جستجوی مقالات مرتبط با کلیدواژه « neoformation » در نشریات گروه « کشاورزی »

Minerals are one of the main components of soils which play different roles in the soils. Minerals make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases plant nutrients which are retained by other minerals through adsorption, cation exchange, and precipitation. Minerals are indicators of the amount of weathering that has taken place, and the presence or absence of particular minerals gives clues to how soils have been formed. The physical and chemical characteristics of soil minerals are important consideration in planning, constructing, and maintaining of buildings, roads, and airports. Clay minerals can be used for understanding of soil formation, optimum management of dry and wet lands and interpretation of paleo environments. Moreover, clay minerals can provide some valuable information such as the origin of sediments, transportation and precipitation of sediments and also some information about intercontinental weathering regimes. Quaternary sediments have occupied most of the agricultural and natural resources of Urima plain and recognition of mineralogical of these soils is essential to optimum and stabile use of these soils. Additionally, caly mineralogical investigation can provide some information about the intensity of weathering processes and climate change in this area. Thus, in this study clay minerals of quaternary sediments in northeast of Urmia and the mechanisms of their formation and also tracing probable climate change in this area were investigated.
This study was performed in theUrmia plain in west Azerbaijan Province. The study area is located on quaternary sediments and physiographically, this area is a part of a river alluvial plain with the gentle slope toward Urmia Lake. The mean annual precipitation and temperature of this area are 345.37 mm and 10.83 °C respectively and the soil moisture and temperature regimes are dry xeric and mesic respectively. In this study, eight soil profiles in quaternary sediments were dug and sampled and the morphological, physical, chemical and mineralogical properties were determined using standard methods.
According to the results, Illite, smectite, Kaolinite, chlorite, vermiculite and hydroxy interlayer vermiculite (HIV) were the dominant clay minerals in these soils. The origin of illite, chlorite and kaolinite were related to inheritance from parent material. Regarding to the present of some smectite in the parent material of these soils, some of smectites have been inherited from parent material. Nevertheless it seems that, the most of smectites in these soils have pedogenic origin. Based on mineralogical results and trends variation of smectite and illite along studied profiles, we concluded that some of smectites in these soils have been formed from illite transformation. In profiles 4 and 6, regarding to low depth water table and consequently poor drainage, high pH and high values of calcium and magnesium cations, provide suitable conditions for the neoformation of smectit and so, some of smectites have been formed via neoformation from soil solution. In these soils, vermiculites were pedogenic and have been formed during transformation of illite to smectite. Small amounts of hydroxy interlayer vermiculites were present in buried horizons and regarding that they were not present in parent material, it might be because these minerals are pedogenic and have been formed in a past wetter climate. The transformation of illite to smectite in lower horizons needs high moisture and regarding to recent semiarid climate of study area, the suitable amount of moisture for this transformation, especially in lower depths and also in buried horizons, is not present. Thus, it seems the transformation of illite to smectite in lower depths and buried horizons has been taken place in a wetter past climate. So we concluded that smectite and hydroxy interlayer vermiculite are evidences of a wetter past climate in this area.
In this study the origin of smectite in buried horizons was related to transformation of illite. According to high moisture condition which is necessary for the weathering of illite, the occurrence of this process related to more humid climate of the past. Additionally, the presence of hydroxy interlayer vermiculites was related to previously wetter climate as well. So results of this study can be used for recognition of climatic change in the study area.

Gypsiferous soils comprise an important part of soil resources in arid and semiarid areas in the world and gypsum is the most common sulphate mineral in the soils of arid and semiarid areas. Accumulation of gypsum in the soils affect the most of physic-chemical, mineralogical and engineering properties of soils and in the most of cases results in serious problems for human activities. In this research, 9 soil profiles that all mostly located on the gypsiferous parent material in Nooshi Shahr region, were dug, described and sampled and their morphological, physical, chemical and mineralogical properties were determined using standard methods. Finally, soils were classified according to American soil taxonomy (2014). According to the results, gypsum content of soils varied from 62.91% in Cyy horizon of profile 1 to 2.91% in Ap horizon of profile 8 and each change in gypsum content of soils followed by variations in other properties of soils. Results showed that the soils with higher gypsum content had lighter color, lighter texture, lower values of organic Carbone and cation exchange capacity and higher values of electrical conductivity. These parameters reversely changed with decreasing of gypsum content of soils. Mineralogical studies revealed the presence of smectite, illite, chlorite, vermiculite and palygorskite as major clay minerals in these soils. The origin of illite, chlorite and kaolinite were related to the inheritance from parent material and the origin of vermiculite was related to the transformation of illite. Smectite group of clay minerals in these soils have been resulted from three origin of inheritance from parent material, transformation of other minerals (especially from illite) and neoformation. Palygorskite had pedogenic origin and has been formed in the soil via neoformation. The comparison of clay mineralogy of soils with different gypsum values revealed the presence of higher smectites in soils with higher gypsum and palygorskite was identified just in soils with higher gypsum. But, in soils with lower values of gypsum, illite and chlorite were the predominant clay minerals and palygorskite has not been identified in these group of soils. Finally, regarding to the effect of gypsum on morphological, physical, chemical and mineralogical properties of studied soils, in order to optimum use of these soils, revision in their management is necessary.

Salinization and solonization are of common processes in the soils of arid and semiarid regions and are serious problem in agricultural development and sustainable use and management of soil and water resources. Now a day, these processes are extremely active in lands around Urmia Lake and the most of agricultural and horticultural lands around Urmia Lake have been destructed due to these processes and as a result excluded from crop production cycle. In this study physical, chemical and mineralogical properties and classification of six soil profiles in the lands affects by Urmia Lake and two profiles in the lands which unaffected by Urmia Lake were investigated.
The study area has been located at the east of Urmia. Mean annual precipitation and mean annual temperature of this area are 345 mm and 10.83 ºC respectively and the soil moisture and soil temperature regims of this area are Dry Xeric and Mesic respectively. In order to perform this investigation, the position of six soil profiles in saline-sodic soils in the west of Urmia Lake were determined in which include nearly all of saline-sodic soils of this area. In order to control the effect of management and land use, all of soil profiles were dug in non agricultural lands. Additionally, two soil profiles in nonsaline-nonsodic soils which had the same conditions as saline-sodic soils were studied as representative profiles. Soil sampling was done from all of characteristic horizons and the physic-chemical properties of soils were determined using standard methods and soils were classified according to the last version of soil taxonomy. In order to mineralogical studies, pure clay samples were studied using SHIMADUZ XRD 600 diffractometer with 0.4 second time delay in 2θ angels between 2-30 degree, using beam source of Cukα with 30kv voltage and 30 mili ampere.
The results of this study revealed that the soils around Urmia Lake have been extremely salinized and alkalized and their physico-chemical and mineralogical properties were greatly different in comparison with the soils that have not been affected (or less affected) by Urmia Lake. According to the results, saline- sodic soils had more clay content, electrical conductivity, cation exchange capacity, exchangeable sodium and soil evolution, whereas, the content of organic carbon and calcium carbonate equivalent were higher in nonsaline-nonsodic soils. Clay mineralogical investigations revealed that the clay minerals in both groups of saline-sodic and nonsaline-nonsodic soils were mainly smectite, illite, kaolinite, chlorite, vermiculite, hydroxy interlayered vermiculite, mixed layered minerals and quartz. The origin of illite, kaolinite, chlorite, and hydroxy interlayered vermiculite were related to inheritance from parent material, the origin of vermiculite were related to transformation of illite, and smectites have been formed under inheritance from parent material, illite transformation and neoformation from soil solution. It seems that the neoformation is the main mechanism for the formation of smectites in saline-sodic soils. The saline-sodic soils contain more smectite than nonsaline-nonsodic soils and it might that the formation of smectite via neoformation is the main cause of high amounts of smectite in studied saline-sodic soils.
Accordingly, salinization and solonization which have been resulted from Urmia Lake, have caused mineralogical changes in soils around Urmia Lake and presence of more smectite in saline-sodic soils. Differences in morphological and physico-chemical properties of studied soils have been lead to extreme variety in their classification, in which these soils were classified in three orders, three suborders, four great groups and four subgroups.

Differences in physicochemical and mineralogical properties of soils close to Urmia Lake in two groups of soils (affected and unaffected by Urmia Lake), were studied in Dizaj-Dol region. Variance analysis of physicochemical properties of these soils showed that the values of OC and CEC in these two groups of soils were significantly different (P ≤ 0.1), and the values of EC, SAR, ESP and exchangeable Na of these soils were highly significantly different (P ≤ 0.01). However, soil depth and clay content in these two groups of soils were not significantly different. Clay mineralogical studies showed the presence of smectites, illites, kaolinites, chlorites and vermiculites in both groups of soils. Illites, chlorites and kaolinites are inherited from parent material, while smectites and vermiculites have pedogenic origin and have been formed via transformation of illite. In the soils which have been affected by Urmia Lake, neoformation from soil solution is the main origin of smectites. Comparision of clay minerals in the two groups of soils showed that the rising level of Urmia Lake during 1994-1995 caused the presence of high amounts of smectite and some hydroxy interlayer vermiculite in the soils affected by Urmia Lake.

In order to study the effects of Urmia Lake on physicochemical and mineralogical properties of soils in Dizadj Dol region, 24 soil profiles in two soil sequences with the similar parent material, topography and climate were investigated. One of these sequences is affected by Urmia Lake and the other one is not affected. According to the results, all of the profiles which have been affected by the Lake have nitric horizons. Natric horizons in these soils have been formed due to high amounts of sodium ions resulted from UrmiaLake. Varivace analysis of physico-chemical properties of these soils showed that the values of soil organic carbon, CEC, EC, exchangeable Na, ESP and pH of the two sequences were significantly different (P≤ 0.01), but soil depth, clay content and calcium carbonate equivalent were not significantly different. Analysis of clay mineralogy showed that the clay mineral composition in these sequences were mostly smectite, illite, kaolinite, chlorite and vermiculite. Smectites and vermiculites in these soils are mainly of pedogenic origin and have been formed via transformation of illite. In the soils which have been affected by Urmia Lake, the main origin of smectites was neoformation process from soil solution. Illites, chlorites and kaolinite are inherited from parent material. Comparision of results of soils in these two sequences showed that the upraise of Urmia Lake has lead low amount of organic carbon and to high amounts of EC, exchangable sodium, ESP, CEC, pH and higher amounts of smectite in the soils affected by Urmia Lake.