Soil science
M. Eskandari; A. Zeinadini; M.N. Navidi; A. Salmanpour
Abstract
IntroductionSaffron, which its cultivation is compatible with the arid and semi-arid climate of Iran, is one of the most valuable agricultural products in the world. Therefore, the cultivation of this crop in different parts of the country has been enormously developed in recent years. More than 95% ...
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IntroductionSaffron, which its cultivation is compatible with the arid and semi-arid climate of Iran, is one of the most valuable agricultural products in the world. Therefore, the cultivation of this crop in different parts of the country has been enormously developed in recent years. More than 95% of the world production of this precious product is allocated to Iran, which is mainly located in the two provinces of Khorasan Razavi and Southern Khorasan. The objective of this study was to determine the priority of lands for saffron cultivation by using TOPSIS method. Furthermore, in this study, TOPSIS, which is the second most widely used approach among multi-criteria decision making methods, was compared with the conventional parametric one to assess the land suitability for saffron production.Materials and MethodsTo achieve the objective of this study, 135 saffron farms in Khorasan Razavi, Southern Khorasan, Fars, Markazi and Kerman provinces were selected. In each farm, one pedon was dug and studied in detail. Soil samples were collected from different horizons of the pedons and taken to the laboratory for the designated physicochemical analyses. The average quantity of saffron yield in the last three years was recorded for each study point. The selected areas did not have climatic restrictions for saffron cultivation. For this purpose, in addition to local experience, the climate suitability index was calculated using the saffron climatic requirement table by its phenological period in each region. The effective soil criteria conditioned on the saffron yield were obtained using statistical analyses. By constructing a decision matrix and normalizing it, weighting the criteria by ranking order method and constructing a weighted matrix, determining the positive and negative ideal and then calculating the relative proximity of each alternative to the positive ideal, the preference of each alternative by TOPSIS method for saffron cultivation was determined. Then, the prioritization of alternatives was compared with the actual yield of saffron. Soil suitability index was also calculated using the table of soil and landscape requirements for saffron, and then compared with actual yield. Finally, the two schemes were validated and compared with each other.Results and DiscussionThe climate suitability index for saffron cultivation in the five studied areas indicated that the climate conditions in all areas were relatively similar. Consequently, soil properties can be considered as the only factors affecting the priority of lands for saffron cultivation in the studied areas. The results further revealed that three variables of lime content, salinity and exchangeable sodium percentage of soils under saffron cultivation in the country were higher than the critical level for saffron production. Therefore, these three variables are considered as the most important soil properties affecting the saffron yield. The order of weights assigned to the variables included salinity, exchangeable sodium percentage, lime, gravel, gypsum, organic carbon and soil reaction. Comparison of the order of priority of 135 options by TOPSIS with the actual yield of saffron showed an acceptable accuracy (R2 = 0.92) for this method. The soil index calculated by the parametric square root method for 135 soil profiles was also compared with the actual yield. The coefficient of determination obtained in this case was about 0.9, showing that TOPSIS was able to determine the suitability of lands for saffron cultivation better than the parametric method. Due to the ability of TOPSIS to evaluate a large number of evaluation criteria, this method is superior to the parametric method, which can consider a maximum of eight criteria in estimating the index.ConclusionThe outcome of this study showed a high accuracy of TOPSIS method in determining land suitability for development of saffron cultivation. This method is well able to use a large number of criteria that have negative or positive effects on the priority of alternatives. Furthermore, depending on the conditions of the decision making problem, one of the methods of weighting the criteria can be employed and combined with the TOPSIS method. The high accuracy of this method can be attributed to the use of mathematical relationships and matrices, data standardization by Euclidean soft method, and the nature of comparing both distances from the positive and negative ideals.
Soil science
A. Zeinadini; M.N. Navidi; A. Asadi Kangarshahi; M. Eskandari; S.A. Seyed jalali; A. Salmanpour; J. Seyedmohammadi; M. Ghasemi; S.A. Ghaffarinejad; Gh. Zareian
Abstract
Introduction: Iran is one of the most important countries in citrus (oranges) production. Citrus fruits are grown in different soils with a wide range of physical, chemical and fertility properties in the country, although some restrictions in the cultivated lands cause yield loss. In this regard, the ...
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Introduction: Iran is one of the most important countries in citrus (oranges) production. Citrus fruits are grown in different soils with a wide range of physical, chemical and fertility properties in the country, although some restrictions in the cultivated lands cause yield loss. In this regard, the present study was conducted to investigate the effect of physical, chemical and soil fertility characteristics on citrus yield in important areas under cultivation, the regression relationships of characteristics with yield, and the rating of soil and land parameters. Materials and Methods: The 138 oranges orchards (118 orchards for rating and 20 orchards for validation) were selected in Fars, Mazanderan, Kerman and Guilan provinces. In each garden, a questionnaire was completed, a soil pedon was studied and soil samples were taken to carry out the appropriate physicochemical analyses. The selected soil and land characteristics were soil salinity (EC), exchangeable sodium percentage (ESP), pH, gypsum content, soil calcium carbonate (TNV), organic carbon (OC), clay, sand, silt, gravel, and soil available phosphorus and potassium contents. From the whole obtained data, 20 data were considered for validation purpose and the remaining data were used for modeling based on stepwise multivariate and simple regression methods. In these equations, the relationship between yield, as dependent variable, with soil and land characteristics, as independent variables, was investigated. Finally, land characteristics rating was obtained by the FAO method and the proposed crop requirements table was evaluated using the validation dataset. Results and Discussion: The results of descriptive statistics analysis showed that the variance values for available potassium, sand, clay, gravel and TNV were high and for pH and OC and gypsum were negligible. Therefore, most soil properties have a wide range of variation which could be related to the fact that oranges are grown in a wide range of soil types. The value of TNV varied between 10 and 33.3%. The presence of carbonate in soil reduces the availability of macro- and micronutrient elements in direct and indirect manners. The average of EC in the studied orchards was 5.4 dS.m-1. Minimum, maximum and average of ESP were 1.7, 28 and 10.7, respectively. The lowest and highest salinity and sodicity were observed in Mazandaran and Kerman soils, respectively. Maximum, minimum and average percentage of gypsum were 12, 0.36 and 3.54%, respectively. The highest amount of gypsum was observed in Bam and Shahdad regions of Kerman province and the lowest gypsum content was observed in Mazandaran and Guilan provinces. The soil pH varied from 6.63 to 8.8 with the average of 7.8. The soil OC values were between 0.05 and 3.53% and its average was 0.89%, showing the fact that the most studied soils were poor in organic matters. The average of soil available phosphorus and potassium in the studied orchards for citrus was less than the critical level. The average, minimum and maximum of available potassium were 224, 100 and 360 mg.kg-1, respectively. The mean, minimum and maximum amounts of available phosphorus were 21.6, 8 and 45.9 mg.kg-1, respectively. According to the multivariate regression model, among soil properties, EC, ESP, TNV, gypsum, gravel, available phosphorus and potassium were selected by the model. The determination coefficient of the model was 0.95, indicating that these properties have the greatest effect on citrus yield. Simple regression equations demonstrated that TNV, gypsum, EC, ESP, sand, clay, gravel, available potassium and phosphorous had the highest correlation (R2 > 0.6); and soil OC and pH had the lowest correlation (R2<0.2) with yield. The equations also revealed that soil EC, ESP, gypsum, TNV and gravel percentage had the greatest effect in yield loss, and soil organic carbon, absorbed phosphorus and potassium had the greatest effect on increasing citrus yield. As stated in equations, reported permissible and critical thresholds for effective soil properties on citrus yield, were 2.4 dS.m-1 for EC, 5 for ESP, 1.5% for gypsum, 20% for TNV, 22 mg.kg-1 for available phosphorus, 280 mg.kg-1 for available potassium, 110 cm for soil depth, and >2 m for groundwater level. Finally, evaluating the proposed crop requirements table with validation dataset fitted between citrus yield and soil index, resulted in the determination coefficient value of 0.79, denoting the acceptable accuracy of proposed table. Conclusion: Overall results showed that the main land limiting characteristics for orange production were soil salinity and sodicity, high amount of soil calcium carbonate and gypsum. Among unsuitable physical and fertility properties of soil, salinity and sodicity are the most effective factors affecting yield reduction. Consequently, proper management practices such as introducing cultivars compatible with these soil conditions, soil remediation and leaching operations to reduce soil salinity and sodicity are necessary. Furthermore, in most areas under orange cultivation such as Fars and Kerman provinces, the soil calcium carbonate content is more than the critical level for plant growth. In addition, the averages of soil available phosphorus and potassium were less than the critical levels, which should be considered for nutrient management of orchards. The proposed table of crop requirements seems to be accurate enough to conduct land suitability studies for orange varieties, especially cultivars grown in the north and south of the country.
Mohammad Ghasemzadeh Ganjehie; Ali reza Karimi; Ali Zeinadini; Reza Khorasani
Abstract
Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. ...
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Introduction: Playa is one of the most important landscapes in arid regions which covers about 1% of the world's total land area. Study of playas is important from different points of view especially pedology, sedimentology, mineralogy, environmental geology, groundwater and surface water chemistry. More than 60 playas have been identified in Iran. Considering the fact that playas and surrounding landforms are important archive of landscape evolution and paleoenvironmental variations, it seems that less attention has been paid to them so far. Soils are known as indicators of the landscapes evolution. Previous studies in arid regions of Iran imply different periods of deposition and soil formation in playa and alluvial fans or pediments. Bajestan playa is one of the known playa in northeastern Iran, and the largest clay flat exists in this playa. There is no information on the soils and their evolution in Bajestan playa. The objective of this study were to 1) identify the soils in different landforms along a transect from alluvial fan to clay in Bajestan playa 2) determine the morphological, micromorphological and mineralogical characteristics of these soils 3) determine the periods of soil and landform evolution and 4) comparison of soils evolution of the study area to other arid regions of Iran.
Material and Methods: The study area of approximately 20000 hectares is located in southeastern of KhorasanRazavi province. The climate of the study area is hot and dry with mean annual temperature and rainfall of 17.3 °C and 193 mm, respectively. Soil moisture regime is aridic with subdivisions of weak aridic and soil temperature regime is thermic. Firstly, landforms and geomorphic surfaces of the study area were recognized based on Google Earth images interpretations and field observations. Four main landforms were recognized in the study area. The landforms from north to the south of the study area were alluvial fan, intermediate alluvial fan- clay flat, pediment and clay flat. Considering the diversity of geomorphic units, 11 soil profiles were described and diffrenet soil layers and horizons were sampled. Undisturbed soil samples were taken micromorphological studies. Some horizons were selected for clay mineralogy analysis. The mineralogy of clay fraction was determined using X-ray diffraction method.
Results and discution: All studied soils except the profiles in the pediment were classified in the Aridisols order. There were two geomorphic surfaces in alluvial fans. In the first geomorphic surface a soil with the Bk horizon buried a soil with red Btk horizon. In the second geomorphic surface, it seems that the erosion has been removed the overlying soil. The Bk horizon showed the maximum soil development in the clay flat and intermediate alluvial fan-clay flat landforms. Clay coating on sand in thin section was the evidence of clay illuviation in Btk horizon. Carbonate nodules associated with clay coating are the compound pedofeature in Btk horizon. These evidences reflect polygenetic nature of the soils and different period of climate change and soil formation. Smectite, mica, chlorite and palygorskite are the clay minerals in the studied soils. Similar to soils in arid regions of Iran, palygorskite was found in Bk, Bt and Bz horizons. The existence of Bk horizon in overlying soils, buried Btk horizon, removal of surface horizon in alluvial fan are the evidences of regressive and progressive of pedogenic processes in the study area. Btk horizon represents a warm and wetter and Bk horizon indicates a relatively wetter period in comparison to present time.
Conclusion: Btk was the most developed horizon in the study area that occurred as buried paleosol in alluvial fan. Bk, Bw, By and Bz were the common horizon in other landforms. Clay coating and red color of Btk horizon might seem as indicators of hot and humid conditions in the past, during the argillic horizon formation. Covered carbonate nodules with clay coating can also be mentioned as sign of a hot and wet period which is suitable for clay illuviation and weathering after a period of carbonate accumulation. The buried Btk horizon under alluvial layers in the alluvial fan indicates that after apedogenic period, alluvial processes have been responsible in burying this horizon. Bk horizon in overlying soil of all landforms represents a less intense period of soil formation. The dominant clay minerals in the study area were Illiite, cholorite, kaolinite, and palygorskite. The sequence of Bk and Btk horizons in this research and the occurrence of these soils in central, eastern and northeastern Iran imply the similar pedogenetic conditions in arid regions of Iran.
