نشریه آب و خاک
سال سی و ششم شماره 6 (پیاپی 86، بهمن و اسفند 1401)

Due to climate change, one of the limiting factors of crop production is environmental stress which, by disrupting the natural metabolism of the plant, limit plant growth and finally reduce crop production. Drought stress causes the greatest reduction in crop productivity compared to other environmental stresses. Therefore, the use of methods to reduce water consumption in agriculture is more important due to the lack of freshwater resources. Increasing water use efficiency and maintaining plant yield by reducing water consumption has a particular importance for crop production and should be paid special attention. Drought stress reduces photosynthesis, stomatal conductance, biomass, growth and consequently plant yield. The effects of drought stress on the yield of plants such as potatoes (Solanum tuberosum L.), wheat (Triticum aestivum L.), rice (Oryza sativa L.) etc., which play an important role in the nutrition and food of the world, has a great importance. Achieving the desired soil moisture range is one of the most important approaches to increase water use efficiency and not significantly reduce yield. For this goal, a factorial experiment was conducted in a completely randomized design with five replications in the research greenhouse of Ferdowsi University of Mashhad.

Factors studied in this experiment included three levels of irrigation 1- full irrigation (100% of field capacity), 2- medium drought stress (70% of field capacity), 3- partial root-zone drying (70% of field capacity), time of induction of water stress (two weeks after planting and 50% at flowering time) and two levels of phosphate (CaH4[Po4]2 H2O) fertilizer (based on soil analysis (25 mg.kg-1) and adding 25% more than recommended (31 mg.kg-1)) at the beginning of the period phosphate was mixed with soil inside the pot in greenhouse condition. Fontane potato cultivar was used in this study. In irrigation treatments, one part of the pots was stressed two weeks after planting and the second part of the pots were fully irrigated until the beginning of flowering and irrigation treatments were applied at 50% flowering stage. From the prepared samples, membrane stability index, osmotic potential, and relative water content were measured in the laboratory and at the end of experiment, plant height, tuber weight, biomass and plant water use efficiency were measured. Minitab 18 software was used to analyze the data.

The results showed that with increasing phosphate fertilizer from 25 mg.kg-1 to 31 mg.kg-1, plant biomass increased significantly and in all treatments biomass increased between 2 to 28% . Partial root-zone drying treatment showed a 17.4% increase in biomass. In the medium drought stress treatment, the total growth period and phosphorus level of 31 mg.kg-1, the lowest water use efficiency was observed, and there was no significant difference in the medium drought stress treatment of the total growth period and the phosphorus level of 25 mg.kg-1. Partial root-zone drying treatment of roots from flowering time and 31 mg.kg-1 P, with full irrigation treatment 25 mg.kg-1 P have the same water use efficiency, but the performance of this treatment  compared to full irrigation treatment was reduced by 28%. Water use efficiency in partial root-zone drying (intermittent irrigation) has increased compared to traditional irrigation, which indicates a more optimum use of water in the medium drought stress method. Full irrigation treatment had the highest tuber weight per plant and partial root-zone drying during the growing season treatment had the lowest tuber weight per plant (65%) compared to full irrigation. The partial root-zone drying treatment after flowering, ranked second after full irrigation treatment, for tuber weight per plant and more tuber weight per plant compared to other drought treatments. Using 31 mg.kg-1 phosphate, tuber weight per plant in full irrigation treatment reached 332 g.plant-1 which increased by 13% and was significantly different from all treatments. With increasing phosphate level from 25 mg.kg-1 to 31 mg.kg-1, in the partial root-zone drying treatment from flowering time, tuber weight per plant increased by 28% to 207 g.plant-1. Tuber weight per plant in other drought treatments decreased with increasing phosphate level from 25 mg.kg-1 to 31 mg.kg-1, although this decrease was not statistically significant.

Compared to deficit irrigated methods, partial root-zone drying from the beginning of growth and full irrigation has the ability to use available nitrogen at the end of the growing season and has more greenery than other drought treatments. This effect probably explains the filling of the gland tubers at the end of the growing season and thus the keeping of yieldyield production. The best methods for saving water consumption and maintaining the yield, the partial root-zone drying methods is better than the medium drought stress method.

Showing the rivers as a one-dimensional problem has simplified or eliminated many processes affecting salinity transfer in the river. Storage processes are one of the factors affecting water quality in rivers. Generally, as a substantial factor, the limitation of observational data confines the use of two-dimensional and three-dimensional models, leading to the use of more widely employed one-dimensional models. Most existing computer models are developed based on the Advection-Dispersion Equation (ADE) and do not consider the storage zone. For this purpose, Modified Advection-Dispersion Equation (MADE) is proposed to consider the stagnant area by defining effective velocity and dispersion coefficient. In this study, a solution has been proposed to apply the effect of the Stagnant zone in water quality simulation in one-dimensional models. The river simulation is closer to the natural conditions. In this model, to prove the improvement of the proposed method, the average stagnant zone fraction expressed as the fraction of the average cross-sectional area of the river (η) and employed in a one-dimensional model through the definition of the effective velocity and the dispersion coefficient. This model is considered representative of the one-dimensional models developed only by the Advection /Dispersion relation, and the proposed method was investigated for the Arvand River. Observational data along the river were used to calibrate and validate the model.
Since the available and well-known one-dimensional computer programs are generally developed based on the 1D Advection-Dispersion model, they do not consider factors affecting salinity transport such as topography and river morphology heterogeneities known as storage areas. In such a way, these processes are not expressed by presenting the problem as a one-dimensional equation. In this research, in order to increase the accuracy of the simulation with well-known and available one-dimensional models a corrective solution is proposed. To compare the proposed modified method and the base ADE, at the first, the tidal and transboundary arvand river is modeled as a study area, which is a well-mixed river. The river's upstream and downstream boundary conditions were defined according to the available data in 2014. Manning's roughness parameters ranged from 0.017 to 0.033, and the dispersion coefficient was 285 m3/s according to previous studies. In order to apply the effect of stagnant areas in the modified equations, it is essential to determine the value of η for the river. This study uses three parameters of dispersion factor (a), dispersion exponent (b), and η by ant colony algorithm with the definition of 5 initial ants and 100 repetitions in Sehan station in the study area, Arvand river was optimized. The values of the estimated parameters are respectively η = 0.168, a = 273.4, b = 0.94. Therefore, in the modified model, corrections were made using the speed and effective dispersion coefficient as the modified Advection - Dispersion (MADE) method and considering variable dispersion coefficient depending on the flow's speed in the one-dimensional model. These changes were validated in the other two stations (Faw and Dweeb).
Based on this study results, increasing the parameter η caused the peak of the time series to rise and the river's travel time to decrease. The shortening of the water travel time in the river, although increases the dispersion coefficient due to the influence of the stagnant zone, the effect of this parameter on the time series of the simulated concentration is reduced. Like the observational data, the slope of falling and rising limbs is increased. By comparing the one-dimensional model in the two cases of using the effective dispersion coefficient and velocity and without it, the increase in accuracy in the simulation was determined at Sehan station - 123 km from the river formation site - after optimizing the coefficients with three statistical errors parameters. In addition, these changes at two other stations along the river with distances of 180 and 150 km from the river's source confirm this accuracy. For instance, the simulated and measured concentration in 12 months of the year by applying the optimized coefficients reaches the correlation coefficient (r) of 0.86 to 0.97 at a distance of 150 km from the upstream, and the root means square error (RMSE) improves 1.27 ppt. The remaining difference in the concentration estimation may be caused by the effect of other parameters or even the entry of agricultural runoff from the lands along the river.
Accurate estimation and simulation of concentration in river engineering have always been one of the environmental challenges. This research aimed to improve water quality simulation using one-dimensional model in well-mixed rivers. In order to increase the accuracy of the modeling and become closer to the actual conditions, correction factors such as considering the dead zones along the river have been suggested. Analysis showed that, on average, 16% of the surface of the Arvand River's cross-sections are stagnant areas, and the dispersion coefficient depends on the river's speed. These areas include bed dunes and meanderings of the river. The point that attracts attention is the tidal irrigation channels on the sides of the river. The results showed that in Sehan, Dweeb, and Faw stations, the root means square error decreases to 1.78, 1.27, and 0.84, respectively. Therefore, the modified 1D model estimated the concentration (in this study salinity) closer to the measurement data. In Dweeb and Sehan stations, the effect of dead zones such as river meandering is evident. Still, in Faw station, no significant improvement in the impact of stagnant zones was observed due to its proximity to the river mouth. The results of this research can be used for higher accuracy in one-dimensional water quality simulations and bringing the models closer to the natural conditions in rivers.

The rise in water demand and reduction of water quality and soil in irrigating areas, especially in dry and semi-arid areas of the world, have turned into one of the most crucial challenges for water and soil engineering in recent years. This issue leads us toward optimal quantitative and qualitative management of these valuable resources aimed at achieving economic performance and water productivity. The periodic evaporation and transpiration of the plant in the conditions of simultaneous water and salinity stress are known as one of the most important factors in the qualitative and quantitative growth of the plant yield. Applying mathematical models that simulate the relationship between field variables and yield can be seen as a useful tool in water and soil management issues in such a situation, which has the potential to ensure optimal use of the water and soil resources of any country by providing the plant's water needs and preventing its further loss.

A factorial experiment was performed in 2019 based on completely randomized blocks design with three replications in plots with an area of 9 square meters at the agricultural and animal husbandry farm of Aliabad Fashafuyeh, located in Qom province to examine the simultaneous effect of different levels of water stress and salinity on the periodic evaporation-transpiration and fresh yield of the single cross 704 forage corn cultivar. The applied treatments included the irrigation water salinity at three electrical conductivity levels of 1.8 (S0), 5.2 (S1), and 8.6 (S2) deci Siemens/meter (dS/m), which were prepared by mixing saline well water of the region with fresh (drinking) water and three water stress levels of 100% (W0), 75% (W1), and 50% (W2) of the plant's water requirement. The depth of soil moisture in the corn plant root zone was measured by the TDR device at five depths of 7.5, 12, 20, 40, and 60 cm during different growth stages of the plant using pairs of 7.5, 12, and 20 cm stainless steel electrodes.

The simultaneous water and salinity stresses, which led to the reduced amount of periodic evaporation-transpiration of the yield compared to ideal conditions (without stress), were simulated by additive and multiplicative models. The results suggested a decrease in the evaporation and transpiration with the increased simultaneous water and salinity stresses so that the amount of total evaporation-transpiration in different treatments was measured to be between 692.7 and 344.9 mm and the fresh yield was estimated between 50.4 and 3.2 tons per hectare. Also, the highest amount of periodic evaporation and transpiration in all treatments was found to occur in the development and intermediate stages, and the relative fresh yield in the W0S0 to W2S2 treatments was calculated between 66% and 100%. The results of modeling the relative yield of the crop based on the amounts of relative evaporation and transpiration of corn in different growth stages and under the different treatments of water stress and salinity, indicated that Singh's additive model and Rao's multiplicative model were appropriate, while the Minhas model was recognized to be inappropriate in this estimation.

The research results suggested the significant impact of water stress and salinity at least at the 95% level on evaporation and transpiration and the corn yield. Moreover, the effect of the sensitivity of different growth stages of the plant on the reduction of evaporation and transpiration of corn varies so that in the three treatment groups W0, W1, and W2, the highest average decrease in slope was related to the final stage (13.6%) followed by the middle stage with an average decrease of 8.4% compared to the control treatment. Therefore, the highest decrease rate in evaporation-transpiration slope has been observed in these two growth stages due to the beginning of flowering, fruit formation, and physiological ripening of seeds. These results come from the lack of sufficient water storage and increased salinity of irrigation water in the soil. Water stresses and salinity will reduce water absorption and evaporation-transpiration, and ultimately, reduce crop production due to the decreased amount and potential of water in the soil. Another finding to be mentioned is the priority of water stress compared to salinity stress in reducing evaporation and transpiration and production yield. Also, by managing water and salinity stresses in the critical stages of plant growth (especially the middle stage), which is the time of flowering and the beginning and completion of the maize production process, a significant reduction in the crop can be somewhat prevented.

Surface and underground waters are one of the world's most important problems and environmental concerns. In the last few decades, due to the rapid growth of the population, the water needs have increased, followed by the input load to the water. In order to classify the quality of underground water and water level according to the type of consumption, there are many methods, one of the most used methods is the use of quality indicators. Considering the facilities available in water quality monitoring stations and the need to save time and money, using alternative methods of modern data mining methods can be good for predicting and classifying water quality. The process of water extraction for domestic use, agricultural production, mineral industrial production, electricity production, and ester methods can lead to the deterioration of water quality and quantity, which affects the aquatic ecosystem, that is, the set of organisms that live and interact. Therefore, it is very important to evaluate the quality of surface water in water-environmental management and in monitoring the concentration of pollutants in rivers. The aim of the current research was to estimate the numerical values of the drinking water quality index (WQI) using the tree method and investigate the effect of wavelet transformation, the Bagging method, and principal component analysis.
In this research, to calculate the WQI index from the quality parameters of the Bagh Kalaye hydrometric station including total hardness (TH), alkalinity (pH), electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca), sodium (Na), Magnesium (Mg), potassium (K), chlorine (Cl), carbonate (CO3), bicarbonate (HCO3) and sulfate (SO4) were used in the statistical period of 23 years (1998-2020). Quantitative values calculated with the WQI index were considered as target outputs. By using the relief and correlation method, the types of input combinations were determined. The random tree method was used to estimate the numerical values of the WQI index. Then, the capability of the combined approach of wavelet, principal component analysis, and Bagging method with random tree base algorithm was evaluated. To compare the values obtained from the data mining methods with the values calculated from the WQI index, the evaluation criteria of correlation coefficient (R), root mean square error (RMSE), mean absolute error (MAE), and modified Wilmot coefficient (Dr) were used.
The use of the wavelet transform method and the Bagging method has improved the modeling results. Considering that the Bagging classification method with the random tree base algorithm is a combination of the results of several random trees, so using this method has increased the accuracy of the RT model. So, in general, it was concluded that the use of wavelet transformation and classification methods increases accuracy and reduces errors. The best scenario with the highest accuracy and the lowest error was related to scenario 10 of the W-B-RT model with Total Hardness, Electrical Conductivity, Total Dissolved Solid, Sulphate, Calcium, Bicarbonate, Magnesium, Chlorine, Sodium, and potassium parameters. The results showed that the effect impact of pH in estimating the numerical value of the WQI index is considered lower than other parameters. When the principal component analysis method was used, by reducing the value of the eigenvalue from F1 to F12, the value of the factor also decreased; As a result,so F1, F2, and F3 factors were selected as the basic components. Considering 3 main factors, modeling was done employed and R=0.98, RMSE=2.17, MAE=1.52, and Dr=0.97 were obtained. In general, the results showed that the PCA method, despite reducing the dimension of the input vectors and simplifying it, can improve the accuracy and speed of the model and is introduced as the best method for estimating the numerical value of the WQI index.
The results obtained from the present research showed that the use of wavelet transform, Bagging and PCA methods had a positive effect on improving the results and increasing higherthe accuracy. In estimating the numerical values of WQI index, PCA-B-RT method considering 3 main factors, with correlation coefficient equal to 0.98, root mean square error equal to 2.17, average absolute value error equal to 1.52 and tThe modified Wilmot coefficient equal to 0.97 had the highest accuracy. Considering that all the methods used in the estimation of quantitative values had acceptable accuracy, therefore, in case of lack of data and lack of access to all chemical parameters, it is possible to obtain appropriate and acceptable results by using a limited number of parameters and data mining methods achieved.

The accuracy of determining reference evapotranspiration (ET0) is an important factor in estimating agricultural and garden water requirements. The complexity of the evapotranspiration process and its dependence on meteorological data have made it difficult to accurately estimate this variable. Non-linearity, inherent uncertainty and the need for diverse climatic information in ET0 estimation have been the reasons that have made researchers interested in data mining methods such as artificial neural network (ANNs), random forest (RF) and support vector machine (SVM). Dos et al. (2020) evaluated the performance of machine learning methods to estimate daily ET0 with limited meteorological data. Their results showed that machine learning methods estimate ET0 with high accuracy, even in the absence of some variables. The use of artificial intelligence models in estimating ET0 with high accuracy has become popular in recent years, but the complexity of these models makes it difficult to apply them to regions with different climatic conditions) Feng and Tian, 2021.( Therefore, the aim of this study is to show that different data mining methods are suitable for daily ET0 estimation, which can reach a comprehensive and simple model with high accuracy by using minimal weather data.

In this research, the accuracy of data mining methods in estimating ET0 was evaluated in comparison with the plant water requirement system (FAO-Penman-Monteith standard method). For this purpose, data related to meteorological parameters such as sunshine hour, air temperature, wind speed, and relative humidity air were collected from ten synoptic stations and five climatology stations of Qazvin province in a period of 10 years (1389-1399). The ET0 extracted from the plant water requirement system was calculated based on the Penman-Moanteith method of FAO 56 and on a daily time scale, which is the actual value (measured) with the estimated values obtained by data mining methods (ANNs, RF and SVM) were evaluated. In order to validate the obtained results, the data of each station was divided into two sets of training (two-thirds of data) and testing (one-third of data). Finally, the generalizability of the mentioned methods in estimating ET0 was investigated based on NRMSE, R2, RMSE, MBE, EF and d Criteria.

The results showed that the ET0 values of the plant water requirement system have a good correlation with the estimated ET0 values of ANNs, RF, and SVM methods. In this research, the accuracy of the results of ANNs method was relatively higher than the other two methods. The results of statistical investigations and diagrams showed that ANNs, RF and SVM methods, considering all meteorological parameters (mean air temperature, average relative humidity, sunshine hours and wind speed) as input to the model, in Qazvin synoptic station with altitude 1279 meters and the climatology station of Rajaei power plant with a height of 1318 meters, estimated ET0 with higher accuracy in both training and testing steps.In the ANNs method, the values of NRMSE and R2 at Qazvin synoptic station in both training and testing steps are equal to 0.11 and 0.97, respectively, and at Rajaei Power Plant climatology station in both training and testing steps are equal to 0.10 and 0.97, respectively. In this research, the accuracy of estimating the value of ET0 in two ANNs and RF methods is close to each other and higher than the SVM method. On the other hand, the fitting speed of the ANNs method is very long compared to the RF method, and considering all aspects, it can be said that the RF method has a more suitable approach for estimating the ET0 value. The results of this research showed that the value of ET0 is not only based on air temperature, but may change under the influence of other factors such as air pollution, and is also strongly influenced by regional conditions such as topography and altitude.

The results of this research, in addition to better investigation of ET0, help to know more influential factors in each region and can be used in regions with similar climatic conditions. For example, in the current study area, it was found that the role of average air temperature is greater than other climatic parameters and has a greater impact on ET0. Therefore, it can be said that increasing the average daily air temperature will increase ET0 and subsequently increase the water requirement of plants. As a result, by using these methods and paying attention to these points, it is possible to avoid water stress and possible reduction of the production.

 Control and extraction of water using underground dams in arid regions has been of interest to researchers since not too long ago. Construction of underground dams does not require surface water storage and does not change land use. Therefore, they are environmentally suitable. The lack of groundwater resources on the one hand and indiscriminate and unscientific harvesting on the other hand, and the increasing needs associated with population growth, will cause scientific communities to revise and provide appropriate solutions for managing the exploitation of groundwater aquifers and creating new resources or renewable reservoirs in the country. Nowadays, in many countries of the world, the construction of underground dams has been considered as a new method for utilization of water resources. Several criteria such as physical, socio-economic and hydrological criteria are involved in the location of underground dams. Underground dams have wide applications for feeding groundwater aquifers and water storage, as well as preventing soil erosion and increasing groundwater quality. Due to the limitation of water resources and the lack of equality of the world's share in exploiting this divine gift, it is anticipated that most countries will soon suffer from severe water shortages, so that it is firmly believed that if this problem continues, many international conflicts will be over water for centuries to come. One of the strategies to deal with water shortage is to extract water from new resources, especially the discovery of underground, which can be done by constructing different underground dams and with the knowledge of the world.

 In this study, to determine the susceptible areas of underground dam construction using field visits was selected Pashueeyeh watershed. To communicate between effective criteria and save time and money, a method based on combining maps in GIS and RS system has been used. In the first step, investigations were carried out to identify suitable areas for the construction of underground dam. For this purpose, data extracted from basic maps, findings in this field and expert opinions were used.

 Therefore, a combination of new sciences such as GIS, RS and geoelectrics was used in determining the susceptible areas of underground dam construction, which in turn is a valuable research that provides the situation for creating other combined researches in different climates of the country, stating that a combination of different sciences in addition to the sciences mentioned in this research can increase the quality of studies related to underground dams and even large groundwater discovery are effective and in case of mild to severe droughts can be a way to solve the country's problems in the field of using quality water and lower extraction costs. The results showed that Pashueeyeh watershed is not a susceptible place for underground dam construction in Lut desert region for water storage. According to the results of geoelectric sodages and field evidences, the bedrock at the proposed location has dense clay that have many salts and the depth of impact on the bedrock varies between at least 2.6 meters and a maximum of 7 meters. On the bedrock is a river alluvial layer consisting of two wet and dry horizons. Also, the river alluvial layer consists of sequences of layers with different aggregation and permeability. The results show that the electrical resistance of different layers rarely reaches more than 30 ohms per meter; this is due to fine grain texture and high density of sediments as well as water salinity.

 One of the strategies to deal with water shortage is to extract water from new resources, especially the discovery of underground aqueous, which can be done by constructing different underground dams and with the new knowledge of the world. Underground dams in the world are expanding in different climates, especially in arid and semi-arid regions, which are likely to become one of the most important sources of water extraction in the future years, especially if they are associated with new technologies and combination of GIS, RS and geoelectric. the results showed that the combined role of GIS, RS and geoelectric in determining the susceptible areas of underground dam construction makes the accuracy of proper site construction of underground dams and even the discovery of underground aquifers much higher and achieved valuable results.

 Overuse of antibiotics and their entry into the environment is a global concern today. Much of the antibiotics taken by animals and humans are excreted unchanged and found in their feces which enter the environment through livestock waste and municipal wastewater disposal. Uncontrolled release and continuous introduction of antibiotics to the environment induced antibiotic resistance in microorganisms living in other habitats which pose a potential hazard to existing aquatic ecosystems and animals. Rivers act as the main sink for the effluents that distribute antibiotics and antibiotic resistant microorganisms in the environment. This study aimed to investigate the antibiotic resistant index (ARI) in Goharrood River. Seasonal variations and source of contamination, focusing on urban surface wastewater of Rasht, were investigated through sampling of river water and sediment in different points along the river during four seasons of a year.

The water and sediment of the river were sampled at three points along the river (focused on river course in Rasht city), in autumn, 2016 and in winter, spring and summer, 2017. The number of antibiotic resistant heterotrophic and coliform bacteria were counted via colony count method in the antibiotic supplemented 100 µg/mL Nutrient Agar and Eosine-Methylene Blue agar media respectively. Cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim antibiotics were tested in this study. ARI was calculated by dividing number of bacteria colonies (heterotrophic and coliform bacteria) in plates supplemented with antibiotics to the number of colonies in control plate (without antibiotic). Escherichia coli as an indicator coliform bacterium was isolated from water and sediment samples (12 strains; 4 season and 3 sampling points) and their resistant pattern to these antibiotic was also tested by disk diffusion (Kirby-Bauer) method in Mueller-Hinton agar medium. The inhibition zone (ZOI) of E. coli growth was measured and its sensitivity/resistant was assessed based on CLSI standard protocol. The calculated ARI of heterotrophic and coliform bacteria of water and sediment of the River and the determined ZOI of E. coli isolated from water and sediment were analyzed by repeated measures of factorial arrangement in a completely randomized design format by SAS software package. Factors included sampling point at 3 levels (before entering river to the Rasht city; A, in the Rasht city; B, and after river exit from the Rasht city; C), and antibiotics at 5 levels (cephalexin, gentamicin, doxycycline, ciprofloxacin, and trimethoprim) as main plot and sampling time at 4 levels (autumn, winter, spring, and summer) as sub-plot.

 The highest ARI value of water heterotrophic bacteria was obtained to cephalexin at the sampling point C. Mean ARI of water heterotrophic bacteria to all antibiotics (regardless of type of antibiotic) at three points of A, B and C was 3.77, 4.54 and 7.53%, respectively. The highest ARI levels of heterotrophic and coliform bacteria in water were obtained in the summer season. In fact, the change of seasons and clearly the summer season controlled the ARI in water bacteria rather than the type of antibiotics. So that in this season 30.78% of water heterotrophic bacteria were resistant to ciprofloxacin antibiotic and about half (50.78) of the river water coliforms were resistant to cephalexin. Although ARI for heterotrophic and coliform bacteria was lower in sediment rather than that in water, the highest ARI levels of heterotrophic and coliform bacteria in sediment were obtained against cephalexin in autumn and winter, respectively. In general, the mean ARI in water and sediment bacteria was as follows: cephalexin > gentamicin > ciprofloxacine > doxycycline > trimethoprim. The lowest ZOI value for E. coli was obtained against cephalexin. Therefore, in all three sampling points, isolated E. coli bacteria from water and sediment were resistant to cephalexin. In the study of the sampling time and sampling point interaction, it was also seen that the lowest ZOI of E. coli was in autumn and at sampling point C. Therefore, it seems that E. coli has become resistant to antibiotics when river crosses the city.

 According to the results of this study, Goharrood river is contaminated with antibiotic-resistant, especially cephalexin resistant bacteria and it may distribute pollution downstream. If the river water is used in aquaculture and irrigation of downstream agriculture fields, the antibiotic resistant bacteria may be spread in the other ecosystems and finally may enter the human food chain.

Boron (B) has a dual effect on living systems, so that the concentration range within which B is changed from a nutrient to a pollutant is rather narrow. Although B plays essential roles in all living organisms, its long-term excessive uptake has adverse effects on either human beings or plants and animals. Furthermore, part of the B that can be used as fertilizer is highly soluble and easily leached into the soil profile leadsing to some problems such as decrease of fertilizer efficiency. Therefore, to improve agricultural productivity through its gradual uptake by plants, the increase of B adsorption in the soil solution is necessary. Many adsorbents have been used for the adsorption of B from aqueous solutions; however, layered double hydroxides (LDHs) have been considered as one of the most effective adsorbents as well as slow releaser fertilizers of inorganic anions such as nitrate, phosphate, etc. The formula of LDHs are typically denoted as [M1-x 2+M x 3+ (OH)2]x+ (An-) x/n .m(H2O), where M2+ and M3+ are divalent and trivalent cations, respectively, the significance of x is the molar ratio of M3+/(M3++ M2+) and An- is the intercalated anion. Although LDH materials are commonly prepared by combining two divalent and trivalent metals, more metals can be introduced in the brucite layer to achieve a large variety of composition and higher adsorption capacity. Stability of LDHs in soil can be affected by numerous factors (e.g. low molecular weight organic acids (LMWOAs)) leading to release of structural cations in addition to interlayer anion. However, there are scarce investigations that have evaluated the potential of ternary LDHs (e.g. Zn–Mn–Al LDH) in desorption of B (as interlayer anion) and release of Zn and Mn (as structural anions) in a simulated soil solution. Therefore, the objectives of this study were, i) to compare the desorption of B capacity of binary LDH (Zn–Al LDH) and ternary LDH (Zn–Mn–Al LDH) in the simulated soil solution, and ii) to investigate the effect of three different electrolytes (potassium nitrate, oxalic acid, and citric acid) on the release of Zn and Mn from synthesized LDHs.
 A modified urea hydrolysis method was employed to synthesize Zn–Al and Mn-substituted Zn–Al LDHs with Zn(+Mn)/Al molar ratio of 2. Herein the contents of Mn with respect to Zn corresponded to 2% and 10% molar ratio. Accordingly, the synthesized materials denoted as Zn–Al, Zn–Mn1 and Zn–Mn2 for the samples without Mn, with 2 and 10 mol% Mn with respect to Zn content. For investigation of B desorption at a concentration of 10 mM, 15 mL from equilibrium solutions were substituted with 15 mL of 0.03 M KNO3 and shaken for 240 min. Substitution was repeated four times and A modified urea hydrolysis method was employed to synthesize Zn–Al and Mn-substituted Zn–Al LDHs with Zn (+Mn)/Al molar ratio of 2. Herein the contents of Mn with respect to Zn corresponded to 2% and 10% molar ratio. Accordingly, the synthesized materials denoted as Zn–Al, Zn–Mn1 and Zn–Mn2 for the samples without Mn, with 2 and 10 mol% Mn with respect to Zn content. For investiigatigatingon of B desorption at a concentration of 10 mM, 15 mL from equilibrium solutions were substituted with 15 mL of 0.03 M KNO3 and shaken for 240 min. Substitution was repeated four times and B concentrations in extracts were measured by Azomethine-H method. Furthermore, the supernatant Zn and Mn concentrations were determined by GF-AAS (PG 900). This process was repeated for 1.25 mM oxalic acid and 1.25 mM citric acid to study the effect of these compounds on B desorption as well as release of Zn and Mn. B concentrations in extracts were measured by Azomethine-H method. Furthermore, the supernatant Zn and Mn concentrations were determined by GF-AAS (PG 900). This process was repeated for 1.25 mM oxalic acid and 1.25 mM citric acid to study the effect of these compounds on B desorption as well as release of Zn and Mn.
The adsorption and desorption isotherm were carried out to describe the distribution of B between the liquid and adsorbent. The isotherm data of synthesized LDHs were matched with Freundlich model. The values of 1/n in this model were found between 0 and 1 for all LDHs indicating favorable sorption of B on these compounds. The highest adsorption was observed for ternary LDHs (particularly Zn–Mn2) due to their higher specific surface area and also due to the ion exchange mechanism in combination with surface adsorption. However, the results showed that the percentages of B desorption by potassium nitrate, oxalic acid and citric acid were lower for Zn–Mn1 (19.4, 29.1 and 38.2%, respectively) and Zn–Mn2 (18.6, 28.2 and 35.9 %, respectively) than Zn–Al (30.8, 41.2 and 46.2%, respectively). This observation suggests that the type of LDH, B adsorption mechanism and background electrolyte can affect the amount of B desorption. Furthermore, after 4 successive desorption cycles, the concentration of Zn and Mn increased in the supernatants (particularly in organic acid electrolytes) suggesting dissolution mechanism possibility happened for the studied LDHs. Among the background electrolytes, citric acid was the most effective compound in releasing Zn and Mn, followed by oxalic acid and potassium nitrate. A reason for this such observations could be that with respect to chemical structure, citric acid by three carboxyl groups can form more chelate rings compared to oxalic acid, which contain two carboxyl groups. Therefore, it seems that B containing Zn–Mn–Al LDH may have potential to be used as a slow release fertilizer in soils to supply three essential elements, including B, Zn and Mn simultaneously. However, further studies are required to support such a hypothesis.

Conservation agriculture (CA), as a sustainable cultivation system, aims at efficient use of natural resources with least environmental impacts, while achieving food security through increasing yield and crop diversification. CA consists of three main principles: 1- reduction or elimination of mechanical soil disturbance; 2- maintaining a permanent cover of crop residues on soil; and 3- diversification of crops. However, the total area under CA in Iran is less than 5% of arable lands. In Hamedan province, CA is mostly implemented in rainfed farming. Therefore, there is a necessity to expand CA in irrigated areas. Nonetheless, a lack of sufficient technical and local knowledge about CA acts as a barrier for its expansion in irrigated lands. Despite the large body of research conducted on CA, there is no detailed information about the combined effects of cover crops and conservation tillage systems on soil functioning and corn productivity in semi-arid regions of Hamedan province. Therefore, our aim was to study three-year effects of conservation tillage practices (no tillage and minimum tillage) and cover crops (hairy vetch and grass pea) on ​​selected soil quality indicators and yield components of corn in a clay loam soil of a semi-arid region in Hamedan. 

Combined effects of various tillage practices and cover crops on selected soil quality indicators and corn productivity were examined in a three-year experiment conducted in the research field of Bu-Ali Sina University. A factorial experiment in the basis of randomized complete block design with 3 replications and 2 factors were carried out, in which three levels of tillage practices (no tillage (NT), minimum tillage (MT), and conventional tillage (CT)), and three levels of cover crops (hairy vetch (V), grass pea (L), and no cover crop) were the treatments. Surface soil samples (0-15 cm) were collected two weeks after corn harvesting in the third year of experiment. Total organic carbon (TOC), organic carbon stock (CS), active carbon (AC), carbon management index (CMI), basal respiration (BR), alkaline phosphatase activity (APA), bulk density (BD), mean weight diameter of water-stable aggregates (MWD), and available phosphorous (P) and potassium (K) were determined. Corn yield components (including number of kernel rows per corn, number of grains per corn row, ear cob weight, hundred weight of grains, ear weight, grain weights per ear, biological yield and grain yield) were measured.

The highest TOC (0.96%), CS (18.7 ton/ha), AC (398 mg/kg), CMI (74.8), BR (0.118 mgCO2/g.d) and MWD (1.82 mm) were observed in MT treatment. However, no significant difference was detected between MT and CT in terms of AC, CS and CMI. Moreover, the lowest TOC (0.74%) was measured in NT, which showed no significant difference with CT treatment (0.83%). Reduced destruction of soil structure coupled with the increased MWD, and increased inputs of crop residues through MT, resulted to the protection of organic matter against microbial decomposition. Soil structuring, represented by BD, was improved under conservation tillage treatments (NT and MT).Among cover crops, hairy vetch treatment demonstrated the highest TOC (1.0%), CS (19.5 ton/ha), AC (427 mg/kg), CMI (80.3) and MWD (1.73 mm). However, these indicators, except CMI, were not significantly different between the two cover crops. On the contrary, these indicators were lowest in the control (no cover crop). Moreover, AC and CMI were not significantly different between grass pea and the control. Carbon stock was increased by 54 and 40% in hairy vetch and grass pea treatments, respectively, relative to the control. In general, cover crop cultivation combined with conservation tillage practices introduced additional biomass to the soil which in turn improved soil organic matter over time and enhanced soil quality.The lowest amounts of biological yield (1663 g/m2), grain yield (507 g/m2), hundred weight of grains 11.0 g), ear weight (91.4 g), grain weights per ear (62.9 g), and number of kernel rows per corn (13) were measured in CT system. In contrast, the highest grain yield (637 g/m2), hundred grain weight (13.6 g), ear weight (108.4 g), and grain weights per ear (81.9 g) were measured in NT treatment. However, the biological yield showed no significant difference between NT and CT. Soil quality improvement in conservation tillage treatments explains the enhancement of certain yield components. Biological yield and number of grains per row demonstrated significant difference between cover crop treatments; the maximum of biological yield (2103 g/m2) and of number of grains per row (44) was measured in hairy vetch treatment. Moreover, the lowest of biologigal yield (1589 g/m2) was observed in the control (no cover crop) treatment.

All soil quality indicators, except available P, were improved under MT as compared with CT. Our three-year study revealed that among conservation tillage treatments, MT improved majority of soil quality indicators compared to NT. Therefore, minimum tillage practice seems to be more sustainable in this study area. Conservation tillage treatments (MT and NT) also enhanced corn grain yield, grain weights per ear and number of grain rows per ear compared to to the CT. Both cover crops improved most soil quality indicators. Moreover, both cover crops induced significant effect on biological yield, although hairy vetch was more effective than grass pea. As a whole, the integration of minimum tillage with hairy vetch cover crop is considered as a sustainable cropping system for the improvement of soil quality and corn yield in this area.