مجله تحقیقات آب و خاک ایران
سال پنجاه و یکم شماره 11 (پیاپی 59، بهمن 1399)

One of the requirements for sustainable operation of soil, water and environment resources in agricultural sector is addressing the sustainable development criteria in dam construction projects. In current research, multi-criteria decision making methods (MCDM) including ELimination Et Choice Translating REality (ELECTRE), as a non-compensatory model, and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), as a compensatory model, were applied to select proper site for Kandoleh dam in Kermanshah province. For this porpose, after determining the suitable criteria with the help of studies and experts' opinions, group decision making was applied to identify the weight of the criteria by measuring the decision-makers' agreement. Then, the four selected sites for the Kondoleh dam were ranked based on technical, economic, social, environmental criteria and the relevant sub-criteria. At the end, the results were compared togeather. In order to reach a consecsus in the rankings of the two mentioned models, integration methods such as grade average, Copeland and Borda were employed and finally the average method was employed to finalize the results of the integrated methods. Also, 17 sub-criteria were ranked for choosing the dam's site. Based on the results, alternatives ranking for the two models; ELECTRE and TOPSIS, was different. However, the results of the ELECTRE model are more consistent with the final result of the integration methods. The results presented in this study are applicable for selecting storage reservoirs based on sustainable development criteria in soil and water resources development projects.

In an experiment, the effect of soil surface plotting on leachinguniformity of soil profile was investigated. The experiment was performed in a physical model with dimensions (height×width×length) of 1×0.5×2 meters. The leaching of the soil profile was simulated in presence of subsurface drainage pipe. The plots were made by separating the soil surface into four equal parts (with dimensions of 0.5×0.5 m), in order to prevent water mixing on the soil surface. An equal water depth was applied for soil leaching, before and after soil surface plotting. After leaching, the ECe of soil samples taken from different depths (20, 40 and 60 cm) and different distances from the drain pipe (25, 75, 125 and 175 cm) were measured. The amount of standard deviation of soil salinity data were 2(dS/m) and 0.63(dS/m) before and after soil surface plotting, respectively. The uniformity coefficient of salinity distribution in the soil profile before and after soil surface plotting was estimated to be 45% and 76%, respectively. The results showed that the presence of drain pipe was effective on infiltration rate at different parts of the soil surface. So that the infiltration rate was estimated to be 1.9, 1.7, 1.56 and 1.47 (mm/h) at 25, 75, 125 and 175 cm far from the drain pipe, respectively. Through soil plotting, the unbalanced water infiltration to the soil surface was prevented, in order to have a uniform soil washing at different places. The results showed that the soil leaching uniformity can be achieved by adopting a management strategy. Therefore, more drainage water production, depletion of soil nutrients and environmental pollution are prevented.

The present study aimed to investigate the periodic behavior, frequency and severity of drought along with introducing one or several adopted indices for each climate region in Iran. Daily data of 42 synoptic weather stations for a 23-year statistical period (1993-2016) were used in this study. Using the "efficient measure" hypothesis, the drought characteristics of each climate zones were investigated in the country. The years 1999-2000 in the arid zone and 2007-08 in other climate types were considered as a year of widespread drought throughout the country. According to "efficient measure", the results showed that the percentage of normal precipitation index (PNPI) was not a suitable indicator, especially for humid regions. Whereas, the standardized Precipitation Evapotranspiration index (SPEI) showed better performance on drought monitoring in wetter regions. Unlike the performance of other indices, the standardized precipitation index (SPI) had the same results in drought monitoring in all climates. This finding does not seem logical and indicates that the use of SPI should be done more carefully. With regard to the droughts persistence, except for the Chinese-Z index which in some cases showed completely opposite results in the wetter and dry periods, not all indices differed significantly. In addition, the results of this study revealed that the pattern of drought changes was not periodic.

Studies have shown that irrigation efficiency is low in Iran and Khuzestan province. However, it is essential to increase irrigation efficiency and reduce irrigation water losses in the field according to the water resources status. The main purpose of this study was to evaluate the performance of furrow irrigation in the fields of Shahid Beheshti Agriculture and Industry Company in Dezful and to offer some proposed solutions using optimization of design parameters by WinSRFR model. Three fields in Deylam region and three fields in BC region were selected to determine the irrigation efficiency. The results showed that the deep percolation and runoff losses in the fields of Deylam region varied between 4.9 to 81.5% and 24.3 to 62.3%, respectively. These values were detemined at 3.2 to 49.2% and 5.6 to 62.3% in the fields of BC region, respectively. Overall, the results showed that the amount of runoff losses is more than the amount of deep percolation losses in all the studied fields in Deylam and BC regions. However, despite the high losses, some fields were under deficit irrigation and their water requirement efficiency was less than 100%. The application efficiency in all fields varied between 13-45%. Generally, investigations showed that the management of the amount and duration of irrigation was not appropriate; this is due to the lack of awareness of farmers about the amount of water needed and cut-off of the inflow at the appropriate time. After evaluating the current situation, the presentation of management solutions using the WinSRFR model showed that if proper management of the length, slope and flow rate to the furrows is done, the water application efficiency will be significantly increased 35.8% (from 29.8% to 65.6%) and runoff losses decreased 49.7% (from 59.7% to 10%).

Plant Available Water (PAW) is the most common criteria for Soil Available Water (SAW) to plants which assumes uniform water availability between two matric potential limits (field capacity to permanent wilting point) and ignore other limiting factors for plants. Integral Water Capacity (IWC) is one of the most recently developed criteria for SAW that consider all soil restrictions including unsufficient aeration, rapid drainage, resistance of root penetrability and salinity, in order to estimate the SAW properly. In this study, in order to compare the applicability of PAW and IWC criteria in irrigation management, soil physical and hydraulical properties of a pistachio garden, with drip irrigation system, were measured and PAW and IWC ​​were calculated. Based on these criteria, two irrigation regimes ( and) were determined. According to the results, the irrigation periods for  and were 8 and 12 days and irrigation duration were obtained 6 and 12 hours, respectively. Soil salinity distribution and root water uptake in two irrigation regimes were simulated using HYDRUS-2D model after validation for garden condition which showed a high accuracy for modeling. The results showed that in , soil salinity is driven to areas farther from the root of the tree and the area with low salinity levels, which plays an effective role in water absorption, are expanded. Based on the simulation, 63.7% and 48.1% of crop water requirement were provided through  and  managements, respectively. Therefore, by using IWC index, irrigation management could have a better accommodation to field conditions and leads to less water and salinity stress.

Pesticides consumption, especially in fresh-use crops creates some concerns. The aim of this study is to investigate the effect of chemical synthesis of essential and quasi-essential elements along with complexing compounds and their effects on pest control of two spotted spider mite in Strawberry. Treatments included the combination of virogard commercial fertilizer in two concentrations (2 and 5 per thousand, recommended by the manufacturer) and protective fertilizer synthesized in this study at a concentration of 10 per thousand (effective concentration determined in the pre-test) and the combination of protective fertilizer + pesticide (half permissible concentration) and control treatment (distilled water) in two stages of application of fertilizer treatments (pre-infested and post-infested plants to mites) with six replications which were performed in greenhouse conditions. In the growth period after fertilizer application, the death mites percent was estimated by Henderson-Tilton formula. Also, after three months, the plants were harvested and some morpho-physiological and nutritional characteristics were measured. Determination of nutrient concentrations of potassium, phosphorus and silica in aerial parts of the plant as well as determination of pH and titratable acidity, Vitamin C, Total Soluble Solids and Antioxidant Levels of Fruit as Postharvest Properties of Strawberries were also measured. The highest death percentage of mite (79.2%) was due to the protective fertilizer + acaricide treatment in both stages before and after plant infestation to mite. The synthesized fertilizer had the greatest effect on fresh and dry shoots weight.  Virogard composition at 5/1000 concentrations, It had the greatest effect on fresh and dry weights. The highest concentration of potassium (29.26 g/kg) was belong to protective fertilizer+ acaricide and the highest concentration of phosphorus (6.48 g/kg) and silicon (753 mg/kg) was belong to the synthesized protective fertilizer individually. Considering the efficacy of the compounds used, it is recommended to use these compounds as inducers of plant resistance in order to reduce the use of pesticides and improve the product quality.

Copper is an essential micronutrient to plants, which it`s deficiency is common in calcareous soil. Most of the soils are calcareous in Iran, therefore farmers and gardeners may observe the deficiency of this element during the growing season. Given the importance of copper in the nutrition of date trees, especially in calcareous soils, a better understanding of the mechanism and kinetics of copper release from the soil can provide useful information about the factors affecting the bioavailability of this element. Therefore, this study was conducted to investigate the influence of depth and canopy of three palm cultivars on kinetics release of copper. For this purpose, soil samples were collected from three depths of 0-20, 20-40 and 60-40 cm and two locations (under canopy and outside the canopy) with three replications, for three cultivars of date palms; Shahani, Ghasab and Halvan. Extraction was performed in eight different time periods with ammonium bicarbonate Diethylene Triamine Penta acetic acid (AB-DTPA). Results showed that the power function, simple Elovich, and parabolic diffusion were the best fitted models for describing Cu release. The pattern of copper release was fast during the first two hour and decreased at subsequent time. The results of this study indicating the positive effect of date palm canopy on the availability and rate of copper release from calcareous soils. So that the rate of copper release related to the depth of 40-60 cm of the soils under the canopy was higher than the one in the same depth outside the canopy, which can be attributed to root exudations and pH reduction. Among the three cultivars studied in this research, Shahani cultivar had the highest amount of copper release.

Poor vegetation cover on the surface and lower content of soil organic matter are main factors influencing the sensitivity of soils to erosion from cultivation strips in semi-arid regions. The aim of this study was to investigate the effect of raindrops impact on runoff and soil loss from rills in different soil textures in the semi-arid region. Soil samples were taken from dominant soil textures in hillslopes affected by rill erosion in Zanjan province. For this purpose, three soils with different textures (clay loam, silty loam and sandy loam) were examined with three replications in a flume with 1 m in length and 0.6 m in width and 10% slope under simulated rainfall. Each soil sample was subjected under direct and non-direct raindrop impact with an intensity of 50 mm/h for 30 minutes. Runoff production and soil loss from the rills were measured at a time-scale of 5-min to reach a steady state runoff flow. The results showed that runoff production and soil loss were affected by raindrop impact (p < 0.01). The highest and the lowest impact of raindrops on runoff production were found in clay loam (2.95 times) and sandy loam (2.02 times), respectively. In terms of soil loss, sandy loam was the most sensitive to raindrop impact (3.66 times), whereas clay loam was the most resistant soil (2.47 times) to raindrop impact. An increasing trend was observed in runoff production during rainfall time, while soil loss varied irregularly in the rills. This study revealed that runoff production is significantly affected by the distribution of particle size, while soil loss is remarkably dependent on the aggregate stability. Therefore, maintaining soil surface cover plays an effective role in preventing soil loss by raindrop impact in the rainfed furrows.

Because the range between boron (B) deficiency and toxicity thresholds in soils for many plants is very short, accurate evaluation of available soil B status by soil testing is necessary for proper use of B fertilizer. This study was conducted to compare ICARDA and Soil Science Society of America (SSSA) procedures as the most commonly used methods to determine available soil B. A total of 20 surface soils with different physical and chemical properties were selected and their available B concentration was measured by ICP method and the colorimetric procedures proposed by ICARDA and SSSA. The effect of activated carbon application and the presence of suspended colloids on B concentration was also investigated. Mean available B concentration in the soils for ICARDA and SSSA methods by ICP were 2.59 and 2.86 mg/kg, whereas those by azomethine-H were 2.43 and 2.69 mg/kg, respectively. The relationship between B measured by ICP and azomethine-H for SSSA indicated a higher correlation ( ) and a better fit to 1:1 line than ICARDA ( ). Mean B concentrations were 2.86 mg/kg using hot 0.02 M  and 2.84 mg/kg using hot water. The use of activated carbon decreased B in extracts significantly. The mean of available B extracted from the soils using hot water with carbon was 2.59 mg/kg, whereas it was 2.84 mg/kg without carbon. Use of 0.2, 0.4 and 0.6 g carbon per 40 ml of B solutions with different initial concentrations yielded the mean B recovery of 104.9, 100.4 and 97.6%, respectively. Because of suspended colloids, B concentrations in extracts filtered through Whatman 40 filter-paper were higher than those filtered through Whatman 42. Without the use of carbon, predicted error in B determination due to color in extract ranged from 0 to 0.88 mg kg-1. Generally, the SSSA method measured available soil B more accurate than ICARDA and it is therefore recommended to use.

Today, the occurrence of dust storms, in addition to having a direct impact on people's lives, has adversely affected the agricultural sector, including agronomy, horticulture, natural resources and the environment. This study was carried out to investigate the trend of frequency changes of days with dust storms and its relationship with Standardized Precipitation Index (SPI), using hourly and daily dust data and monthly rainfall data of 21 selected synoptic station in the west and southwest of the country with a seasonal scale over a 25 years (1990-2014) statistical period. After quality controlling all dust data for abnormality, using Kolmogorov-Smirnov test, and also measuring the long-term memory of time series using the Hurst coefficient, non-parametric Mann-Kendall and Spearman tests were used at a 95% confidence level to examine the trend of abnormal data. Then, the seasonal SPI drought index was calculated in the proposed stations and its trend was analyzed by parametric linear regression test method. Also, the zoning of the Mann-Kendall statistics and the linear regression of the variables were performed by IDW method in ArcGIS software. Then, to investigate the climatic relationship with dust storms, stations with SPI index and also variable frequency of days associated with dust storms had a significant trend (dust storms in both Mann-Kendall and Spearman methods and SPI index in the method of linear regression), were analyzed by Pearson correlation technique. The results showed that out of a total 21 series of seasonal data; the stations of Hamedan (Nozheh), Ilam, Islamabade-Gharb, Keramnshah, Sarpole-Zahab, Abadan, Bandare-Mahshahr, Bostan, Dezful, Masjedsoleyman, Safiabad, Dogonbadan, Sanandaj, and Khorramabad have a high correlation between standard precipitation climatic index and the frequency of dusty days. So that the highest correlation between the number of dusty days and SPI drought index was attributed to Dezful, Bostan and Masjedsoleyman stations with the Pearson coefficients of -0.920, -0.913 and -0.911 and P-Values of 0.002, 0.025 and 0.044, respectively. The results of this study could be useful in managing the consequences of dust storms in the study areas.

In recent years using modified biochar has been considered as an adsorbent to removal of inorganic pollutants such as nitrate from aqueous solution. Because of the increase of nitrate concentration in water resources and its environmental consequences, in this study the efficiency of nitrate adsorption by iron-modified common reed biochar from aqueous solution was investigated. For this purpose common reed biomass was modified by one molar iron chloride solution and then pyrolyzed at 500 °C and its physicochemical characteristics were measured. Nitrate adsorption was evaluated in batch experiments. The results indicated that the yield, cation exchage capacity (CEC), anion exchange capacity (AEC) and surface area of the biochar increased through modification by iron chloride. The adsorption efficiency of nitrate increased by increasing contact time, but it reduced by increasing initial concentration of nitrate in the solution. The pseudo-second-order kinetics model provided a good description for adsorption processes of biochar produced at 500 ºC (R2= 0.98) and iron modified biochar (R2= 0.99). Among the adsorption isotherms, Langmuir model (R2= 0.99) illustrated the best fit with the experimental data for both biochars. In general, the results of this study showed the high potential of iron-modified biochar for nitrate sorption (81.30 mg g-1). Thus, it could be concluded that the iron-modified biochar has high potential for nitrate removal from aqueous solutions.

This research was conducted to evaluate the effect of land use changes on the land quality under deforestation in semi-arid regions. Soil quality of the top layer (0-15 cm) was compared for two land uses. The results show that the organic matter (OM), aggregate stability (AS) and dispersible clay (DC) were changed from 1.19, 2.22, and 2.4% in oak forest to 0.67, 2.08, and 22.8% in deforestation area, due to land use change. These results showed a severe decrease in soil quality due to deforestation. Aggregate stability was decreased and dispersible clay was increased due to deforestration. In addition, the canopy cover and soil organic matter were reduced. With increasing the DC, it was increased the soil surface crust and accelerate the splash erosion. Bulk density increased, since the OM decreased. Also, the percentages of gravel, sand, coarse and fine silt changed from 6.3, 56, 12.6, and 5.4% to 35.6, 64.3, 14.6, and 2.5%, respectively, due to deforestration. Direct sunlight and higher soil heat, especially in hot seasons, accelerated the volatilization of soil nitrogen and despite the addition of nitrogen fertilizers to the farmland, the amount of nitrogen in the farmland decreased. Data analysis by PCA method showed that the different factors affect the varimax due to land use changes. Deforestation was the main factor changing the soil characteristics and seriously reducing the land quality. Land use change not only does not benefit the production of more food, but also destroys the quality of the land, causing floods and increasing sediment from these areas.

Vortex drop shafts, with a primary function of dissipating flow energy, are used to transfer flow from higher to lower elevations. In the present research, the physical model of the vortex drop shaft of the eastern Tehran sewage system in Iran are studied and the effects of the inflow Froude number, inlet bottom slope, and the ratio of sump depth to vertical shaft diameter on the flow energy dissipation rate are surveyed. This study was performed with Froude numbers of 1.79, 2.01, 2.18 and 2.31, the inlet bottom slopes of 0.251, 0.4, and 0.571, and the sump depth to vertical shaft diameter ratios of 0, 1, and 2. Accordingly, 36 experiments were designed. For the purpose of increasing accuracy and analysis of results, each experiment is repeated 3 times. Consequently, 108 experiments were done. The results showed that the flow energy is dissipated  in the range of 93.7% to 98.5% by changing the parameters. In addition, increasing the inflow Froude number and the sump depth to vertical shaft diameter ratio cause the reduction of the flow energy dissipation rate in the vortex drop shaft by 2.2% and 3%, respectively. Also, increasing the inlet bottom slope increases the flow energy dissipation rate by 2.4%. According to the interaction between the flow energy dissipation and the outflow Froude number, the appropriate sump depth to vertical shaft diameter ratio proposed 0.3-1.2. Furthermore, a nonlinear relationship using the variance analysis was presented to estimate the flow energy dissipation rate.

The objective of this study was to reduce the hydraulic gradient and consequently to weak the piping phenomenon. For this purpose, various models of geometric dimensions and hydraulic performance of clay core and toe drainage in earthen dams were investigated. Therefore, by using experimental modeling in both homogeneous and heterogeneous states, the seepage rate and the ferritic level in the earthen dam body with water level readings in seven observation wells and piezometric pressure measurement in 30 piezometers installed on the channel wall have been examined. Accordingly, three dimensionless ratios  with three heights (0.12, 0.20 and 0.28 m) at different angles (45, 60 and 90 degrees) were chosen to evaluate the performance and provide the optimal index  in the toes drainage design of earthen dams. Then the results of PLAXIS numerical model were validated by experimental data through calibration parameter and P-VALUE and RMSE statistical tests. The results showed that the optimal geometric dimensions of toe drainage due to direct relationship of reservoir water level with the position of the ferriatic line and its exit from the lower slope of homogeneous and heterogeneous earth dams are directly related to hydraulic conductivity and water level in the reservoir. In heterogeneous earthen dams, these values ​​are inversely related to the thickness of the clay core. By comparing and using regression analysis, an equation was proposed to predict the drain height of the homogeneous dam, which is more accurate for larger values of . Finally, the toe drainage size of homogeneous earth dam with an angle of 45 degrees and index of  and in heterogeneous state, the angle of 45 degrees with index of  have been reported as the optimal state.

There are several methods for desalination which could be divided into two classes of membrane and thermal processes. Other methods are also existed, of which, bioremediation (including phytoremediation), is the most important method. Halophytes are recognized as plants associated with the capability of tolerating those amounts of salt concentrations that could not be tolerated by other plants. Current investigation utilizes Atriplex Lentiformis plant as the purifier and solution of 15000 μS/Cm as the saline water. Three levels of plant density (0, 12, 24 plants) and four retention times (7, 14, 21 and 28 days) were considered in this study. This experiment was carried out without and with the presence of zeolite. Different parameters including; electrical conductivity (EC), concentration of calcium, magnesium, sodium, and chloride ions were measured before and after the treatment and the average reduction percentages of the proposed factors were measured. It was found that the zeolite treatments with 0, 12 and 24 plants reduced the EC 4.1, 13.4and 15.9%, respectively. Also, the concentrations of calcium, magnesium, sodium, and chloride ions were reduced 35.9, 25, 18, and 16.9%, respectively.

In areas where annual rainfall is less than the crop water requirement, providing water for plant is necessary to grow properly without stress. One of the methods that have least damaging to the environment is rainwater harvesting techniques. The Kajaveh system is a local rainwater harvesting system that can be used in very low-slope areas and can be used in a mechanistic manner for annual crops. In order to investigate the operation of the rainwater harvesting system, computer simulations were performed. Estimating rain infiltration on sloping surfaces is the main part of this simulation. In this research, a semi conceptual- experimental method was used to estimate the infiltration of rainfall on sloping surfaces and find a structure with suitable geometric dimensions to rainwater harvesting. The results of the simulation that was prepared using this method were compared with the experimental data and after calibrating the simulation, it was used to study structures with different wall slopes. The results indicate that there is an optimal slope in which the maximum ability of the Kajaveh system to water concentrate occurs. For the soil whit Sand-Loam type, Aggregate structure, precipitation intensity of 11.49 cm per hour, rainfall duration of 10 minutes and in the conditions of structure formation in this research, a square base structure with 50 cm length and cavity depth of 10 cm (wall slope of about 22 degrees) showed the highest efficiency in water concentrating.

Sediment transport in irrigation canals is an important issue in the design and operation of irrigation systems. The vortex‐settling basin (VSB) is a small scale, efficient, and economical device that using only the flow vortices to remove sediments. Most studies which explain flow patterns in VSBs are experimentally based on velocity measurements inside the VSBs in the laboratoary, and mathematical modeling studies are rare. The SSIIM model was used in this study to simulate the three-dimensional velocity distribution in a VSB, and the flow distribution obtained from available turbulence models in SSIIM were compared with experimental measurements. The results showed that the SSIIM model is able to capture the main features of the flow field, including the central vortex and secondary flows near the walls. The results also indicate that tangential velocity follows the combined Rankin vortex only in regions far from the inlet and outlet channels; however, this statement is not true in other regions. The k-ε turbulence model produces unacceptable results for the tangential velocity distribution, while both the tangential and radial velocity distributions obtained from the k-ω model are in reasonable agreement with laboratory measurements.

Inappropriate distribution of precipitation measurement stations has led to the use of gridded precipitation datasets, consisting of satellites, reanalysis and ground-based precipitation datasets in recent years. In this study, one of the important precipitation products named Era5 has been evaluated in Ardabil province. The observation data were first interpolated during the 2004–2014 statistical period and compared with Era5 data based on daily, monthly and annual time scales. Evaluations were performed using RMSE, correlation coefficient and contingency table indices consisting of POD, FAR, CSI and POFD. The results showed that the correlation coefficient for Era5 at the daily time scale was above 0.75 for most of the cells and RMSE was below 3 mm. Also, the correlation coefficient for monthly time scale was above 0.8 and the RMSE was below 20 mm in most of the cells. Evaluation using contingency table indices showed that POD index in the studied cells ranged from 0.7 to 0.85, FAR ranged from 0 to 0.25, POFD ranged from 0.1 to 0.2 and the CSI was in the range of 0.4 to 0.5. Precipitation values of both precipitation sources were classified into 6 classes using Ward cluster analysis method. The results of k-means method and Wilkes-Lambda model confirmed the classification accuracy and the difference between the means of the clusters. In general, it can be concluded that the Era5 precipitation product at both daily and monthly time scales can be used as an appropriate alternative to data scarce regions after bias correction.

High nitrate concentrations, especially in leafy vegetables, is a great threat to human health. Various factors play a role in reducing nitrate accumulation in vegetables, one of which is the availability of iron. The purpose of this study was to compare the effect of different sources of iron on the accumulation of nitrate in lettuce in hydroponic system. Therefore, the experiment was performed in a completely randomized design with 4 treatments and 5 replications. Treatments included different sources of iron including iron sulfate, iron chelate (Fe-EDTA) and iron amino chelate with the same iron concentration of 20 μM. An iron free solution was also considered as control. The results showed that iron amino chelate application increased root dry weight (138%), shoot dry weight (59%), stomatal conductance (80%), photosynthesis rate (107%), chlorophyll content (91%), Fv/Fm (60%) and iron concentration of shoots (113%) as compared to the control. Also, iron amino chelate increased the activity of nitrate reductase (168%), nitrite reductase (33%) and glutamine synthetase (67%) enzymes compared to the control. Application of iron amino chelate, iron chelate and iron sulfate reduced the nitrate concentration by 55%, 11% and 18% compared to control, respectively. Generally, the results showed that the application of iron amino chelate reduced nitrate accumulation by increasing the activity of enzymes involved in nitrate metabolism. According to the results, iron amino chelate can be used to reduce nitrate concentration and increase lettuce yield in hydroponic cultivation.

Soil temperature (ST) variation can affect the earth energy balance. Moreover, the awareness of the soil thermal regime and its thermal fluctuations can prevent possible damages to agriculture and can increase crop productivity. In this study, using the singular spectrum analysis (SSA), trends and oscillation components, as well as the degree of the coincidence of the soil temperature (ST), air temperature (AT) and precipitation time series were investigated in three thermal regime classes namely: Mesic, Thermic and, Hyper thermic, in 28 high quality weather sites during 1993-2017. The results showed that the highest and lowest rates of ST increases have occurred in the Mesic and the Thermic thermal regime, respectively. The precipitation fluctuations were in the opposite phase with the ST fluctuations. The dominant return periods in the annual series were 2.3 and 11-12 years that could be related to quasi-biennial oscillation (QBO) variations, and 11-year cycles of sunspots. By the implementation of the coincidence which exists between the short and long term oscillations of ST and AT time series, one can generate and reconstruct ST data gaps based on AT.