مجله تحقیقات آب و خاک ایران
سال پنجاه و دوم شماره 12 (پیاپی 72، اسفند 1400)

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.

Human is under threat due to the shortage of fresh water, its deteriorating quality, and rising water stress around the world. Proper management of water resources is very important to ensure the sustainable social and economic development in any country in the world. In order to sustain freshwater resources, they must be used efficiently without compromising the needs of future generations. The present study was conducted to ensure the sustainable management of groundwater resources. For this purpose, four indicators of vulnerability, resilience, reliability, and combined stability, each of which includes aspects of sustainability, were used as the objective function of management issues. Using the combined simulation-optimization model of Namdan plain aquifer and the ant colony optimization algorithm, a decision model was created. The results indicate the effectiveness of four indicators of vulnerability, resilience, reliability and combined stability to increase groundwater level and positive changes of water storage. So that the aquifer storage change under each scenario was 11.7, 13, 12.3 and 12.4 million cubic meters, respectively. According to the results obtained from four management issues, analyzed in this study, the most important effect in improving the aquifer with a significant reduction in pumping from well while the such reduction should be measured at the aquifer level.

In this study, the function of the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor to estimate the concentration of PM2.5 and PM10 pollutants in Tehran was assessed by using the data obtained from this sensor. In this study, linear and non-linear models for estimating the concentration of aerosols were presented in six meteorological and ground pollution monitoring stations in Tehran province. The results of the models were compared to the ground station observations by using statistical tests and the most appropriate model was elected from the regressions. The developed model (based on aerosol optical depth which was extracted from MOD04-L2 products of TERRA satellite MODIS sensor), 24-hour precipitation, average water vapor pressure, and sunshine) showed high accuracy, very low RMSE, and rather high R2 in Tehran province (R2 = 0.75 and RMSE= 7.47 ug / m3) and stations. In this model, PM2.5 concentration and sunshine hours have a negative correlation, also the positive relationship to other variables is observed. The results demonstrated that utilizing meteorological variables and attention to the prevailing atmospheric phenomena enhance the performance of MODIS sensor data in estimating PM2.5 pollutant concentration. Undesirable as MODIS sensor data might be in terms of certainty and accuracy, they are undoubtedly beneficial considering elimination defect of ground-based pollution monitoring stations in estimating aerosols concentration and complement each other suitably.

Germination plays a vital role in crop establishment and its yield. Most oilseeds are sensitive to salinity at germination, so cannot be irrigated with saline water. Although camelina is considered as a tolerant crop to water stress, but its tolerance to salinity must be investigated. To quantitatively evaluate camelina response to salinity at germination stage, an experiment with a completely randomized design was conducted including 17 water salinity levels of 0.85, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 dS m-1, each with three replicates. Germination indicators were calculated using the SeedCalc package in R software and MATLAB. The optimization procedure was carried out with frequent changes in the model parameters based on reduced RMSE and minimizing least squares error. Then, parameters of salinity models including Maas-Hoffman, van Genuchten-Hoffman, Dirksen-Augustijn and Homaee et al. were derived and compared. The obtained threshold values of germination rate (GSI), seed vigor (SV), SeedCalc seed vigor (SV-S) were 2, 12 and 12 dS m-1, respectively; The corresponding reduction slope for these variables were 2.4, 7.7 and 1.7%, respectively. Based on the obtained EC* and the slope, it was concluded that camelina is very tolerant to salinity at this growth stage. So that, it can be established quickly and produce strong seedlings at very high salinity levels. Further analyses of model performance statistics indicated that the examined nonlinear models provide better performance. Best performance of fitted models was obtained by HVG and H models, respectively. Germination indices were decreased by increasing the salinity levels, a lower GSI was associated with decreased seeds water uptake. The higher the seed vigor, the higher the GSI and seedling growth, as well as the lower MGT. Overall, camelina can be considered as a suitable alternative for oilseed cultivation in semi-arid regions.

Detailed information about soil moisture and its spatial and temporal distribution provides opportunity for optimized land resources utilization. Our study aimed to estimate soil surface moisture through readily availabile soil parameters and spectral index obtained from Sentinel-2 sensors using two methods, artificial neural networks (ANN) and support vector regression (SVM). There were 124 soil samples collected from three regions of Iran (Tehran, Garmsar, and Lorestan). After normalizing the data, the significance of the correlation between input variables (spectral indices and basic soil properties) and output variables (surface moisture) was evaluated statistically. In the next step, the mentioned methods were used to perform a modeling process, and the results were evaluated. The results showed that the ANN method outperformed the SVM method. Based on ANN technique, the Root Mean Square Error (RMSE), Akaike Information Criterion (AIC), coefficient of determination (R2) and Relative Improvement (RI) in the training step were 0.033, -538, 0.71, 21.25, and in the testing step they were 0.410, -266, 0.69, and 16.06, respectively. Also, RMSE, AIC, R2, and RI in the SVM method in training step were respectively 0.035, -474, 0.71, and 35.16 and in testing step were respectively 0.046, 252, 0.63, and 20.21. Using the ANN method, soil color index (CI) has been shown to estimate soil moisture more accurately than other spectral indices. Therefore, the ANN method constructs a nonlinear relationship between soil surface moisture and input parameters, which enables soil moisture to be estimated with acceptable accuracy in the study area.

Increasing the soil mechanical resistance firstly strengthens the soil and causes its stability against external factors, and on the other hand, restricts root development and the process of root water uptake from around soil. In this study, the limitations and possible benefits of soil mechanical resistance in an optimal moisture condition were investigated. Two factors of compaction and cementation were used to increase the soil mechanical resistance at wet soil and to prevent the effects of moisture fluctuation on the initial soil mechanical resistance, a suction buffer system was used to stabilize soil moisture at the matric suction of 40 cm (aeration porosity equal to 10%). 132 experimental units at different levels of compaction (bulk densities equal to 1.52, 1.56, 1.6, 1.66, 1.69, and 1.71 Mg.m-3) and cementation (added cement equal to 0, 0.3, 0.6, 0.9, 1.2 and 1.5 percentage) treatments, maize and wheat plants were cultivated to determine the possible effect of root development on increasing the initial soil mechanical resistance. The results showed that the soil mechanical resistance increased from low to restricting values due to both compaction and cementation treatments, and a range of loose to strong soils was created due to these two treatments. Soil mechanical resistance in the control treatment and some initial levels of the two compaction and cementation treatments were in the range of loose soils, but the root development caused a significant increase in soil strength in control and compacted treatments. On the other hand, root development caused the soil limitation in terms of soil water availability to exceed the critical limit (2.5 MPa). Therefore, according to the expected function of the soil, changes in mechanical strength due to compaction, cement, and root development can be considered as an opportunity or constraint.

Rice is one of the most important crops in the world and after wheat has the second place in terms of annual production. Considering the importance of yield per unit area in agriculture, this study aimed to investigate the effect of direct cultivation and transplanting on yield and yield components of rice under different irrigation systems as split plot based on randomized complete block design at the Agricultural Research Station of Golestan province in 2019 and 2020. According to the results, there was a significant difference in terms of irrigation and planting method for all studied traits. The results of mean comparison of cultivation method showed that the highest and lowest amount of grain yield were obtained for the treatments of puddled transplanted and direct seeding, which were equal to 7506 and 4284 kg/ha, respectively. Also, according to the results of mean comparison of irrigation method, the highest grain yield was 6899 kg/ha, which was obtained for the permanent flood irrigation system, and there was a significant difference with other treatments in the level of 5% probability of LSD test. Grain yield had a positive and significant correlation with harvest index, plant height, number of fertile tillers, panicle length and number of full grains per panicle equal to 0.89, 0.87, 0.75, 0.53 and 0.73, respectively and had a negative and significant correlation with the number of empty grains per panicle equal to 0.81. According to the results, sprinkler irrigation system had the lowest values in terms of number of full grains per panicle, number of fertile tillers, panicle length and consequently grain yield compared to other irrigation treatments. Also, transplanting cultivation methods performed better than direct seeding cultivation method in terms of yield and yield components.

In the present study, the efficiency of animal bone (RB) and its bone char (BC) (from the pyrolysis process at 500 °C) application effects on nickel (Ni) behavior was evaluated in a Ni-spiked calcareous soil. For this purpose, RB and BC at 1.5 and 3% (w/w) were added separately to Ni-spiked soil (350 mg kg-1) and after incubation process (3 months) under field capacity moisture, soil Ni behavior were investigated through desorption kinetics and sequential extraction techniques, in the laboratory of environment department, graduate university of advanced technology, Kerman (1399). Based on the results, BC due to the very high specific surface area (95.9 m2 g-1), the process of nickel exchange with calcium in its surface, and the formation of orthophosphate-Ni surface complex caused a significant reduction of Ni desorption compared to the control soil sample (without treatment). The mechanism of hydrogen ion release in RB-treated soil increased the Ni desorption compared to the control sample. The results of chemical forms of Ni in soils treated with BC and RB, showed a significant decrease (43.23-23.22%) and increase (15-97-9.9%) in Ni mobility factor, respectively, compared to the control sample (38.8%). The Two first-order reactions model, considering the biphasic process of Ni desorption in all soil samples, showed a good prediction (R2>99%) of Ni desorption kinetics. In general, the results of this study showed that the pyrolysis process, by changing the physical and chemical structure of RB, has improved the stabilizing properties of CB and finally stabilized soil Ni, which requires more attention to the application and increase of efficiency (physical and chemical modifications) of this stabilizer in future research.

This study was conducted to investigate the effects of biochar and nitrogen sources on agronomic traits and soil and plant nitrogen in rice Tisa in Tonekabon rice research station. The statistical design used was factorial in the form of randomized complete blocks with three replications. The treated treatments included biochar at three levels (control, 20 and 40 t ha−1) and nitrogen sources at three levels (control, nitrogen fertilizer at 200 kg ha-1 and inoculation of seeds with nitrogen-fixing bacteria (Azospirillum, Aztobacter and Pseudomonas). The results showed that among different nitrogen sources, the application of nitrogen chemical fertilizer led to a significant increase in some yield components, grain yield and nitrogen concentration in the plant, so that the number of fertile tillers per hill, grain yield, and nitrogen concentration in the grain and straw were increased by about 20.4%, 33.6%, 17.8% and 24.7%, respectively, compared to the control or without use of nitrogen.The results showed that in field conditions the interaction of treatments (Nitrogen chemical fertilizer × 20 tha−1 biochar, nitrogen chemical fertilizer × t ha−1 biochar, bacterial application × 20 t ha−1 biochar, bacterial application × 40 t ha−1 biochar) on straw nitrogen was significant. Nitrogen application in field conditions led to a significant increase in plant height, number of fertile tillers per mound, grain yield, biological yield and nitrogen concentration in grain. In greenhouse conditions the highest grain yield (90.71 g) in the interaction application of nitrogen fertilizer With 40 t ha−1 biochar of and the highest concentration of grain nitrogen (0.64 mg kg-1) were observed in bacterial inoculation treatment with 40 t ha−1. According to the results of this study, the application of nitrogen fertilizer in the amount of 200 kg ha-1 to achieve maximum rice grain yield and also the use of biochar in the amount of 20 and 40 t ha−1 to improve soil fertility is recommended.

Rill erosion is an important form of water erosion on cultivated slopes. Rills are flow paths that are created by concentrated flow on hillslope and causes higher rates of soil loss. The amount and type of particles transferred through the rills or the selectivity of the particles may be affected by various factors, especially the flow rate. This study was conducted to investigate the rill erosion and the particle selectivity under the flow characteristics. Field experiment was done in a rainfed land with a slope gradient of 10% in the rills/furrows with 6 m in long under different flow intensities (2, 2.5, 3, 3.5 and 4) using a randomized complete block with three replications. Field measurements were performed using a flow rate of 3 lit min-1 at intervals of 5-min for 60 min. Rill erosion and the particle selectivity were determined along with flow characteristics for various flow intensities. Significant correlations were found between flow intensity and flow characteristics (velocity, shear stress and power), rill erosion and the selectivity of particles. With an increase in flow rate, flow characteristics increased in the rills and enhanced rill erosion as well as the selectivity of sand and clay, whereas the selectivity of silt decreased in the rills. Silt showed the highest sensitivity to selection by concentrated flow, so that flows with lower shear stress could erode it from the rills. Wholly, this study revealed that the flow rate is the most flow characteristics influencing rill erosion and the selectivity of soil particles.

Despite the diversity of land use in arid and semi-arid areas of the country, land use can change the soil quality characteristics, as well as soil physical quality. The aim of this study was to investigate the effects of different land use on soil characteristics in the Baghan watershed in the southeast of Bushehr province with an area of about 929 square kilometers. That region has an important role in the production of agricultural products. From the surface soil (0-20 cm) of range, croplands and orchards, 120 composite soil samples were taken. Sampling sites were determined using the Latin hypercube technique. sand (Sa), silt (Si), clay (Cl), bulk density (ρb), porosity (F), air content (AC), effective porosity (Φeff), macro pores (MAP), mean weight (MWD), geometry mean of aggregate diameter (GMD), water aggregate stability (WSA), aggregate stability index (SI), relative water content (RWC), saturated moisture (ΘS), field capacity moisture (FC), permanent wilting point (PWP) and availaible water content (AWC) were determined by conventional methods and fractal dimension (Db) was calculated by mass-diameter method. range, crop land and orchard land uses had significant effect (P <0.01) on all studied characteristics except AC. Mean comparison showed that in range and crop land, among all studied characteristics, only PWP, FC and ΘS were significantly different. In orchard, compared to range, there is a significant increases trend in Sa, F, Φeff, MAP, MWD, GMD, WSA, SI, ،S, FC, PWP, AWC and RWC and a significant decreases trend in Si, Cl , Ρb and Db were observed. Fitting of the linear equation to the measured data showed that with decreasing the clay and silt and increasing the sand, the fractal dimension decreased. The coefficients of explanation of the linear function of the fractal dimension with the percentages of sand, silt and clay were 0.8, 0.55 and 0.82, respectively. Based on the studied characteristics, the most desirable physical quality of soil was observed in orchard land use.

Soil contamination with heavy metals in addition to reducing the production and quality of agricultural crops enters the human body through the food chain. The objective of this study was to investigate the adsorption capability and clean up time required for phytoremediation of Pb-contaminated soils by white horseradish. For this purpose, a randomized block experimental design with five treatments of 10 (control), 150, 300, 600 and 900 mg Pb/kg soil and three replicates was established in the Faculty of Agricultural Sciences, University of Guilan. Plants were harvested when fully developed. The lead concentrations in the soil, roots and shoots were measured afterwards. TF and BCF indices, clean up time and uptake rate of Pb for 5%, 10%, and 15% of contamination were then calculated. The results indicated that by increasing the lead concentration, plant dry matter decreased significantly. Also, lead accumulation occurred mostly in roots rather than in shoots. The maximum lead concentration in the root and shoot in the 900 mg/kg treatment were 191.9 and 28.56 mg/kg, respectively. The variation range of TF and BCF indices were 0.15 to 0.55 and 0.22 to 2.86, respectively. Results further revealed that it takes 8 years to remediate 15% of Pb when soil Pb contamination is 300 mg/kg treatment. Generally, with increasing lead concentration, the time needed for phytoextraction is also increased. However, since the complete removal of heavy metals does not need to clean up them from the soil, phytoremediation is a suitable method for remediation of heavy metal contaminated soils. Due to high biomass and capability of lead accumulation of white horseradish, this plant might be used to remediate lead from moderate Pb-contaminated soils.

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.

Karkheh catchment in Kermanshah province is considered as one of the agricultural potential areas of Iran, thanks to its rich water and soil resources. However, the management of water resources at the farm level is not optimal. In order to improving the management of water resources in this area, achieving a comprehensive understanding of the status of water resources is essential. Therefore, the purpose of this study is to zoning the plains of Karkheh catchment in Kermanshah province based on the Enhanced Agricultural Water Poverty Index. In this study, from 12 plains of Karkheh catchment in Kermanshah province, 6 plains including: Islamabad Gharb, Kermanshah, Ravansar-Sanjabi, Mahidasht, Biston-Dinavar and Kangavar were selected based on different climates. In order To evaluate the Enhanced Agricultural Water Poverty Index, 41 positive and negative sub-indices were used. Using the Savara method based on opinions of 15 experts in water affairs and soil and water management of Jihad Keshavarzi and Kermanshah Environmental Protection Organization the Weighting of each of the criteria and related indicators was calculated and the Enhanced Agricultural Water Poverty Index was calculated using the formula of this index for each mentioned plains. The zoning results of the studied plains showed that Ravansar-Sanjabi and Mahidasht plains with a score of 0.383 and 0.394, respectively, had more unfavorable situation and Biston-Dinavar plains and Islamabad with a score of 0.517 and 0.485, respectively, had more suitable situation than other plains studied. Finally, in order to improving water poverty index in studied area some recommendations including: implementation of watershed management and aquifer feeding plans, limiting the uncontrolled use of groundwater resources, supporting the development of irrigation methods based on pressurized irrigation technologies and modifying and changing Cultivation pattern towards low water crops was recommended.