نشریه تحقیقات کاربردی خاک
سال هشتم شماره 1 (بهار 1399)

Biochar application can affect nutrient availability and biological properties of soil. The objective of this study was to evaluate the effect of biochar derived sugarcane bagasse at different pyrolysis temperature on nutrient availability and biological properties of a calcareous soil. Therefore, biochars were produced at 200, 350 and 500˚C and mixed at 1 and 2% (w/w) with the soil. The soil samples were incubated in ambient temperature (25 ± 2°C), for 90 days. At the end of experiment, nutrient availability and some of chemical and biological properties of soil were measured. The experiment was carried out as a factorial experiment based on a randomized complete design with two factors including biochar type and application rate in three replications. The results indicated application of biochars increased soil cation exchangeable capacity (1.9-12.9%), organic carbon (54-192%), available P (2.0-76.0%), K (5.2-18.1%) and Mn (12.6-17.5%). Application of B500 decreased the concentration of available Fe, Zn and Cu but application of B200 significantly increased of these nutrients. In addition, application of biochars significantly increased microbial respiration (20.0-108%), substrate-induced respiration (16.5-142%), microbial biomass carbon (8.2-124%) and activities of dehydrogenase (19.3-129%) and catalase (34.4-178%). The greatest increases in available concentration of micronutrients and microbial properties were observed in B200 treatment at 2% application rate. In general, the results indicated that sugarcane bagasse derived biochar produced at low temperature (200 and 350˚C) especially 200 ˚C can be suitable organic amendment for improving soil organic matter, nutrient availability and biological properties of calcareous soils in arid and semi-arid regions.

Potassium (K) plays a vital role in increasing the tobacco yield and controlling important quality parameters such as leaf combustibility. In order to evaluate chemical extractants ability to extract available soil K, a greenhouse experiment was conducted in a complete randomized block design with 26 soil samples with 3 replicates in some tobacco-cultivated soils in northwest of Iran. Evaluated K extractants were 1M NH4OAc, 1M NaOAc, 1M NaCl, 0.1 BaCl2, 0.1M HNO3, 0.01 HNO3, 0.01M CaCl2, NaTPB (5min.), NaTPB (4hs), H2O, NH4HCO3-DTPA, Mehlich I, Mehlich III and Morgan- Wolf methods. There was positive and significant correlation among potassium extracted by all the extracting methods. Leaf yield and potassium concentration in tobacco leaves were highly correlated with potassium extracted with 1M NH4OAC (r= 0.88, r= 0.94, respectively), NaTPB 4h (r=85, r=0.91, respectively), and 0.1 M HNO3 (r= 0.87, r=0.93, respectively). In soils with Kave /clay ratio less than 9, correlation coefficients between tobacco quantitative components and Kext significantly decreased. It was conluded that 1M NH4OAC and 0.1M HNO3 is suitable as soil testing methods for determining available K for tobacco in the soils of tobacco fields in northwest of Iran. These extractants showed high correlation with leaf potassium concentration and tobacco leaf yield. In addition, these two methods are simple procedure and cost effective.

The stabilization of the dried-up lakebeds is necessary. Recently, biocrust formation/ restoration through the microbial inoculation has been considered to stabilize the moving sands. Accordingly, this study planned to evaluate the possibility of using cyanobacterial inoculation and stimulation in stabilization of the moving sands beds of Lake Urmia at the laboratory conditions. To this end, the bulk samples were taken from Jabal-Kandi region (from Urmia) as a hotspot region for the moving sands, and the samples poured into the erosion trays. The most suitable existing cyanobacteria for the soil stabilization were selected, purified and proliferated from the origin soil. The stimulant nutrient (CHU10) was also prepared by dissolving various nutrients in sterile water. Then, the three treatments of control, stimulation of cyanobacteria, and inoculation of cyanobacteria were prepared by adding 1 l m-2 of sterile water, CHU10, and cyanobacterial solution at three replications. After 120 days, the wind (72 km h-1 for 30 min) was simulated on the trays. The rate of the wind-induced sand transport from the control, stimulated, and inoculated treatments were 1.58, 1.35, and 0.05 kg m-2 min-1, respectively. We found that both stimulated and inoculated methods significantly reduced (P< 0.01) the wind-induced sand transport by 14 and 96%, respectively, as compared to control. However, the inoculation of cyanobacteria was more effective than the stimulation of cyanobacteria. Assessing the scanning electron microscopy images from the soil surface also confirmed the ability of cyanobacteria in increasing the strong bindings between soil particles. Furthermore, inoculation of cyanobacteria increased the soil organic matter content and aggregate stability of the study soil, as important indicators of soil stability, by 162 and 106%, respectively. However, the inoculation of cyanobacteria under natural conditions is necessary to achieve an effective way in stabilizing dried-up beds of Lake Urmia.

The main purpose of this research was to study the effect of soil physicochemical properties on aggregate stability and magnetic susceptibility in two aeolian geomorphic units (desert pavement and aeolian clay flat) of Davarn plain in Rafsanjan. After taking 50 samples from the surface soil (0 to 10 cm) of desert pavement and 43 samples of aeolian clay flat, the magnetic susceptibility, mean weight diameter of aggregates and some of their most important physical and chemical characteristics were determined. Results showed that the mean magnetic susceptibility in desert pavement was 842.53 and in clay flat was 632.13 (*10-8 m3 kg-1) which is very high compared to those in soils of Iran and its main reason could be attributed to the parent material of the area. The low mean frequency-dependent magnetic susceptibility in the both study units also confirms this issue. The mean weight diameter of aggregates in the desert pavement varied from 1.20 to 1.93 mm and in the clay flats from 0.54 to 1.80 mm. The findings of this research showed a direct correlation between iron forms (Fed and Feo) with aggregate stability in the both of studied geoforms; however, the level of this correlation was high and significant for Fed. The results also indicated that there is a negative correlation between magnetic susceptibility with electrical conductivity (EC), organic matter (OM) and calcium carbonate equivalent (CCE) in the both of studied units. A positive and significant correlation was seen between total silt, total sand and its fractions with magnetic susceptibility in both geomorphic units. In addition, a negative correlation was seen between the mean weight diameter of aggregates and magnetic susceptibility, which its possible reason can be the presence of a large amounts of sand resulted from aeolian losses and its adverse effects on aggregate stability. The results of regression model indicated that dithionate iron and sand had a significant effect on the magnetic susceptibility; and sand, clay and electrical conductivity had a significant effect on aggregate stability.

In this research, suspended sediments of the Roze-Chay River, which were located on west part of Urmia Lake, were used to investigate the influence of ionic strength on sorption of cadmium. Adsorption of cadmium on the suspended sediments was investigated using batch experiments. The studied sediments (40 g l-1) was equilibrated in 6, 12, and 25 mmol l-1 ionic strength at definite pH with different cadmium concentrations (0-350 µmol l-1). The results indicate the more ionic strength; the less cadmium sorption occurs in all the samples. This effect of ionic strength on sorption can be attributed to the increased competition between competitive ions (Ca2+) and Cd2+. Isotherm data were described by using Freundlich, Langmuir, and Van-Huay models and better fitting were introduced Freundlich and Langmuir models. The average maximum adsorption capacity (b) of cadmium onto the suspended sediments was obtained 15.3 µmol g-1. Therefore, the suspended sediments have a very low potential for the sorption and transfer of cadmium. That means, even if cadmium is present in the bed of the river, these suspended sediments have no significant ability to sorb cadmium ions and cannot be considered as a carrier of cadmium in the environment.

Humic acid has a pseudo hormonal activity that increases plant growth and nutrient uptake. In the present study, the effects of different levels of humic acid and phosphorus fertilizer on vegetative growth indices (Plant height, Fresh and dry weight of stem and leaf, number of flowers, number of leaves and branches) and phosphorus availability in canola (Brassica napus L.) cv. Hyola 50 were investigated. For this purpose, the pot experiment as factorial based on completely randomized design in three replications has been conducted. Treatments include phosphorous fertilizer as super phosphate in three levels 0, 50 and 100 mg/kg, humic acid in three levels 0, 0.5 and 1 g/kg and application methods of phosphorous and humic acid. Based on the results, the effect of different concentrations of phosphorus, humic acid and its method of application, and their interaction in all studied traits, except for the number of branches, were significant (p≤0.01). Results of the interaction effect of humic acid concentration and its application methods in the presence of phosphorous treatments showed that the highest amounts of fresh and dry weight of leaves and stem obtained in 100 mg/kg phosphorous and 1 g/kg humic acid applied with irrigation water. The highest phosphorous content in leaves and stem by 0.3 percent observed in 1 g/kg humic acid and 100 mg/kg phosphorous applied with irrigation water. Additionally, different concentrations of phosphorous and humic acid and their application methods and their interactions decreased canola flowering period from 144 days to 93 days. Combined application of 100 mg/kg phosphorous and 1 g/kg humic acid within irrigation water resulted in maximum increase in vegetative growth indices and phosphorous content in canola shoot.

Determination of the row spacing cultivation for each tillage direction is essential to prevent water and soil losses in rainfed lands. Therefore, this study aimed to investigate the simultaneous effects of cultivation direction and row spacing on wheat field for preventing soil and water losses in rainfed lands. To this end, twenty plots with dimensions of 5×5 m2 were planted to investigate the effect of two tillage direction (along slope and on contour lines) and two row spacing (20 and 25 cm) early autumn 2015. Soil and water loss were measured after each natural rainfall resulting runoff during the growing period of rainfed wheat (from October 2015 to July 2016). Data analysis showed that both the tillage direction and row spacing significantly affected on soil and water loss (P<0.001). Soil and water loss in tillage on contour line was 5.9 and 3.5 times less than that the tillage along slope, and for the 25-cm row spacing was 47 and 34% less than the 20-cm row, respectively. Soil and water loss in the contour lines tillage with 25-cm row spacing decreased about 2.6 times and 90.3% as compared with the along slope tillage with 20-cm row spacing, respectively. The role of tillage on contour lines and cultivation with 25-cm row spacing was very obvious early cultivation, when sufficient vegetation cover wasn’t formed on the soil surface. Wholly, this study revealed that tillage on contour lines and cultivation with 25-cm row spacing is an effective strategy to control runoff and soil loss in wheat rainfed lands especially early growth period.

The distribution of phosphorus (P) forms is very important to evaluate the soil P in calcareous soils. Organic fertilizers increase the soil P dynamics by adding organic matter. This experiment was conducted by using 50 mg P kg-1 soil from sheep manure (SM), municipal solid waste compost (MSWC) and triple superphosphate (TSP) treatments with control (without fertilizer) in a calcareous soil in greenhouse conditions. At the end of the plant's physiological growth, dry weight of shoots, phosphorus concentrations of wheat, organic and inorganic forms of soil P were measured. The results showed that by using of 50 mg P kg-1 soilfrom SM, the highest P uptake by wheat was obtained from TSP treatment. All organic P forms significantly increased (P<0.05) in comparison with the control, but Highly Resistant Organic Phosphorus (HROP) showed invers trend. Moderately Resistant Organic Phosphorus (MROP) had the highest of organic P fraction and the Labile Organic Phosphorus (LOP) was the least. The highest fraction of mineral phosphorus was the apatite form. By applying of 50 mg P kg-1 soil from SM and TSP, Ca2P form increased by 4.2 and 3.9 times compared to control respectively. The AlP form increased by applying SM. MSWC and TSP treatments at 31.0, 44.0 and 46% compared to control, respectively. According to the research data, with the application of 50 mg P kg-1 soil from the source SM, increased organic phosphorus forms and by 50 mg P kg-1 soil from the source TSP, increased phosphorus absorption and its mineral forms in wheat cultivation.

Healthy lifestyle on dry land depends on monitoring and maintenance of the ponds. The aim of this study was to assess the effects of surface water-inflows on biological characteristics of wetland soils around Arak Meyghan-Lake. Two soil layers (0-30 and 30-60 cm) in the 4 sites of surface water-inflows were sampled in May and November 2014. The sites were the release sites of treated-municipal-wastewater, Shahrab-River, Farah-River and sodium sulfate-processing plant wastewater. The number of culturable microorganisms in the samples was counted on solid media and the soil basal-respiration (BR), substrate-induced-respiration (SIR), metabolic-quotient (MQ) and microbial-coefficient (MC) were measured. The number of soil fungi in the site Farahan-River site and the numbers of soil bacteria, enteric bacteria and actinomycetes in the release site of municipal wastewater especially in topsoil and in spring were significantly higher compared to those in the 3 other sites (respectively 4.85, 6, 5.51 and 3.92 log numbers). The numbers of the studied microorganisms in soil in the release site of sulfate-plant wastewater were significantly low and the numbers of fungi and actinomycetes were negligible in the most samples. Soil SIR was the most susceptible and responsive index among the studied biological properties. The release of municipal-wastewater in the playa improved the soil biological indices like BR (0.102 mg CO2 g-1 soil day-1), SIR (3.688 mg CO2 g-1 soil day-1), and MC (0.196 mg Cmic mg-1 Corg) significantly. In contrast, the MQ was significantly high in the release site of Shahrab-River and sulfate-plant wastewater (2.60 and 2.52 (mg C-CO2 g-1 Cmic h-1) respectively), showing the negative effects and the higher salt tension in these sites. Although the release of municipal-wastewater in Meyghan-Lake had positive effects on soil biological characteristics, it may have negative effects on biodiversity of these salty soils.

The most important factors which are effective for landscape analysis is spatial resolution of digital elevation model (DEM).In this study, the effect of spatial resolution on soil parameters and modeling of soil properties have studied. For this research 6 parameters including (height, slope gradient, slope aspect, minimal curvature, upland area and sediment transportation index) from 5 different spatial resolutions (10, 30 (base), 60,90 and 120) have originated and for modeling of soil properties (soil texture, K, P,EC,pH and soil depth) have used. The differences between mean of each parameter of spatial resolutions accomplished using Kruskal-Wallis test and multi linear regression, then the best model in each spatial resolution was selected based on AICC index. Our results depicted that with coarser DEM, the mean of slope gradient (G), sediment transportation index (STI) and the minimum curvature (Cmin) were decreased whereas the mean and minimum of upslope area (UP) was enhanced. Statistical indices of height showed the low sensivity to spatial resolution variations. Changes of mean and maximum slope aspect in different spatial resolutions have no regular trend. Only minimum curvature and upland area have significant difference relating to different spatial resolutions. With changes of DEM spatial resolution, the best combination of parameters for modeling of soil properties and AICc and R2adj will be change. Finally, our results illustrated that for an area with high variability of geomorphic conditions, there is no capability to use only one specific resolution for all soil properties.

Kanibarazan wetland is one of the most important satellite wetlands in the South of Lake Urmia, which due to biodiversity; it has been promoted as a wildlife refuge and Ramsar site. In this research, 15 stations were selected in the Kanibrazan wetland of Mahabadfor sampling of water quality parameters in 4 seasons of 2015 and a systematic sampling was carried out. Additionally, 6 bed sediment samples were collected to determine the bioavailable phosphorous content of the wetland during the summer season. Water quality parameters in this study included: nitrogen, phosphorus, transparency, chlorophyll a, biological oxygen demand (BOD), chemical oxygen demand (COD) and bacterial load in the wetland determined by standard laboratory methods. The results for BOD and COD showed that in all seasons the values of these parameters were much higher than the standards. The results also showed that TSI (TNs) was high in the first and second seasons and the increase in TSI (TP) and TSI (SD) values in the autumn and winter seasons were compared to the previous seasons. The average bioavailable phosphorous content in sediment samples was 29.4 mgkg-1 which indicates high risk of the phosphorous release from the bottom sediments to the overlying water and accelerating of the eutrophication process. In addition, the significant (r = 79, P < 0.01) correlation between Colwell-P of sediments and single-cell algae indicated Colwell-P can be used as a bioavailable phosphorous indicator in Kanibrazan wetland. Finally, based on the trophy indices, it was observed that the conditions of the wetland in the spring, summer, autumn and winter seasons are located in the state of Mild Mesotrophic, Oligotrophic, Mesotrophic and Acute Mesotrophic, respectively, and it can be stated that the status of the wetland is passing to the nutritional stage, due to lack of water supply with quantity and quality, especially in summer.

The continuous and incorrect application of herbicides can cause irreparable damage to the environment and life of living beings. Knowledge about the persistence of pesticides in soil is necessary due to the importance of identifying their potential for contamination of the environment and damage to crops. This study was conducted to investigate the effect of manure and biochar on the stability of metribuzin under saturated and unsaturated conditions in a completely randomized design with factorial arrangement. The treatments were two organic amendments (manure and biochar) and moisture condition (saturated and unsaturated) in 7 sampling times (0, 8, 16, 36, 64, 90 and 110 days). The results of measured concentration of herbicide in the treatments from the time of consumption up to 110 days in both saturated and unsaturated states showed that in treatments with organic amendments, reduced concentration of herbicide was higher than control soil. Degradation of herbicide followed first-order kinetics in the soil. A minimum degradation coefficient (k) was observed in control soil and maximum degradation coefficient was observed in biochar treatment that indicates the herbicide stability in control treatment and the positive effect of organic modifiers on increasing the rate of degradation of herbicide. The half-life of treatments was in the range of 34 to 38 days, maximum half-life (38 days) was related to the control soil in unsaturated condition and minimum half-life (34 days) was observed in biochar treatment in saturated moisture. The results of the experiment showed that degradation of herbicide in treatments with organic amendments under saturated moisture was higher than unsaturated condition.

Small gully due to high density per unit area is one of the most important causes of soil and water losses in watersheds that have gully erosion. In this research, with the selection of 81 small gullies in three watersheds from Ordadagh, Mulla Ahmad and Sarcham in Ardebil province, the size of gullies was determined with a one-year interval and the change in length, average width, depth and volume of them were recorded. Also, gullies size was estimated using the REGEM model with a one-year interval and the correlation between observed and estimated values was investigated. In order to modify and optimize the model for the studied areas, the model was corrected using regression models and again evaluated for estimating the gullies size and its variations over one year. To correct the model, the regressive shear stress parameters and soil erosion parameters of the REGEM model were used to estimate the dimensions of the gully including length, average width and moderate depth. The results show that the REGEM model only in Sarcham area had the useful efficiency in estimating gully erosion and its estimation correlation coefficient with measured gullies volume changes was 0.66. While estimating the size of the gullies with the modified model, in all three regions, showed a significant correlation with the measured values. The correlation between the measured and estimated values by modified model for gullies volume change was determined to be 0.76, 0.67, and 0.78, for Ordadagh, Mulla Ahmad and Sarcham respectively. Therefore, in order to apply the model in other regions, it is necessary to correct the model according the conditions of the region.

Soil cation exchange capacity (CEC) is defined as the amount of positive charge that can be exchanged per mass of soil. Modeling and estimating of CEC is a useful index of soil fertility. Assessing and designing various management scenarios requires having accurate information regarding the soil data bank. In order to estimate the soil CEC, 32 profiles were dug in Tabriz plain, and 131 different samples were collected from different depths and physiochemical experiments such as particle size distribution, organic carbon, pH and CEC of soil samples were performed. Then using seven regression models that were selected based on previous studies, were calibrated and evaluated for the study area. Also seven different architectures of artificial neural networks were designed to predict the CEC of soil and the results of artificial neural networks and multivariate regression models were evaluated using correlation coefficient (R2), root mean square error (RMSE). Results revealed that artificial neural network with R2 = 0.86 and RMSE= 2.14 is better than regression based functions due to the existence of nonlinear relations between the easily available soil properties (independent variables) and the CEC (dependent variable).

Understanding the capability of soils and land use limitations is a key factor in allocating the lands to the most appropriate use and also improving the growth conditions of plants in those lands. This research aimed to study the soils and recognize their limitations in cypress forest of Mobarakeh Steel Complex in order to prevent deterioration and decline of the trees. In the first step, plots were selected in the forest and a soil profiles was drilled in each plot. Soil samples were collected from the profiles. Also, soil and leaf samples were collected from the canopy of the healthy and unhealthy trees, separately. The results indicated that the soils have variety of limitations, including high gravel content (more than 50%), lack of organic matter (less than 0.5%) and nutrients, high calcium carbonate and pH coupled with soil compaction. There was a significant difference in the uptake of iron, manganese, zinc, copper, chlorine and sodium from the soil between healthy and unhealthy cypress trees. To improve the soil conditions in order to prevent the decline of cultivated trees, soil fertility and plant nutrition management program should be considered in the study area. Also, the use of organic fertilizers is recommended.