نشریه تحقیقات کاربردی خاک
سال هشتم شماره 3 (پاییز 1399)

Considering that Khuzestan province has a large area of land susceptible to dust generation, novel approaches such as Hyperspectral images could be used in the determination of soil characteristics. One of the main challenges in using hyperspectral images for evaluation of soil properties in these areas is the presence of some compounds such as gypsum which may lead to some errors in estimating other soil properties. This research has mainly been conducted to determine the soil-gypsum key wavelength in the dust center of Khuzestan province. To achieve this goal, at first the original soil spectrum was preprocessed using FieldSpec3 setup via five methods including the Savitzky-Golay filter, the first derivative with the Savitzky-Golay filter (FD-SG), the second derivative with the Savitzky-Golay filter (SD-SG), the Standard Normal Variant (SNV) and the Continuum Removal method (CR). Two Multivariate regression models including Partial Least Squares Regression (PLSR) and Support Vector Machine (SVR) were used and compared in the estimation performance of soil gypsum. The results showed that the SVR model had better performance rather than the PLSR model in estimating soil gypsum. Also, in the SVR model, the continuum removal method (R2cal=0.93, RMSEcal=2.47, RPDcal=3.71) and the main spectra (R2cal=0.76, RMSEcal=6.32, RPDcal=1.59) had the best and weakest performance in estimating soil gypsum, respectively. It is noteworthy that the continuum removal method (R2val=0.88, RMSEval=3.57, RPDval=2.49) and the original spectrum (R2val=0.52, RMSEval=7.81, RPDval=1.12) in the validation group showed the best and the weakest performance, respectively. In the present study, wavelength ranges around 1450, 1550, 1700, 2100, 2200, 2400 nm which had the highest level of correlation with soil-gypsum content, was obtained as the key wavelengths of the soil in sensitive areas to dust production.

The addition of heavy metals to the soil leads to change of their original distribution pattern. Distribution of heavy metals in soil depends on the type of metal, application level, time and soil characteristics as well. In order to study the effect of organic amendments (bichar 640 and 420) and inorganic amendments (zeolite, bentonite, leca and pumice) on chemical forms of Cd during incubation time in a calcareous soil, a factorial experiment was conducted in a completely randomized design (CRD) with 3 levels of amendments application in soil (0, 1 and 5 %) in three replications. Chemical distribution of Cd in soil was determined using Tessier sequential extraction method during 90- and 180-days incubation time. Results showed that during incubation time, Cd concentration increased in exchangeable (6.05%), carbonated (13.25) and decreased the oxide fraction (7.41%), organic fraction (10.74%) and residual fractions (2.98%) during the time. The application of bentonite (5%) were the most effective treatment in decreasing Cd concentration in exchangeable fraction during the incubation time that this decrease was 1.89%. Application of the organic amendments (biochar 640 and biochar 420) and inorganic amendments (pumice, leca bentonite, and zeolite) decreased the exchangeable fraction of Cd compared to the control. Application of 5% (w/w) of biochar 640 showed the highest decreasing the exchangeable fraction of Cd that compared to the control, it showed a decrease of 41.79%. The organic and inorganic amendments were effective on the immobilization of Cd in soil. However, the organic amendments were more efficient in immobilization of Cd than the inorganic amendments. These results might due to the high amount of organic carbon and cation exchange capacity of the organic amendments than the inorganic amendments.

Organic mulches improve the hydraulic and mechanical properties of agricultural soils and are one of the most important tillage practices. In this research, the effects of sunflower pate residue were studied on mechanical, hydraulic and physical properties of soil in laboratory scale. Experiments were carried out in the form of completely randomized design factorial at three levels of organic mulch including 0, 10 and 20 ton ha-1 and three levels of compaction energy including 121.41, 242.83 and 364.25 kJ m-3 via the Proctor's density test apparatus with three replicates. According to the results in the compaction energy of 121.41 kJ m-3, the dry soil bulk density with mulch of 10 and 20-ton ha-1 decreased to 2.85% and 5.1% compared to the soil without mulch. In addition, the saturated hydraulic conductivity increased to 794% and 905%, field capacity 5.29% and 7.01%, and permanent wilting point 2.34% and 10.27% respectively. In the compaction energy of 364.25 kJ m-3 similar results were observed. So that, in soil containing 10 and 20 ton ha-1 of mulch, compared to the soil without mulch, the dry bulk density decreased to 1.87% and 4.48% and the saturated hydraulic conductivity increased to 200% and 300%, the field capacity 2.79% and 7.31% and the permanent wilting point 7.56% and 14.43% respectively. The results of this study showed that Sunflower pate mulch improves the mechanical, hydraulic and physical properties of soil under different compaction energies, and with increasing compaction energy, the amount of improvement these characteristics decreases.

The content of gypsum and salts in soil profiles is one of the major challenges in arid and semi-arid region which comprise un-arable lands in Iran and their reclamation need their complete identification. Shoshab region is one of these lands which areas under cultivation reduced due to high salinity and gypsum content. The purpose of this study was to investigate the physico-chemical and micro-morphological properties of gypsic-alkaline soils in this area. Sampling of eight soil pedons were conducted in order to analysis of physical, chemical and micropedological characteristics and soil profiles were classified according to the Keys to Soil Taxonomy. The results showed that soil gypsum and calcite increased with increasing soil depth. The range of soil pH was high and was not affected by the soil depth. The presence of gypsum induced soil texture to  silt and sand fractions. The exchangeable sodium content was more in surface horizons and reduced with increasing soil depth. Micromorphological observations demonstrated hypocoating, coating, loose continuous, dense complete and dense incomplete infilling of gypsum in voids and channels walls. Lenticular, prismatic, and allabasrtin of gypsum crystals were observed in thin sections as well. Lenticular gypsum form was common in all soil thin sections because of the xeric moisture regime in this region. The dominant presence of gypsum and sodium in the soils induced to angular and sub angular blocky micro-structures and the aggregation effect weakened. The crystallites form was the usual observed b-fabric in all thin sections and in some cases identified as undifferentiated b-fabric. Generally, the existing of salt and gypsum in the soils of this area led to unsuitable soil voids and soil structure which is a serious environmental issue and plant growth promoting.  New great group and subgroups of Xerepts (Gypsic Calcixerepts) are suggested to be included in soil Taxonomy based on the properties of the some studied soil pedons.

In order to study the effect of different sources of sulfur on inorganic phosphorus fractions in a calcareous soil, an incubation experiment was conducted in a completely randomized design with five treatments in three replications. Treatments were including: control (without sulfur compounds), Al2(SO4)3, FeSO4, S + Ti (sulfur + thiobacillius) and H2SO4 at 2% (w/w). Amendments were incubated at 25±1 °C for a period of 12 days. Then, available-P (Olsen-P) and different forms of inorganic phosphorus were determined by sequential extraction method. The application of sulfur compounds caused significant changes (p≤0.05) in the amount of P-Olsen and inorganic forms of phosphorus (Ca2-P, Ca8-P, Al-P, Fe-P, Ca10-P) compared to control. The amount of available phosphorus in H2SO4, Al2(SO4)3 and S + Ti compared to control increased 240, 70 and 50%, respectively. Also, these amendments caused to insoluble forms of phosphorus, Ca8-P and Ca10-P, significantly reduced and in more soluble forms of Ca2-P and available-P could be used. In the amendments, FeSO4 caused 30% decrease in available-P and 4% increase in apatite compared to control. The results of correlation studies showed that available phosphorus (Olsen extracted phosphorus) had a significant correlation with Ca2-P, Ca8-P, Ca10-P and residual-P; the results of this study showed the effect of sulfur compounds on the distribution of phosphorus in different forms, so it is expected that Sulfur sources affect the usability and phosphorus chemistry.

Cadmium (Cd) is one of the most common and dangerous environmental contaminants. The effect of soft almond husk compost and its biochar was studied in the kinetic of cadmium desorption on a calcareous soil in the field of Shahid Bahonar Agricultural College, Kerman. For this purpose, compost and biochar of soft almond husk were used in three Levels (0, 2 and 4 % w/w) and were added to calcareous soil contaminated with three levels of cadmium (0, 40 and 80 mg kg-1). Sampling from treated soils was carried out 45 and 90 days after the contamination of soils with cadmium. Samples from treated soils were extracted by EDTA in 5 to 2880 minutes in different periods of time and the concentrations of cadmium were measured. The results showed that the application of compost and soft almond husk biochar reduced the desorption of cadmium compared to the control. The lowest amount of cadmium desorption occurred at level 4% w/w biochar and compost, while biochar had the highest reduction amount in the desorption of cadmium compared to the soft almond husk compost. Based on the experimental results, the cadmium desorption was highest in all treatments at initial times and decreased over the time. In other words, 50% of cadmium desorption occurred in the first 2 hours. In 90-day sampling compared to 45-day one, cadmium desorption from soil showed the highest decrease. Based on the determination of coefficient and standard error, the power function equation is considered as the best predictor of the cadmium release kinetics trend in the studied soil.

The preferential flow is enhanced by the nature of the soil structure and by providing a direct and rapid flow for transferring pollutants, leads to pollution of groundwater. Therefore, the purpose of this study was to investigate and compare some quantitative and qualitative preferential flow indices in different soil structures in Lorestan province. The study was conducted on un distributed soil columns with three different structures namely: (Granular, Blocky, and Massive) and a distributed soil with 3 replicate in a completely randomized design. In order to the plot breakthrough curve in each soil structure, injections of bromide at a concentration of 50 mg/L were carried out using a tension infiltrometer device under tension of 15-millimeter to soil columns. The breakthrough curve of different structures was plotted and accordingly the quantitative parameters of the preferential flow such as the mean time of breakthrough curve ( ) and the skewness index of the breakthrough curve (S) were calculated. For the study the paths of preferential flow, the infiltration of the dye tracer and image processing in different soil columns were performed. The results showed that soil structure had a significant effect on preferential flow occurrence in different soils. The comparison of breakthrough curve shape for different structures, showed the occurrence of preferential flow in blocky and granular soils and non-occurrence of this phenomenon in massive and disturbed soils. Also, the index of mean breakthrough time (0.2 and 0.39) and the skewness of breakthrough curve (1.17 and 1.45), in blocky and granular structures respectively confirmed the occurrence of preferential flow in these soils. The results of image processing showed that the infiltration depth of the tracer material in blocky structure was 29, 62 and 70% higher than granular, massive and disturbed structures, which demonstrated the role of type and enhancement of structure on occurrence preferential flow.

Various evaluations have shown that agricultural operations can have a dramatic impact on the quality of soils. Therefore, knowledge of soil quality in agricultural and natural resources is essential for optimal land management and achieving maximum economic efficiency. In this research, the long-term effects of conventional agricultural management in three areas of Ziveh, Nazlo, and Sirdagh with different moisture properties. Four soil samples (including two cultivated soil samples and two adjacent un-cultivated soil samples as control) were collected from each region in West Azerbaijan province. Some soil biological and chemical properties were investigated. Basal respiration rates, respiration due to substrate, microbial biomass, microbial population and nematode populations were investigated. The results showed that cultivation reduced basal respiration, substrate induced respiration, microbial population and nematode population in the studied areas. Also in uncultivated land use basal respiration rates (1.25, 1.1 and 1.75) and substrate respiration (1.8, 2.2 and 1.4) increase related to cultivated in the studied areas Sirdaghi, Naslow and ziveh, respectively. Basal respiration, substrate-induced respiration, carbon availability index and population of nematodes were 1.25, 1.8, 1.6 and 3.28 times higher in uncultivated related to cultivated in Sirdaghi, respectively. In general, it can be concluded that unscientific cultivation operations and lack of increasing organic matter will result in a loss of biological properties, and in the long- time result a decrease in soil quality.

Identification and synthesis of new organic iron chelates with higher efficiency than conventional synthetic chelates seems to be necessary to improve the nutritional status of iron in calcareous soils of Iran. In this study, first the amino acid chelates of tyrosine-iron (Fe-Tyr) acid-hydrolyzed chitosan-iron (Fe-Chi) were synthesized by laboratory methods and then some of their properties were characterized. A greenhouse experiment was designed as a factorial experiment based on completely randomized design with three replications including three types of iron chelate, Fe-Chi, Fe-Tyr and Fe-EDDHA (control) and three methods of soil application, fertigation and foliar application. Bean plants were grown and some growth parameters and total iron content in shoot and root were determined. The activity of root and leaf FCR (Ferric Chelate Reductase) enzymes were measured. The results of experimental and theoretical data showed that the tyrosine and chitosan were complexed with iron metal. The results showed that the highest shoot dry weight was observed in soil application of Fe-Chi and fertigation of Fe-Tyr. Also, fertigation of Fe-Chi increased root dry weight compared to control significantly. The highest content of total iron (10.3 mg pot-1) was observed in soil application of Fe-Chi in bean shoots which showed 36% higher Fe uptake than Fe-EDDHA. There was a significant positive correlation between shoot dry weight with iron and nitrogen content in shoots of bean plants. Investigation of root FCR enzyme activity revealed that soil application of Fe-Chi and fertigation of Fe-Tyr had the highest mean of FCR activity. In the foliar and fertigation application of Fe-Tyr, leaf FCR activity increased to 40 days after the start of the experiment. Soil application of Fe-Chi and foliar of Fe-Tyr during plant growth can improve the nutritional status of iron in bean plant

Aggregate stability of soils informs about their relative strengths against erosive forces and mechanical disruption. In this research, a hybrid Genetic Algorithm-Artificial Neural Network method was used to select the best subset of features affecting the mean weight diameter (MWD. In addition, the ability of ANNs and multiple linear regression (MLR) for quantifying the relationship between the MWD index and some soil properties was assessed. After the modeling process, the importance of the selected features in relation to spatial variability of aggregate stability was investigated. In order to prepare a suitable data set; MWD index and some soil features were measured in collected soils from 90 sampling points. Feature selection results showed that six soil features including clay, sand, organic matter, calcium carbonate, electrical conductivity, and sodium adsorption ratio had the greatest effect on the aggregates stability of the studied soils. According to the MWD modeling results, the obtained values of coefficient of determination (R2), mean absolute error percentage (MAEP), and root mean square error (RMSE) for the ANN model performance were 0.94, 21.39, and 0.07% respectively. These findings indicated that the developed ANN model was able to predict the complex and nonlinear relationships between the MWD index and the soil properties selected by the algorithm. Based on the sensitivity analysis results, calcium carbonate equivalent, sand particles, and organic matter were identified as key factors in estimating aggregate stability. Overall, this study provides a robust framework for the prediction of aggregate stability and identifying the most determinant parameters influencing it in arid and semi-arid soils that could be applied to other regions with similar challenges.

The drought crisis reveals the necessity of saving and optimal use of water in various sectors, especially in agriculture. One of the strategies to optimize use of water resources is the application of organic materials and natural (bio) and synthetic sorbents. The purpose of this study was to investigate the effect of polyvinyl acetate polymer, wheat straw biochar and cellulose hydrogel on the water retention capacity (at suctions 33, 100, 300, 500 and 1500 kPa), bulk density, aggregate stability and amount of organic carbon in the sandy soil. Therefore, a factorial experiment was conducted in a completely randomized design with three replications. A sandy soil was collected from the southeast Ahvaz. The factors included (1) amendment (Polyvinyl Acetate polymer, biochar and cellulose hydrogel of wheat straw), (2) amendment concentration (Polyvinyl Acetate polymer: 5 and 10 g/L, biochar and cellulose hydrogel: 1 and 3 % w/w) and (3) time duration (21, 42, 63 and 126 days). The results showed that all experimental treatments, at all pressure heads, increased soil water retention significantly (p<0.01). The addition of amendments reduced the soil bulk density and increased the organic carbon and aggregate stability. Minimum bulk density was observed in the cellulose hydrogel and biochar treatments at 126-days and in the polyvinyl acetate polymer at 21-days. Maximum organic carbon and aggregate stability were observed in the cellulose hydrogel treatment at 126-days. In hydrogel treatments with passing time, aggregate stability and water retention increased, but water retention of polyvinyl acetate polymer decreased with increasing time. Moisture absorbent biopolymer is a suitable replace to super absorbent synthetic polymers because not only increase soil organic matter but also enhance soil aggregate stability and water retention capacity.

The biochar produced from organic matter and agricultural residues is a soil amendment that can increase porosity, decrease bulk density and increase moisture content in the soil. In this study, the effects of different levels of 1.5 and 3.5 by weight percent of biochar produced from wheat straw and 1.5 and 3 by weight percent of fertilizers on wheat yield and soil characteristics were investigated. Water use efficiency and water consumption were also studied. The results showed that the highest average dry weight of wheat was 3% (B2) with 2.69 and the lowest was 1.05% by weight (2.22 g / plant). The average volume of moisture content in treatment B2 was 29.36% higher than other treatments, and the addition of biochar to soil increased the electrical conductivity related to fertilizer and control treatment. The highest mean water use efficiency in dry weight of wheat was related to B2 treatment with 2.87 g / liter, indicating a significant difference of 5% of the treatment with control and 1.5% fertilizer.

The aim of this study was to investigate the effect of straw mulch on water content distribution in a soil profile and simulating water flow in soil under shallow saline groundwater using HYDRUS-1D. Lysimetric experiments were conducted in two soil textures (sand and loam) at three water table salinity levels of 5, 10 and 15 dS m-1 mulch and no mulch with three replications in a three-month interval. Soil moisture content was continuously monitored in the depths of 5, 10, 20, 30 and 50 cm. Evaporation was also measured using Marriott bottle technique on a daily basis. The results showed that mulch cover retained soil moisture by 16 % and 20 %, and reduced evaporation by 27 % and 8% in surface layer of loamy and sandy soil, respectively. Our findings highlighted a strong correlation between measured and simulated soil moisture data using HYDRUS-1D with R2 ranging from 0.89 to 0.97 and 0.90 to 0.96 in sand and loamy soils, respectively. The numerical model estimated soil moisture with RMSE of 0.0121- 0.0489 cm3 cm-3 for loamy and 0.0129-0.0521 cm3 cm-3 for sand. The simulation results revealed that HYDRUS-1D overestimates moisture content of layers close to water table.

The cement production process is a major source of heavy metal contamination through dust emissions due to massive use of minerals and fossil fuels in this industry. The purpose of this study was to investigate the effect of distance from the source (Electrophilter) on the amount of heavy metals in the surrounding soils of Nahavand cement factory. Soil samples were collected at 300, 500, 800, 1000 and 2000 meter from the cement factory and also Electrophilter dust were sampled.At these intervals, 4, 4, 3, 4 and 2 points with three replicates were sampled, respectively. Also, 6 samples were collected 11 km from the factory as control area. Samples were prepared, digested and then the concentration of heavy metals was measured by atomic absorption spectrometry. According to the results, there was a significant difference (p<0.05) in the heavy metals concentration (Cd, Pb, Zn, Cr and Mn) between different distances and Electrophilter.The highest values of the pollution indices were observed at the distance of 300 meter and pollution decreased along with increasing distance from the cement factory. Meanwhile, the heavy metal concentrations in the control area were less than their concentration around the cement factory. The highest values of contamination factor (CF) and Igeo index were determined for cadmium, lead and nickel. The results of principal component analysis showed that the first component include Cd, Mn, and Pb and the second component include Zn, Ni, and Cr. Regarding to the, statistically significant difference between the distances, and higher concentrations around the cement factory than the control area, it can be concluded that Nahavand cement factory is the main source of heavy metals pollution in its surrounding soils.

There are innumerable challenges for digital soil mapping in the world full of change. One of these challenges is the sampling method which plays an important role in providing appropriate information for digital soil mapping and increasing its efficiency. Sampling method efficiency, with considering the number of samples, space changes, and cost, is a way to identify a set of scattered sampling locations in geographical space that have good location coverage of features. A good space coverage of features ensures accurate estimation of regression parameters and it makes effective spatial interpolation. In soil evaluation, the number of samples collected is limited by time and cost. Also, lack of roads, dense vegetation, and rugged terrain are caused more restrictions when visiting the area. These deficiencies lead to the use of stronger sampling methods. Methods that can provide a good description of space changes of soil and its features to reduce the number of samples, time, and cost are needed. So that it supports the final quality of the maps. Here are checked several methods of statistical sampling and geometric that optimize the geometric sampling pattern in geographical space. The strengths and weaknesses these methods considering spatial coverage, simplicity, accuracy, and efficiency briefly expressed. The results showed in terms of accuracy and efficiency; classified random sampling has the highest accuracy and has been widely used. In terms of spatial coverage; spatial coverage sampling is the best method. Due to the simplicity in the design and implementation stages; Simple random sampling, network sampling, and spatial sampling are the simplest sampling methods. Among the sampling methods studied, the Latin conditional sampling method is the most common method. It is widely used and recommended, and stratified random sampling and spatial sampling are the most efficient methods that optimize the sampling pattern in geographical space.