نشریه پژوهش های حفاظت آب و خاک
سال سی‌ام شماره 3 (امرداد و شهریور 1402)

The average annual evaporation rate in Iran is 2100 millimeters, which is three times the global average. This figure indicates that if the evaporation rate of reservoirs decreases with appropriate methods, we can make better use of these resources. Neglecting the high evaporation rate in the country has caused billions of cubic meters of water to evaporate from the reservoirs of more than 600 dams in the country every year. In this research, the effectiveness of composite plates in reducing evaporation from the free surface of water under real conditions was studied. The present study was conducted in the meteorological station of Ahvaz airport, with a geographical latitude of 31° 32', a geographical longitude of 48° 66', and an altitude of 16 meters above sea level. Class A evaporation pans with a diameter of 120.7 millimeters and a depth of 25 centimeters made of galvanized iron were used. All experiments were conducted between July and December 2022. In this study, composite plates with aluminum coating were used to reduce evaporation from the water surface with a thickness of 4 millimeters and consisted of two layers of aluminum sheet in the outer shell and a layer of polyethylene in the middle were used. In order to investigate the effectiveness of composite plates, floating balls, which are a relatively common method of reducing evaporation, used. In addition, the effect of various meteorological variables such as temperature, relative humidity percentage, average vapor pressure, wind speed and solar radiation on the efficiency of composite panels was investigated. Two-way analysis of variance was used to investigate the effect of various weather variables on the performance of composite plates. Experiments showed that square composite plates had an efficiency of 69%, triangular composite plates had an efficiency of 67%, and floating balls had an efficiency of 73% in reducing evaporation from the water surface. Therefore, floating balls had a slightly greater effect on reducing evaporation from the free surface. The empty space between square composites, due to their larger dimensions compared to triangular composites, is less, which can be considered as one of the reasons for the reduction of evaporation in square composites compared to triangular composites. According to the results of the analysis of variance, two parameters, relative humidity and wind speed, have a significant effect on the efficiency of composite plates in reducing evaporation from the water surface. Based on the results of the analysis of variance considering the interaction effects, none of the interaction effects have a significant effect on the efficiency of composite plates. However, considering the interaction effects in addition to the main effects increased the R-squared value of the created model to 0.669, which indicates that the interaction effects had a contribution of about 0.2 to this value. Based on the results of the analysis of variance considering the main effects, two parameters, relative humidity and wind speed, have a significant effect on the efficiency of composite panels in reducing evaporation from the water surface. Relative humidity has an effect of 0.182, and wind speed has an effect of 0.197 on the efficiency of composite panels. Relative humidity and wind speed are among the parameters that have a significant impact on the rate of evaporation from the water surface, causing a decrease and an increase in evaporation from the water surface, respectively. The presence of composite panels has greatly reduced the effect of these two parameters on the evaporation rate from the water surface.

For reduction of water deficiency effects in agricultural sector, it is needed to management of optimal water consumption. Irrigation scheduling should be based on the actual water requirement during the crop growth period. So that the crop growth stages sensitivity is considered in the water uptake process. The application of water uptake reduction functions (α(h)) in water stress conditions, is one of methods for irrigation scheduling. In past researches, the calibration and evaluation of water uptake reduction functions have been done by constant coefficients in the crop growth period. But the aim of this research, is to compare the water uptake reduction functions by application of constant and separate coefficients, in crop growth stages. Therefore, the accuracy of estimation of actual α(h) data, is investigated in crop growth period. This research was conducted on maize S. C 704, in Qazvin region. The mini-lysimeter with diameter of 40 cm and height of 70 cm was used for crop cultivation. The main factor was defined as soil water depletion at levels of 45%(I1), 55%(I2), 60%(I3), 65%(I4), 70%(I5), 75%(I6), 80%(I7) and 85%(I8), relative to total available water. Sub main factor was selected as the sensitivity to water stress in growth stages of initial (P1), development (P2), mid (P3) and late (P4). So that, the effect of soil water depletion (water stress) on water uptake amount, was investigated in maize growth stages (as separately). The experiment was performed as factorial and in a completely randomized design, with 32 treatments and three repetitions. Daily soil moisture was measured by moisture meter (HH2 model and made by ΔT company). For simulation the water uptake reduction (in water stress conditions), were applied the models of Van Genuchten (1987), Dirksen et al (1988) and Homaee et al (2002). The actual data of α(h) in I1, I3, I5 and I7 treatments, were used for models calibration. For this work, the models coefficients were estimated constantly (in whole growth period) and variably (in 4 growth stages). The models evaluation were performed for estimation of α(h) actual values in I2, I4, I6 and I8 treatments. The statistics indicators of CRM, EF, R2, RMSE and ME were used for models evaluation. The effect of soil water depletion and crop growth stages sensitivity on water uptake, was significant at the level of 1%. From I1 to I8 treatments, the water uptake amount in the whole of growth period, was decreased by slope of 7.4%. But the water uptake amounts in the initial, development, mid and late stages were decreased to 5%, 6.9%, 9% and 4.6%, respectively. As a result, the most sensitive growth stage of maize (relative to water stress) was included the mid, development, initial and late, respectively. The models calibration showed that in a specific model, the function coefficients amounts were different in growth stages (compared to whole of growth period). The best priorities for optimal model choosing, was assigned to application of separate coefficients in the crop growth stages. Among the different models, the Van Genuchten model with statistical indices of CRM=0.032, EF=0.928, R2=0.942, RMSE=0.057 and ME=0.1, was determined as the optimal model. The results of this research showed that the modeling accuracy was increases, by application of variable coefficients in water uptake reduction functions. Due to different sensitivity in crop growth stages, is done a better estimation of actual water uptake amount, in water stress conditions. As a result, the actual crop water requirement is calculated by more accurately. Also, the water consumption amount is considered according to actual crop needs, which will cause to better management of water resources.

Phosphorus (P) is one of the most important components and a limiting factor for the growth of plants due to its low mobility and availability in soil. Application of organic materials such as biochar is one of the main choices to increase the availability of P in soil. Biochar is a carbon-rich material derived from pyrolysis of organic feedstocks under limited or no oxygen conditions. Biochar can influence the availability of P by improving the physicochemical, biological, and enzymatic conditions of soil, in addition to directly increasing the concentration of nutritional elements, particularly P. Soil pollution by heavy metals such as Cadmium (Cd) has been one of the environmental concerns in the last several decades. Cadmium alters the activity and diversity of soil microbial communities, and it also lessens soil function by decreasing the activity of enzymes related to nutrient cycling. Application of organic materials such as biochar in contaminated soil can reduce the availability of heavy metals in the soil, and as a result, increase the biological properties. It is hypothesized that application of biochar in heavy metal-contaminated soil influences the availability of P not only directly but also indirectly by improving microbial and enzymatic activity. This issue depends on the type of biochar and soil. Therefore, this study was conducted to investigate the interaction effect of biochar (cow manure and wheat straw) and Cd on microbial respiration, acid and alkaline phosphatase activity and available P in two soils with different physicochemical characteristics. A factorial experiment was conducted using a completely randomized design with three replicates. The experimental factors included 4 levels of Cd contamination (0, 5, 10 and 20 mg kg-1), 3 levels of biochar (control, wheat straw and cattle manure biochar) and 2 types of soil (corck sofla and research center). Two types of soil contaminated with different amounts of Cd from CdCl2, were amended with 2.5% of the biochar, then were incubated for 14 and 90 days at laboratory temperature and 70% field capacity. At the end of each incubation time, available Cd and P, basal respiration and acid and alkaline phosphatase activity were measured. The application of cattle manure and wheat straw biochar in soil reduced the available Cd by 70-86% and 61-85%, respectively. At all levels of Cd contamination, the amount of available Cd in the research center soil with sandy loam texture was higher than that of the Kark Sefala soil with clay texture. Higher concentrations of Cd also reduced the microbial respiration and the enzyme activities in the research center (31-46%) more than in the corck sofla (21.5-35.5%) soil. The decrease in microbial respiration and enzyme activities due to Cd contamination in the soil without biochar (10-41.5%) was more than the soil amended with wheat straw (5-39.8%) and cow manure (0.8-37.9%) biochar. The results also showed that available P increased with biochar addition and decreased with increasing Cd concentration in soil, so that the highest amount of available P was observed in the soil amended with cow manure biochar and without Cd contamination. Positive and significant correlation between available P with microbial respiration (r=0.385-0.604), alkaline (r=0.764-0.879) and acid (r=0.761-0.883) phosphatase activity was obtained, indicating that microbial activity and the enzymes involved in P cycling, play a significant role in the availability of P in the soil. These findings indicated that the application of biochar in Cd-contaminated soils can increase the bioavailability of P in the soil by decreasing the availaility of Cd and increasing microbial activity and alkaline and acid phosphatase activity. This issue was affected by the biochar and soil type.

The cucumber is one of the semi-tropic vegetables of economic importance that is widely cultivated worldwide. To optimally grow this plant in the greenhouse environment, the requirements for cucumber moisture should be fulfilled. Due to the high efficiency of the irrigation method, two methods of capillary wick irrigation and drip irrigation, among the different irrigation methods, are of interest for this purpose. Thus, the current research was undertaken to determine the effectiveness of the wick irrigation method compared to the drip irrigation method on the yield and some growth characteristics of greenhouse cucumber plants in three different soil textures under the conditions of pot cultivation in the greenhouse environment.

This study was conducted for two cultivation periods as a factorial, based on a complete randomized design with three replications in different soil textures including clay-loam (CL) marked with (S1), sandy-clay-loam (SCL) marked with (S2), and sandy-loam (SL) marked with (S3) on greenhouse cucumber Nagene cultivar with two methods of capillary wicking and drip irrigation as well as same nutrition program. The greenhouse used in this project was in the form of a tunnel with a plastic coating, with a height of 3 meters, and an opening width of 4.4 meters. The cultivation of the cucumber plant was carried out in the first half of March and the second half of August of the following year using a pot method with a soil culture bed. Several investigated characteristics, including plant height, stem dry weight, number of leaves, fruit weight, fruit number, main root length, number of root branches, root dry weight, and plant fresh weight were subjected to statistical analysis after sampling as well as measuring in SAS and Excel environment.

The results revealed that the effect of irrigation method, soil texture, and their interactions on vegetative traits of cucumber, the effect of irrigation method on vegetative and reproductive traits, and the impact of soil texture on root organs were different at 0.01 level of significance. In the vegetative part, the stem height, stem dry weight, total leaves, total plant weight; and in the reproductive part, the number of fruits and total fruit weight; and in the root section, the root length, number of root branches, and dry root weight in soil texture CL were affected by drip irrigation method. In wick irrigation, the reproductive traits and root organs in SL soil texture outperformed others. The effect of wick irrigation on fruit production and plant biomass was observed to increase in three soil textures of CL, SCL, and SL with values of 760.98, 782.58, and 995.56 grams, respectively; in drip irrigation, it was observed to increase with values of 1315.81, 1131.71, and 736.22 grams respectively. In all three soil textures, the effect of wick irrigation on root organ traits was almost the same, while the influence of drip irrigation on root traits in CL, SCL, and SL textures diminished, respectively.

The results indicated that in the reproductive part and root organ, the wick method was not preferable to the drip method, while the opposite trend was observed in the vegetative part. Although the wick irrigation method was not superior to drip irrigation in the production of cucumber, being successful in its application due to the simple management of the system by eliminating pumping and advanced irrigation equipment, its self-irrigation and its superiority in the production of vegetative traits can be successful in plants with economic value in the vegetative sector.

Burning plant residues is one of the most common methods of agricultural land management, but the concern about its negative environmental consequences is spreading. The purpose of this research is to investigate the effect of burning wheat straw and stubble on soil water repellency and its temporal changes in soil properties. For this purpose, the remains and stubble left from the wheat fields were collected and placed on the surface of the field with a thickness of 0, 2, and 10 cm, and fire was carried out. Then, three times (24 hours, 10 and 30 days) after the fire, together with the Blank (before the fire), samples were taken from the 0-5 cm layer of the surface soil and some soil characteristics including soil pH, Electrical conductivity (EC), Organic matter (OM), abundance percentage of soil particles, permeability, soil water repellency were measured using molarity of ethanol droplet (MED) and water drop penetration time (WDPT). A total of 36 plots (4*3*3) were factorial designs implemented in a randomized complete block. In the WDPT method, by placing three drops of water with a medical dropper on the smooth surface of the soil, the duration of penetration and absorption of the drops by the soil was measured. To measure the amount of water infiltration into the soil, it was measured with three repetitions of the double cylinder test. Variance analysis of the effect of fire time on some soil characteristics of the studied area showed that fire affects the soil characteristics with a probability of 99% for electrical conductivity, soil pH, organic matter, sand, silt, clay, Mean Weight Diameter, phosphorus and Sodium. The results showed that after the fire, the amount of water infiltration into the soil decreased from 21.2 to 7.54 mm/h and electrical conductivity, soil reaction, phosphorus, potassium and absorbable, exchangeable sodium and silt were 29.50, respectively. 2.53, 169.84, 5.68, 9.79 and 10.48% increased and organic matter, sand, clay and MWD decreased by 16.09, 13.67, 7.11 and 45.8% respectively. The results showed that in terms of hydrophobicity, the soil of the region is in the Wettable class, after 24 hours after the fire, the WDPT reached 67.55 seconds and it turned into a soil with Slightly Water Repellency, so that with increasing depth, the number of residues and WDPT increased and reached its maximum of 67.79 seconds. The burning of wheat residues in the fields of Dezful City increased soil nutrients including phosphorus, potassium, sodium and the relative percentage of silt compared to before the fire. After the fire and the increase in soil temperature, the hydrophobicity class of the soil changed from hydrophilic to low hydrophobicity. The results showed that the water repellency caused by fire depends on the duration of time after the fire so that it returns to a lower level with the passage of time and then its changes stop. Also, burning the residues decreased the permeability of the soil so that the permeability class changed from Very rapid to medium. Fire and burning of plant remain increase soil salinity and pH, which can be effective in reducing crop efficiency.

Drought is a natural event that faces many countries with water shortage every year. Arid and semi-arid climate and improper distribution of rainfall in terms of space and time have increased the negative effect of water resources in Iran. In the present study, the meteorological drought condition of the Urmia Lake catchment was investigated using network data of precipitation, temperature and evapotranspiration in 10 synoptic stations from 1955- 2019. For this purpose, the performance of network data of CRU (Climatic Research Unit) and GPCC (Global Precipitation Climatology Center) in estimating climatic parameters using ground data was evaluated. Then, network data was used to calculate RDI (Reconnaissance Drought Index) and drought monitoring was observed and analyzed during the statistical period study.

The watershed is located in the northwest of Iran in the provinces of West and East Azerbaijan and Kurdistan, and its western border is the heights of Iran and Turkey. In the present research, at first, by referring to the Meteorological Organization of the Iran, the rainfall and temperature data of the studied stations were received and processed during a period of 65 years (1955-2019). Then, in order to introduce and use network data for places and times without statistics, from monthly precipitation data GPCC and (minimum, average and maximum) temperature components of CRU was used for 10 selected synoptic stations of Urmia Lake basin during the statistical period. In order to analyze the long-term drought and calculate the RDI index, the data of precipitation, temperature and evapotranspiration obtained from the network data were used.

In this study, two general approaches were used to calibrate the data used. The first is that all ground data extracted from meteorological stations are drawn in against the network data and a regression relationship is fitted to them. In the second, the monthly changes of the network data are taken into consideration and the calibration is done for each month separately. Therefore, monthly recalibration was done in all stations for the available data and the results showed that the calculation error in the CRU data for temperature and evapotranspiration was much smaller and the temperature data values were able to estimate evapotranspiration with less error and better performance. For example, in Urmia station for ETo estimation, the value of the RMSE evaluation index between ground and CRU data is 0.918 mm/ day. While after calibration, this value decreased to 0.671 mm/day. This process of reducing the error between ground data and CRU has been repeated in all the stations studied. In Piranshahr and Saqez stations, the estimation of reference evapotranspiration was associated with more error than other stations. So that the MAE standard in the mentioned stations before calibration was 1.087 and 0.965 mm/day, respectively, and after calibration, this index decreased to 0.309 and 0.467 mm/day. In this section, in addition to statistical indicators, a violin chart was also used to show the data distribution. In general, it can be concluded that the climate data obtained from the CRU and GPCC databases show a good agreement with the time values, but the bias correction in them should always be considered.

The analysis of droughts in the catchment area indicates that from 1998-2019, RDI has more negative values, which indicates severe drought, and in other words, human activities and climatic conditions in the region with It faces a crisis. The results of the present study show the appropriate performance of CRU and GPCC network data in estimating hydrological parameters and it is recommended to use the above databases in areas where long-term ground data is not available.

Soil moisture is one of the most important variables required from different aspects of research such as agriculture (soil water balance, irrigation schedule, agricultural drought index) and hydrology (infiltration, runoff, recharge). Although the measured soil moisture data is the most accurate data available to researchers, it has disadvantages such as the length of statistical period, missing data in some stations, point source and the inability to extend them to an area such as a basin. Soil moisture data in global products do not have these disadvantages, but their accuracy must be evaluated before using. In the present study, in order to investigate the possibility of using surface soil moisture data from global products in Iran, the accuracy of the global products databases has been evaluated. The main aim of this research is to evaluate the accuracy of surface soil moisture data of global products based on the measured data of soil moisture variable in different climates of Iran. In this regard, the measured data of soil moisture in 43 agricultural meteorological stations across Iran were collected at 7 different depths (5, 10, 20, 30, 50, 70 and 100 cm from the soil surface) with a time step of three hours. After the preprocessing on the collected data, 14 stations from different climates of Iran with the longest and most complete soil moisture data for two depths of 5 and 10 cm with a monthly time step during the period of 2014-2021 were selected in order to compare with the data of global products. In the next step, soil moisture data in different soil layers were extracted from 5 different global products including GLEAM3.6a, ERA5, TERRA, MERRA2 and GLDAS2.1 with a monthly time scale. Surface soil moisture in the measured data, the average soil moisture at two depths of 5 and 10 cm, and in global products, the first layer of the soil surface was considered. The evaluation of the accuracy of surface soil moisture data has been done using three statistical criteria including Pearson's correlation coefficient (R), Mean Bias Error (MBE) and Normalized Root Mean Square Error (NRMSE). Generally, among the studied stations, the highest and lowest values of correlation coefficient are 0.55 and 0.04 respectively for Kahriz and Zahak stations. Between the seasons, the highest correlation has been obtained in the spring, April, equal to 0.51, and the lowest correlation has been obtained in the summer, September, equal to 0.11. The highest correlations are related to the GLEAM product, especially in the months of May, June, November and December. The results of MBE indicate that soil moisture is underestimated in most stations in humid and semi-humid climate stations (Gorgan, Karakhil and Amol stations). The GLEAM products with a range of [-0.03 ~ +0.13] has the least MBE changes among the studied products. The highest accuracy related to the ERA5 product, especially in the humid climate with NRMSE equal to 0.29. In addition, the lowest accuracy among the studied products is related to the GLDAS, especially in dry climate with NRMSE equal to 2.16. The results of this research show that the accuracy of the global products of soil moisture varies according to the temporal and spatial of case study. In order to select the appropriate product with the high accuracy based on the spatiotemporal changes of soil moisture, the present research provides practical results to the researchers.

Situated in northern Iran, the Haraz River stands out as a significant ecosystem, hosting diverse aquatic life and serving as a vital water source for dynamic commercial and industrial activities in its vicinity. This study employed both the Iran Surface Water Quality Indicators (IR-WQIsc) and the National Health Foundation Quality Index (NSF-WQI) to evaluate the water quality of the Haraz River.

Monthly water samples were collected from the central segment of the Haraz River, at a depth of 30 cm, throughout the year (1399-1400). An array of parameters including water temperature, pH, dissolved oxygen (DO), electrolyte conductivity (EC), total dissolved solids (TDS), turbidity, ammonium nitrogen (N-NH+ 4), nitrate nitrogen (N-NO3), phosphate (PO4), biochemical oxygen demand (BOD5), and total suspended solids (TSS) were meticulously measured and subjected to analysis.

According to the IR-WQIsc index, the Haraz River's water quality shifts from relatively good in the upstream direction to relatively poor as it progresses downstream during the spring, autumn, and winter seasons. Notably, spring marks the peak of upstream water quality, while winter exhibits the highest downstream quality. However, during summer, the river's water quality is comparably lower than in other seasons. On average, as per the IR-WQIsc index, water quality is categorized as "relatively good" during spring, autumn, and winter, while it declines to a "moderate" level in summer. Conversely, analysis using the NSF-WQI index reveals that river water quality is at its best during spring and least favorable in summer. In autumn and winter, water quality demonstrates consistent patterns and maintains an average level. An in-depth interseasonal assessment consistently identifies the summer season as having the lowest water quality across all three monitoring stations.

The assessment of water quality across seasons through distinct indicators yields insightful findings. The summer season experiences reduced water quality due to tourist activity in northern regions and environmental factors such as heightened temperatures. Furthermore, a discernible trend emerges wherein water quality demonstrates improvement from downstream to upstream, likely influenced by population density fluctuations along the river's trajectory. Conclusively, a comparative analysis of the two methods indicates a degree of concurrence in water quality assessment outcomes. However, the IR-WQIsc index emerges as a more precise classifier, underscoring its efficacy in such evaluations.