مجله تحقیقات آب و خاک ایران
سال چهل و نهم شماره 5 (پیاپی 37، آذر و دی 1397)

Water deficit in arid and semi-arid regions is the major yield-limiting factor of crop plants in arid and semi-arid regions. So, prevention of water loss is the first major step to obtain proper crop yield in rainfed lands of these regions. This study was conducted to investigate the effect of mulch application on soil water retention under rainfed conditions in a semi-arid region. Toward this, five wheat straw mulch levels (0, 25%, 50%, 75%, and 100% of land surface cover) were used according to the randomized complete block designat three replications in a rainfed land with 10% steepness in Zanjan. About 6 ton straw mulch was used in 100% treatment. Fifteen plots with 2m×5m in dimensions were installed in the land and S was measured using the volumetric method in each mulched plot at 7-day interval during wheat growth period (from October 2015 to July 2016). Results indicated that SWR temporally varied during the growth period, so that the highest value of SWR in the mulched plots was observed in March, when the heavy rainfalls were occurred in the area. SWR was significantly related to straw mulch level (R2= 0.95, p< 0.001). Increasing SWR in the mulched plots was attributed with increasing soil water holding capacity. Application of straw mulch positively affected on the soil water holding capacity. The highest SWR was observed in 100% mulch (10.62%), about 11% more than that one in the contour plot. There was no significant difference between 75% mulch and 100% mulch in SWR as well as soil water holding capacity, so the application of 75% straw mulch can be considered as the optimum level for increasing soil water holding capacity as well as SWR in the rainfed lands of semi-arid regions.

Soil and groundwater contamination due to leachate from municipal solid waste landfills is one of the most important environmental challenges for management of soil and water resources. This study was aimed to propose a landfill liner from the existing natural materials that in addition of having proper permeability, provides more capacity to absorb leachates. Two natural amendments including bentonite and DCP were applied to coarse landfill soil of Evaz city in Fars province between zero to a maximum 9% and 0.2% of base materials dry weight, respectively. The required permeability tests were conducted with both water and synthetic leachate. Results indicated that for the materials containing 6% bentonite, application of 0.2% DCP was considerably reduced the permeability compares to the bentonite application. Due to larger viscosity, the permeability of synthetic leachate in base liner materials and containing 3% bentonite, was less than the water. However, in the 6% bentonite application, due to its acidity, the permeability of leachate was increased. In 9% bentonite, synthetic leachate had minor effect in reducing or increasing the soil permeability. This can be attributed to significant increase of fine particles and the increase of soil buffering properties.

The amount of dissolved oxygen (DO) in water is an important parameter of rivers water quality. Installation of weirs in channels is one of the methods entering air babbles into the falling water and increase DO. In this research, the performance of trapezoidal labyrinth weirs was investigated as compared with the linear weirs under various geometries and hydraulic conditions in terms of DO Experimental observations and result analysis showed that the length of cycle in the flow direction, thickness of weirs and nappe patterns are three effective parameters on DO amount in trapezoidal labyrinth weirs. The results of this study indicated that the three cycles-labyrinth weirs had better performance compared to two cycles-labyrinth weirs. Also, the results showed that the three cycles-trapezoidal labyrinth weirs with the lower length in the flow direction at low relative head and with the longer length in the flow direction at high relative head had the best performance in terms of DO that increased 58 and 44 percent, respectively. The results of this study indicated that, by increasing the ratio of falling height to weir height from 0.4 to 0.8, the DO efficiency increases (13%) by labyrinth weirs.

Water restriction is one of the most important factors inhibiting the crop production. Accordingly, application of pressurized irrigation systems to optimize utilization of water resources is inevitable. This study was conducted in Behbahan Agricultural Research Station during three cropping seasons (2013-2016) and based on a randomized complete block design with a split plot and three replications. The main plots were consisted of Subsurface Drip Irrigation (SDI) system that applied irrigation water at three levels of 75, 100 and 125% of water requirement and a surface Drip Irrigation (DI) system with application of 100% water requirement. The sub-plots were consisted of two varieties of date palm; Khasi and Zahedi. The crop water requirement was estimated based on Penman-Montheith method and using a daily weather information data collected from Behbahan weather station. Analysis of variance showed a significant difference (5%) between water use efficiency of different levels of irrigation water. As, the SDI system with 75% irrigation level showed the highest water use efficiency to be 0.698 kg/m3. The comparison of interaction effects showed that the water use efficiency of Zahedi dates in 75% SDI system with 0.744 kg/m3 is higher than that of Khasi dates. In the other hand, the 75% SDI system saved 2509.6, 5019.2 and 2630.3 m3/ha irrigation water as compared with 100% and 125% SDI and 100% DI systems, respectively. According to the results, the interaction impact of irrigation levels and varieties on water use efficiency was significant but the interaction of irrigation systems and varieties were not significant. The stiffness of fruits was measured to be 11.3 lb per square meter in 75% SDI system which was the highest as compared to those for other treatments. The results of this study showed that the SDI system could be used for palms trees without restriction while use less water without significant impact on yield.

This study was conducted in Qazvin plain (with latitude 50˚ 8’ and longitude 36˚ 8’ and elevation 1240 m) during 2010-2012 to evaluate AquaCrop model for simulation of canola yield. The results showed that this model is very sensitive to transpiration crop coefficient and low to medium sensitive to other input parameters. Normalized root mean square errors (NRMSE) were 0.10, 0.04, 0.11 and 0.04 for yield, biomass, water use efficiency and harvest index, respectively. The values of agreement index (d) for the all parameters were greater than 0.98. Although, AquaCrop model tended to overestimate outputs; however, the simulation results could be acceptable.

One of the most effective techniques to reduce evaporation rate is to use suspended shade covers to create shadow on the water bodies. Black polyethylene is a material that can be used for covering as porous fabric like sheets. In this study, energy balance analysis was used to evaluate the effects of using this type of covers in dam reservoirs on evaporation rate. Minab dam was selected as case study and energy modeling was conducted with respect to different scenarios. Results show that the use of black porous polyethylene can reduce evaporation by an average of 77% and 83% in the case of using single-layer and double-layer, respectively. This amount of evaporation reduction could be lead to reduce 11, 22 and 33 million cubic meters for 30%, 60% and 90% covering scenarios, respectively, for Minab dam reservoir.

Remote sensing can be used to provide agricultural land use map and to estimate crop cultivated area and crop yield. The purpose of this study was to estimate wheat yield by satellite imageries in Moghan Agro-Industry which is one of the important centers of agricultural production in Iran. Wheat is one of the strategical crops. Field data were collected from Moghan Agro-Industry during 2013 to 2015. Landsat 8 images which were coincided to field observation were collected to determine eight vegetation indices. Landsat-8 with high spatial resolution and ease facility images has presented acceptable results. The obtained results showed that NDVI parameter with R2=0.71 and RMSE, MAE and MBE equal to 797, 637 and 87 kg per hectare, respectively, has a higher precision for crop yield prediction as compared to other vegetation indexes. Thus, wheat yield could be predicted by Landsat 8 imageries before harvesting time in Moghan plain. This can help Moghan Agro-Industry, water resources, food providers, agricultural insurance, and transportation managers to manage their decisions before time is going.

Regarding to the amount of water resources and per capita water consumption, Iran is one of those countries which faces with water shortage. Therefore, water resources forecasting and planning could have a considerable role on future water consumption decisions. Today, the researchers’ findings about strong correlation between large scale climatic changes and hydrological phenomena have doubled the necessity of considering hydro-climatological discussions in hydrology. Accordingly, the use of statistical methods and advanced models has greatly contributed in forecasting hydrological phenomena. In the present study, the estimation of spring discharge in Cheshmeh kile's stream was investigated through common climatic signals related to the Pacific Ocean and the Atlantic includes Niño’s, AMO, SOI, NAO and PDO and also through the Caspian Sea surface temperature in winter by using conceptual model of ANN. The stream flow forecasting error with ANN model and climatic signals entry-SOI-NINO4-NINO3.4 using RMSE was calculated to be 8.61 m3/sec. This error with signal entry NINO3.4 was decreased to 3.31 m3/sec. Also, the forecasting error with precipitation entry and the Caspian Sea surface temperature was reduced to 0.08.

Obtaining appropriate levels of deficit irrigation is necessary to improve water productivity and performance of irrigation networks in deficit irrigation conditions. This study was carried out to develop a nonlinear programming model for determination of an optimal cropping pattern in deficit irrigation conditions. A non-linear model with the objective function of economical water productivity index (Net profit to water consumption ratio) was combined with a crop growth model and it was evaluated using the data of Shahid Chamran irrigation network. Results showed that the highest cultivation area in all scenarios is related to wheat crop. The wheat cultivation area for the 10, 20 and 30 percent deficit irrigation were estimated to be 674, 949 and 1362 ha, respectively. The increased cultivation area in 30 percent deficit irrigation scenario was estimated 92 percent as compared to the full irrigation scenario. The lowest cultivation area in the network was for sunflower with an area of 189 hectares (in 30 percent scenario). The results of this study for the 10 percent scenario indicated that the overall economical water productivity of the network can be increased up to 19% by managing cropping pattern as compared to the full irrigation scenario. While in the 20 and 30 percent deficit irrigation scenarios, the economical water productivity index values increased 21 and 23 percent respectively by implementing optimal cropping pattern. Also studies show that the different combinations of deficit irrigation scenarios for the crops could present different results. Accordingly, the overall water productivity of the network can be increased to a maximum of 15250 Rls/m3, if 10 percent for broad bean and bean, 20 percent for sunflower and potatoes and 30 percent deficit irrigation for wheat are considered.

Existence of susceptible agricultural lands with loess deposits in the South and West of Gorgan, with plowing in down-slope direction and failure in promoting contour plowing based methods have led to use alternative control practices such as cultivating buffers in the marginal lands. The under-studied hillslope with an area of 5.1 hectares includes four long agricultural lands and three permanent vegetation buffer strips between them with an average width of 7 meters and a field under fallow with 55 meters length located in the down slope. In this study, the climate files of the WEPP model were built by using the BPCDG software for the year 2015 based on the data of the recording rain-gauge in the Hashem Abad synoptic station. To increase the accuracy of the model, the slope file was created using a digital survey camera with a resolution of 0.2 meter. In order to verify the WEPP model, the plot observation data of a rainfall simulator were used. Then two cases of lack and existence of current buffer strips in the hillslope were evaluated by the WEPP model. WEPP model estimated the amount of erosion and the specific sediment for the existing buffers modes in hillslope to be 27.36 and 18.08 tons per hectare per year respectively, and for the scenario of a lack of buffer strips, they were estimated to be 37.11 and 35.28 tons per hectare per year, respectively. Also, the model estimated runoff rate for the existence and lack of buffer strip scenarios to be 32.66 and 40.54 mm, respectively. The results showed that the buffer zones in the under-studied hillslope have decreased the amount of erosion and sediment to 9.75 and 17.20 tons per hectare per year respectively, as well as reduce the runoff rate 7.88 millimeter per year. Therefore, the buffer zones were able to control a significant amount of sediment (49 percent), which cause remarkable damages in the downward.

Salicylic acid plays a vital role in increasing the resistance of plants to alkalinity stress. In this research, the interaction of alkalinity stress, salicylic acid and soil type on Mung bean growth parameters were investigated. This experiment was conducted as a factorial based on a complete randomized design with three replications in greenhouse of Razi University. Treatments included alkalinity stress (Sodium bicarbonate at three levels 0, 20 and 40 mM), salicylic acid at four levels (0, 250, 500 and 750 μM) and two soil types. The results showed that although alkalinity stress significantly reduced the growth parameters such as plant height, root/shoot ratio, number of active root nodes, leaf area and leaf relative water content and increased proline content of the plant at 1% level, but in contrast, salicylic acid spray mitigated them. Furthermore, there was a significant difference between the two soil types in terms of reducing the effects of stress. In general, the concentration of 500 mM salicylic acid, as an optimum concentration, could neutralize the effects of extreme tension in alkalinity.

Lopac gates, controlling and regulating water level in irrigation canals, have recently been considered due to their practical advantages. So far, a few researches have been conducted on Lopac gate. In this study, the stage-discharge relationships of Lopac gate with different structures including no transition, sudden and gradual transition, in free and submerged condition were investigated. The experiments were performed to provide a wide range of effective non-dimensional parameters including gate angle and relative submergence. It was found that there is a relationship between the non-dimensional form of discharge () and the ratio of upstream water depth to gate opening for free condition and between the Q* and the submergence ratio for submerged conditions. In each of the above mentioned circumstances, using dimensional analysis and regression methods between the effective non-dimensional parameters, some explicit equations were presented for stage-discharge relationship of Lopac gates, with no transition, gradual and sudden transitions under free and submerged condition.

Soil organic matter (SOM) is an important soil quality factor that affects physical, chemical and biological properties of the soil. Accurate estimation of SOM spatial variabilities provides critical information especially in precision agriculture. The objective of this study was to estimate SOM spatial variabilities and to assess its status using regression kriging (RK) in Ghorveh plain in Kurdistan province (Iran). Therefore, 150 soil samples from a depth of 0-15 cm were taken systematically in a grid spaced 2 Km × 2 Km. Particle size distribution and SOM content of the soil samples were measured in the laboratory. Stepwise multiple linear regressions (MLR) was used to estimate SOM variabilities based on the soil texture data (percentages of sand, silt and clay) and vegetation indices obtained from Landsat Enhanced Thematic Mapper (ETM) imagery. The MLR model was used to provide an initial map of SOM content. Furthermore, the residuals of MLR model were interpolated using ordinary kriging (OK) and they were combined with the initial map of SOM to produce the final map of RK SOM. The SOM status map was derived from overlaying of soil texture and SOM maps in four different levels (very low, low, medium and high). The results of MLR indicated that both clay content and soil adjusted vegetation index (SAVI) variables have a significant effect on SOM content (p <0.05). The cross-validation results indicated that the RK method was able to explain about 84% of the spatial variabilities of SOM. The SOM status map indicated that more than 96% of the soil in the proposed region is in a low condition in terms of organic matter.

Understanding of the fate of temporal and spatial distribution of pollutionis an essential subject for prediction of damages, caused by pollution, on the ecology of rivers and coastal areas. It is also necessary to provide efficient solutions for both pollution control and environmental protection. In this study, shallow water equations have been used to simulate pollution transport by 2-dimensional finite volume method. Calibration-modification and frequent changing of the amount of parameters is a known issue in hydraulic and hydrologic models. Therefore, it is necessary to utilize methods for sensitivity analysis and reduction of the parameters number to calibrate models. In this study, the RSA sensitivity analysis method was used for each parameter in which the ratio of sensitivity and cumulative distribution function for the sets of good and bad parameters are computed.. For this purpose, 5000 iterations from uncertainty domain of calibration parameters of pollution transport model in a Standard issue of shallow water were performed by using uncertainty algorithm GLUE. With enforcing the acceptable threshold values for the sumof square error index on the total simulation results, 1000 premier simulations were introduced as an efficient simulation. The corresponded set of parameters was considered as good set parameters and the others as bad set parameters. Thus, the sensitivity index was calculated for the Manning coefficient and the floor slope in the x and y directions. The comparison of sensitivity analysis of parameters based on the RSA methods and variation coefficient of parameters indicated that RSA is an efficient method for sensitivity analysis of model parameters.

Soil phosphorus (P) buffering capacity of the soil is very important in plant nutrition and it is the most important soil property for determination of P release potential. In this study, 23 soil samples from different horizons of five orders along a climo-toposequence were collected to determine P sorption characteristics, P buffering indices and their relationship with the soil properties. According to the results, the L-shaped adsorption isotherm obtained from all the soil samples showed a high relatively tendency of the soils for P adsorption at low concentrations, which was well-fitted by the Freundlich, Langmuir and Temkin equations. This study also indicated that the adsorption processes in P concentrations less than 20 mg/l and precipitation processes in P concentration greater than 20 mg/l control the soil phosphorous. Among the different soil characteristics, organic matter and cation exchange capacity have a significant positive correlation with most of the P sorption properties. The overall results of this study showed that the Histosols and Mollisols orders (located at the end of the studied area), Aridisols and Inceptisols (located at the beginning of the study area) and Alfisols (located in the middle of the study area) have had the high to the low values of P buffering capacity, respectively. Therefore, simultaneous low and frequent application of organic and chemical fertilizers are suggested to reduce the P adsorption and to increase the P release at the end of the study area due to high phosphorus adsorption capacity.

In this study the drought characteristics of Zainehrud Basin have been evaluated under climate change condition using Standardized Runoff Index (SRI), Standardized soil moisture Index (SSWI) and SWAT model. The SWAT model was calibrated and validated over the period 1987-2010 using four meteorological stations and five hydrometric stations. The SRI and SSWI indices were calculated for all sub-basins during the base period (1981-2010) based on the runoff and soil moisture derived from SWAT model. Then, the downscaled results of AOGCM models presented at the AR5 under two emission scenarios were introduced to the SWAT model and the drought indices were simulated for the future period (2017-2046) and they were compared with the ones of based period. The results showed that the mean highest occurrence and continuity of drought of the whole basin in the future compared to the based period will increase by 23%, under the scenario 3 (BNU-ESM model under RCP2.6 emission scenario), and by 19.7% under scenario 4 (model BNU-ESM under the RCP8.5 emission scenario) based on SRI and SSWI respectively. Also, according to the results, agricultural drought is more sensitive to climate change than hydrological drought. Thus, it can be said that Zarinehrud basin is still in danger of continuous and long term droughts due to current trend of activities and possible climate changes in near future.

Due to the downfall of groundwater table caused by the drilling of several illegal wells, unlimited groundwater extraction and sea water intrusion, the precise identification of saline groundwater zone in shorelines is highly crucial. This research was conducted to compare three different methods (geoelecteric, electromagnetic, Verruijt equations) to detect the interface of subsurface fresh and saline water in western and eastern part of Babolsar city, northern Iran. Due to the insufficient hydrogeological data in the study area such as occurred spread across the Mazandaran province, the Verruijt equations could not predict the saline and fresh water interfaces precisely, but the geoelecteric method showed relatively higher precision. The results of both studied sites (eastern and western part of Babolsar city) were approximately identical. The electromagnetic method with the highest significant correlation (R=0.97 and 081; CCC=0.95 and 0.80) and the lowest errors (ME=-2.22 and 0.28; RMSE=4.83 and 1.96) respectively in the western and eastern part of the area and also the insignificant t-test was identified as the best approach for accurate prediction of the saline and fresh water interfaces. Considering the insufficient hydrogeological data in shoreline of Mazandaran province and due to the high performance, rapid determination and more reliability of the electromagnetic-based data, this method could be recommended for determination of the subsurface saline and fresh interface in coastal aquifer.

Land use and land cover (LULC) maps are necessary for many management activities, hydrology and erosion analysis. Remote sensing data have a high potential for providing up-to-date LULC maps. The objective of this study was to provide and evaluate the LULC maps of Gavshan dam watershed in west of Iran using Landsat 8 satellite images and artificial neural network. Hence, 1320 ground control points or reference points were used to train and test the ANN model for providing LULC maps. Land use classification at each point was specified with a land survey or using Google Earth images. The identified LULC classes in this basin included agriculture, buffer forests (riverside trees), orchards, bushes, forage grasslands, residential areas, roads and water. The ANN used in this study was a feed-forward perceptron that was trained using a coupled conjugate gradient backpropagation algorithm. The input variables for the ANN model were the revised spectral reflectance of bands 1 to 7 of Landsat 8 satellite images. The evaluation of the ANN model made by the ground control data showed a high accuracy for the used method with a general accuracy of 78.5% and kappa coefficient of 68.5%. The results of this study indicated that the utilization of the ANN and Landsat 8 satellite images provides an opportunity to produce LULC maps with high accuracy.

Environmental pollutions caused by petroleum polymers and the limitation of petroleum resources have led to the development of bio based polymers and progress in reducing dependence on fossil fuels. In recent years poly(vinyl alcohol) (PVA) has received much attention in paper coatings, films, packaging materials and biomedical fields because of water-solubility, nontoxicity, excellent chemical resistance, proper barrier and biodegradability properties. In spite of its growing use, information on its destruction, especially the role of Bactria in this process is relatively low. The aim of this study is isolation and identification of PVA degrading bacterium from the municipal solid wastes composted. Compost samples were collected from solid municipal wastes in Karaj Compost plant during the process of compost production. Poly (vinyl alcohol) films were prepared by using liquid nitrogen, freeze drying and hot press techniques. The specimens were buried in municipal solid waste for 150 days. Then, the number of bacteria was counted on the culture medium. Isolation of the bacterium was done by culturing the bacteria on poly (vinyl alcohol) films. New poly (vinyl alcohol) degrading bacteria were isolated from municipal solid waste composted by using enrichments on poly (vinyl alcohol) films. Then isolated bacterium was identified by PCR with 16S rDNA method. In this study, the maximum number of bacteria was 280±0.1 at a medium with poly (vinyl alcohol) films, and the minimum number of bacteria was 110±0.3 at control medium. Following molecular identification and sequencing of 16S rDNA gene, the BLAST showed high similarity sequence of the sample with Pseudomonas geniculate. This paper is the first report on polyvinyl alcohol degradation by Pseudomonas geniculate.

The nitrogen (N) consumption management during the plant growth season plays an important role in achieving maximum crop yield and reducing environmental hazards. Determination of N nutrition index (NNI) is one of the methods for diagnosing plant N status. The main objective of this study was to investigate the role of monitoring NNI in improving nitrogen consumption management. The field experiment was carried out during the growth period of summer maize in Pakdasht region, southeast of Tehran, in 2015 and 2016. Grain yield, dry matter and nitrogen concentration of crop samples from seven treatments including: 0 (N0), 50 (N1), 100 (N2), 150 (N3), 200 (N4), 250 (N5) and 300 kg N. ha-1 (N6) were measured during the growing season. The results showed that NNI monitoring during the growing season could show the variation of N status in different treatments. In addition, NNI was closer to one in the optimal treatment (N4), which produced maximum dry matter with less N application, as compared with other treatments. Moreover, the relative grain yield decreased with a constant rate whenever the NNI was less than one. Agronomy and recycling efficiencies for the N4 treatment were higher than the ones in the other treatments. Water use efficiency of N4, N5 and N6 treatments in both cultivation years was almost equal and more than the ones of other treatments. These results indicated that the water and nitrogen use efficiencies were higher in treatment with NNI closer to 1 (optimal treatment) as compared to other treatments.