جستجوی مقالات مرتبط با کلیدواژه « کربن آلی » در نشریات گروه « آب و خاک »

Soil aggregate stability is a crucial indicator for evaluating soil structure, quality, and health. This index affects the physical and hydrological functions of the soil, which, in turn, depend on plant primary production and the capacity of organic carbon decomposition. Soil organic carbon plays a positive role in the formation and stability of soil aggregates. Soil organic carbon (SOC) causes a rapid decrease in water penetration into soil aggregates by creating a water-repellent coating around them and increases their stability against instant wetting stress. Land use and management, including cultivation systems and tillage methods, have an important impact on the stability and size distribution of soil aggregates. Mechanized sugarcane cultivation has a long history in Khuzestan province, particularly in Haft Tepe sugarcane cultivation and industry. Haft Tepe Agriculture is the first sugar production unit in Iran. Despite the increase in the use of chemical fertilizers, the yield of sugarcane crops has been decreasing due to the destruction of the physical properties of the soil. The study aimed to investigate the effects of different sugarcane cultivation systems on soil physicochemical-biological properties and soil stability indices in parts of Khuzestan province.

Soils were sampled from the surface of five farms in the Haft Tepe sugarcane cultivation complex located in the northwest of Khuzestan province. The farms included single-row, new planting cultivation (S-P); single-row, third ratoon cultivation (S-R3); double rows, new planting cultivation (D-P); double rows, first ratoon cultivation (D-R1); and uncultivated land (barren) that had been left unused for a long time. Soil organic carbon content, active carbon content, basal respiration, induced respiration, water-stable aggregates, and aggregate organic carbon fractions were measured in the sampled soil. Mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates were also calculated.

The study found that the organic C content was highest in the double-rows+new planting (D-P) method and lowest in uncultivated land (0.95% and 0.12%, respectively). The increase in plant density, biomass, and plant residue addition in D-P cultivation has led to an improvement in SOC content. The higher SOC content in cultivated lands compared to uncultivated land indicates the positive effect of many years of cultivation and irrigation. Among the different cultivations, double-row new planting (D-P) cultivation had significantly higher active carbon. In D-R1 cultivation, returning plant residues to the soil increased the SOC (0.59%) and active carbon content. The burning of sugarcane plant residues during harvesting and land preparation for new sugarcane cultivation in S-P fields appears to have led to a decrease in active carbon. Basal respiration and induced respiration values were significantly higher in single-row, third ratoon (S-R3) and double-row, new planting (D-P) cultivations, respectively. In S-R3 cultivation, the older plants and increased root biomass provided more rhizospheric organic C for microorganisms, resulting in higher microbial activity and respiration.   Microorganisms transform and decompose soil organic matter, which is a source of energy for their metabolic processes. Therefore, there is a close relationship between organic matter and soil microorganisms. Lower basal respiration in newly planted lands may be due to the process of land preparation for cultivation. Additionally, single-row new-planted farms had a clayey texture, which could reduce soil respiration. In general, the recycling of organic matter and microbial activity is lower in fine-textured soils compared to coarse-textured soils. The highest MWD and GMD were found in single-row, third ratoon (S-R3) and single-row, new planting (D-P) cultivations. The uncultivated land had the lowest MWD and GMD, indicating unstable soil structure due to low SOC content. The lower MWD observed in S-P cultivation could be related to tillage and hilling up operations. S-R3 cultivation had more plant residues compared to other cultures. Higher plant ages and increased root biomass and rhizodeposits led to an increase in soil aggregate formation and stability. Soil tillage, which reduces soil organic carbon, can decrease the stability of soil aggregates and structure. The S-P and D-P cultivations had the highest value of coarse aggregates (larger than 2 mm) and fine aggregates (0.53-2 mm). The highest amount of medium aggregates were observed in S-P, D-P, and D-R1 cultivations. Agricultural operations can break large soil aggregates into smaller ones, while low SOC content and burning of sugarcane residues can reduce the formation of large aggregates. The study found statistically significant differences in the OC content of aggregates among the different cultivations. The highest content of aggregates OC was found in coarse aggregates (0.25-2.0 mm) of D-R1, D-P, and S-P cultivations.

This study investigates the impact of mechanized and long-term sugarcane cultivation on the physical and biological properties of soil. Overall, the water stable aggregates and MWD were found to be unsuitable in some of the studied fields due to the low amount of SOC. This is primarily caused by the annual burning of sugarcane residue. Therefore, returning plant residues after harvesting is suggested as a significant solution to improve problems related to compaction, soil instability, and their harmful consequences.

In this research, the effectiveness of five organic matter treatments were investigated to determine the amount of soil organic matter, rhizosphere fungal and bacterial population. Microbial population in rhizosphere and nutrients concentration in the aerial part of corn were carried out in the form of a randomized complete block design in three replications. Before planting maize, soil organic matter was measured before and after adding five organic matter treatments for one year. Then, maize was planted and harvested before it reached seed production, and the concentration of some nutrients in the aerial part of maize was determined. Also, the bacterial and fungal populations were determined in the rhizosphere and non-rhizosphere soils. The results showed that the largest population of rhizospheric bacteria in the treatments of Leonardite (231×104 cfu g-1 soil), fulvic acid (229×104 cfu g-1 soil) and calcium lignosulfonate (218×104 cfu g-1 soil) and the largest population of rhizospheric fungi in the treatment of calcium lignosulfonate (263×103 cfu g-1 soil) was observed to show a significant increase compared to the control treatment. The highest maize leaf nitrogen was observed in the treatment of fulvic acid (35.78 g kg-1) and calcium lignosulfonate (33.9 g kg-1), and the highest leaf phosphorus was observed in the treatment of fulvic acid (4.27 g kg-1) compared to the control treatment. In the treatments of fulvic acid, calcium lignosulfonate, and Leonardite, the highest amount of potassium was measured, and in the treatment of calcium lignosulfonate, the highest amount of calcium and magnesium was measured. Leaf sulfur was the highest in Leonardite treatment, but there was no significant difference with calcium lignosulfonate and fulvic acid treatments. The amounts of leaf micronutrients were the highest in the fulvic acid treatment, but iron and copper in the leaves were also the highest in the calcium lignosulfonate treatment.

The reduction of water resources due to the issue of global climate change and population growth is one of the most critical issues facing the designers and planners of the development of green spaces in cities. Against these challenges, there is an urgent need to improve the efficiency of water consumption and chain use of water resources with suitable options. Due to the significant volume of urban wastewater Effluent, its reuse in green space irrigation is important from the point of view of water resource management from an ecological and economic point of view. The effect of the Parand city wastewater treatment plant on the chemical properties of soil under the cultivation of three types of cover crops (Frankinia (FR), Festuca (FE), Dichondra (DI)) in a bed with sandy loam soil is investigated. This study was conducted as a factorial experiment based on a completely randomized design using mixing of water and Effluent at 4 levels with irrigation treatments of zero (control), 50, 75, and 100% compared to fresh water and 3 replications, and then the soil chemistry characteristics such as pH, EC, OC, Na, Cl, Ca, and Mg were evaluated. The results obtained from the soil chemical analysis parameters showed that the pH value decreased in all the treatments with effluent compared to the control, and this decrease was not significant in any treatment. The values of EC and Cl have increased in all plants, and these values were significant in the FR100 treatments with an increase of about 195 and 561% compared to the control, and in the FE100 treatment with an increase of about 54 and 162%, respectively, at the 5% probability level. The amount of OC in the FR100 treatment was significant with an increase of about 41% compared to the control treatment, but in other plants, this ratio was not significant in any treatment. The maximum amount of Mg in the FR50 treatment was 30.27, which has a significant effect compared to other treatments. The amount of Na and Ca in the FR100 treatment was significant with an increase of about 343% and 130%, respectively, compared to the control treatment, while in FE and DI plants, this ratio was not significant in any treatment.

Large amounts of agricultural waste such as straw, leaves and pulps, with high nutritional value are produced every year. Grape pomace (GP) is rich in macro- and micro-nutrients and can be used as a soil amendment. However, due to its slow decomposition rate and the spread of diseases and pests, it should not be applied directly to the soil. Therefore, GP is composted in combination with other wastes. There is not enough information about the composting of GP and the effect of the produced composts on soil fertility in Iran. Hence, the aims of this study were twofold: to explore the impact of various GP composts on both soil fertility and spinach yield, relative to two levels of urea fertilizer, through a pot experiment conducted over two consecutive cultivation seasons; to categorize soil treatments based on fertilization regimes and timing (season), thus elucidating any patterns or trends in the observed effects. 

To investigate the effects of GP composts on soil fertility and spinach (Persius hybrid) yield, was conducted as a randomized complete block design with eight compost treatments, two levels of urea fertilizer (46%), and a control treatment (C0), in three replications and two continuous cropping seasons (spring and fall). Compost treatments included: high grape pomace (HG) (60-63%) with chickpea straw and alfalfa (HG-Ch-A), high GP with chickpea straw and sugar beet pulp (HG-Ch-B), high GP with alfalfa and sugar beet pulp (HG-A-B), high GP combined with chickpea straw, alfalfa, and sugar beet pulp (HG-All); four other compost treatments included low level of grape pomace (LG) (37-42%) combined with other residues/wastes similar to the first four treatments (LG-Ch-A, LG-Ch-B, LG-A-B, and LG-All). Urea treatments included: 150 kg per hectare (C150) (two-step top dressing) and 500 kg per hectare (C500) (three-step top dressing). A sandy loam soil was used for this experiment. The composts were separately mixed into the soil at a rate of 2% (by weight(. The first crop was grown for 50 days in May 2018 and the second crop was grown for 45 days in September 2018. In both seasons, the fresh and oven-dried weigh of spinach shoot and root were determined. Also, total concentration of K, Na, Ca, Mg, P, Fe, Zn, Cu, and NO3- were measured in spinach to determine the amount of soil elements taken up by the crop. In both seasons, soil pH and EC, and contents of soil organic carbon (OC), active carbon (AC), total nitrogen (TN), NO3-, NH4+, and exchangeable K, Ca, Mg, and Na, as well as available forms of P, Fe, Cu, and Zn were determined. One-way ANOVAs were applied separately to spring and fall data, and mean comparisons were made using Duncan's test at 0.05% level. To determine the similarities and dissimilarities of the different treatments based on their effect on soil characteristics, cluster analysis was performed on all soil characteristics that showed significant differences between treatments. 

In both cultivation periods, TN levels exhibited no significant variance across treatments. Notably, the highest potassium (K) levels were consistently observed in the HG-All and LG-All treatments, while the lowest K levels were consistently recorded in the C0, C150, and C500 treatments. In the initial cultivation period, no notable differences were observed between the C0, C150, and C500 treatments, except for potassium (K) and ammonium (NH4+), with significantly higher levels detected in the C0 treatment. Conversely, during the second cultivation period, significant disparities were observed among the C0, C150, and C500 treatments solely in terms of nitrate (NO3-) content, with notably higher nitrate levels detected in the C150 and C500 treatments. Through cluster analysis, all treatments from both cultivation periods were categorized into five distinct groups. Specifically, the C0, C150, and C500 treatments for each season were consistently grouped together, respectively, into groups one and two. All compost treatments of each season, except the HG-All treatment in the spring cultivation, were grouped into one class. In the second cultivation, the HG-Ch-A showed significantly higher EC than all treatments, except the HG-Ch-B. The LG-A-B treatment showed the highest amount of OC and C/N (in both cultivations), and NH4+ and Cu (in the second cultivation). The HG-Ch-A and HG-Ch-B treatments increased TN, P, K, Mg, OC, and AC in the second cultivation compared to the first. The amounts of all macronutrients and micronutrients, except Fe and Ca, increased in the compost treatments compared to the control and chemical treatments. In addition, an increase in EC was observed in the compost treatments compared to the control and chemical treatments, and an increase in pH compared to the C500 treatment. In the first cultivation, the LG-Ch-A and C500 treatments had significantly higher yields than the control. In the second cultivation, the LG-All, HG-All, HG-Ch-A, and LG-A-B treatments were the best compost treatments, while the LG-Ch-B and HG-Ch-B treatments were the weakest treatments in terms of soil fertility and plant yield. In both seasons, the absorption of elements by spinach depended on multiple factors, including the element type, its available content in the soil, its initial content in the composts (or fertilizer), soil pH, and yield. 

The application of GP composts over two consecutive growing seasons increased the levels of nitrogen, phosphorus, potassium, magnesium, zinc, copper, active carbon and organic carbon in the soils. These results are very important as magnesium, copper and zinc are rarely applied by farmers. In contrast, depletion of all elements, except organic carbon, occurred in the control and chemical fertilizer treatments due to plant uptake of elements. The combination of chickpea straw with sugar beet pulp is not recommended for the production of GP compost, especially at low GP levels, due to its minimal effect on soil fertility and plant yield. Despite the positive effect of the GP composts in increasing soil fertility, the continuous application of large amounts of these composts is not recommended in the arid regions due to the increase in soil EC and pH. The difference between the compost treatments after two applications of GP composts was less than after one application; these results were confirmed by cluster analysis, in the sense that all compost treatments in the second season were placed in one cluster.

Biochar is a carbon-rich charcoal material resistant to decomposition, which is produced by heating biomasses in an oxygen-free environment or with limited oxygen. It is used with the aim of increasing organic carbon and improving the physical, chemical and biological characteristics of the soil. Thus its use in the low-fertile soils of hot and dry regions of Iran, which are often deficient in organic carbon, is important. Addition to its high stability in the soil, biochar can sequester atmospheric carbon dioxide in the soil for several hundred to several thousand years. In addition, it can improve soil fertility for a long time by affecting its physical, chemical, and biological properties. The stability of biochar is affected by several factors, such as the characteristics of biochar and soil, the interaction of biochar with soil components and environmental factors, which are examined in this article. Therefore, it is important to use biochar in the soils of arid and semi-arid regions of Iran, which are often deficient in organic carbon.

In this review article, while investigating the evidences of the high stability of biochar in the soils, the   most effective factors the fate of biochar in the soil, including the mechanisms of biochar removal from the soil, biochar stabilization in the soil, and interactions of biochar with soil components, and the gaps and required research areas are presented.

Biochar is higher resistant to degradation than the original carbon compounds in biomass. However, by interacting with soil components, biochar undergoes changes over time and is removed from the soil. The intensity of these changes and biochar residence time in the soil depends a lot on the type of biochar; So, biochars produced from grassy biomass and biochars produced at low temperatures are less stable. In addition, biochar interacts with all soil components, including organic matter, mineral particles, nutrients, living organisms, and soil water and atmosphere, and the result of these interactions determines the stability of biochar in soil. External factors such as the presence of plant and induced root changes, wind and water erosions, leaching, and fire also affect the fate of biochar in the soil. Among these, considering the interactions between microorganisms and biochar in soil, it seems that soil microorganisms play the most important role in the decomposition and destruction of biochar in soil. However, mechanisms such as the entrapment of biochar particles inside aggregates, binding of biochar with organic and inorganic components of soil, and inactivation of soil enzymes by biochar can increase the stability and durability of biochar in soil.

Considering the very high stability of biochar in soil and the necessity of increasing soil organic carbon as the main factor of soil fertility factor, the use of biochar in Iranian soils it can directly and indirectly improve the fertility of these soils while increasing soil organic carbon. However, after biochar is added to the soil, it interacts with the soil components and its characteristics change and evolve over time (aging). However, due to the novelty of biochar technology and the wide range of its application fields, our information on its interactions with various soil components, its long-term changes and developments in the soil and environment, and its long-term effects on the soil and the environment are not yet clearly defined and much research is needed in this field.

More than 80% of Iran's area is arid and semi-arid. Arid and semi-arid soils have various problems and limitations. One of the most important factors limiting soil fertility and crop production in these areas is the lack of soil organic matter (SOM). In more than 60% of Iran's agricultural lands, the amount of SOM is less than 1%; While its optimal level in soils should be 2-3%. SOM, as one of the most important indicators of soil health, plays a vital role in soil fertility and crop production; So, by increasing the amount of SOM, the physical, chemical, and biological characteristics of the soil and crop yield can be improved. However, the stability and residual effects of the fertilizers and organic wastes in the soil are low. Nowadays, converting organic wastes and residues into biochar and adding them to the soil is one of the new methods of increasing soil organic carbon, which enhance soil fertility and crop yield and has high residual effects due to its high stability. However, due to the specific characteristics of the soils of arid and semi-arid regions, using biochar in these regions is associated with challenges and has received less attention. In this review article, while reviewing the positive effects of biochar on soil quality indicators and crop production, the challenges of using biochar in the soils of arid and semi-arid areas, especially in drylands, and the solutions to overcome these challenges have been reviewed.

The purpose of this research was to investigate the impact of pH, EC, and organic carbon (OC) on the amount of total nitrogen in the soil of the Zarin Shahr Region using statistical analyses (borderline analysis and step-by-step regression). In the Zarinshahr region, a comprehensive study was conducted for a duration of one year across all four seasons. The study employed GPS technology to select a total of 60 points in agricultural, tree plantations, and bare soil areas while ensuring an average distance of 546 meters between each point. The plots areas were 50x50x20 cm in length, width, and height. The various soil samples collected from these plots were analyzed. Then, the maximum reaction of a biogeochemical process to a certain environmental factor was determined using borderline analysis. According to the findings, the soil's EC exhibited higher readings during the hotter seasons of the year, in comparison to other seasons. Specifically, during the summer, the maximum value of this parameter was approximately 1587 dS/m, while in the winter, the values were nearly 1140 dS/m. Also, pH levels of the soil was generally alkaline. The seasonal variations in soil OC and organic matter percentage were evident, with notably lower values (ranging from 0.04-2.52) in the autumn and winter, followed by a marked increase during the summer and spring (0.12-2.39). Boundary line analysis was used to investigate the relationships between variables and the values of indicators that caused the maximum increase in soil nitrogen. It was ascertained that OC percentage and soil nitrogen percentage exhibited a significant linear correlation in all land uses. Hence, increase in OC percentage resulted in an increase in the total nitrogen content in the soil. The step-by-step regression analysis in a systematic manner revealed that, within the variables under investigation, the percentage of total nitrogen in the soil can be determined based on the impact of two key parameters, namely, EC and the percentage of OC. The results suggest that use of boundary line analysis and step-by-step regression represent a viable approach for determining the effects of the significant factors on the levels of nitrogen content in the soil.

Zagros forests play an essential role in providing groundwater resources, air conditioning, soil protection and preventing erosion, and providing wildlife habitat. Today, the ecosystem of these forests has become completely fragile due to improper exploitation and destruction. This study was conducted in areas of Zagros forest in Kermanshah province that were included in the implementation of the protection plan, including Sorkhak and Tappeh Goleh in Islamabad and Qeshlaq in Ravansar. The main purpose of this study was to evaluate the implementation of the forest conservation plan on soil properties.

For this purpose, composite soil samples were collected by random-systematic method from the mentioned area and their respective control area, and their physical, chemical, and biological properties were measured. Soil characteristics in Tappeh Goleh, Sorkhak and control sites were analyzed by one-way analysis of variance and Qeshlaq soil characteristics were analyzed by T-test. The soil samples collected from the forest were air-dried in the laboratory environment and sieved (2 mm). Then their physical and chemical properties (pH, EC, bulk density, and soil organic carbon content) were measured. Soil samples were collected with sterile equipment and sieved through a 4 mm sieve. Fresh and moist soil was kept at a temperature of 4 °C for soil biological tests (basal soil respiration, metabolic quotient, and microbial biomass carbon).

The results showed that no statistically significant changes in soil EC and pH were observed in all study areas. The amount of organic carbon in Sorkhak was significantly higher. Among the measured biological properties of soil, no significant change was observed in organic carbon mineralization in all study areas. However, microbial biomass carbon and soil metabolic quotient in Sorkhak were significantly higher than those in control and Tappeh Goleh areas.

The results of this study showed that the forest protection plan if properly implemented in the field (Sorkhak area) will be able to revive some soil quality indicators. The provisions of forest protection management and the process of soil regeneration in these forest lands should be investigated. Among the studied indicators, soil organic carbon and microbial biomass carbon were among the indicators that responded well to the correct and complete implementation of the forest protection plan, and we have witnessed the improvement of these parameters in managed lands. This suggests that biological soil quality indicators are more sensitive to responding to land management and respond more quickly to these changes.

In recent years, one of the most suitable options for saving water resources is the recycling of urban and industrial wastewater for irrigation which is common practice in different parts of the world, but if the use of wastewater Sewage can not be managed properly for irrigation, which may cause environmental problems. the purpose of this study was to investigate the effects of long-term irrigation with municipal treated wastewater (TWW) compared to well water (WEW) as a control treatment on soil chemical in three layer with three replications in a two-year split plot trial design was performed. in three It has been repeated. due to the availability of this source and the possibility of leaching, the risk of saltinification of this land has been somewhat overcome. the risk of sodiumization of this land has led to the fact that, due to the high clay content of this land, its future consequences include traps and reduced permeability. Irrigation with TWW resulted in a significant increase of 0.3 units of pH in irrigated soils with wastewater compared to WEW. The TN content varied between %11.30 and %25, which indicates the variable percentages of this parameter at the region of the study area. Also, the results of soil organic carbon (OC) changes as a result of irrigation with TWW showed that this irrigation effect was significant and increased by 55% for irrigation compared to treatments irrigation with WEW due to Organic contents in the wastewater.

The aim of this study was to investigate the effect of crop type on soil carbon accumulation in soybean (Glycin max L.) and wheat (Triticum aestivum L.) rotation, in 150 fields of soybean and 89 wheat fields in Gorgan county, in the cropping years of 2016-2017 and 2017-2018, respectively. In order to determine the amount of organic carbon and its changes, soil samples from two depths of 0-15 cm (first depth) and 15-30 cm (second depth) were prepared and then soil carbon was measured by Walkley-Black method. Spatial distributions of soil organic carbon and carbon accumulation potential at different depths and also, in the pre-sowing and post-harvest stages were performance using different types of interpolation methods in ArcGIS enviroment. The results of interpolation methods showed that Kriging was the best model for interpolation of organic carbon distribution and carbon accumulation in agricultural fields of Gorgan. Average amounts of soil organic carbon in the first depth of soybean fields were as 14.84 mg ha-1and 13.41 mg ha-1for the second depth in the pre-sowing stage. Also, it was estimated as 16.85 mg ha-1 in the first depth and 15.52 mg ha-1 for second depth, in the post-harvest stage. The amounts of soil organic carbon in the wheat fields were determined about 16.78 and 15.25 mg ha-1for first and second depths in the pre-sowing stage, respectively. Those were 13.68 and 12.30 mg ha-1for of first and second depths in the post-harvest stage sampling, respectively. The results showed that the eastern, northern, northeastern, southern, southeastern and central parts of the county had the highest carbon accumulation due to access to modern irrigation systems, more water resources, better crop management, suitable return of crop residue to the soil, develop of minimum tillage, minimizing the burning of residue and using manure. Results showed that the western and southwestern parts of the county had the lowest carbon accumulation.

Investigation of soil attributes is one of the ways to evaluate and manage forest ecosystems. Altitude is considered as one of the effective factors on the soil quality, especially soil organic carbon (OC). However, variation of the soil OC stocks at different altitudes of Arasbaran forests is still unknown. Therefore, this study was conducted to examine the spatial distribution of OC values, and some other chemical properties in different soil depths affected by altitude in Arasbaran forests.

In this study, a factorial experiment was conducted in a randomized complete block design in three replications. Overall, 60 soil samples were collected on a north slope of the region at four different altitude ranges, including 0–600, 600–1200, 1200–1800, and 1800–2400 m, and from five soil depths of 0–20, 20–40, 40–60, 60–80, and 80–100 cm. Then, the amounts of OC, cation exchange capacity (CEC), dilute-acid-soluble and hot-water-soluble carbohydrates, calcium carbonate, available phosphorus and potassium as well as soil acidity (pH) were determined in the soil samples.

The results showed the significant effect of soil depth, altitude and their interaction on most of the studeid soil properties. In fact, with increasing elevation and soil depth, the amount of OC, CEC, and dilute-acid-soluble carbohydrates increased and decreased, respectively, and a very strong correlation was found between them. Additionally, on average more than 50% of the OC was allocated to the top 20 cm of the soils at all four elevations that reduced averagely about 79% with increasing soil depth to the depth of 80–100 cm. Moreover, the highest increase rate of OC contents with altitude of about 9% was observed between the elevation ranges of 600–1200 and 1200–1800 m. Furthermore, with increasing altitude and soil depth, other soil properties such as pH, calcium carbonate, and available potaium showed a decraese of about 2%, 16%, and 16%, and an increase of around 4%, 16%, and 18%, respectively. In addition, with increasing soil depth, the amount of soil available phosphorus increased; meanwhile, the effect of altitude on this parameter was not significant.

Based on the findings of this study, soil OC stocks and overall the quality of Arasbaran forest soils are significantly affected by the factors of altitude and soil depth so that surface soils of higher elevations in the study area are of higher quality in terms of OC content, CEC, and dilute-acid-soluble carbohydrates, which should be given more attention. In fact, considering the significant role of these soils in carbon sequestration, these areas should be preserved intact and undisturbed through proper management as well as various protection practices.

Recognition of effective Parameters in sediment Production has an important role in understanding the phenomenon of erosion and its consequences and is one of the important principles of optimal management of a watershed. In the study of the relationship between watershed environmental and hydro geomorphological parameters with erosion and sediment, the quantity and amount of sediment has been considered so far, while in this research, has been studied the relationship between important climatic parameters including average annual rainfall, average annual temperature, altitude, slope, aspect and geological factor (formation) with sediment organic carbon as an important parameter and qualitative indicator in some of the Ardabil province watersheds. 98 samples of sediment after collecting from the study area, were analyzed in the laboratory by Walkley - Black method to extract the amount of organic carbon, then performed statistical analyze on samples using stepwise regression and partial least squares regression (PLSR) models. Findings showed that among the hydrogeomorphological parameters, slope and formation with regression coefficients of - 0.293 and -0.078, respectively, were identified as factors affecting the sediment organic carbon, so that both parameters have an inverse correlation with the sediment organic carbon and aspect parameter is more effective than the formation and output of both regression models is almost the same. Therefore, sediment organic carbon, in addition to the quantity and amount of sediments, can be considered as an important indicator for studying the degradation processes, watershed erosion and loss of soil organic carbon.

Nowadays, vast areas of forests have been changed to farmlands, and the change in land use is one of the important factors reducing soil quality. The purpose of this research is to investigate the effect of land use change from forest and pasture to agriculture on some soil characteristics in Sarab Badia area (Kermanshah province). Sampling was done in 2018 from points with the same slope in the form of a nesting site. For this purpose, four areas near each other that have the same landscape and include 3 uses of forest, pasture, and agriculture and also two depths of 0-20 and 20-40 cm were considered. Composite samples were prepared from each depth. After transferring the samples to the laboratory, the important characteristics of the soil were measured based on standard methods. The results showed that among the physical characteristics of the soil, MWD was affected more than the other physical characteristics due to the change in land use, so that by changing the land use from forest to agriculture in the subsoil layer (20-40 cm), MWD decreased by 51.04%. Among the soil chemical properties, organic carbon and total nitrogen with 52.95% decrease in top layer of the soil (0-20 cm), had the most variability due to the change of land use from forest to pasture. The metabolic coefficient was sensitive to the change in land use from forest to agriculture, as its value decreased by 92.92% in the sub layer (20-40 cm). Characteristics such as; MWD, organic carbon, total nitrogen, and metabolic coefficient are highly sensitive to changes of management conditions at the field level, so these characteristics can be used to monitor soil quality.

Soil entities depends on its physical, chemical, and biological characteristics. Soil organic carbon (SOC) stocks is one of the main factors whose variations affect all these parameters. So, this study was performed for mapping the coefficient of variations (CV) of SOC stocks in some parts of the Simineh Roud watershed. Soil sampling performed using the Latin Hypercube method (cLHm) at 210 points from 0 to 30 cm of the soil surface, and the organic carbon was measured, then SOC stocks was calculated. In the next step, using Random Forest (RF) model the effective parameters were calculated (in this step, to model the SOC stocks, standardized spectral reflectance index and extracted data from digital elevation model were used). Finally, RF model was performed 100 times, as well as mapping of the values of upper (95th %), lower (5th %), and average SOC stocks for each pixel with a spatial resolution of 30 × 30 m was obtained. To obtain the CV with a confidence coefficient of 90%, the percentile of 95% and 5% were subtracted. The CV was obtained by dividing it by the mean. The results showed that the accuracy coefficient (R2) for modeling SOC stocks by the RF model was 0.81 and the mean accuracy coefficients including RMSE and MAE were 0.44 and 0.34 (kg/m2), respectively. Also, the results of CV mapping for the amount of SOC stocks in the study area showed that the amount of variation of this parameter varies between 3.9- 55%. Based on the results of the CV mapping of the study area, the most and lowest variations were observed in dry farming and grasslands, respectively. Probably, continuous cultivation and low return of organic matter in dry farming have increased the CV of SOC stocks in dry farming use.

Soil enzymes are considered as the effective indicators of soil quality. In the present study, the activity of some soil enzymes, including β-glucosidase, urease, cellulase, arylsulfatase, dehydrogenase, and acidic and alkaline phosphatase was investigated in Arasbaran forest soils affected by two factors of altitude and soil depth. For this purpose, a factorial experiment was conducted using a randomized complete block design and three replications. Enzyme activity was measured in soil samples taken from different soil depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm) at various altitudes (0–600, 600–1200, 1200–1800, and 1800–2400 m) on a northern aspect. The results showed significant effects of soil depth, and altitude on the activity of the enzymes studied, but the reaction of different enzymes to these factors was not the same. The highest activity of urease, β-glucosidase, cellulase, arylsulfatase, and acidic and alkaline phosphatases was measured at the surface layer (0–20 cm) of the soils, which on average decreased by 50, 81, 71, 71, 59, and 66% as soil depth increased, respectively. However, dehydrogenase activity increased by 15 to 43 times with increasing soil depth. Additionally, with the increase in altitude from 0–600 to 1800–2400 m, while the activity of urease, arylsulfatase, and β-glucosidase increased on average by 1.15, 1.4, and 1.19 times, the activity of cellulase, and acidic and alkaline phosphatases decreased by 26, 10.4, and 9.6%, respectively. But, the effect of altitude on the dehydrogenase activity was not significant. The results also showed a significant positive correlation (P ≤ 0.01) between organic carbon and microbial biomass carbon, and the activity of all studied enzymes except dehydrogenase. Findings of this study reveal how the activity of different soil enzymes changes with two factors of soil depth and altitude.

Changes of soil carbon is one of the most important indicators showing the climate impacts on the soil genesis. Soil organic carbon management requires knowledge of its amount and the effective factors. In the current study, the distribution of soil properties especially soil organic carbon were studied in 76 soil profiles consist of different climatic zones arid (Alborz province), semi-arid (Alborz and Qazvin province) and semi-humid (Guilan and Mazandaran province) and humid (Mazandaran province) with aridic, xeric and udic moisture regimes and thermic and mesic temperature regimes. Changes in climatic parameters cause changes in species diversity in the ecosystem and ultimately effect on various forms of carbon, especially soil organic carbon. One of the most important climatic factors in this study is the temperature that increasing the soil temperature in arid and semi-arid regions compared to the two wetter regions causes intensification of mineralization and as a result, soil organic carbon is reduced. The results showed that the amount of organic carbon in the studied soil decreases with increasing depth and the average amount of organic carbon in Mollisols was higher than Alfisols= Inceptisols > Entisols > Aridisols. The general results of this study showed that increasing the parameters of soil electrical conductivity (salinity), soil acidity and clay content have a negative effect, while increasing the parameters of cation exchange capacity and silt content have positive effects on soil organic carbon content.

The effect of various biochars and nano-clay on Cd immobilization and uptake by plants has been widely studied, but few studies have focused on the migration of different Cd fractions in saline-alkaline soils. Moreover, the remediation potential of biochar and nano-clay in saline soils polluted with heavy metals is still to be studied. Therefore, it was hypothesized that the Cd movement is influenced by biochar and nano-clay application in soil contaminated with the matter. The aim of the present study was to evaluate the effects of biochar and zeolite on the uptake of cadmium by green bell pepper (Capsicum annuum) and its downward movement in saline-alkaline and cadmium-contaminated soils.

The present study was carried out under two soil modification materials including wheat straw biochar (Triticum ( and zeolite nanoparticles at the level of 5 g/kg of cadmium-contaminated soil. The soil was collected at 0 to 30 cm depth from a plain in Sejzi, Esfahan. The soil was air-dried and stones, as well as plant litter, were removed, and then the soil was passed through a 5 mm sieve and prepared for the experiment. The heavy metal contaminated soil was created by placing 500 g air-dried soil into a 2 L glass beaker and mixing it with 250 mL cadmium nitrate (1.2 g Cd, Cd(NO3)2· 4H2O). In the Sejzi plain area, three plots were filled with biochar and zeolite at the level of 5 g/kg of cadmium-contaminated soil. After preparing the contaminated soils, green bell peppers (Capsicum annuum) were planted in them under natural conditions. 

The results showed that biomass of green bell pepper increased significantly by 79.2% and 18.3% using biochar and zeolite, respectively. The concentration of cadmium in green bell pepper’s fruit in biochar application was reduced by almost 30% compared to both control and soil treatments with zeolite. Cadmium absorbed by green bell pepper stems was about 50% of the total plant cadmium. Application of 5 gr of biochar and zeolite per kg of soil increased 42% and 78% of soil cadmium in topsoil (0-12 cm), respectively, compared to the subsoil.

According to the results, it can be stated that green bell pepper can be introduced as a cadmium absorber. The results also show the superiority of zeolite treatment over biochar treatment in reducing contamination transfer to the underlying layers of saline and alkaline soils and the addition of biochar caused a greater increase in green bell pepper biomass compared to zeolite nanoparticles in cadmium-contaminated soil.

In order to investigate the effect of forage maize biochar and urea fertilizer application on bell pepper cultivar, a factorial experiment in a completely randomized design with three replicates and nine treatment was conducted. The treatments consisted of three levels of forage maize biochar (zero, 2, and 5% Soil weight) and three required urea fertilizer (75% 100%, and 120%). One bell pepper was transferred in 4-leaf pots containing 5 kg of soil and biochar, then in three stages and in each stage, 236, 314, and 376 mg kg-1 N of urea fertilizer was added to the pot. At the end stage of cultivation, EC, pH, Na, K, Ca+ mg, carbon organic, total nitrogen and wet yield fruit bell pepper measurements were done. The results indicated that the treatment of 120% urea fertilizer and 5 percentage biochar EC, pH, sodium, and total nitrogen cumulative in soil 41.7, 12.5, 2.1 and 58.3% and soil organic carbon 4.16 times, were compared to the control treatment. respectively. In 120% urea fertilizer and 5 percentage biochar treatment soil potassium increase by 96.8% in comparison with the control treatment. Also, the highest increase calcium and magnesium the treatment 100% urea fertilizer and 2 percentage biochar cumulative in soil by 58.3%. In addition, the results indicate that the treatment of 120% urea fertilizer without biochar increased the wet yield fruit of bell pepper by 61.5% compared to the control treatment.

The aim of this study was to investigate the effect of land use age on dynamic of different forms of soil organic carbon in Chahar Dangeh region of Kiasar, Mazandaran province. In this area, the studied habitats include pastures conversion to agricultural lands (barley) and orchards (apples and walnuts) in three different ages (more than 30 years, more than 20 years and less than 10 years) in Era, Erost and Vavsar villages. In each land use, soil sampling was performed systematic- randomly from 0-15 and 15-30 cm depths. In total, ten soil samples from land uses were transferred to the laboratory for analysis of soil organic carbon, particulate organic carbon, microbial biomass carbon, labile organic carbon. The variance analysis results indicated that the higher values of soil organic carbon, particulate organic carbon, microbial biomass carbon, labile organic carbon found in orchard use during 30 years old, which was located at a depth of 0-15 cm. Due to the conversion of rangeland to orchard use (age more than 30 years), soil organic carbon, particulate organic carbon, microbial biomass carbon, labile organic carbon increased in 86.18%, 68.42%, 61.13% and 66.94% respectively. Also, the highest amount of EC was found in orchard use older than 30 years. But pH in barley land use older than 30 years at a depth of 15-30 cm had the highest value. In general, the results of this study indicated that the effects of the studied factors on different forms of soil organic carbon depend on the time. Therefore, soil organic carbon management strategies should be adjusted according to the time period.

Heavy livestock grazing is a severe threat to soil quality in the rangelands, particularly in the semiarid regions. However, grazing exclusion is the effective and low cost management measure combating improper grazing impact. The purpose of this study was to investigate the effects of grazing exclusion on soil physicochemical properties in Dalahoo Rangeland, Kermanshah, Iran, and was carried out during 2016-2019. For this purpose, two linear transects were performed in exclosure (Ex) and grazed (Gr) sites. In each transect, 12 sampling points were selected with 250 m interval and soil samples were taken from topsoil and repeated annually. The results of this study revealed that the respective value of soil organic carbon (SOC) in Ex and Gr was 1.10 and 1.09 %, showing no significant differences between them in the first year. However, in the fifth year, SOC was enhanced to 3.70% in Ex, which was significantly higher compared to Gr (p <0.05) and 5.5 times higher than the first year. The bulk density (BD) in the Ex and Gr soil in the first year was 1.56 and 1.57 gcm-3, respectively. Over five year time, the BD of Ex significantly decreased to 1.266 gcm-3, while there was no significant change in Gr site. Furthermore, the respective ratio of coarse soil aggregate (CSA) with > 1 mm diameter in Ex and Gr was, respectively, 9.18% and 8.09% in the first year, while it was, respectively, 30.29% and 6.90% in the fifth year, which was significantly higher in Ex (p<0.05) and indicated 3.3 times improvement through exclosure measure. Finally, the limitation class for soil quality in the Ex was changed from high (1st year) to no limitation (5th year), while Gr site, which was in “high limitation class” in the first year, showed no change during five year. This study demonstrates that five years grazing exclusion significantly improved soil quality.