مجله تحقیقات آب و خاک ایران
سال پنجاه و سوم شماره 6 (پیاپی 78، شهریور 1401)

In general, comprehensive watershed management depends on achieving an eco-hydrological balance of watersheds and improving the livelihood of stakeholders. One of the main principles of watershed management measures is sediment management through soil protection operations using new techniques such as the Sediment connectivity index. Sediment connectivity is an emerging term in watersheds that are often used to describe the internal relationships between runoff and sediment sources in the upper parts to the outlet of the relevant watershed. The purpose of this study was to monitor the spatial changes of sediment accurately, using structural Sediment connectivity index and analysis of sediment flow from upstream to the outlet in the basins, which was carried out in AbolAbbas watershed of Khuzestan during the summer period of years 2020-2021. The present study is based on the use of Borsley's proposed approach and cover land weighted layer. The results showed that the dimensionless index of sediment connection was estimated with a spatial accuracy of 30 m, ranging from -7.9 to 3.4 and obtained with an average of -5.50. The accuracy of the sediment connection index with determination coefficient of 0.56 has a good accuracy in monitoring the sediment transport potential from the upstream to the basin outlet. However, the results showed that the new method of sediment connectivity index in modeling sediment flow could be a pixel (cellular) tool to identify homogeneous areas in terms of distribution of sediment connection and make management decisions and programs.

In the present study, the effects of biochar (produced by slow pyrolysis process) and hydrochar (produced by hydrothermal carbonization process) of cypress cones application on nickel (Ni) stabilization in a soil spiked with this element were investigated. For this purpose, the raw cypress cone and its biochar and hydrochar are added separately at 1.5 and 3% (w/w) to a Ni-spiked calcareous soil (350 mg kg-1) and after 3 months of incubation process, under field capacity moisture condition, desorption kinetics and chemical forms of Ni, in the laboratory of environment department, graduate university of advanced technology, Kerman (2020), were measured and investigated. According to the results, hydrochar had higher specific surface area and functional groups containing reactive oxygen, as well as more irregular porosity morphology compared to biochar. The values ​​of final desorbed Ni in the treated soils showed a decrease of 27-37% and 11-16.5% of desorbed Ni in the soil treated with hydrochar and biochar, respectively, compared to the control sample. The fitness of the two first-order reaction model on Ni desorption data in all treated samples showed the high accuracy of this model (coefficient of determination>99%) in predicting Ni desorption. Evaluation of Ni mobility factor obtained from the Ni chemical forms shows a decrease in this factor in samples of soils treated with hydrochar (29.2-30.2%) and biochar (31.9-33.3%) in comparison with control soil sample (38.8%). In general, the presence of functional groups containing reactive oxygen and higher specific surface area of ​​hydrochar compared to biochar has resulted in more stabilization of Ni in the soil compared to treated soils with biochar. Due to lower production costs and reduced production of destructive greenhouse gases in hydrochar production compared to biochar, the need for more attention to hydrochar and engineered hydrochar application is required in future studies of heavy metals stabilization in the soil environment.

Due to limitation of available water resources, improving agricultural water productivity has become an inevitable necessity. Therefore, it is important to have reliable estimates of the seasonal applied water and water productivity under current irrigation and farm management. In this paper, the seasonal applied water and physical and economic water productivity of soybean were studied through monitoring 29 farms under actual conditions located at the tail end region of Moghan irrigation and drainage network, Ardabil Province, Iran, during the growing season 2020-2021. The net water requirement estimates of soybean during the growing season 2020-2021 and its 10-year average ranged from 417-719 mm and 457-797 mm with a mean of 539 and 581 mm, respectively, over the studied farms. The total applied water (irrigation + effective precipitation, I + Pe) and the grain yield ranged from 3859-7105 m3 ha-1 and 1.30-2.80 ton ha-1, with a mean of 5664 m3 ha-1 and 2.35 ton ha-1, respectively. The lack of flexibility in water allocations led irrigation schedule to be not adapted with the crop water requirement. The limiting factors of soybean production in the study area caused the observed maximum grain yield to be significantly lower than the potential level of soybean yield in Moghan plain (4.00 ton ha-1). The soybean grain yield exhibited a quadratic correlation with I + Pe. Total water productivity (WPI+Pe) and economic water productivity (WP$) ranged from 0.33 to 0.47 kg m-3 and 21.18 ´ 103 to 48.29 ´ 103 Rials m-3 with a mean of 0.42 kg m-3 and 39.89 ´ 103 Rials m-3, respectively. The mean Israelsen's application efficiency (AE) over initial, development, and mid-season plant growth stages in the study fields were obtained 19, 95, and 100%, respectively.

River bed control is a critical issue that river engineers facing with it today. Block ramps are grade control structures, implementing as a countermeasure to overcome successive erosion in rivers bed, having suitable environmental conditions in terms of aquatic migration to upstream reaches, and also increasing the dissolved oxygen in the water. One of the important issues in designing and safetying these structures is to predict and reduce the magnitude of scour depth in the downstream pools. In the present study, the effect of apron installation on the reduction of scour in the downstream of the block rams under the smooth and rough surface of the structure was investigated, experimentally. The experiments were performed for slopes of 1:3 and 1:5, the ratio of the critical depth to the height of the structure 0.14-0.2, roughness elements height of 1.15-5.2 cm with different arrangements; as well as apron installation with a length of equal and half of the height of the structure at the hydraulic and physical hydraulic lab of University of Guilan in 2020 and 2021. The comparison of the results of all slopes of the structures showed that the apron installation is directly related to the reduction of the maximum scour depth, so that by installing an apron with length of equal to the structure height, the maximum scour depth for slopes 1:3 and 1:5 reduced by an average of 58 and 43%, respectively, compared to the smooth block ramp. By increasing the roughness height, the maximum scour depth over the range of minimum and maximum flow discharges and the structures slopes reduced by an average of 39 to 62 % compared to the corresponding smooth block ramp. A comparison of the results shows that for block ramp with the slope of 1:3, changing the roughness arrangement from staggered to compact in case of large roughness, had no effect on reduction of the maximum scour depth, but in the slope of 1:5, reduced the maximum scour depth in the range of 18 to 42 %.

Soil water repellency is an important physical phenomenon. In sub-critical water repellency conditions, many studies have reported positive repellency impacts. It seems that the presence of soil water repellency in a Specified range (Optimum water repellency) is not only a cause of destructive impacts in the soil but also is a positive factor in improving the soil physical quality. In this study, pre-treatment of organic matter (as a hydrophobic agent) was applied on 0, 1, 3, 5, 8 and 10% by weight of manure, on sandy loam and clay loam samples (In Kerman province; through 2020-2021). After three months incubation period and wetting and drying cycles of soils, soil water repellency was calculated using WDPT (Water drop penetration time), RI (Repellency index) and β methods. Then 21 soil quality indices (water availability and soil stability structure characteristics) were measured in the samples, and MDS (Minimum data set) indicator were selected using PCA (Principal component analysis). The Optimum water repellency, which is equal to 0.95 of the predicted values with the equation fitted to data, was calculated by plotting the data of MDS indicator and water repellency index. Considering the significant effect of manure on soil water repellency indices, and also the significant correlation of RI with most of the water availability and soil structure characteristics, RI was selected to determine the optimum water repellency. After checking the results of graph and 11 MDS indictors, it was determined that DC, TS and Ql indictors had a decreasing and then increasing trend with increasing water repellency, and the rest of indictors showed an increasing trend and then a decreasing trend. The Range of Optimum water repellency (0.95LL-0.95UL) is defined in an extensive range (4.40-4.86), when the soil structure indictors are investigated and in a limited range (3.72-4.28) when it is only affected by water availability. Finally, in unlimited conditions, the lower limit of 3.72 and the upper limit of 4.28 were considered for the optimum water repellency.

The significantly high rate of evaporation from the surface of water results in a notable reduction in utilizing water reservoirs and farm ponds. Floating physical covers are considered to be one of the most effectual approaches toward reducing the rate of evaporation from the surface of water. In the present study, the following six types of covers were utilized with three repetitions for each type of cover on the surface of the standard Sunken Colorado Evaporation Pan. The covers included: polystyrene, wood parts, synthetic honey wax, Perlite and Leica grains, and threshed straw. Three varying percentages of 60, 70, and 80 were examined for polystyrene, wood, and wax covers. Water depth alterations for both covered and uncovered reservoirs were scrutinized in the period starting from May 23rd, 2018 until August 22nd, 2018 in Semnan University in Semnan city. The economical effectiveness of the plan was estimated for each separate type of coating. The findings of the study indicated that the average amount of reduction in surface evaporation in comparison with the control reservoir relevant to polystyrene covers with 60, 70, and 80% coverage, wood parts with 60, 70 and, 80% coverage, synthetic honey wax with 60, 70, and 80% coverage, and Perlite, Leica, and straw are approximately 43, 54, 65, 10, 19, 26, 9, 18, 25, 36, 22 and 20 %, respectively. Regarding the economic analysis of the study, surveys were carried out on a farm pond located at a distance of approximately 3.8 km from the site. The findings displayed that bearing in mind the 5-year economic life of the plan, polystyrene and Perlite covers are deemed to be economical. Conclusively, the Internal Rate of Return (IRR) for polystyrene covers with 60, 70, and 80% covering, and Perlite covers are 571, 722, 872, and 32, respectively.

Global warming have led to an increase in the frequency of severe weather events, including droughts. Monitoring and predicting spatio-temporal behavior phenomenon is very important to prevent negative socio-economic consequences and environmental planning. There has been no comprehensive long-term assessment of drought spatial analysis for Iran. For this purpose, first a decade of droughts with the PDSI index from 1980 to 2020 were extracted and then analyzed spatially. The results showed that the intensity of Palmer drought index in Iran increased from -2.12 to 1.45 to -5.73 to 1.34 and changed from dry to extremely dry.The elliptical direction showed three standard deviations in each of the four decades studied northwest and southeast, which was in the direction of unevenness, following the direction of Iran's rainfall. In order to clarify the type of spatial pattern, the G-Star clustering index was calculated and the results showed that in the first decade of the interval, hot spots (severe drought clustering) were found in small parts of the center of Iran and on low rainfall provinces and deserts. Second, hot spots in the southwest of Iran, including Bushehr and Khuzestan provinces, located in the third decade in many parts of the center of Iran, including Tehran, Semnan, Isfahan, Fars, Kohkiloyeh and Boyer Ahmad provinces, and in the fourth decade, hot spots in the south and southeast of Iran. including Hormozgan province and Sistan Baluchistan showed itself as meaningful cluster patterns.The spatial distribution of drought intensities indicates the displacement and intensity of rainfall systems over the decades, indicating that all parts of the country may be at risk of drought. Such research can identify areas at high drought risk and be used in environmental planning.

There is little information about the spatial distribution of elements involved in assessing the fertility of soils in Khuzestan province, especially the available phosphorus contents of the soils. Therefore, this study conducted to determine the most effective soil properties controlling the concentration of available phosphorus contents of soils in the north of Khuzestan province and to introduce the most appropriate method for modeling the spatial distribution of available phosphorus contents of the soils analyzed using linear regression and random forest algorithm. For this purpose, 250 composite soil samples (0-10 cm depth) were randomly collected using the Conditional Latin Hypercube sampling approach from December 2020 to February 2021. Then, the physical and chemical properties of the samples were determined using standard laboratory methods. The experimental data were then analyzed for descriptive statistics using SPSS software. To model the spatial variability of available phosphorus contents of the soils, the experimental data were modeled using linear regression and random forest models in RStudio software. The results showed that according to the measured amounts of absorbable phosphorus in the soil samples in 32.4% of the samples, the concentration of available phosphorus is less than 5 mg/kg. Evaluation of multiple linear regression and random forest models based on model evaluation metrics including mean absolute error (MAE), root mean square error (RMSE) and coefficient of determination (R2) using training, test and the whole dataset, showed that the random forest model provides better and more accurate estimates due to higher coefficients of determination as well as lower error values. The results also illustrated that the organic carbon content of the soils has the greatest contribution in the study area to predict available contents of soil phosphorus. In conclusion, models that include non-linear relationships between variables seem to be more suitable in predicting soil properties.

Cadmium is one of the heavy metals, which the results of recent research indicate the severe biological toxicity, irreversibility, accumulation and non-degradability of this element in nature, and its accumulation in the soil causes a decrease in soil fertility and crop yields. One of the ways to improve the fertility of contaminated soils is the use of waste materials such as fly ash and its derivatives. The aim of this study was to investigate the effect of fly ash derivatives and genotype treatments on rice yield. The experiments of two cropping years 2019-2020 and 2020-2021 were performed in two forms of field and pot cultivation in private lands located in Kheyber town of Dezful city. This research was done by split plot method and in the form of randomized complete block design. The main factor included four amendments; soil with zero ash (as control), ash, intermediate material and zeolite. The sub-factor included two cultivars; Champa and Anbarbo. The studied traits are grain yield and plant dry weight. Comparison of treatment averages were done by Duncan's method and at two probability levels of 1% and 5%. According to the results, the effect of fly ash treatment and its derivatives on rice yield had a significant effect at 1% level. Genotype also had a significant effect on rice yield at 1% level. Also, the interaction effect of fly ash treatment and derivatives and genotype treatment had a significant effect on rice yield at 1% level. So that the lowest and the highest amount of yield with the amount of 3065.42 and 3555.96 kg/ha in the field experiment and 3162.54 and 3668.1 kg/ha in the pot experiment were corresponeded to the control treatment and Anbarbo variety and fly ash Champa treatments respectively. It was found that the treatment of fly ash and Champa variety was statistically higher than the other treatments at 5% level according to Duncan's test. According to the comparison results, the highest yield in both field and pot tests was observed in intermediates treatment and Champa variety.

Evapotranspiration is an essential component of the hydrological cycle and a key element of water resources management, especially in arid and semi-arid regions. Today, remote sensing technology has made it possible to estimate evapotranspiration on a large scale, so using this technology can be considered as a promising method to reduce the spatial variation of evapotranspiration. In this study, the daily, monthly and seasonal changes of actual evapotranspiration were investigated using the global model of WaPOR product and PYSEBAL algorithm in Qazvin plain during the period from 2015 to 2021. The results obtained in this study were compared with Hargreaves and Samani evapotranspiration data, which is an accurate empirical method in the region. The mean deviation of the estimated and observed data in the daily scale in both models shows that the PYSEBAL algorithm has a more negligible difference and, in most cases, is close to the data obtained from the empirical method. While in WaPOR product, it was associated with underestimation compared to the empirical method during the almost entire period. WaPOR product was able to show the amount of seasonal evapotranspiration changes to a good extent, but it did not have good accuracy. This product had acceptable accuracy in spring and summer, but in autumn and winter, its accuracy decreases. The results showed that the WaPOR product can provide water needs for each time period, so it can play an important role in managing water resources, determining the required water consumption. PYSEBAL algorithm presented more accurate results than WaPOR product, so that the correlation coefficient values in PYSEBAL algorithm and WaPOR model are equal to 1.51 and 2.86 mm / day and the correlation coefficient values were 0.87 and 0.64, respectively. Therefore, if the studies on estimation of the amount of evapotranspiration for large areas (such as basins) and long periods are considered, the use of WaPOR products due to the lack of missing data can play a suitable role in managing water resources and water needs for the region or basin.

Increasing groundwater consumption and water table level leads to changes in hydrodynamic properties of the aquifer especially the parameters of hydraulic conductivity and specific yield. In this study, that was conducted in 2021 using GMS model version. 10 in Qazvin aquifer, the coefficients of hydraulic conductivity and specific yield of aquifer in three census periods of 2002, 2009 and 2018 after calibration and validation of the model in two cases steady and unsteady were determined and compared. The root mean square errors in the steady state  for the proposed periods were 0.86, 0.73 and 0.84 m, respectively, and in the unsteady state were 1.7, 0.93 and 1.06 m, respectively. That shows high accuracy of the model simulation. The average hydraulic conductivity in the aquifer was estimated for the years of 2002, 2009 and 2018 which was 19.13, 16.85 and 14.06 meters per day and the average specific yield was 0.078, 0.071 and 0.064, respectively. The results showed that over time and by decreasing the groundwater level, the parameters of hydraulic conductivity and specific yield decrease. Since 2015 due to the measures taken for balancing and artificial recharge plan, the slope rate of hydraulic conductivity has decreased from 0.38 to 0.31. Also the slope rate of special discharge has decreased from 0.00117 to 0.00078. The main reason for this decreasing trend can be the destruction of soil structure and effective reduction of porosity indicating the irreversibility of the aquifer to its previous state. Therefore, it is necessary to pay attention to these changes regarding the recharge of aquifers and return water from irrigation systems.

Periphyton is a biological layer that is widely present in flood plains such as paddy fields and plays an important role in the nutrient cycle in such ecosystems. The role of this biological layer in dissolving and absorbing insoluble phosphorus in the country's paddy fields has not been recognized so far. This study was performed in the research laboratory of the department of soil science and engineering, university of Tehran in 2020 to investigate the role of periphyton grown in paddy fields of Guilan province in the release and absorption of phosphorus. For this purpose, 20 paddy fields in Guilan province were sampled from epipelon (LON) and epiphyton (TON). The results showed that about 68% of the population of autotrophic components in epipelon and epiphyton samples belonged to Chlorella and Chlorococcum. The genera Lyngbya, Scenedesmus, Nostoc and Navicula were the most abundant in the next ranks. The results of phosphate dissolution showed that samples of LON 6 and 13 and TON 8 have the highest solubility of phosphorus. Phosphorus uptake capacity was also very high in LON 6 and 13 samples and increased by 1840 and 2000% compared to the initial biomass, respectively. This amount was 825 percent in the TON 8. The results also showed that epipelon samples showed a higher ability than epiphyton samples in terms of phosphorus absorption and retention. In general, the results of this study showed that the periphytic biofilm has a high ability to absorb phosphorus, which reduces the waste of fertilizer used and therefore helps to increase its efficiency, and thus reduces non-point pollution.

The use of measured data to evaluate reference evapotranspiration (ET0) estimation models in various studies has been limited due to the problems in the measurements. The types of grass and soil textures used in lysimeters differ in different studies, while these factors affect the amount of lysimetric measurements. This study evaluated 19 physical-experimental and experimental models in the combined, radiation, temperature, and mass transfer groups for three consecutive years (2017-2019) by lysimetric measurements in the Tabriz region with a semi-arid climate located in northwestern Iran. Also, to investigate the effect of reference plant species and soil texture on ET0, two grass species including Festuca Arundianacea Schreb and Lolium perenne were applied in three soil textures of sandy loam, clay, and silty loam in weight lysimeters. The Kimberly Penman-1996 (KP), Penman-1963, FAO.ppp.17 Penman (FAO.ppp.17), FAO24 Blaney Criddle (FAO24 BC), and FAO56 Penman-Monteith (FAO 56 PM) had the best performance among used models. Group comparison of models showed that the combination models had the best performance among the studied groups. The ET0 values estimated by the models were more consistent with the lysimeters filled with sandy loam soil than the ones filled with silt and clay lysimeters. The study of the effect of grass species on the performance of the models showed that the accuracy of the experimental models in lysimeters planted with grass Lolium was higher than the Festuca grass.

In this paper, more than one hundred studies on soil salinity  which conducted  by researchers in the Department of Soil Science and Engineering, University of Tehran in the last fifty years, are reviewed  and then classified as; measuring and estimating the properties of saline and sodic soils, the effect of salinity and sodicity  on soil characteristics, the relationship between plant and soil salinity, the effect of vegetation and biological crusts on soil salinity, leaching and modeling of solute movement, genesis and development of saline soils and salinity warnings and finally,  biological relationships in saline soils. Summarizing these results reveals that the methods of soil analysis, crop management as well as sustainable soil management, the relationship between soil and micro and macroorganisms and plant nutrition and soil fertility are considerably different from non saline conditions. In addition, the salinity is developing  and the need to use the salt affected soils is inevitable. Some findings would be worthwhile in the use and management of  these soils. Subsequently it is necessary to define a comprehensive research program for saline sodic soils in Iran.

In modern agriculture, silicon (Si) is considered as an essential and anti-stress nutrient for a number of plants, especially grasses and C4. There are arguments confirming that it is a quasi-essential element in relation to plants growth, development and reproduction. The present study aims to review a decade research in the field of chemistry and plant nutrition of the Si in soil and plants in the Department of Soil Science and Engineering, University of Tehran. The objectives of this article is to present the most important achievements of researches in the field of Si efficiency of maize and soybean cultivars and to investigate the effect of Si application on nutritional, physiological and morphological characteristics of different plants including wheat, corn, sorghum, etc. under stress conditions and also to assess the effect of Si application on immobilization of heavy metals in the soil. General conclusions of this study show that Si supplied by both chemical fertilizers and silicon-soluble bacteria, increase plant growth and yield via increasing the root system of plants, regulating the biosynthesis of plant hormones, stimulating the production of some antioxidant enzymes, increasing resistance to salinity/ drought/heavy metal toxicity stresses and also increasing plant accessibility to some nutrients such as phosphorus and nitrogen. In addition to these results, the fraction of Si in different soils have been studied and analyzed. It seems by focusing on researches done on this element in the "soil, plant and rhizosphere", it can be hopefull that these results will be more practical in the future of the country's agriculture.