainfall of 240–300 mm and >400 mm, reproductive stage rainfall of 14–17 mm, annual average temperature of 11.5–14.5 ◦ C, elevation levels between 1200 and 1400 m, slope of 2–5%, soil pH range of 6.5–7, 20–30 frost days, rel-
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Table 4 The distribution of land suitability degree for saffron cropping in Azadshahr Township, Iran. Suitability degree
Area (ha)
Zone area/total agricultural lands area (%)
Zone area/total area of township (%)
Highly suitable (S1) Moderately suitable (S2) Marginally suitable (S3) Currently unsuitable (N1) Permanently unsuitable (N2) Total
1743.25 3197.30 5895.00 8543.72 12450.64 31829.91
5.48 10.04 18.52 26.84 39.12 100
2.03 3.72 6.85 9.93 14.47 37
Fig. 9. Highly suitable classes for saffron cropping in Azadshahr township, Iran.
ative humidity of 50–60%, and soil texture classes of clay loam, silty loam, and silty clay loam. The optimum annual sunshine hours for saffron are 2480–3100 h per year. According to the recorded sunshine hours in the studied area (Fig. 3b), the number of sunshine hours in the central and southern parts of the study area is not restrictive.
3.2.3. Marginally suitable (S3) zone Marginally suitable (S3) zone was located in the center and southeast of Azadshahr Township (Fig. 11). This class is characterized by reproductive period rainfall of 20–25 mm, growth period rainfall of 37–46 mm, annual rainfall of 180–240 mm, annual average temperature of 9.5–11.5 ◦ C, slope of 5–12%, EC of 4–8 dS m−1 , and 30–40 frost days. According to the generated agricultural land use suitability map, it was observable that 18.52% (5895 ha) of this region is marginally suitable (S3) for saffron production (Table 4). Saffron must be planted in areas where relative humidity is low. Areas where the relative humidity exceeds 50% are unsuitable for the production and growth of saffron. In this study, it was found that the northern part of the study area with high relative humidity is unsuitable for saffron cultivation, while the southern part, which is in the vicinity of Semnan province (with arid and semiarid climate), poses no restrictions for saffron cultivation in terms of relative humidity.
Fig. 10. Moderately suitable classes for saffron cropping in Azadshahr township, Iran.
3.2.4. Currently unsuitable (N1) and permanently unsuitable (N2) zones The results of land suitability indicated that the largest parts of the surveyed region were classified as currently unsuitable (8543.72 ha) and permanently unsuitable (12,450.64 ha) (Table 4). These classes are located in the northern, central and northeastern parts of Azadshahr Township (Fig. 12). The results of this research indicated that high rainfall in reproductive stage (25–30 mm), slope >12%, low annual rainfall, high elevation (>2700 m), and unsuitable class of soil texture were the main limiting factors in these classes. Elevation was one of the most important determinants. This area is between 700 and 2700 m of altitude and meets mountains and valleys in central and south. The results indicate that saffron is associated with more damage caused by critical temperatures and frost at higher altitudes compared to lowlands. Also, in a part of the studied zone, soil texture was unsuitable. Basically, the bed of saffron growth or soil texture/structure significantly affects flower and corm yield. Gresta et al. (2009) concluded that the best medium for saffron cultivation is a sandy soil with manure mixture. Furthermore, Behzad et al. (1992) reported that organic matter and cow manure applications improved soil fertility of saffron fields. When cow manure is applied before saffron planting, soil water retention increases and soil structure improves in irrigated conditions. In another study, the use of organic materials, e.g. composted cattle manure, was considered for sustainable production in saffron fields (Koocheki and Seyyedi, 2015).
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ing the quality of the lands under cultivation in Shandong Province, China. They used five indicators, i.e. slope, light-temperature potential productivity, Normalized Difference Vegetation Index (NDVI), Temperature-Vegetation Dryness Index (TVDI), and yield. Their results showed that the quality of cultivated lands in this region decreased from the southwest to the northeast. 4. Conclusion
Fig. 11. Marginally suitable classes for saffron cropping in Azadshahr township, Iran.
The results also revealed that in the central and southern parts, slope acts as a limiting factor for cultivation of saffron in the study area. From a geomorphological viewpoint, slope in Azadshahr Township varies, decreasing from the south to the north (Fig. 6). Basically, agricultural operations and machinery were assumed not to work correctly on slopes exceeding 10%. Furthermore, in steep terrains, soil erosion losses will increase (Gasolet al., 2011). Zhen et al. (2012) adopted an appropriate procedure for evaluat-
The results of this research can be valuable for future decisions about the cultivation of saffron and can lead to a reduction in saffron expansion into high-risk areas in the investigated region. The present study provided a methodological approach to assess the suitability of agricultural lands for saffron cropping in Iran. Saffron land suitability analysis is a prerequisite to achieve optimum utilization of available environmental resources for sustainable production. According to experts’ opinions, higher weights were assigned to the climate than to all other criteria. The results also demonstrated that climatic conditions and soil-related characteristics play the main role in saffron expansion. Analysis of suitability showed that 5.48% (1743.25 ha) of total land in the study areas was high suitable for saffron production, 10.04% (3197.30 ha) were moderately suitable, and 65.96% of the study area (20,994.36 ha) were located in unsuitable zone. These results lead to the conclusion that rainfall in reproductive stage, slope, high relative humidity, annual rainfall, frost days, elevation, and soil texture are the most significant variables affecting the sustainability of the saffron production. FAO recommended an approach for land suitability evaluation for plants in terms of suitability range from highly suitable to unsuitable based on climatic and terrain data and soil properties crop-wise (FAO, 1976). In this case, the MCA method is particularly applicable when large numbers of criteria are involved (Liu et al., 2007). Our results stated that an integrated GIS-MCA approach is a practical and applicable method for determining land suitability for saffron crop. These results could help decision-makers to determine the quality of croplands for saffron as a decision and
Fig. 12. Currently and permanently unsuitable classes for saffron cropping in Azadshahr township, Iran.
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planning support tool. We recommend similar studies using other soil parameters such as organic matter, phosphorus, potassium, magnesium, and calcium contents. Acknowledgments We thank the Gorgan University of Agricultural Sciences and Natural Resources (GUASNR) and Jihad-e-Agriculture Management of Azadshahr Township (Iran) that supported this research. Also, we sincerely thank Mr. Sadin for his kind helps. References Abdullaev, F.I., Frenkel, G.D., 1999. Saffron in biological and medical research. In: Negbi, M. (Ed.), Saffron: Crocus sativus L. Harwood Academic Publishers, Australia, pp. 103–114. Alizadeh, A., 2006. Irrigation. In: Kafi, M., Koocheki, A., Rashed, M.H., Nassiri, M. (Eds.), Saffron (Crocus sativus) Production and Processing. Science Publishers, Enfield, pp. 79–90. Behzad, S., Razavi, M., Mahajeri, M., 1992. The effect of various amounts of ammonium phosphate and urea on saffron production. Acta Hortic. 306, 337–339. Benschop, M., 1993. Crocus. In: De Hertogh, A., Le Nard, M. (Eds.), The Physiology of Flower Bulbs. Elsevier Science Publishers, Amsterdam, The Netherlands, pp. 257–272. Botella, O., de Juan, A., Mun˜oz, M.R., Moya, A., Lo´ıpez, H., 2002. Descripcio´ınmorfolo´ıgica y cicloanualdelazafra´ın (Crocus sativus L.). Cuadernos de Fitopatologı´ıa 71, 18–28. Chen, H.S., Liu, G.S., Yang, Y.F., Ye, X.F., Shi, Z., 2010. Comprehensive evaluation of tobacco ecological suitability of Henan province based on GIS. Agric. Sci. China 9 (4), 583–592. Collins, M.G., Steiner, F.R., Rushman, M.J., 2001. Land-use suitability analysis in the United States: historical development and promising technological achievements. J. Environ. Manage. 28 (5), 611–621. De Juan, J.A., Corcoles, H.L., M-Munoz, R., Picornell, M.R., 2009. Yield and yield components of saffron under different cropping systems. Ind. Crops Prod. 30, 212–219. FAO, 1976. A Framework for Land Evaluation Publication Division. Food and Agriculture Organization of the United Nations, Rome. Feng, Q., Chaubey, I., Engel, B., Cibin, R., Sudheer, K.P., Volenec, J., 2017. Marginal land suitability for switchgrass, Miscanthus and hybrid poplar in the Upper Mississippi River Basin (UMRB). Environ. Model. Softw. 93, 356–365. Fernandez Pérez, J.A., Escribano Martinez, J., 2000. Biotecnologia del azafran. Ediciones de la Universidad de Castilla-La Mancha, Cuenca, Espana. Ghafari, A., Cook, H.F., Lee, H.C., 2000. Integrating climate, soil and crop information: a land suitability study using GIS. In: 4th International Conference on Integration GIS and Environmental Modeling (GIS/EM4), 2–8 September, Banff, Alberta, Canada. Golestan Province Government, 2009. Land Use Planning of Golestan Province, 2. Hamoon Jointstock Company and Golestan Province Government, pp. 239–515. Gresta, F., Avola, G., Lombardo, G.M., Siracusa, L., Ruberto, G., 2009. Analysis of flowering: stigmas yield and qualitative traits of saffron (Crocus sativus L.) as affected by environmental conditions. Sci. Hortic. 119, 320–324. Gresta, F., Santonoceto, C., Avola, G., 2016. Crop rotation as an effective strategy for saffron (Crocus sativus L.) cultivation. Sci. Hortic. 211, 34–39.
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Grilli Caiola, M., Caputo, P., Zanier, R., 2004. RAPD analysis in Crocus sativus L. accession and related crocus species. Biologia plantarum 48, 375–380. In: Gram JCS, 1996. saffron (Crocus sativus L.). Trop. Sci. 11, 1771–1784. Kazemi, H., Sadeghi, S., Akinci, H., 2016. Developing a land evaluation model for faba bean cultivation using geographic information system and multi-criteria analysis (A case study: Gonbad-Kavous region, Iran). Ecol. Indic. 63, 37–47. Koocheki, A., Seyyedi, S.M., 2015. Relationship between nitrogen and phosphorus use efficiency in saffron (Crocus sativus L.) as affected by mother corm size and fertilization. Ind. Crops Prod. 71, 128–137. Lai, V., Wong, B.K., Cheung, W., 2002. Group decision making in a multiple criteria environment; a case using the AHP in the software selection. Eur. J. Oper. Res. 137 (1), 134–144. Liu, Y., Lv, X., Qin, X., Guo, H., Yu, Y., Wang, J., Mao, G., 2007. An integrated GIS-based analysis system for land-use management of lake areas in urban fringe. Landsc. Urban Plan. 82, 233–246. Mashayekhi, K., Soltani, A., Kamkar, B., 2006. The relationship between corm weight and total flower and leaf number in saffron. In: 2nd International Symposium on Saffron Biology and Technology, Mashhad, Iran, 28–30, October, pp. 93–96. Molina, R.V., Valero, M., Navarro, Y., Guardiola, J.L., Garcia-Luis, A., 2005. Temperature effects on flower formation in saffron (Crocus sativus L.). Sci. Hortic. 103, 361–379. Mollafilabi, A., 2006. Saffron production technology. In: Kafi, M., Koocheki, A., Rashed Mohassel, H., Nassiri, M. (Eds.), Saffron (Crocus sativus) Production and Processing. Science Publishers, New Hampshire, pp. 59–78. Nasrollahi, N., Kazemi, H., Kamkar, B., 2017. Feasibility of ley-farming system performance in a semi-arid region using spatial analysis. Ecol. Indic. 72, 239–248. Negbi, M., 1999. Saffron cultivation: past, present and future prospects. In: Negbi, M. (Ed.), Saffron (Crocus sativus L). Harwood Academy Publishers, Amsterdam, The Netherlands, pp. 19–30. Pérez, M., 1995. Elazafran, Historia, Cultivo, Comercio, Gastronomia. Ediciones Agrotécnicas, Madrid, Spain. ˜ C., Martinez-Llario, J.C., Navarro, A., 2013. Multi-criteria assessment in GIS Perpina, environments for sitting biomass plants. Land Use Policy 31, 326–335. Rhebergena, T., Fairhurstc, T., Zingorea, S., Fisherd, M., Oberthüre, T., Whitbread, A., 2016. Climate, soil and land-use based land suitability evaluation for oilpalm production in Ghana. Eur. J. Agron. 81, 1–14. Saaty, T.L., 1980. The Analytic Hierarchy Process: Planning, Priority Setting Resource Allocation. McGraw-Hill International, New York, NY, USA. Trong Due, T., 2006. Using GIS and AHP technique for land use suitability analysis. International Symposium on Geoinformatics for Spatial Infrastructure Development in Earth and Allied Sciences. Wang, G.Z., 1997. The foundation of tropical crops land suitability evaluation model of three Asia city based on GIS. Mapp. Eng. 2, 23–28 (In Chinese). Wilkins, H.F., 1985. Crocus vernus: Crocus sativus. In: Halevy, A.H. (Ed.), Handbook of Flowering, vol. 2. CRC Press, Boca Raton, FL, pp. 350–355. Yalew, S.G., van Griensven, A., van der Zaag, P., 2016. AgriSuit: a web-based GIS-MCDA framework for agricultural land suitability assessment. Comput. Electron. Agric. 128, 1–8. Yarami, N., Sepaskhah, A.R., 2015. Physiological growth and gas exchange response of saffron (Crocus sativus L.) to irrigation water salinity, manure application and planting method. Agric. Water Manage. 154, 43–51. Yarami, N., Kamgar-Haghighi, A.A., Sepaskhah, A.R., Zand-Parsa, S., 2011. Determination of the potential evapotranspiration and crop coefficient for saffron using a water-balance Lysimeter. Arch. Agron. Soil Sci. 57, 727–740. Zhang, J., Su, Y., Wu, J., Liang, H., 2015. GIS based land suitability assessment for tobacco production using AHP and fuzzy set in Shandong province of China. Comput. Electron. Agric. 114, 202–211.
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Ecological Engineering journal homepage: www.elsevier.com/locate/ecoleng
Development of a land use suitability model for saffron (Crocus sativus L.) cultivation by multi-criteria evaluation and spatial analysis Fahimeh Maleki, Hossein Kazemi ∗ , Asieh Siahmarguee, Behnam Kamkar Department of Agronomy, Faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural Resources (GUASNR), PO Box 49138-15739, Gorgan, Iran
a r t i c l e
i n f o
Article history: Received 4 February 2017 Received in revised form 6 May 2017 Accepted 29 May 2017 Keywords: GIS Land use suitability MCA Saffron
a b s t r a c t The principle purpose of agriculture land use feasibility is to predict the potentials and limitations of land for plant production. The present study provides a model to assess land suitability for cultivation of saffron (Crocus sativus L.) in Azadshahr Township, located in the north of Iran. The goal is to provide a special methodological approach to assess land use suitability for saffron cultivation in Iran and other similar regions. This suitability model integrated the perspectives of local saffron experts using an analytic hierarchy process (AHP) from Multi-Criteria Analysis (MCA) to determine the criteria weights such as climate, soil, and topographic used in land use suitability analysis. In the present model, 21 ecological variables were selected for saffron land suitability analysis and thematic maps were developed for each of the parameters in Geographic Information System (GIS).The results showed that the soil and climatic variables have a major role in the development of saffron cultivation. The final land suitability map indicated that the most suitable areas (1743.25 ha) for growing saffron were located in the south and east of Azadshahr township. Also, the largest parts of this region were classified as currently unsuitable (8543.72 ha) and permanently unsuitable (12,450.64 ha) zones. These classes were located in the northern, central and northeastern parts of Azadshahr. The results highlighted that these areas face with limitations for development of saffron cultivation. According to this result, the main limiting features in these classes were high rainfall in the reproductive stage of saffron (25–0 mm), inappropriate slope (12%<), high relative humidity, low annual rainfall, high elevation in north (2700 m<), and unsuitable classes of soil texture. These results can be useful for decision makers and farmers as a planning support tool in saffron cultivation. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Saffron (Crocus sativus L.) is a flowering plant belonging to the Iridaceae family(Gresta et al., 2016). It is the world’s most expensive crop among aromatic and medicinal plants (Turhan et al., 2007) and the most strategic crops in Iran. Saffron cultivation dates back to ancient times (2500–1500 BCE) and probably has originated from Iran and Greece, then became prevalent in India, China, the Mediterranean region, eastern Europe and other regions (Grilli Caiola et al., 2004; Negbi, 1999). In Iran, saffron is one of the most important cash crops and the main crop of smallholders who are farming in water-deficient regions (Mashayekhi et al., 2006; Mollafilabi, 2006). Generally, Iran is the’ world’s biggest producer of saffron. Iran’s share of global production is 90%, while the total
∗ Corresponding author. E-mail addresses: [email protected] (F. Maleki), [email protected] (H. Kazemi), [email protected] (A. Siahmarguee), [email protected] (B. Kamkar). http://dx.doi.org/10.1016/j.ecoleng.2017.05.050 0925-8574/© 2017 Elsevier B.V. All rights reserved.
cultivation area of saffron in Iran is 60 percent of the entire world. Other countries such as Greece, Spain, Morocco, India, Switzerland, Italy, Argentina, Azerbaijan, and Turkey are next in line (Fernandez Pérez and Escribano Martinez, 2000). Saffron has long been cultivated as a medicinal and spice plant. It has been also used for food (natural dye, flavor and aroma) since ancient times (Rios et al., 1996; Basker and Negbi, 1983; Rios et al., 1996; Gresta et al., 2009). Recently, its biological roles (especially those based on cytotoxic, anti-carcinogenic and antitumor properties) in medicine has been highlighted (Abdullaev and Frenkel, 1999; Fernandez Pérez and Escribano Martinez, 2000). Today, saffron is widely used as a condiment for different foods such as rice dishes, pastas, soups, cakes, saffron bread and numerous sweets. Also, it can be used as a refreshing drink. The plant is further used for the production of natural food colors, flavor enhancers, as well as pharmaceutical products (Pérez, 1995; De Juan et al., 2009). Reproductive, vegetative, and dormancy are the main typical phenological stages of saffron (De Juan et al., 2009). In Iran, saffron flowering occurs during the autumn followed by a vegetative stage
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throughout the winter and formation of replacement corms at the base of shoots. At the beginning of dry season, the leaves senesce and wither, and the bulbs go into dormancy (Wilkins, 1985; Botella et al., 2002). Flowering and yield of this plant are directly related to ecological conditions and field management (Yarami et al., 2011). Although this plant is grown in environments with diverse climatic conditions, few landscape-scale studies have been conducted to determine suitable areas for its cultivation. Precise and comprehensive evaluation of suitability based on climatic, soil, topography, and landforms suitability for a given land use is referred as land use suitability assessment. The Food and Agricultural Organization (FAO, 1976) proposed a framework for evaluating the suitability of lands for crops in terms of a suitability rating ranging from highly suitable to unsuitable. This framework is based on soil, topography, features, and crop characteristics. Wang (1997) developed a model for land suitability evaluation of tropical crops in three Asian cities through the Geographic Information System (GIS) media. In another study, Chen et al. (2010) investigated tobacco ecological suitability in Henan Province of China based upon an integrated GIS-hierarchy analysis method. Their results showed that highly suitable regions for tobacco cultivation were located in the western and southern parts of this province. Many works have been also established on GIS-Multi-Criteria Analysis (MCA). These integrated GIS-MCA techniques have been considered within a large number of disciplines using the suitable ˜ et al., 2013). Using MCA, alternative options and criteria (Perpina preferences of land use could be determined. For this goal, suitable objectives and related attributes and criteria should be identified ˜ et al. (Liu et al., 2007). Through the MCA-GIS analysis, Perpina (2013) showed that the most suitable areas for biomass production in Valencia (Spain) were located in the vicinity of residential zones. In this study, physiographic characteristics, involved crops, vegetation state, potential demand, and transport-related cost were the most important factors determining the biomass production. Chen et al. (2001) integrated GIS and MCE in order to assess natural risks in China. They presented three different evaluation methods for the same analysis and compared the results for the purpose of decisionmaking. In another research, Collins et al. (2001) reviewed the application of GIS-based methods for land use suitability analysis in the US. These methods were classified as follows: computerassisted overlay mapping, MCA, and artificial intelligence method. Furthermore, Yalew et al. (2016) developed a web-based GIS-MCDA framework for agricultural land suitability assessment (AgriSuit), based on remote sensing, GIS techniques, and Google Earth Engine (GEE). Based on a fuzzy logic based land suitability evaluation procedure, Feng et al. (2017) assessed the suitability of marginal lands in Upper Mississippi River Basin (UMRB) for three promising biofeedstock crops, i.e. switchgrass, Miscanthus and hybrid poplar. The results showed that 60% of marginal lands in UMRB were moderately to highly suitable for growth of the targeted biofeedstock crops. Moreover, Rhebergena et al. (2016) evaluated land suitability for oil palm production in Ghana and found that the major climatic factor limiting suitability for oil palm production is the annual water deficit. In Iran, Kazemi et al. (2016) developed a land evaluation model for faba bean cultivation using geographic information system and multi-criteria analysis in Gonbad-Kavous region (Golestan Province). Their results revealed that the share of highly suitable, moderately suitable, and marginally suitable lands for faba bean cropping were 23.48% (48,354.5 ha), 25.38% (52,237.37 ha) and 25.03% (51,522.85 ha) of the study area, respectively; in addition, the share of unsuitable lands was just 26.11% of total agricultural lands. Nasrollahi et al. (2017) also demonstrated that high EC, low organic matter, and low annual rainfall are the key limiting vari-
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ables to perform ley-farming systems in the Aq-Qala township, in the north of Iran. Saffron cultivation has been extensively favored in the past few years. The high tendency to develop the culture of this plant is due to its high economic value, low input requirement, and its conformity to small size arable lands. For these reasons, cultivation of this plant is developed in different provinces of Iran such as Golestan, Isfahan, Kurdistan, among others. Most of the information available about this plant in Iran is restricted to farm management methods and their related effects on the qualitative and quantitative traits and little is known about the land suitability for cultivation of saffron in Iran. Therefore, this study aimed to investigate the feasibility of saffron cultivation in Azadshahr Township, Golestan province (north of Iran) using an integrated GIS-MCA framework. 2. Material and method 2.1. Study area The study was carried out in Azadshahr township of Golestan Province, Iran, with a warm, temperate and mountainous climate during 2014–2015 (Fig. 1). The total study area covers approximately 872 km2 . The area coordinate ranges from 36◦ 48.2 to 37◦ 11.5 N latitudes and 55◦ 3.7 to 55◦ 38.3 E longitudes with an altitude range of 92 m to 2800 m a.s.l, respectively. The average annual temperature and precipitation in the region are 378 mm and 17.7 ◦ C, respectively (Golestan Province Government, 2009). 2.2. Parameters used in the suitability analysis 2.2.1. Climatic data Annual rainfall, average temperature, rainfall, maximum and minimum temperature for reproductive, dormancy, and growth stages, sunshine hours, relative humidity, and number of frost days were considered as climatic factors affecting saffron-land suitability. For this purpose, thematic maps for all aforementioned factors were provided in GIS (ArcGIS 10.0 software). The recorded climatic data from 36 weather stations within the target study area and the surrounding areas were used. All data from 1995 to 2014 were averaged. Some interpolation methods, e.g. Local Polynomial Interpolation (LPI), Ordinary Kriging (OK), and Inverse Distance Weighted (IDW), were selected to provide a raster-based spatial distribution of climatic parameters (Table 1). Interpolated or reclassified layers of these parameters are presented in Figs. 2–4. 2.2.2. Soil data Soil data (i.e. pH, EC, and texture classes) were sampled from 200 profiles in Azadshahr Township and adjacent regions. Soil samples were randomly taken on Oct 2015. Samples were taken at depths of 0–30 cm and air-dried to remove stones and coarse plant residues. Three samples from each sampling site were collected from the surface soil layer and were thoroughly mixed; one sample was ground to pass a sieve and subsequently stored in plastic bags prior to analysis. The spatial distribution of soil characteristics on studied lands was mapped in ArcGIS using aforementioned interpolation methods for climatic factors (Table 1). Soil-related maps of the study area are shown in Fig. 5. 2.2.3. Topographic data A 40 × 40 m resolution Digital Elevation Model (DEM), along with required updated political boundaries, were obtained from the Natural Resources Organization of Golestan province and used to provide topographic data. For this, some topographic characteristics such as slope, aspect, and elevation were mapped using surface analysis functions in GIS (Fig. 6).
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Fig. 1. Location of the study area in Azadshahr township, Golestan province, Iran.
Table 1 The best-fitted method/models for interpolation of some variables in agricultural lands of Azadshahr township, Iran. Variable
Method/model
RMSE
Variable
Method/model
RMSE
Annual rainfall Rainfall of reproductive stage Rainfall of growth stage Annual average temperature Maximum temperature of reproductive stage Maximum temperature of growth stage Maximum temperature of dormancy stage
OK − Exponential OK − Circular OK − Circular LPI − 3 OK − Stable
108.38 14.08 106.65 0.325 1.37
Minimum temperature of reproductive stage Minimum temperature of growth stage Minimum temperature of dormancy stage Sunshine hours Relative humidity
LPI − 1 LPI − 1 LPI − 2 LPI − 1 LPI − 1
0.82 0.77 0.70 349 5.74
OK − Spherical
0.57
Number of frost days
LPI − 1
5.79
OK − Stable
1.33
pH
IDW − 1
0.163
EC
OK − Exponential
0.474
OK: Ordinary Kriging, LPI: Local Polynomial Interpolation, IDW; Inverse Distance Weighted, RMSE; Root Mean Square Error.
2.3. Model description 2.3.1. Analytical hierarchy process (AHP) A nine-point scale-based AHP hierarchical model (Saaty, 1980; Table 2) including objectives, criteria, sub-criteria, and alternatives
was constructed to weight affecting factors. The objective was set as the land use suitability analysis for saffron cropping in Azadshahr Township, and the criteria included soil, climatic, and topographic traits. Twenty saffron experts were invited to fill a pairwise comparison table of the mentioned factors to determine the relative
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Fig. 2. Rainfall (mm) maps in Azadshahr township, Iran; a: Annual rainfall, b: Rainfall in reproductive stage, c: Rainfall in growth stage.
importance of the criteria (raw data for AHP model). The final step of AHP, the weight of factors for land use suitability, was obtained from local experts through a pairwise comparisons statistical analysis in Expert Choice Software (version 2001).The obtained weights made it possible to allocate a suitable value for each land mapping
unit. The parameter that is used to check accuracy of comparisons is called the Inconsistency Ratio (IR).This ratio is a measure of low variation allowed and must be less than 10% (Saaty, 2000; Trong Due, 2006).
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Fig. 3. The maps of, a: Relative humidity, b: Sunshine hours, c: Number of frost days in Azadshahr township, Iran.
2.3.2. Land suitability analysis performance For all raster layers (with 100 × 100 m resolution), spatial references were selected as UTM (WGS1984-Zone 40 N). Query analysis was used to extract agricultural lands from all other land uses
(i.e. bare lands, industrial and residential areas, forests, rangelands, water bodies, and impervious lands). In order to follow the main goal, i.e. land suitability assessment for saffron cultivation in Azadshahr Township, the reclassified lay-
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ers (based on 4 categorized classes) were overlaid. The base raster layers were reclassified according to the compliance of all involved layers of different factors with the ecological requirements of saffron; the requirements had been determined via a comprehensive literature review and asking local experts’ opinions. Graphical representation of the land suitability evaluation process is presented in Fig. 7.
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A crucial step of land suitability assessment for crop production is weighting all the parameters affecting the land suitability (Zhang et al., 2015). For this purpose, AHP-acquired weights were assigned to the criteria. Then, land suitability was carried out by the Weighted Overlay Technique (WOT) in GIS. Finally, the land suitability map for this plant was classified into five categories, including highly suitable (S1, the land unit is very favorable for saf-
Fig. 4. The temperature maps (◦ C) in Azadshahr township, Iran; a: Minimum temperature of dormancy stage, b: Maximum temperature of dormancy stage, c: Minimum temperature of growth stage, d: Maximum temperature of growth stage, e: Minimum temperature of reproductive stage, f: Maximum temperature of reproductive stage, g: Annual average temperature.
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Fig. 4. (Continued)
fron production with no limitations), moderately suitable (S2, the land unit is almost favorable with some limitations), marginally suitable (S3, the land unit is marginally desirable with severe limitations), currently unsuitable (N1) and permanently unsuitable (N2). Unsuitable land (N1 and N2) was supposed to have severe limitations, which could rarely or never be overcome by economic use of inputs or management practices (Zhang et al., 2015; Ghafari et al., 2000; Nasrollahi et al., 2017).
3. Results and discussion 3.1. Results of AHP analysis The AHP results based on experts’ pairwise comparisons indicated that the most important criteria, according to their specific weighting, were climate (0.696), soil (0.215) and topography (0.089). Also, among the climate criteria, temperature and rela-
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Fig. 5. The soil properties maps of Azadshahr township, Iran; a: EC, b: pH, and c: Texture.
tive humidity had the highest and lowest weights, respectively. It should be noted that among the temperature sub-criteria, minimum and maximum temperatures of reproductive period had major roles in describing the suitable areas for saffron cultivation (Table 3). In a similar study, AHP was introduced as the best method for land suitability analysis of tobacco production in Shan-
dong province of China (Zhang et al., 2015). Besides, the results of Nasrollahi et al. (2017) demonstrated that climate, soil, and topography were the most important criteria based upon AHP weights for ley-farming performance. Also, among the climate criteria, rain and minimum temperature had the highest and lowest weights, respectively. Based on the results of the experts’ opinions, final weights
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Fig. 6. Topographic maps of Azadshahr township, Iran; a: Slope, b: Elevation and c: Aspect slope.
of 0.150 and 0.131 were assigned to sunshine hours and number of frost days in relation to saffron crop production, respectively (Table 3).
The MCA has been used effectively for the development of decision support systems which are able to rank decision options by simultaneously considering multiple criteria relating to range of
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Table 2 Criteria for delineating land suitability of saffron in Azadshahr region, Iran. Highly suitable (S1)
Moderately suitable (S2)
Marginally suitable (S3)
Currently unsuitable (N1)
Permanently unsuitable (N2)
Climatic factors Annual rainfall (mm)
300–400
180–240
120–180
<120
Rainfall of reproductive period (mm) Rainfall of growth period (mm) Annual average temperature (◦ c) Maximum temperature of reproductive period (◦ c) Maximum temperature of growth period (◦ c) Maximum temperature of dormancy (◦ c) Minimum temperature of reproductive period (◦ c) Minimum temperature of growth period (◦ c) Minimum temperature of dormancy (◦ c) Sunshine hours Number of frost days Relative humidity (%)
17–20 >58 >14.5 >23 23.5 35–40 >9 >−14 >12 >3100 <20 40–50
240–300 and >400 14–17 46–58 11.5–14.5 18.5–23 19–23.5 28–35 7–9 (−18) to (−14) 9.5–12 2480–3100 20–30 50–60
20–25 37–46 9.5–11.5 14.5–18.5 15–19 >40 5–7 (−22) to (−18) 7.5–9.5 1984–2480 30–40 60–70
25–30 30–37 7.5–9.5 11.5–14.5 12–15 22–28 5 (−26) to (−22) 6–7.5 1587–1984 40–50 70–80
>30 <30 >7.5 <11.5 <12 <22 <5 <−26 <6 <1587 >50 >80
2–5 East and northeast 1200–1400
5–12 Southwest and northwest 900–1200
12–17 West and south
>17 –
Elevation (m)
0–2 South, southeast and no direction 1400–2300
700–900 2300–2700
<700 >2700
Soil factors EC (dS m−1 ) pH
<2 7–8
2–4 6.5–7
4–8 8–8.5
8–12 6–6.5
Soil texture
Sandy loam, loam
Clay loam, silty loam, silty clay loam
Clay, clay sandy
Silty clay
>12 <6 >8.5 Other classes
Feature
Topography factors Slope (%) Slope aspects
Fig. 7. Schematic diagram of land use suitability for saffron in Azadshahr region, Iran.
planning and natural resource management issues (Graymore et al., 2015). The superiority of AHP in group decision-making was compared to other techniques proposed by Lai et al. (2002). In another
study, Mbugwa et al. (2015) highlighted that using GIS along with spatial decision support systems (SDSS) procedures can be beneficial in land use suitability.
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Table 3 The weights of criteria and sub-criteria in land suitability analysis of saffron in Azadshahr region, Iran. Criteria
Weight
Rank
Sub- criteria 1
Weight
Sub- criteria 2
Weight
Climate
0.696
1
Temperature
0.434
Annual average temperature Minimum temperature
0.516 0.288
Maximum temperature
Soil
0.215
2
Topography
0.089
3
Rainfall
0.199
Sunshine hours Number of frost days Relative humidity EC Texture pH Elevation Slope aspects Slope
0.150 0.131 0.086 0.441 0.323 0.236 0.510 0.252 0.238
Rainfall of growth stage Rainfall of reproductive stage Annual rainfall
0.197
Sub-criteria 3
Weight
Minimum temperature of reproductive stage Minimum temperature of growth stage Minimum temperature of dormancy Maximum temperature of reproductive stage Maximum temperature of dormancy Maximum temperature of growth stage
0.538 0.286 0.176 0.448 0.304 0.248
0.415 0.328 0.248
Inconsistency 0.03 Ratio (IR)
3.2.1. Highly suitable zone The area with highly suitable degree was identified as the zone that has highly valuable for saffron production. This zone covered an area of 1743.25 ha (5.48% of total arable area) (Table 4). Highly suitable class was characterized by annual rainfall of 300–400 mm during the crop growth cycle, elevation range of 1400–2300 m, slope of 0–2%, soil pH level range of 7–8, EC < 2 dS m−1 , reproductive stage rainfall of 17–20 mm, number of frost days <20, relative humidity of 40–50%, annual average temperature >14.5 ◦ C, and soil texture classes of sandy loam and loam. Based on optimal environmental conditions, it was found that some of lands situated in the south of Azadshahr are in the highly suitable state (Fig. 9). From a climatic viewpoint, some authors reported that the optimal climatic conditions for saffron species are rainy autumns, mild winters, and warm summers (Mollafilabi, 2006). Temperature and soil water content certainly play a vital role in saffron flowering induction and flower appearance (Molina et al., 2005; Yarami and Sepaskhah, 2015). Moreover, saffron has low water requirements and is typically cultivated under rain-fed conditions because it is well adapted to the rainfall pattern of diverse Mediterranean regions (Alizadeh, 2006).
Fig. 8. Land suitability map for saffron cultivation in Azadshahr township, Iran.
3.2. Land suitability Fig. 8 presents the final map of land suitability for saffron cultivation in Azadshahr Township. The comparison of intentions and possible achievement indicated that the study area can be divided into different classes with diverse capacities for saffron cultivation, which includes highly suitable potential, moderately suitable, marginally suitable, and unsuitable. The last class was further divided into two zones, i.e. currently unsuitable and permanently unsuitable.
3.2.2. Moderately suitable (S2) zone The final map of land suitability showed that less than 10.5% of agricultural lands for saffron production are situated in moderately suitable class (Table 4). These regions are in parts of the south and east of the township (Fig. 10). In general, climatic factors have an important role in the saffron cultivation expansion. For example, a frost occurrence in the range of sowing and rosette development months can be very harmful to saffron and cause production losses (Gasolet al., 2011). In this regard, Benschop (1993) concluded that temperature is the most important ecological variable controlling growth and flowering of Crocus species. This is done by affecting enzyme activity in plant metabolism. Principally, moderately suitable class was characterized by annual rainfall of 240–300 mm and >400 mm, reproductive stage rainfall of 14–17 mm, annual average temperature of 11.5–14.5 ◦ C, elevation levels between 1200 and 1400 m, slope of 2–5%, soil pH range of 6.5–7, 20–30 frost days, rel-
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Table 4 The distribution of land suitability degree for saffron cropping in Azadshahr Township, Iran. Suitability degree
Area (ha)
Zone area/total agricultural lands area (%)
Zone area/total area of township (%)
Highly suitable (S1) Moderately suitable (S2) Marginally suitable (S3) Currently unsuitable (N1) Permanently unsuitable (N2) Total
1743.25 3197.30 5895.00 8543.72 12450.64 31829.91
5.48 10.04 18.52 26.84 39.12 100
2.03 3.72 6.85 9.93 14.47 37
Fig. 9. Highly suitable classes for saffron cropping in Azadshahr township, Iran.
ative humidity of 50–60%, and soil texture classes of clay loam, silty loam, and silty clay loam. The optimum annual sunshine hours for saffron are 2480–3100 h per year. According to the recorded sunshine hours in the studied area (Fig. 3b), the number of sunshine hours in the central and southern parts of the study area is not restrictive.
3.2.3. Marginally suitable (S3) zone Marginally suitable (S3) zone was located in the center and southeast of Azadshahr Township (Fig. 11). This class is characterized by reproductive period rainfall of 20–25 mm, growth period rainfall of 37–46 mm, annual rainfall of 180–240 mm, annual average temperature of 9.5–11.5 ◦ C, slope of 5–12%, EC of 4–8 dS m−1 , and 30–40 frost days. According to the generated agricultural land use suitability map, it was observable that 18.52% (5895 ha) of this region is marginally suitable (S3) for saffron production (Table 4). Saffron must be planted in areas where relative humidity is low. Areas where the relative humidity exceeds 50% are unsuitable for the production and growth of saffron. In this study, it was found that the northern part of the study area with high relative humidity is unsuitable for saffron cultivation, while the southern part, which is in the vicinity of Semnan province (with arid and semiarid climate), poses no restrictions for saffron cultivation in terms of relative humidity.
Fig. 10. Moderately suitable classes for saffron cropping in Azadshahr township, Iran.
3.2.4. Currently unsuitable (N1) and permanently unsuitable (N2) zones The results of land suitability indicated that the largest parts of the surveyed region were classified as currently unsuitable (8543.72 ha) and permanently unsuitable (12,450.64 ha) (Table 4). These classes are located in the northern, central and northeastern parts of Azadshahr Township (Fig. 12). The results of this research indicated that high rainfall in reproductive stage (25–30 mm), slope >12%, low annual rainfall, high elevation (>2700 m), and unsuitable class of soil texture were the main limiting factors in these classes. Elevation was one of the most important determinants. This area is between 700 and 2700 m of altitude and meets mountains and valleys in central and south. The results indicate that saffron is associated with more damage caused by critical temperatures and frost at higher altitudes compared to lowlands. Also, in a part of the studied zone, soil texture was unsuitable. Basically, the bed of saffron growth or soil texture/structure significantly affects flower and corm yield. Gresta et al. (2009) concluded that the best medium for saffron cultivation is a sandy soil with manure mixture. Furthermore, Behzad et al. (1992) reported that organic matter and cow manure applications improved soil fertility of saffron fields. When cow manure is applied before saffron planting, soil water retention increases and soil structure improves in irrigated conditions. In another study, the use of organic materials, e.g. composted cattle manure, was considered for sustainable production in saffron fields (Koocheki and Seyyedi, 2015).
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ing the quality of the lands under cultivation in Shandong Province, China. They used five indicators, i.e. slope, light-temperature potential productivity, Normalized Difference Vegetation Index (NDVI), Temperature-Vegetation Dryness Index (TVDI), and yield. Their results showed that the quality of cultivated lands in this region decreased from the southwest to the northeast. 4. Conclusion
Fig. 11. Marginally suitable classes for saffron cropping in Azadshahr township, Iran.
The results also revealed that in the central and southern parts, slope acts as a limiting factor for cultivation of saffron in the study area. From a geomorphological viewpoint, slope in Azadshahr Township varies, decreasing from the south to the north (Fig. 6). Basically, agricultural operations and machinery were assumed not to work correctly on slopes exceeding 10%. Furthermore, in steep terrains, soil erosion losses will increase (Gasolet al., 2011). Zhen et al. (2012) adopted an appropriate procedure for evaluat-
The results of this research can be valuable for future decisions about the cultivation of saffron and can lead to a reduction in saffron expansion into high-risk areas in the investigated region. The present study provided a methodological approach to assess the suitability of agricultural lands for saffron cropping in Iran. Saffron land suitability analysis is a prerequisite to achieve optimum utilization of available environmental resources for sustainable production. According to experts’ opinions, higher weights were assigned to the climate than to all other criteria. The results also demonstrated that climatic conditions and soil-related characteristics play the main role in saffron expansion. Analysis of suitability showed that 5.48% (1743.25 ha) of total land in the study areas was high suitable for saffron production, 10.04% (3197.30 ha) were moderately suitable, and 65.96% of the study area (20,994.36 ha) were located in unsuitable zone. These results lead to the conclusion that rainfall in reproductive stage, slope, high relative humidity, annual rainfall, frost days, elevation, and soil texture are the most significant variables affecting the sustainability of the saffron production. FAO recommended an approach for land suitability evaluation for plants in terms of suitability range from highly suitable to unsuitable based on climatic and terrain data and soil properties crop-wise (FAO, 1976). In this case, the MCA method is particularly applicable when large numbers of criteria are involved (Liu et al., 2007). Our results stated that an integrated GIS-MCA approach is a practical and applicable method for determining land suitability for saffron crop. These results could help decision-makers to determine the quality of croplands for saffron as a decision and
Fig. 12. Currently and permanently unsuitable classes for saffron cropping in Azadshahr township, Iran.
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