Soil science
F. Ebrahimi Meymand; H. Ramezanpour; N. Yaghmaeian Mahabadi; K. Eftekhari
Abstract
Introduction: Delineating landscape into homogenous units is fundamental to managing resources and delivering sustainable development. The importance of this has long been recognized as a critical issue in various studies and it has been examined from different aspects. In soil mapping, the geopedologic ...
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Introduction: Delineating landscape into homogenous units is fundamental to managing resources and delivering sustainable development. The importance of this has long been recognized as a critical issue in various studies and it has been examined from different aspects. In soil mapping, the geopedologic approach is used for landscape classification, which was defined by Zinck (1989). This approach differentiates landscapes into landforms to increase the purity of soil map units. Therefore, the aim of this study was preparing geopedologic maps of the study area on the level of landform phases intending to make more homogeneous soil units.Materials and Methods: Honam sub-basin in Lorestan province is one of the most important agricultural areas in the Karkheh River watershed. Soil moisture and temperature regimes of the area were Xeric and Mesic, respectively. After a primary interpretation, a geopedology map of the study area at the landform level was prepared according to the geopedologic approach. After soil surveying, 31 profiles were excavated, described, and sampled in the largest delineation of this map. Ultimately, this landform unit was differentiated to the landform phase units using morphometric features and normalized difference vegetation index. Pedodiversity index was computed for each landform phase unit to investigate the credibility of the geopedological approach for this unit. The conditional probability of each soil family was also measured in each landform phase unit to compare statistical differences between landform phase units. Furthermore, statistical comparisons were made between the Shannon indices of each unit.Results and Discussion: The soils of the study area were classified into seven soil families according to Soil Survey Staff (2014). Based on the geopedology map, this area includes two landscapes of Piedmont plains and valleys. These two landscapes were differentiated to 6 and 3 relief/molding, respectively. Geologically, the study area has 5 lithologic units. Finally, 22 landform units were identified in this area. The area of the widest landform with the code of Pi461 was 1223.35 ha. With individual use of NDVI, TRI, and aspect map, this landform unit was differentiated into 3 phases, and with the use of these 3 maps collectively, 11 phases were differentiated. The results showed landform map unit of Pi641 with 31 soil profiles and 7 soil families has the highest value of diversity indices, such as 1.59 for the Shannon index. In addition, this map unit is a compound map unit consisting of several soils, where the highest probability of observing soils is related to soils A and B with 32.5% probability. By differentiating this landform unit into phases, the Pi461 map unit is separated into smaller units that are more homogeneous. For example, when it is separated according to the vegetation characteristics, the three phases Pi4611 (N), Pi4612 (N), and Pi4613 (N) were differentiated that have medium, low, and high vegetation, respectively. In this case, Pi4612 (N) map unit with 75% probability of soil C observation and Pi4613 (N) map unit with 87.50% probability of soil B observation are two homogeneous map units. The Shannon index of these two units is 0.56 and 0.37, respectively, which indicates the purity of these map units. The results also showed that diversity indices and conditional probabilities, respectively, were decreased and increased in most of the landform phase map unit compared to the landform map unit. The use of normalized difference vegetation index compared to other environmental features has been effective in separating the landform phase units and preparation of homogeneous map units. So, the most probability of observing the dominant soils of the study area increased from 32.25% in the landform unit to 52.63, 75.75, and 87.50% in the landform phase unit, and the Shannon index decreased from 1.59 in the landform unit to 1.36, 0.56, and 0.37 in the landform phase units. The use of other environmental features to increase the purity of the landform phase map unit is suggested in future studies.Conclusion: Results of using geopedological approach at landform level in the study area showed that this level is useful at highest levels of soil classification (from order to great group), but due to the complex nature of soils at lower levels of classification (family and soil series) does not have enough efficiency. Therefore, for improving the geopedology method accuracy and to present more uniform map units at lower levels of classification, landform phase maps were presented according to the environmental characteristics of the selected landform. The statistical comparisons between Shannon indices calculated for each map unit in the landform phase map showed a significant difference at the 90% probability level between most of the units, which indicates an increase in the purity of these units at the soil family level.
farrokh asadzadeh; Kamal Khosraviaqdam; Nafiseh Yaghmaeian Mahabadi; Hassan Ramezanpour
Abstract
Introduction: Soil texture is the average size of soil particles which depends on the relative proportion of sand, silt and clay contents. Soil texture is one of the most important features used by soil and environmental scientists to describe soils. Soil texture directly affects the soil porosity, which ...
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Introduction: Soil texture is the average size of soil particles which depends on the relative proportion of sand, silt and clay contents. Soil texture is one of the most important features used by soil and environmental scientists to describe soils. Soil texture directly affects the soil porosity, which in turn, determines water-retention and flow characteristics, nutrient-holding capacity, internal drainage, sorption characteristics and long-term soil fertility. High-resolution soil maps are essential for land-use planning and other activities related to forestry, agriculture and environment protection. Given the soil texture roles in controlling the soil functions, it is necessary to understand the spatial distribution of this feature in regional scale. As soil texture is a staticproperty, regional scale soil texture maps can thus help environmental scientists to predict different soil-related processes. The objective of this study was to develop a soil textural class map using Terra satellite MODIS sensor images.
Material and Methods: To achieve this goal, the digital elevation model SRTM radar of the studied area for soil samples from different altitudes and slopes was prepared in foursen consecutive 30 meters time frame. The nearest neighbor method with an error of less than 0.5 pixels was used and the elevation layers were mosaicked and transmitted to the UTM ZON-38 coordinate system and GIS Ready Became. The normalized difference vegetation index of bands 1 and 2 of the matrix was obtained to isolate the reflection of the electromagnetic spectrum of vegetation and soil. This final mosaicked digital elevation model was then divided into different altitudes to accurately evaluate the surface texture. The 60 spatial points were selected to estimate the texture of surface soil in thestudied area with systematic randomized sampling. In the current study, soil texture was determined forthe air-dried samplesusing hydrometer. The SWIR bands of MODIS with resolution of 500 meters were selected for sampling dates. After corrections, DN values of the bands for sampling points were extracted. The Pearson correlation coefficient and step wise regression techniques were used to establish proper relationships between the DN values of the SWIR bands and the soil particles. Kriging and cokriging methods were also employed to create a spatially distributed map of the soil textural classes.
Results and Discussion: The results showed that there is a close correlation between the SWIR bands of the terra satellite and the MODIS sensor with band 3, and using this auxiliary variable significantly reduces the estimation error. The best model for fitting semivariogram for clay, silt and sand contents were spherical, spherical and exponential models and the best fitting Cross-semivariogram for clay, silt and sand contents were spherical, exponential and exponential models, respectively. The highest and lowest error estimation was, respectively, related to sand and clay content. The maximum and minimum decrease of estimation error by the auxiliary variables was found for sand and clay content, respectively. The nugget/sill ratio of the kriging semivariograms was greater than 25%for sand and claycontentand lower than 25%for sand and silt content. This indicates that sand and silt contents had a strong spatial dependency, and clay content hada moderate spatial dependency. These ratios for cokriging cross-semivariograms of sand, silt and clay contentsware less than 25%. The interpolation of estimated soil texture was also determined using the cokriging method with 70% of the soil texture measured in the laboratory.
Conclusions: Our results indicated thatcokriging method estimated the soil particles more accurately as compared with linear multi-variable stepwise regression and kriging methods. Application of cokriging method also reduces the number of sampling points and the estimation error of soil texture zoning. Therefore, cokriging method seems to be better suited in impact assessments for data-scarceregions such as Iran.
Samaneh Abduolrahimi; Nasrin Ghorbanzadeh; Hasan Ramezanpour; Mohammad Bagher Farhangi
Abstract
Introduction: Rapid development of industrialization, heavy metal and radionuclide contaminants from industrial activities have posed a major threat to the environment owing to their toxicity, non-biodegradability and persistent accumulation. So various ecosystems are continuously contaminated with high ...
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Introduction: Rapid development of industrialization, heavy metal and radionuclide contaminants from industrial activities have posed a major threat to the environment owing to their toxicity, non-biodegradability and persistent accumulation. So various ecosystems are continuously contaminated with high levels of high-risk chemicals with different structures and levels of toxicity. Cadmium is one of the high-risk elements that enters the environment and can accumulate in the body of fish and other aquatic organisms, plants and livestock and be transferred to the human body. Therefore, the remediation of contaminated soils with cadmium in order to protect human health is very important. One method for remediation of pollutants is immobilization of them in the soil by adsorbents. Among the absorbents, bentonite has been identified for its unique properties, including high surface area and cation exchange capacity and adsorptive affinity for organic and inorganic ions, low cost and ease of access. If the physical and chemical properties of natural bentonites are improved by a special modification process, the adequate supplies for environmental purposes can be obtained. Among the biosorbents, rice husk has also been reported to be suitable for adsorption of cadmium and other heavy metals. This research was designed with the aim of decreasing the amount of cadmium in the soluble and exchangeable phase of a polluted soil under laboratory conditions in the presence of bentonite and rice husk. Considering that biological properties of the soil are an indicator of soil health and quality, so, after application of adsorbents, biological properties and some soil ecophysiological indices were also investigated.
Materials and Methods: The experiment was done with 13 treatments and 3 replications in a completely randomized design. Treatments were bentonite (B) and modified bentonite with iron (B-Fe), manganese (B-Mn), iron and manganese together (B-Fe-Mn), rice husk (RH), modified rice husk with phosphoric acid (RH-P) in two levels (2 and 5%) and control treatment (without adding adsorbent). Modification of bentonite was done with iron chloride (FeCl3.6H2O), manganese chloride (MnCl2.6H2O) and a mixture of FeCl3.6H2O and MnCl2.6H2O. Some of the characteristics of bentonite and rice husk adsorbents including pH, electrical conductivity, cation exchange capacity and organic carbon were measured. The contaminated soil with CdCl2 was treated with adsorbents and incubated for 2 months under constant lab conditions. After the incubation time, soil biological properties such as basal respiration, substrate-induced respiration (SIR), microbial biomass carbon (MBC), activity of some enzymes and also some ecophysiological indexes were measured.
Results and Discussion: The results showed that the basal respiration, SIR, MCB, activity of phosphatase, dehydrogenase and urease were less in the control treatment. The basal respiration and phosphatase activity in RH-P 5% treatment were 2.6 and 2.25 times more than those in the control, respectively. SIR and urease activity were highest in RH-P 5% treatment. The application of adsorbents to contaminated soil reduced soluble and exchangeable cadmium fraction. The lowest amount of soluble and exchangeable fraction of cadmium was in RH-P 5% treatment that showed 2.5 times reduction in comparison to control. In other words, immobilization of cadmium from these fractions improved soil conditions and caused increasing of biological soil properties and activity of microorganisms. The metabolic quotient was higher in the control treatment, probably due to lower microbial content, and decreased by adding adsorbents. Microbial quotient in control treatment was lower than other treatments which prove again the lower biomass carbon of control treatment. Carbon availability that is the ratio of basal respiration to SID, also was more in control in comparison to other treatments, perhaps due to the suppress or inhibition of dormant or zymogenous microbes by cadmium in the control treatment which can be stimulated to growth in the SIR experiment.
Conclusions: The results of this study revealed that cadmium with concentration of 30 mg kg-1has a toxic and inhibitory effect on the microbial activity of the soil. The addition of bentonite and rice husk adsorbents in particular modified form reduced mobility of cadmium and thus improved the biological properties of the soil and also had a positive effect on ecophysiological indexes.
The use of these adsorbents can be a cost effective, succeeded, and operative management strategy for immobilization of cadmium in contaminated soils that reducing the risk of plant reclamation, washing and entry into groundwater and food cycle.
javad seyedmohammadi; leila esmaeelnejad; Hassan ramezanpour
Abstract
Introduction: With regard to increasing population of country, need to high agricultural production is essential. The most suitable method for this issue is high production per area unit. Preparation much food and other environmental resources with conservation of biotic resources for futures will be ...
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Introduction: With regard to increasing population of country, need to high agricultural production is essential. The most suitable method for this issue is high production per area unit. Preparation much food and other environmental resources with conservation of biotic resources for futures will be possible only with optimum exploitation of soil. Among effective factors for the most production balanced addition of fertilizers increases production of crops higher than the others. With attention to this topic, determination of soil fertility degree is essential tobetter use of fertilizers and right exploitation of soils. Using fuzzy logic and Analytic Hierarchy Process (AHP) could be useful in accurate determination of soil fertility degree.
Materials and Methods: The study area (at the east of Rasht city) is located between 49° 31' to 49° 45' E longitude and 37° 7' to 37° 27' N latitude in north of Guilan Province, northern Iran, in the southern coast of the Caspian sea. 117 soil samples were derived from0-30 cm depth in the study area. Air-dried soil samples were crushed and passed through a 2mm sieve. Available phosphorus, potassium and organic carbon were determined by sodium bicarbonate, normal ammonium acetate and corrected walkly-black method, respectively. In the first stage, the interpolation of data was done by kriging method in GIS context. Then S-shape membership function was defined for each parameter and prepared fuzzy map. After determination of membership function weight parameters maps were determined using AHP technique and finally soil fertility map was prepared with overlaying of weighted fuzzy maps. Relative variance and correlation coefficient criteria used tocontrol groups separation accuracy in fuzzy fertility map.
Results and Discussion: With regard to minimum amounts of parameters looks some lands of study area had fertility difficulty. Therefore, soil fertility map of study area distinct these lands and present soil fertility groups for better management of soil and plant nutrition. Weight of soil parameters was0.54, 0.29 and 0.17 for organic carbon, available phosphor and potassium, respectively. Fuzzy map of study area includes five soil fertility groups as: 22.9% very high fertility, 27.7% high fertility, 35.53% medium fertility, 10.48% low fertility and 3.39% very low fertility. Consequently, a separated map for soil fertility prepared to evaluate soil fertility of study area for rice cultivation. Toinvestigatethe efficiency of fuzzy model and AHP in increasing the accuracy of soil fertility map, soil fertility map with Boolean method prepared as well. Boolean map showed 58.88% fertile and 41.12% unfertile.15 soil samples from different soil fertility groups of study area were derived fromcontrol of maps accuracy. 13 renewed samples of 15 and 9 soil samples have matched with fuzzy and Boolean map, respectively. Comparison of parameters mean in fuzzy map fertility groups showed that parameters mean amounts of very high and high fertility groups are higher than optimum level except potassium that is a few lower than optimum level in high fertility group, therefore, addition of fertilizers in these groups could not be useful to increase rice crop production. Phosphorus parameter amount is lower than the critical level in very low, low and medium fertility groups, then in these groups phosphorus fertilizer should be added to the soil toincreaserice production. The amount of potassium parameter is higher than the critical level and lower than optimum limit in very low, low, medium and high fertility groups, then in these groups addition of potassium fertilizer will results in theincrease of production. Organic carbon amount is lower than optimum level in very low and low fertility groups. With regard to the relation between organic carbon andnitrogen and phosphorus, therefore, the addition of organic carbon fertilizer could compensate deficit of nitrogen and phosphorus in these groups as well. Attention to the presented explanations and comparison of fuzzy and Boolean maps using parameters amounts in renewed sampling points for control of maps accuracy, it is distinct that fuzzy logic could influencetheoptimum using of fertilizers with increasing map efficiency and accuracy. In addition, relative variance and correlation coefficient amounts showed that fuzzy map has separatedquite wellparameters changes.
Conclusion: Effective parameters in soil fertility, includingorganic carbon, phosphorus and potassium were used topreparesoil fertility map for rice cultivation. With regard to the minimum amounts of parameters looks some lands of study area had fertility difficulty. Therefore, soil fertility map of study area distinct these lands and presents soil fertility groups tobetter management of soil and plant nutrition. Fuzzy and Boolean methods were used topreparesoil fertility map. Comparison of these two approaches showed that fuzzy method with AHP caused to increase theefficiency and accuracy of fertility map for rice. Separated and distinguish soil fertility groups in fuzzy map help suitable distribution and optimum use of fertilizers for rice production.
javad seyedmohammadi; leila esmaeelnejad; hassan ramezanpour; kamran eftekhari
Abstract
Introduction: Paddy soils are important and the base of agriculture in Guilan province. It is necessary to recognize these soils for understanding of their limitations and optimum use. Unsaturated soil submerging is the cause of collection of chemical and electrochemical process that has significant ...
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Introduction: Paddy soils are important and the base of agriculture in Guilan province. It is necessary to recognize these soils for understanding of their limitations and optimum use. Unsaturated soil submerging is the cause of collection of chemical and electrochemical process that has significant effects on soil fertility. Eh, rH and pH are important indexes that are used to investigate oxidation and reduction condition in submerged soils and have abundant effects on activity and sorption rate of nutrients. Decrease of Eh and rH in poorly drainage of paddy soils affects availability and solubility of nutrient. Different Fe forms are used for analysis of soils evolution trend and submerging influences on changes of Fe forms. The aim of the present study was conducted to investigate the effect of redox potential changes on soil characteristics and analysis of soils evolutional trend in different physiographic units.
Materials and Methods: The study area with 40000ha (at the east of Rasht city) is located between 49° 31' to 49° 45' E longitude and 37° 7' to 37° 27' N latitude in North of Guilan Province, Northern Iran, in the southern coast of the Caspian sea with different water table depth. The climate of the region is very humid with the mean annual precipitation of 1293.6 mm. The mean annual temperature is 15.8°C. The soil moisture and temperature regimes are Aquic, Udicand Thermic, respectively. The parent materials are derived from river sediments. The soils formed on the plateaues and upper terraces, river alluvial plain and lowland physiographic units were classified as Inceptisols and the soils formed on coastal plain physiographic unit as Entisols. Air-dried soil samples were crushed and passed through a 2mm sieve. Particle-size distribution, organic carbon and cation exchange capacity were determined by hydrometric, wet oxidation and ammonium acetate methods, respectively. Eh by Eh electrode, total iron, free iron and amorphous iron were determined using nitric acid, dithionite-citrate-bicarbonate and ammonium oxalate methods, respectively. The means of different Fe forms values compared through LSD test.
Results and Discussion: It can be seen especial morphological and physicochemical characteristics in studied paddy soils with high groundwater table due to artificial submerging in rice growing seasonDifferent Fe mottles such as orange mottles include lepidocrocite mineral was observed in studied soils. Low redox potential with average 145/7mV and rH with average 19.6 in lowland and coastal soils implicate intense reduction condition. In lowland soils Eh was lower than other units and it was lower in top horizons than to sub horizons in all of units. Eh index had inverse relationship with organic matter, because of high organic matter amount caused high activity of anaerobic micro-organisms, increase of iron reduction and reduction soils degree decrease. rH index amounts showed that studied soils had reduction condition and presence of brown iron and black manganese minerals proved this condition. CEC was high in top soil of physiographic units due to high amount of organic matter and clay content. Clay particles in plateaues were lower than other units because of alteration and suitable aeration and showed high evolution in these soils. Clay coatings were not observed due to high ground water table and its alternative fluctuation. Results showed amorphous iron in surface horizons with average amount of 24.3g kg-1 was higher than subsurface in all soils and had positive correlation with organic matter, because of high activity of anaerobic micro-organisms that prevent from transformation of amorphous iron to crystallized iron, therefore amorphous iron amount increased in presence of organic matter. Pedogenic iron was high in A and B horizons with regard to BC and C horizons due to aeration and weathering. In lowland and coastal land Fed was lower than plateaues and upper terraces and river alluviums units because of ground water presence and its alternative fluctuation. Fed-Feo index showed crystallized iron oxides, high amount of Fed-Feo index proved soils evolution and high weathering. Feo/Fed ratio was related to amorphous pedogenic iron and high amount of this index showed few evolution of soil. Fed/Feo and Fed-Feo indexes indicated the lower rate of crystallized iron with average 6.8g kg-1 in lowland and coastal soils and implicated the lower evolution of these units' soils, due to higher surface groundwater and its more fluctuation than soils of plateaues, upper terraces and river alluviums unites with average amount of crystallized iron 15/8g kg-1.The comparison of different Fe forms using LSD method showed significant difference at the 0.01 level for different Fe forms values in different physiographic units.
Conclusion: Submerging, high groundwater table and severe fluctuation caused noticeable changes in morphological, physical, chemical and electrochemical properties of studied paddy soils. Noticeable organic matter amount added to soil and their burial by puddling operation and slow decomposition were effective factors in redox potential changes of studied wet soils. In equal anaerobic condition, more organic matter caused to decrease redox potential in surface horizons of soils with aquic condition and reverse, lower organic matter caused increasing in redox potential. lower amount of Eh and rH proved severe reduction condition in lowland. Investigation of Fed-Feo and Feo/Fed showed that their amount in lowland and coastal land were lower than plateaus and river alluviums, therefore lowland and coastal soils had lower evolution. Mean comparison of different Fe forms values using LSD method showed significant difference at the 0.01 level for different Fe forms in different physiographic units.
