نشریه پژوهش های حفاظت آب و خاک
سال بیست و نهم شماره 3 (مهر و آبان 1401)

Phytoremediation is one of the most efficient and cost-effective biological methods for removing contaminants, including petroleum products, from the soil. Understanding the mechanisms of phytoremediation and examining the parameters involved in the phytoremediation process leads to better management and increase the efficiency of this method. Therefore, the aim of this study was to investigate the effect of factors such as diesel concentration, type of irrigation water and type of plant on phytoremediation of diesel-contaminated soil, using Grass pea (Lathyrus sativus L.) and Tall fescue (Festuca arundinacea).

A two-year pot experiment was conducted in greenhouse conditions to evaluate the phytoremediation during 2018 and 2019. The experiment was conducted in a randomized complete block design with three replications. The treatments of this experiment were diesel contaminated soil at two levels of 1.5 and 3% and irrigation water at two levels of freshwater and wastewater (treated municipal wastewater). Drainage water, soil and plants were sampled three months after planting and the amount of diesel in the samples was measured using the gravimetric method. Based on the initial concentration of diesel in the soil, the participation of different factors in diesel removal was determined and compared with each other.

The results showed that the Tall fescue plant reduced the amount of diesel in the soil by a maximum of 62.4 % and a minimum of 47.9 % and the amount of removal diesel in phytoremediation by Grass pea was achieved with a maximum of 63.0 % and a minimum of 44.2 %. Among the diesel removal mechanisms, Phytoextraction mechanism had the lowest participation (2-12%) and Phytodegradation-Rhizodegradation mechanisms had the highest participation (71-84%). The amount of diesel in drainage water was 11-21%. All of D3% treatments were significantly different with D1.5% treatments only in the amount of diesel in drainage water in Tall fescue-2018 experiment and the amount of Phytoextraction in Tall fescue-2019 experiment. In other experiments, no significant difference was observed between the two levels of diesel. Evaluation of the effect of irrigation water quality on diesel removal mechanisms showed that the amount of diesel in drainage in the D1.5%-wastewater-Tall fescue-2019 treatment was significantly less than other treatments. Phytoextraction had the highest value in the D1.5%-freshwater-Grass pea-2019 treatment and the lowest value in the D3%-wastewater-Grass pea-2019 treatment, no significant difference was observed between the two types of irrigation water in other experiments. In the Phytodegradation-Rhizodegradation mechanisms, only D1.5%-freshwater-Tall fescue-2018 treatment was significantly different from other treatments.

The results showed that changes in factors such as plant species, diesel concentration and type of irrigation water can have a significant effect on diesel removal, but the degree of effectiveness of each factor is different depending on the diesel concentration, the treatment degree of irrigation water, and the resistance of plants and soil microorganisms against diesel toxicity.

Different agricultural policies tend to minimize the environmental risks caused by the continuous use of pesticides and other synthetic chemicals and look for alternative methods. Wood vinegar and biochar can be used in organic agriculture as soil conditioners. This study aimed to investigate the effect of biochar and wood vinegar on some chemical and microbiological properties of soil under forage corn cultivation.

For this purpose, a research was carried out in greenhouse condition. The experiment was a factorial experiment in a completely randomized design in 3 replications. The studied treatments include wood vinegar in 6 amounts of zero (W0), 0.02 (W1), 0.04 (W2), 0.1 (W3), 0.2 (W4), and 0.4 (W5) g/Kg (first factor) and soil conditioner including raw material (wood of pomegranate and plum trees) in 2 levels 1% (B01) and 2% (B02) amounts and biochar (biochar prepared from pomegranate and plum trees at temperature 4500C) was applied at 2 levels of 1% (B1) and 2% (B2) amounts (second factor). The chemical properties of the soils such as soil acidity (pH), electrical conductivity (EC), soil organic carbon (OC), total nitrogen (TN), soluble sodium (Na+), soluble potassium (K+), soluble calcium (Ca+2), soluble magnesium (Mg+2) and available phosphorous (P); and the soil microbiological properties including basal respiration and microbial biomass carbon and the physical characteristics of forage corn such as height, stem diameter, dry weight, and wet weight were measured.

The results showed that co-application of conditioner and wood vinegar increased soil acidity (5.3%), electrical conductivity (EC), soluble calcium (Ca+2), soluble magnesium (Mg+2), organic carbon (OC), basal respiration, and microbial biomass carbon. The most significant increase in electrical conductivity (EC), soluble calcium (Ca+2), soluble magnesium (Mg+2), and organic carbon (OC) were observed in W5B2 treatment, which were 5.3, 3.9, 2.2, 3.6, and 7.2 times more than the control. Also, the basal respiration with the highest amount of emitted CO2 during one month of incubation in all three times intervals was observed in W5B2 treatment. So that in the first, second, and third ten days, the rate of soil microbial respiration in W5B2 treatment was observed 6.91, 6.54, and 6.4 times more than the control, respectively. The co-application of wood vinegar and biochar led to increase in the stem diameter, dry weight, and wet weight of the plant. In contrast, the co-application of wood vinegar and the soil conditioner decreased the plant's stem diameter, wet and dry weight compared to the control. Addition of conditioner material alone increased soluble sodium (Na+), soluble potassium (K+), Fe, Cu, Zn, and Mn, while decreasing total nitrogen (TN) and available phosphorous (P).

The results illustrated that the effect of using biochar and wood vinegar on increasing, the concentration of elements and improving the qualitative characteristics of soil and plants depends on the amount of nutrients, organic carbon in biochar and wood vinegar, soil acidity and their consumption. Considering the positive effect of biochar and wood vinegar on increasing soil organic carbon, increasing the availability of nutrients, stimulating soil microbial activity and increasing plant growth, it is recommended to use biochar and wood vinegar in calcareous soils of Iran.

According to drought type including meteorological, agricultural and hydrological, drought can start with a decrease in variables such as precipitation, soil moisture and runoff compared to the average values. Agricultural drought, which indicates a lack of soil moisture, will have important effects such as a decrease in crop yield. One of the most widely used drought monitoring methods is the use of standardized indices. The main aim of this study is to modify the standardized soil moisture index (SSI) by selecting the appropriate distribution fitted on soil moisture variable over various climate of Iran.

In this regard, daily measured data in 40 synoptic stations and monthly soil moisture data in the first (0-7 cm) and second (7-28 cm) layers from the ERA5 database during 1979-2020 have been used. In the second step, after collecting the required data, in order to evaluate the accuracy of the ERA5 database, the measured variables including precipitation, average temperature and potential evapotranspiration using the coefficient of determination (R2), mean bias error (MBE) and scatter index (SI) were compared with the ERA5 database. In the third step of the research, the best fitted distributions on the soil moisture variables of the first and second layer among 49 different distributions in EasyFit 5.5 software were identified by performing the Kolmogorov-Smirnov test at a significance level of 1 and 5 percent. Then, 12 SSI indices have been calculated for 40 studied stations in time scales of 1, 3, and 6 months. In the final step, the characteristics of drought including the number of drought events, frequency, duration and intensity of drought were calculated for all indices and compared with each other in different climates.

Generally, based on the SI, the highest accuracy of ERA5 data is related to temperature, potential evapotranspiration and precipitation, respectively. The results of fitting distributions show the significant fitting of gamma distribution as the superior distribution in only 11 and 5% of the first and second layer soil moisture in different stations, respectively. The three superior distributions fitted on the soil moisture of the first layer are Lognormal, Beta, and Logistic distributions, and for the soil moisture in second layer, Logistic, Beta, and Normal distributions, respectively. The minimum and maximum frequency of drought occurred in Abadeh, Anar, Minab and Kerman stations equal to 7, 3, 4 and 2% and in Iranshahr, Bam, Zabol and Iranshahr stations equal to 18.4, 17.8 and 21.0 and 25.4 percent, respectively. The minimum and maximum duration of agricultural drought occurred in Sanandaj and Anar stations, equal to 18 and 64 months, respectively. The intensity of droughts from the index based on the gamma distribution to the index based on the superior distribution decreases from 1.53 to 1.44 in the first soil layer (severe to moderate drought) and from 1.91 to 1.65 in the second soil layer.

The change in the characteristics of agricultural drought based on the change in the distribution used in calculating the index is greater in drier climates than in wet climates and in the soil moisture of the second layer compared to the soil moisture of the first layer. So that in some cases it changes according to the type of distribution used in calculating the drought class index. In general, the results of the research indicate the necessity of examining and selecting the superior distribution instead of the gamma distribution in the calculation of the standardized agricultural drought index.

The uniformity of water distribution in the field affects all irrigation indicators from the aspect of water and soil conservation. When the uniformity coefficient is low, application efficiency decreases; consequently, the product yield decreases and increases surface water and deep percolation losses. Factors affecting water distribution uniformity in sprinkler irrigation are classified into four groups: sprinkler building, irrigation system, system management, and climatological factors. In this study, the effect of rotation speed and rotation factor of sprinkler (sprinkler building), sprinkler riser height, working pressure, arrangement and distances of sprinklers (irrigation system), and irrigation time (system management) in field conditions on uniformity coefficient were investigated. Also, the diameter of water collection containers was evaluated on the tests results.

This research was conducted on the research farm of Kurdistan University located in Dushan village of Sanandaj city. In the present study, were used from R8 Komet and Luxor Sprinklers. The Sprinkler irrigation model was performed by the single sprinkler method, and the experiments were done according to ISO15886-3: 2021 standard. An area of 3600 m2 was networked to the center of the sprinkler, a square grid of 3*3 meters. In each network vertices, two models of containers with two inner diameters of 80 and 180 mm and a height of 90 and 200 mm, respectively, were placed to collect water. The pressures tested for both sprinklers were 30 and 40 m. The experiments used two test times (1 and 3 h), two average rotation speeds (1.5 and 3.5 rpm), and two sprinkler riser heights of 1 and 2 m. The sprinklers arrangement and distances included 18×18, 24×24, and 27×27 in the square and triangular arrangements, and 21×15, 27×21, and 24×30 in the rectangular arrangement. At the end of each experiment, the water volume of the collection containers was measured by a graduated cylinder. All experiments were performed in 3 replications. Also, the wind speed was measured every 15 minutes by EXTECH 45158 tricycle device. Christiansen uniformity coefficient (CU) was used to calculate the uniformity of sprinkler water distribution. The research was conducted in a completely randomized block design with the factorial experiment. SPSS 22 software was used to analyze the data.

1. The effect of container diameter on CU was not significant. 2. The uniformity coefficient of the two sprinklers has a significant difference. 3. The effect of the arrangement and riser height of the sprinklers in the two low and mild wind speeds on the CU is insignificant. 4. The effect of two low and mild wind speeds on CU was insignificant. 5- The effect of working pressure and sprinkler distances in the two low and mild wind speeds on CU are significant. 6- The effect of irrigation time on the uniformity coefficient is significant. 7- The effect of sprinkler rotation speed was significant on CU.

The minimum diameter mentioned for water collection containers, according to the ISO15886-3 standard, is sufficient for the conditions of the experiments of the present study. The Sprinkler rotation is effective on the uniformity coefficient. CU of Komet sprinkler is acceptable for all crops of agronomy and garden, but the Luxor sprinkler is only suitable for garden crops. Only part of the decrease in uniformity due to increasing the distance of sprinklers can be compensated by increasing the pressure. Increasing the irrigation time is effective in improving the uniformity coefficient. Increasing the rotation speed of the sprinkler due to repairs can effectively reduce the uniformity coefficient.

Understanding the behavior of plants in relation to ecological factors provides basic information in order to improve and properly use rangeland. Also, determining distribution area of species and studying the characteristics of their habitat helps to choose the right place for their establishment. Rheum species is one of the rangeland species which, in addition to having important medicinal properties, is valuable for soil protection in dry and semi-arid rangeland. Considering the decrease in the density of this species in natural habitats during recent decades, knowing the characteristics of the habitat can be an effective help in the improvement and development of Rheum. Therefore, in this research, the effect of environmental factors on the vegetative characteristics of rhubarb species in three different habitats is investigated.

In this research, the habitat characteristics in three habitats of Chubak, Targh and Karkaz in the Kouhsorkh region located in Kashmar city and the relationship of ecological factors with characteristics of Rheum ribes L. including excluded base weight, stem weight without pods, length of stems of a plant, and number of stems in each base have been investigated. The ecological factors included soil factors such as EC, pH, N, P, K, organic matter, clay, silt, sand and physiographic factors include slope, aspect and altitude. in each the studied habitat, 10 samples of Rheum ribes were collected. In the first stage, the weight of each harvested stem was measured and then the weight of stems without pods was determined. Also, the number of stems in each sample was counted and the length of each stem was measured separately. Finally, the matrix of environmental conditions and vegetative characteristics of Rheum ribes was analyzed using redundancy analysis (RDA).Method

The findings of the research showed that the characteristics of the soil in Chubak, Targh and Karkaz sites are different and in the same site it is different in different soil depths. Among the physiographic factors, the altitude has the greatest role on the characteristics of the Rheum ribes. The altitude has a positive and strong relationship at a significant level of 5 percent with the length and number of Rheum ribes stems. So that with the increase in altitude, the length of their stem also increases. Among the soil characteristics, the percentage of sand, silt, P, K and lime percentage are the most important factors affecting the characteristics of Rheum ribes. The percentage of sand has a srtrong correlation with the weight of the Rheum stem, and with the increase of the percentage of sand, the weight of the stem increases. EC parameters and silt percentage have a negative relationship with Rheum ribes characteristics. So that with the increase of these parameters in the soil, the number and length of stems as well as their weight decreases.

The results of this study showed that Rheum ribes in Chubak site has the highest amount of growth characteristics, therefore Chubak region has provided more suitable conditions for growth of this species than the other regions. In this site, the samples of Rheum ribes have the highest number of stems and the highest average weight of the stems at 1316 gr. Therefore, this site can be introduced as the best growing area for Rheum ribes. Also, in terms of environmental parameters affecting the growth characteristics of Rheum ribes, among the topographic factors, altitude, among soil properties, the percentage of sand, silt, phosphorus, potassium and lime are the most important factors affecting the characteristics of Rheum ribes.

Surface irrigation is the most common method of irrigation. over 80% of agricultural lands in Iran are irrigated by this method. Generally, this technique, has lower investment and energy requirements than pressurized irrigation methods. Many efforts are applied to improve the economic output of water use and to preserve the environment in Iran. Modifying the design and management parameters at the farm level, can improve the performance of irrigation systems. The main objective of this study, is to optimize surface irrigation efficiency, with low-cost tools, using a simulation model.

The study areas were selected fields of Molla-Sani region in Khuzestan province, located in southwest of Iran. Field experiments were carried out in two fields, irrigated using a surface irrigation system. Three irrigation events and three plots (as repeats) were applied per field. Experiments were conducted on the three borders of 150 m length, 7 m width, and 0.125 % slope, in Field 1, and on three borders of 200 m in length, 7 m width, and 0.1 % slope, in Field 2. The inflow rates of 25 and 35 L/s were applied in the fields 1 and 2. Inflow rate was checked using a W.S.C flume. The borders were divided into parts of 10 m distances to measure the advance and recession times. The best combination of parameters was determined with the simulation model. The objective function (OF) including the application efficiency and the distribution uniformity was applied to optimize the irrigation performance.

This study showed that, based on simulation model, changing the inflow rate, has no effect on the best value of objective function. The optimal inflow rate and cut-off time are recommended as 35 L/s and 30 min in a border with length of 50 m, in the Field 1, and, the best performance in the Field 2, are obtained from the inflow rate of 20 L/s and the cut-off time of 48 min and length of 50 m. Field experiments showed that, the difference of infiltration rates, were not significant, during this study. Based on the data obtained from three events, in both fields, and analyzed via the simulation model, the average NRMSE (Normalized Root Mean Square Error) index values for the evaluation of the advance curves were 12.7, 12.5, and 11.6%, while of the recession curves were 6.9, 6.8, and 6.6%.

The pressurized irrigation has the high investment and energy requirements than surface irrigation. Furthermore, the evaporation rate is much, in the research region. Because of the inflow rate and cutoff time are the most effective parameters in improving irrigation, thus, in this region, prediction and selection of the optimum combination of cut-off time and inflow rate are the low-cost tools to improve the surface irrigation performance compared to modifying length and slope in border irrigation or transform of surface to pressurized system, in the farm level.

Downstream of slope control structures in watershed engineering, it is necessary to create a hydraulic jump to dissipate excess energy to prevent the destruction of the structure. Stilling basins of the hydraulic jump type with a rough bed to increase the amount of energy loss and reduce the length of the hydraulic jump can lead to economic savings in watershed affairs. In this research, a new type of roughness, which is similar to the appearance of the ripple bed in alluvial rivers, was used to reduce the length of the hydraulic jump and increase the energy loss.

The experiments of this research were carried out in a rectangular flume with width, height and length of 0.3, 0.4 and 12 meters respectively. Five different arrangements of the bed form along with the control bed form were made in five different Froud numbers from 3.5 to 5.5. An Ogee weir with a height of 32 cm was installed 3 meters downstream of the flume inlet to create a hydraulic jump, and the minimum flow depth on the crest of the weir was set to be more than 3 cm to avoid the effect of surface tension. During the experiment, the water level profiles at the hydraulic jump site were measured by a depth gauge with an accuracy of ±1 mm. During the experiment, digital photos were also taken and the required data was extracted by digitizing these photos. The average flow depth measured and extracted from the photos was used in the analysis to reduce the error. Rolling length, jump length and water surface profile were measured in each experiment and repeated three times. These lengths were also extracted from the photos and the average values were used in the analysis.Results and

The results of the investigation of the change of the ratio of conjugate depths showed that by changing the layout of the bed form from type 1 to type 4 of the current research, the ratio of conjugate depths of hydraulic jump decreases. This change is such that in the type 4 bed form compared to the control bed form, a maximum decrease of 10.2% was observed. The study of the change in relative energy loss also showed that by changing the layout of the bed form, similar to the above process, the relative energy loss increases, and in the type 4 bed form, compared to the control bed form, a maximum of 23% increase in energy loss was observed. In the investigation of the relative length of the hydraulic jump and also the relative length of eddying, it was observed that by changing the bed form from type 1 to type 4 of this research, the relative length of hydraulic jump and the relative length of rolling decreased and in the type 4 bed form, it was 32 and 34 respectively. percentage, compared to the smooth bed, decreased.