Calcareous Soils Of Southern Iran Research Articles

Improving Soil Texture Digital Mapping Using Landsat 8 Satellite Imageries in Calcareous Soils of Southern Iran

Improving Soil Texture Digital Mapping Using Landsat 8 Satellite Imageries in Calcareous Soils of Southern Iran

Vis-NIR-spectroscopy- and loss-on-ignition-based functions to estimate organic matter content of calcareous soils

ABSTRACT The study was carried out to derive pedotransfer (PTFs) and spectrotransfer (STF) functions to estimate soil organic matter (SOM) content measured by time-consuming and expensive Walkley–Black wet combustion (W-B), using SOM content obtained from loss on ignition (LOI) and spectra reflectance bands at visible (Vis) and near infrared (NIR) regions. In total, 171 soil samples were collected from calcareous soils of southern Iran. The SOM content of the samples was determined using W–B wet combustion (SOMW-B) and LOI at temperatures of 360 °C during 2 h (LOI360-2); 550 °C during 3 h (LOI550-3); and 375°C during 16 h (LOI375-16). For the spectroscopy method, partial least squares regression (SpectPLSR) and forward stepwise multiple linear regression (SpectSMLR) approaches were used for function development. The LOI360-2 procedure with R2 val of 0.9 for the validation dataset provided the best match with SOMW-B content. Furthermore, the SpectSMLR provided a STF using spectral reflectance bands at 495, 730, 970, 1906, 2262 and 2342 nm which predicted SOMW-B with R2 val of 0.87. Results indicated both the SpectSMLR and LOI360-2, as easy and inexpensive approaches, could be recommended to accurately assess SOM content of calcareous soils.

Soil Sensitivity to Wind and Water Erosion as Affected by Land Use in Southern Iran

Land degradation by soil erosion is one of the most severe environmental issues that is greatly dependent on land use management. In this study, the effects of long-term land use management (including annual cultivated field (ACF), fallow field (FF), rangeland (R), and orchard field (OF)), soil depth (0–10 and 10–20 cm), and soil organic matter content (SOM) on wind- and water-erosion indices were investigated in calcareous soils of southern Iran. Soil samples were collected from four above-mentioned land-use types, and some soil properties and erosion indices were measured. Results showed that the most of soil aggregates stability indices in the surface layer (0–10 cm) of OF were higher than those in ACF, FF, and R, respectively, by nearly 39%, 32%, and 47% for dry mean weight diameter of aggregates (MWDdry); 10%, 10%, and 48% for dry geometric mean weight diameter of aggregates (GMDdry); 21%, 17%, and 15% for water-stable aggregates (WSA); and 11%, 16%, and 31% for aggregate stability index (ASI). Moreover, the mean of the soil wind erosion indicators in OF (0–10 cm) were lower than those in ACF, FF, and R, respectively, by nearly 18%, 24%, and 26%, for wind-erodible fraction (EF); 43%, 38%, and 49% for soil erodibility to wind erosion (K); and 36%, 32%, and 41% for wind erosion rate (ER). In ACF, despite the high clay content, some aggregate stability indices such as MWøDdry and WSA were the lowest among studied land-use types which showed the negative effects of conventional tillage practices. Depth factor had only a significant effect on dust emission potential (DEP) in ACF, FF, and OF. In addition, there were significant and strong correlations between SOM and MWDdry (r = 0.79), WSA (r = 0.77), EF (r = −0.85), K (r = 0.74), and ER (r = 0.74) in all datasets.

Forms and distribution pattern of soil Fe (Iron) and Mn (Manganese) oxides due to long-term rice cultivation in fars Province Southern Iran

ABSTRACT To assess the effect of long-term rice cultivation and aquic conditions on the physicochemical properties and different forms of iron and manganese and also to make a comparison with non-paddy and adjoining uncultivated soils in calcareous soils of southern Iran. The soil samples were taken from the paddy and non-paddy soils with similar parent materials and landforms. The results showed that in the paddy fields, the amounts of available (extracted by DTPA), total (extracted by nitric acid), and poorly crystalline iron and manganese oxides (extracted by ammonium oxalate) were higher than those in the non-paddy soils and show the highest amount in the surface horizons of paddy fields. In general, the paddy land use increases the iron and manganese oxides with poorly crystalline form, Feo/Fed and Mno/Mnd ratios by 1.84, 1.57, 2 and 3.2, respectively. It also reduces the amount of pedogenic iron and manganese oxides and their crystalline forms relative to the adjacent uncultivated soils. Finally, a significant positive relationship was found between the amounts of poorly crystalline iron and manganese oxides and total form and the amount of organic matter and clay in the soils under study. Also, by changing the land use from the non-paddy to paddy field, the amount of smectite increased and, in contrast, the amounts of illite and chlorite decreased. Therefore, it seems that the significant amount of organic matter introduced and their burial caused by the plowing operation and, on the other hand, their slow decomposition due to the inactivation of aerobic activities in the reduction conditions is among the factors affecting the variations of chemical properties in paddy soils and, generally, wet land soils.

Effect of heating on some soil properties and potassium dynamics in calcareous soils of southern Iran

AbstractPrescribed burning of plant residues in agricultural lands may increase surface soil temperature and change the dynamics of soil potassium (K). In the current investigation, the effects of two hours heating of soil to 25, 100, 225, or 350°C and cycling (one and three cycles) on properties of eight calcareous soils from southern Iran and K dynamics (K forms, release, and fixation) were studied. Results indicated that heating to 100 or 225°C had no significant effect on pH,EC, or CEC but heating to 350°C increased soil EC (from 0.53 to 0.66 dS m−1) and decreased CEC (from 25 to 19 cmol kg−1). The heating to 350°C increased all forms of K including soluble (from 36 to 84 mg kg−1, 133% increase), exchangeable (from 285 to 490 mg kg−1), non‐exchangeable (from 598 to 686 mg kg−1), and HNO3‐extractable (from 922 to 1260 mg kg−1) decreased K fixation capacity of all soils (from 351 to 235 mg kg−1). Cumulative K release from soils to 0.025 M CaCl2 ranged from 114 to 438 mg kg−1 and increased significantly after heating of soils to 350°C and reached between 233 and 783 mg kg−1. Potassium fixation capacity of fine‐textured soils (soils 2, 6, 7, and 8) after 10 times extraction with CaCl2 was increased (65%–190%). Generally, heating of soils to 350°C caused combustion of organic matter and partial destruction or collapse of K‐bearing minerals and increased release of K.

Prediction of soil clay minerals from some soil properties with use of feature selection algorithm and ANFIS methods

Researchers use different methods to investigate and quantify clay minerals. X-ray diffraction is a common and widespread approach for clay mineralogy investigation, but is time-consuming and expensive, especially in highly calcareous soils. The aim of this research was prediction of clay minerals in calcareous soils of southern Iran using a feature selection algorithm and adaptive neuro-fuzzy inference system (ANFIS) methods. Fifty soil samples from different climatic regions of southern Iran were collected and different climatic, soil properties and clay minerals were determined using X-ray diffraction. Feature selection algorithms were used for selection of the best feature subset for prediction of clay mineral types along with two sets of training and testing data. Results indicated that the best feature subset by Best-First for prediction of illite was cation exchange capacity (CEC), sand, total potassium, silt and agroclimatic index (correlation coefficient (R) = 0.99 for training and testing data); for smectite was precipitation, temperature, evapotranspiration and CEC (R = 0.89 and 0.87 for training and testing data respectively); and for palygorskite was precipitation, temperature, evapotranspiration and calcium carbonate equivalent (CCE) (R = 0.98 for training and testing data). An attempt was made to predict clay minerals type by ANFIS using selected data from the feature selection algorithm. The evaluation of method by calculating root mean square error (RMSE), mean absolute error (MAE) and R indicated that the ANFIS method may be suitable for illite, chlorite, smectite and palygorskite prediction (RMSE, MAE and R of 0.001–0.028, 0.004–0.012 and 0.67–0.89 respectively for training and testing data). Comparison of data for all clay minerals showed that ANFIS method did not predict illite and chlorite as well as other minerals in the studied soils.

Potassium fixation of some calcareous soils after short term extraction with different solutions

ABSTRACTThis investigation was done to determine the release of potassium (K) from five calcareous soils of southern Iran using 0.025 M CaCl2, HCl and citric acid during six successive extractions and to study the K fixation capacity of the soils after K release experiment. Mineralogical study indicated that Vertisols and Mollisols were dominated with smectites; while other soils had illite, chlorite, palygorskite and smectite. Results indicated that citric acid extracted more K than CaCl2 and HCl (137 vs. 111 and 113 mg kg−1, respectively). The analysis of calcium (Ca), magnesium (Mg) and K concentrations in the solutions suggests that the exchange of K with soluble Ca and Mg (originated from dissolution of carbonates by acidic solutions) is the main mechanism of K release, but citrate is able to dissolve K-bearing minerals and release K in slightly calcareous soils. Soils with more illite released more K. Potassium fixation capacity of soils increased after extractions of soils with different extractants from 324 to 471 mg kg−1, with no significant difference. It is suggested to apply more K fertilizers in K-depleted calcareous soils and use of different solutions for extracting K from soil minerals may be a temporary and short term solution.

Combination of Fuzzy Logic and Analytical Hierarchy Process Techniques to Assess Potassium Saturation Percentage of Some Calcareous Soils (Case Study: Fars Province, Southern Iran)

This research was carried out to evaluate the capability of a combined fuzzy logic-based approach and analytical hierarchy process (AHP) for potassium saturation percentage (KSP) estimation in some calcareous soils of southern Iran. Based on a reconnaissance soil survey, 52 soil series were selected and different physical and chemical properties were determined. Five soil parameters including clay, cation exchange capacity, calcium carbonate equivalent, electrical conductivity, and organic carbon were chosen for analysis. Mapping was developed with the kriging method for each parameter. Different fuzzy membership functions were employed and weights for all parameters were calculated according to AHP. Finally, KSP classes were provided for each land unit. Results indicated that about 60% of the studied area is classified as having moderate to high KSP content (>3%) and 40% of had low or very low KSP content (<3%). Then 15 sample points were used for determination of the accuracy of the fuzzy method. Results showed that the fuzzy and AHP methods have a high accuracy for KSP estimation in the studied soils. Further development of the fuzzy and AHP methods would be worthwhile for improving the accuracy of KSP analysis.

Adsorption isotherms of some heavy metals under conditions of their competitive adsorption onto highly calcareous soils of southern Iran

ABSTRACTRecently, application of sewage sludge or effluents resulted in raising the concentrations of some heavy metals in some agricultural soils of Iran. Experiments were conducted to evaluate the competitive adsorption of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) on six calcareous soils. Adsorption characteristics were evaluated by equilibration of 1 g of each soil sample with 20 ml of 0, 10, 20, 30, 40, 50, 100, or 200 mg L−1 of their nitrate solutions and 0.01 M NaNO3 as background electrolyte. Furthermore, solid/liquid distribution coefficients (Kd) of studied metals, as an index of soil capacity to resist a change of the soil solution concentration, were calculated. Results indicated that amounts of adsorbed Pb, Cu, Zn, and Cd increased with increase in their concentrations in the contact solutions, but this trend was more pronounced for Pb and Cu than the others. For all studied soils and metals, Langmuir equation described the adsorption behavior fairly well. Furthermore, Langmuir and Freundlich equation parameters were positively correlated to cation exchange capacity (CEC) and smectite contents; whereas, they were negatively correlated to sand content. Considering Kd values, the selectivity sequence of the metal adsorption was Pb > Cu > Zn > Cd. Therefore, the risk of leaching and also plant uptake of Zn and Cd will be higher as compared to those of the other elements.

Canopy influences of five range plant species on the redistribution of chemical forms of iron in a calcareous soil

Iron (Fe) deficiency is common in calcareous soils of southern Iran. Chemical forms of Fe in a calcareous soil were studied in the beneath and the interspace soils of five common range plant species. Results showed that electrical conductivity (EC) and organic matter (OM) content was significantly higher in the soil beneath canopies as compared to interspace soil. The reverse was true for pH of the soil except in case of Salvia compressa. Among different forms of Fe, soluble and exchangeable Fe (SolEx-Fe) form was higher in the soil beneath canopy of all plant species as compared to interspaces. Similar results were recorded for Fe bound to organic materials (Om-Fe) but only in the case of Convolvulus argyracanthus, Echinops glanduloso-punctatus, and Centaurea intricata.In the soil beneath Convolvulus argyracanthus and Centaurea intricata canopies Fe bound to manganese (Mn) oxides (Mnox-Fe) was significantly higher but the amount of residual Fe (Res-Fe) was lower compared to the interspace soil. A reverse trend was, however, observed in the case of Teucrium polium, demonstrating differential distribution of Fe forms at the two locations. The summation of reactive Fe forms [SolEx-Fe, Fe bound to carbonates (Car-Fe), and Om-Fe] known as readily or potentially available Fe was higher in the soil under canopies than in interspace soils. It is assumed that the higher contents of OM and lower values of pH enhanced Fe availability in the soil under plant canopies in comparison with interspace soil.

Factors Affecting Micronutrient Availability in Calcareous Soils of Southern Iran

The present research was conducted to determine iron, manganese, zinc, and copper availability in 59 calcareous soils of southern Iran; to find relationships between micronutrient availability and some major soil properties; and to predict the micronutrient availability of soils from physiographic position, soil development, and climatic condition. Experiments were done by equilibration of 10 g soil sample with 20 ml DTPA extractant for 2 h. Results indicated that DTPA-extractable Fe, Mn, Zn, and Cu in the soils ranged 2.2–90.0, 0.6–15.4, 0.2–12.2, and 0.6–5.4 mg kg−1, respectively. Generally, Zn deficiency was more widespread, followed by Fe deficiency, but Cu and Mn contents in nearly all soils were sufficient. Micronutrient availability was significantly correlated with some soil properties including pH, organic matter (OM), clay, and cation exchange capacity (CEC). Soil development, physiographic condition, and soil moisture and temperature regimes had significant effects on the micronutrient distribution and availability. The highest amount of micronutrients (except Mn) was found in Histosols, lowland soils, and soils with aquic moisture and mesic temperature regimes. On the other hand, the lowest value was measured for Aridisols and soils with aridic and ustic moisture and hyperthermic temperature regimes. It is concluded that these factors may affect soil properties such as clay, pH, CEC, OM, and calcium carbonate equivalent and thereby micronutrient cycling and distribution in the soils.

Potassium fixation in soil size fractions of arid soils

Amounts of potassium (K) fixed in soil fractions of 10 calcareous soils of southern Iran were measured to evaluate the contributions of different soil size fractions to K fixation. Soil particles were fractionated after dispersion of the soils with an ultrasonic probe. Potassium fixation analysis was done by addition of 1000 mg K/kg samples. Mineralogy of the size fractions was determined by X-ray diffraction. The clay fractions were dominated by smectite, chlorite, mica, and palygorskite. Potassium fixation capacities ranged from 104 to 148 mg/kg for clay, from 102 to 155 mg/kg for silt, and from 96 to 187 mg/kg for sand fractions. A positive and significant relationship (P < 0.05) was obtained between K fixation capacity and smectite content for the clay fractions. High amounts of K fixed in the sand fraction may be explained by a larger diffusion path of fixed K out of the frayed edges of micaceous and smectitic minerals into the extracting solution, low cation exchange capacity (CEC) of the coarse fraction and thereby the high concentration gradient along solution and interlayers, physical entrapment of K ions in coarse aggregates cemented by carbonates, and by the presence of clay particles in coarse fractions due to incomplete dispersion of coarse aggregates.

Effect of Soil Minerals on Potassium Release from Soil Fractions by Different Extractants

Kinetics of potassium (K) release from sand, silt, and clay fractions of 10 calcareous soils of southern Iran were examined to evaluate the ability of different fractions to release K. Samples were successively extracted with 0.01 M CaCl2, HCl, and citric acid for 1496 h. Mineralogical analysis indicated that mica, chlorite, smectite, and palygorskite were the main minerals detected in the clay fraction. The sand and silt fractions were dominated by quartz, feldspars, and micas. Results indicated that the clay fractions released more K than the silt and sand fractions to all extractants (620, 283, and 148 mg kg−1 for clay, silt, and sand fractions, respectively, averaged for 10 samples and three extractants). The ability of acidic extractants to release K from the sand and silt fractions was much higher than that of CaCl2 solution. However, this difference was not significant (p < 0.05) for the clay fraction. For CaCl2, first-order equation, and for acidic solutions, all first-order, Elovich, and parabolic diffusion equations can describe the release rate of K from different soil fractions. Significant relationships (p < 0.05) were obtained between cumulative K released to three extractants and b and a values of Elovich equation with mica content in the clay fractions. Generally, the data presented here demonstrate the importance of clay fractions in K supply to plants in calcareous soils of southern Iran.

SOIL-CROP NITROGEN RELATIONSHIPS IN MAIZE GROWN ON CALCAREOUS FIELDS

Maize yield is mainly controlled by nitrogen (N) fertilizers. Failure to predict economic optimum N rate causes over-fertilization of N through traditional application methods. Five field trials were conducted to study soil-crop N relationships in maize under field conditions. Optimum level of N application in this study was much lower than conventional N fertilization in calcareous soils of southern Iran, demonstrating over-fertilization of N fertilizers by farmers. Linear regression equations were found between total nitrogen (TN) and chlorophyll meter readings (CMR) (years 2001 and 2002) in both locations demonstrating that chlorophyll meter might be used in predicting TN in maize shoot. Results indicated that soil sampling location influenced on soil NO3-N concentration at 4–6 leaf stage. In conclusion, N use efficiency can be improved by in-season soil NO3-N testing. It appears that in Kooshkak and Bajgah experimental stations, soil samples for NO3-N testing should be collected from shoulder and bottom of furrows, respectively.

Potassium release from sand, silt and clay fractions in calcareous soils of southern Iran

The release of non-exchangeable potassium from 24 calcareous soils of divergent mineralogy, from southern Iran, was examined. Sand, silt and clay particles were fractionated after dispersion with an ultrasonic probe. Samples were extracted with 0.01 M CaCl2 for 30 successive 2-h periods. The clay fraction released the largest amount of K in each soil. Cumulative K released ranged from 175 to 723, 35 to 128, and 71 to 146 mg kg−1 contributing 20–90, 4–39 and 2–54% for clay, silt and sand fractions, respectively. The lower proportion of K released from sand and silt fractions can be explained by the presence of a high content of CaCO3 and quartz in these fractions. The release kinetics for the non-exchangeable K data showed that parabolic diffusion and power function were the best fitting kinetic models. This indicated that slow diffusion of K from the mica interlayer positions is the main rate-controlling process. Cumulative K released and constant b values of parabolic diffusion model correlated significantly with the mica content of the clay fraction.

Factors affecting potassium fixation in calcareous soils of southern Iran

Potassium fixation capacity and mineralogical analysis of 24 representative soils, collected from southern Iran, were studied. Potassium fixation analysis was performed by adding six rates of K from 0 to 1000 mg kg−1 soil in a plastic beaker and shaking for 24 h. Mineralogical analysis showed that the clay fractions were dominated by smectite, chlorite, mica, palygorskite, vermiculite and quartz. In general, the studied soils fixed 8.5–55% of the added K. The potassium fixation capacity of the studied soils was significantly correlated with smectite content (r 2 = 0.87), clay content (r 2 = 0.60), cation-exchange capacity (r 2 = 0.79) and NH4OAc-K. Wetting and drying treatment and incubation time had significant effects on K fixation. The average percentage increase in K fixation following the wetting and drying treatment was 24 and 30% for surface and subsurface soils, respectively. The average percentage increase in K fixation with increasing residence time was 79 and 56% for surface and subsurface soils, respectively. Because K fixation is a diffusion process, time and increased concentration of soluble K (because of soil drying) are factors affecting the rate of K diffusion from a soil solution to the interlayer positions of the expansible 2:1 clay minerals.

Factors Affecting Potassium Pools Distribution in Calcareous Soils of Southern Iran

Different K pools in 197 surface and subsurface soil samples of southern Iran were determined to accurately assess factors affecting K pools distribution. Mineralogical analysis indicated that smectite, mica, chlorite, and palygorskite were the major minerals in the clay fractions. We obtained significant relationships between exchangeable, non-exchangeable, mineral, and total K with mica content, CEC, calcium carbonate equivalent, and clay content. Although many researchers have stated that mineralogical composition determines K status of soils, our studies indicated that some characteristics such as soil moisture and temperature regimes, soil orders, depth, agricultural activity, leaching, and some soil properties like particle size distribution, soil salinity, calcium carbonate equivalent, and cation exchange capacity could also affect K equilibration in the soils. Generally, Histosols and coarse-textured Entisols had the lowest contents of different K pools, and Alfisols and Vertisols had the highest values. On the other hand, soils with xeric moisture and mesic temperature regimes had the highest contents of different K pools. Further research is required to study the relationship between these findings with plant response and uptake of K.

Kinetics of non-exchangeable potassium release as a function of clay mineralogy and soil taxonomy in calcareous soils of southern Iran

The release of non-exchangeable potassium from 16 calcareous soils collected from southern Iran was examined. For this study, a method was used involving a total of 14 successive 15-min extractions with 0.01 M CaCl2 as an extractant. Cumulative potassium released from soils was in the range of 144–509 mg kg−1 for surface and 115–445 mg kg−1 for subsurface soils. The studied soils were categorized into two groups based on the cumulative K released, clay mineralogy and soil taxonomy. (I): Smectitic soils including Vertisols, Vertic subgroups and some Alfisols and Inceptisols; (II) other soils including Mollisols, Entisols, and other subgroups of Inceptisols and Alfisols. Cumulative K release was significantly (p < 0.01) higher in Group I than in group II. The release kinetics of non-exchangeable K showed the best fit to Elovich, parabolic and power function kinetic models. The Elovich and parabolic release rate constants were significantly (p < 0.05) higher in Group I than in Group II. Greater K release rate constants in Group I soils could be due to the heavy soil texture and domination of expansible clay minerals.

Factors affecting potassium release in calcareous soils of southern Iran

Experiments were conducted on 48 representative surface and subsurface soils collected from different climatic and physiographic conditions in southern Iran to assess factors affecting potassium (K) release and to find the best fitting models to describe the release kinetics of K to 0.01 m CaCl2. Mineralogical analysis showed that smectite, mica, chlorite, and palygorskite were the main clay minerals in the studied soils, whereas quartz, mica, and feldspars were abundant in the silt and sand fractions. Results indicated that cumulative K released ranged from 26.7 to 260 mg/kg (mean 176 mg/kg) for surface soils and from 37.9 to 198 mg/kg (mean 130 mg/kg) for subsurface soils. The predominant source of K in the soils appeared to be mica, because there was a significant relationship between cumulative K released and mica content. The percentage of non-exchangeable K release to CaCl2 during 1496 h was also correlated with the ratio of mica in the coarse fractions to total mica in the whole soil. Results showed that the Elovich equation adequately described the reaction rates of K release from surface and subsurface soils and suggested a heterogeneous diffusion process. We concluded that mica content and its particle size, soil depth, and some soil properties are the main factors controlling K release rate. On the other hand, we found no significant relationships between K release rate and climatic conditions, or physiographic positions.

Manganese‐Release Characteristics of Highly Calcareous Soils

Manganese (Mn) deficiency is common in calcareous soils of southern Iran. The ability of these soils to replenish the soil solution Mn depends highly on their Mn‐release characteristics. Kinetics of native Mn release by ammonium bicarbonate diethylenetriaminepentaacetic acid (AB‐DTPA) from 10 highly calcareous soils were studied for the periods of 1 to 1440 min. Results showed that Mn‐release rates were initially fast, followed by a much slower rate. Among seven kinetic models tested, two constant‐rate, simple Elovich, and parabolic diffusion models best predicted the pattern of time‐dependent Mn release well, much better than zero‐, first‐, second‐, and third‐order models. Significant correlations were observed between constant values of parabolic diffusion with those of simple Elovich model (Kp and Q0 with β s and α s, respectively), which demonstrated that Mn release from calcareous soils of southern Iran is probably a diffusion‐controlled process. Results of stepwise regression analysis between constant values of the best‐fitted models and selected soil properties showed that the content of easily reducible Mn oxides (ERMn) was the only soil property capable of predicting some constant values of the best‐fitted models. According to the equations, Mn‐release rates increased as the amount of ERMn increased. It is therefore concluded that ERMn is probably the main source of Mn release in these calcareous soils. Further research to assess the relationships of constant values of the best‐fitted models with plant growth parameters in calcareous soils is warranted.