Sahar Taghdis; Mohammad Hady Farpoor
Abstract
Introduction: Soil magnetic properties reflect the complex chemical, geological and biological interactions occur in the soil. Thus, knowledge about the factors affecting soil magnetic properties helps better understanding and interpreting the results.. The lithogenic magnetic minerals are often found ...
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Introduction: Soil magnetic properties reflect the complex chemical, geological and biological interactions occur in the soil. Thus, knowledge about the factors affecting soil magnetic properties helps better understanding and interpreting the results.. The lithogenic magnetic minerals are often found in the coarse soil fractions (sand and silt) and they have inherited from parent rocks. Weathering and soil formation factors may lead increasing or decreasing of magnetic susceptibility. Climate and vegetation type are among the other factors affecting magnetic susceptibility too. Amount and distribution of magnetic susceptibility may also be affected by land use. The main objective of this research was to study the effect of different land uses and vegetation types on the magnetic susceptibility of topsoil related to soil properties.
Materials and methods: The study area was located in MahoonakeZiba around the Bardsir region, Kerman Province. The moisture and temperature regimes of the study area were sub aridic and mesic, respectively. The study area is located in the alluvial plain with igneous parent material originated from andesite, volcanic tuff, anddacite. Four land uses including farmland, well-covered pasture, disturbed pasture and degraded dryland farm with similar climate, topography, and parent material were selected. Overall, 60 complex surface samples were collected from the depth of 0-15 cm. The physicochemical analyses were done on the samples after that the soils were air dried, crushed, and passed through a 2 mm sieve. The soils magnetic susceptibility (ᵡ) in low (0.46 kHz) and high (4.6 kHz) frequencies were measured using the Bartington MS2 dual frequency sensor in two replications. The frequency depended magnetic susceptibility (ᵡfd %) was calculated as a development index of soil forming factors reflecting ferrimagnetic particle sizes.
Results and discussion: The pH of studied soils were in the range of neutral to alkaline and had the lowest coefficient of variance between measured parameters. The average of soil EC was 1.76 dS/m with a high coefficient of variance. The lowest amount of organic matter was in land use ofdegraded drylandfarm (0.26 %) and the highest was in farmland (2.15 %). The lowest amount of calcium carbonate with the coefficient of variance 12.37 % measured in the degraded pasture and its maximum was in the farmland. The loamy sand and sandy loam textural classes were found in the area under study. The minimum and maximum amounts ofᵡlf were determined in farmland (134.8× 10-8 m3 kg-1)and well-coveredpasture (1778.9 ×10-8 m3 kg-1 ), respectively and the relatively high mean value was 695.83 × 10-8 m3 kg-1. The topsoil of the study area was formed on alluvial deposits with a parent material originated from igneous andesite, tuff and dacite rocks. The high values of magnetic susceptibility of all soils under study could be attributed to the existence of initial magnetic minerals inherited from the parent material. The statistical analysis revealed a significant difference among ᵡlf values (p
A. Bayat; M. H. Farpoor; A. Jafari
Abstract
Introduction: Soil genesis and development in arid and semi-arid areas are strongly affected by geological formations and geomorphic surfaces. Various morphological, physical, and geochemical soil properties at different geomorphic positions are usually attributed to different soil forming factors including ...
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Introduction: Soil genesis and development in arid and semi-arid areas are strongly affected by geological formations and geomorphic surfaces. Various morphological, physical, and geochemical soil properties at different geomorphic positions are usually attributed to different soil forming factors including parent material and climate. Due to variations in climate, geological formations (Quaternary, Neogene and Cretaceous) and geomorphology, the aim of the present research was the study of genesis, development, clay mineralogy, and micromorphology of soils affected by climate, geology and geomorphology in Bardsir area, Kerman Province.
Materials and Methods: The study area, 25000 ha, starts from Bardsir and extends to Khanesorkh elevations close to Sirjan city. The climate of the area is warm and semi-arid with mean annual temperature and precipitation of 14.9 °C and 199 mm, respectively. Soil moisture and temperature regimes of the area are aridic and mesic due to 1:2500000 map, provided by Soil and Water Research Institute. Moving to west and southwest, soil moisture regime of the area changes to xeric with increasing elevation. Using topography and geology maps (1:100000) together with Google Earth images, geomorphic surfaces and geologic formations of the area were investigated. Mantled pediment (pedons 1, 3, 7, and 8), rock pediment (pedon 2), semi-stable alluvial plain (pedon 6), unstable alluvial plain (pedon 5), piedmont plain (pedons 9 and 11), intermediate surface of alluvial plain and pediment (pedon 4), and old river terrace (pedon 10) are among geomorphic surfaces investigated in the area. Mantled pediment is composed of young Quaternary sediments and Cretaceous marls. Rock pediments are mainly formed by Cretaceous marls. Quaternary formations are dominant in alluvial plains. Alluvial terraces and intermediate surface of alluvial plain and pediment are dominated by Neogene conglomerates. Siltstone, sandstone, and Neogene marls together with Neogene conglomerates are among dominant geological formations of piedmont plain. Eleven pedons affected by young Quaternary sediments, Neogene and Cretaceous marls in aridic, aridic border to xeric, and xeric moisture regimes on above-mentioned geomorphic surfaces were described and sampled using Natural Resources Conservation Service (2012) guideline. Physicochemical properties, clay mineralogy, and micromorphology of soil samples investigated and soils were classified by Soil Taxonomy (2014) and WRB (2015) systems.
Results and Discussion: Calcic, gypsic, argillic, and cambic diagnostic horizons investigated after field and laboratory studies. Typic Calcigypsids, Lithic Torriorthents, Typic Haplogypsids, Typic Haplocalcids, Typic Torrifluvents, Sodic Haplocambids, Typic Calciargids, and Xeric Haplocalcids subgroups were found using Soil Taxonomy (2014) system. Gypsisols, Calcisols, Luvisols, Cambisols, and Regosols reference soil groups identified by WRB (2015) classification system. Developed Alfisols, formed on piedmont plain geomorphic surface in xeric moisture regime. On the other hand, Entisols formed on rock pediments with aridic moisture regime. Soils in aridic moisture regimes were little developed with gypsic horizon, and where calcic horizon was formed, it was near the surface. Moving to the west with increasing humidity, gypsum was leached from the pedon and clay illuviation caused argillic horizon to be formed. Formation of Btk horizon in pedon 9 was attributed to a more paleoclimate. The maximum gypsum content of 44.7 % (gypsiferous soils) was found in soils affected by Quaternary formations and Cretaceous marls, but the maximum calcium carbonate (44 %, calcareous soils) was investigated in soils formed on Neogene conglomerate formations. Moreover, the maximum sodium adsorption ratio (SAR) content (29.2 (mmol(±) L-1)0.5) was determined for soils on unstable surface of alluvial plain. Smectite, vermiculite, illite, kaolinite, and chlorite clay minerals were investigated and smectite to illite ratio increased moving from aridic to xeric moisture regimes that prove the pedogenic source of smectite from weathering of illite. Coating and infilling of calcium carbonate, lenticular and interlocked plates and infillings of gypsum, and clay coatings were observed during micromorphological investigations. Micromorphological observations also showed that gypsum crystals decreased and calcite crystals and thickness of clay coatings increased from aridic to xeric moisture regimes. The minimum amount of gypsum crystals was found in Neogene formations. The results also showed that gypsum pedofeatures are dominant in Cretaceous formations, but calcium carbonate pedofeatures are the main features of Neogene formations. Due to presence of animal voids (channel, regular and star-shaped vughs, chamber, and vesicles), spongy microstructure was formed in agricultural lands.
Conclusion: Results of the research showed the important role of parent material, climate, and geomorphic surface on genesis and development of soils in Bardsir area.
