WATER AND SOIL SCIENCE (AGRICULTURAL SCIENCE)
Year:2015 | Volume:25 | Issue:1|Papers Count:20

Environmental pollution with heavy metals and their transfer to plants is an increasing universal problem. In this study, raw and treated wastewaters were reused for potato cultivation under lysimetric condition. Consequently, a completely randomized test was designed, with four irrigation treatments and three replications. The irrigation treatments were categorized as follows: irrigation with raw wastewater (T1), treated wastewater (T2), a combination of 50% raw wastewater and 50% fresh water (T3), and a combination of 50% treated wastewater and 50% fresh water (T4). The soil of each treatment was sampled in order to assess the Cd, Zn, Cu and Pb pollutions on the basis of the Pollution Index (PI) and to analyze the correlation between the mentioned metals in two soil depths. The results showed that the effects of irrigation treatments on PI of Cd, Pb (p£0.05), Zn and Cu (p£0.01) amounts were significant. The maximum and minimum values of this index were observed in the T1 and T4 treatments, respectively. The ranking of PI magnitude in all treatments was T1> T3> T2> T4. Also, the results showed that the PI values of the mentioned metals except Cu in the soil depth of 0-10 cm was lower than those in the soil depth of 10-20 cm. The maximum Pearson’s correlation coefficient value was observed between Pb and Cu. Also, the values of this coefficient in soil depth of 0-10 cm were more than those in the depth of 10-20 cm (except the values between Pb and Zn and between Cu and Cd). In this study, the PI values of Pb, Zn and Cu, were lower than 1 and the PI values of Cd were between 2 and 3.

Formation of the vortex at the entrance of a dam intake reduces its capacity. One of the common methods for preventing the air entry and reducing the power of the vortex is the use of meshed plates. In this research the effect of dimensions of the meshed plates on the critical submergence in an experimental model of bell-mouth vertical intake has been studied. The results showed that, using the vertical meshed plates could reduce the critical submergence up to 35%. At the end, an equation using Froude number and dimensions of the meshed plates was proposed that could predict the relative submergence, accurately.

Excessive use of chemical fertilizers causes soil, surface water and groundwater pollution. The purpose of the present investigation was to study nano-chelate nitrogen effect on nitrate concentration variations in soil, water and potato tuber (Solanum tuberosum L.) in comparison to the urea fertilizer. A factorial experiment in CRD with 3 replications and factors of urea fertilizer and nano-chelate nitrogen was conducted. In each factor three levels of 46, 92 and 138 kg N/ ha were used. The results showed that the highest soil nitrate (100.5 mg/kg soil) and the highest nitrate leaching concentration (629.2 mg/L) belonged to the third level of the urea treatment. The results of the yield measurements showed that with increase of the urea fertilizer from the first level (46 kg N/ha) to the third level (46 kg N/ha), the yield decreased 2.6%, while similar increasing in the amount of nano-chelate nitrogen fertilizer, increased the yield by 20.7%. Furthermore, the difference between the average tuber yields in the urea treatment (42.8 t/ha) and nano- chelate nitrogen treatment (73.3 t/ha) was significant at 5% probability level. The results showed that the leaf nitrogen in the nano- chelate nitrogen treatment was significantly more than that in the urea treatment. The results of the accumulated nitrogen measurement in the tubers as one of the quality indicators showed that the tuber nitrate concentration in the nano-chelate nitrogen treatment was 121.2 mg/kg and in the urea treatment was 154.2 mg/kg. Therefore, according to the results of this experiment, the use of 138 kg N/ha nano-chelate nitrogen in order to achieve the highest yield, noting the lower nitrate accumulation in potato tubers (Agria cv.) in greenhouse conditions, can be recommended.

Water quality management is a global important issue. In this study, the application of the Fuzzy Set Theory to evaluate groundwater quality for agricultural purposes is shown. The Fuzzy Synthetic Evaluation Model gives the certainty levels for the acceptability of the agricultural water based on the prescribed limit of various regulatory bodies’ quality classes. In this research, seven groundwater parameters including Sodium Absorption Ratio, Total Dissolved Solids, Sodium Solution Percent, Chloride, Sulphate, Sodium, and Bicarbonate, which are important for evaluation of groundwater quality for agricultural purposes, were used. Therefore, the qualitative data of groundwater from 178 wells in the period 2009-2010 in Tehran province, Iran, were used. Based on the Fuzzy Water Quality Model, the groundwater quality was classified in three categories; desirable, acceptable and unacceptable. Results showed only 134 out of 178 Samples were in the desirable class with certainty level of 36.5 to 76.3 percent. About 38 samples were classified in the acceptable category whose certainty level ranged from 23.7 to 54.5 percent and the remaining 6 samples were in the unacceptable category with the maximum certainty level of 28.7 percent.

Stepped chute flows are characterized by intense turbulence and strong aeration, but in most studies the turbulence characteristics are not investigated thoroughly. In this study, a highly turbulent air-water flow skimming down a large-size stepped chute has been investigated systematically. An experimental study of detailed air-water flow characteristic measurements was established for different types of flow regimes on a stepped chute (q = 21.8o, h=0.04m, l=0.10m) model to investigate the location and the flow depth at inception point of air entrainment and velocity profiles distributions. Detailed velocity and turbulence intensity measurements in flow direction were performed by use of a phase detection conductivity probe which had been designed, developed and calibrated before. The results showed that the turbulence characteristics varied in different regions. The study showed further that 1- the turbulence intensity increased rapidly close to the step bottom at the viscous sub layer and maximized at intermediate region (0.4£ y/dc £ 0.5) then decreased gradually in the upper region. 2- The vertical distribution of the velocity in flow direction followed-up a power law and the velocity reached to its maximum value, near the flow’s free surface. 3- The high turbulence levels in the intermediate region of the flow depth were caused by the continuous deformations and modification of the air-water interfacial structure.

In this study the HYDRUS-1D software has been applied to simulate water and salt transport through the soil profiles. Field experiments were performed as a randomized complete blocks design in Zabol University campus. Four leaching treatments with five replications were conducted within the blocks. The treatments included 10 irrigations with 100 mm water every 3 days (T1), 7 irrigations with 150 mm water every 7 days (T2), 5 irrigations with 200 mm water every 6 days (T3) and 4 irrigations with 250 mm water every 4 days (T4). For each treatment, soil samples were taken from five depth intervals 0-20, 20-40, 40-60, 60-80 and 80-100 cm and their water contents and soil chemical properties (ECe, pH, TDS, and Na, K, Ca and Mg) were measured every 7 days. Comparing the mean values of the differences between the studied soil properties amounts before and after leaching over the whole soil profile for different treatments showed that T1 had the highest leaching of TDS, ECe, Na, K, Ca and Mg. However, the differences between the treatments were not statistically significant (p£0.05) for Ca. T1 was statistically (p£0.05) different from T4 for TDS, ECe, Na, and Mg values and from T3 for K and Mg values. The graphical results showed that the HYDRUS-1D had the highest accuracy in simulating TDS, ECe and Ca in depth of 40 cm. The highest simulation accuracy resulted for Na in soil depth of 20 cm and for Mg, and K in the depth of 80 cm. The highest simulation accuracy of SWC was seen for the depth of 40 cm. For all treatments and properties, the values of R2 ranged from 0.72 to 0.88, the RMES values were almost equal to the data standard deviations and the EF values ranged from 0.52 to 0.97, which indicated that the HYDRUS-1D software had a good ability to appropriately simulate water and salt transport in soil and predict water content and ECe profiles, satisfactorily. Therefore, it should be used for better management of irrigation and leaching of saline soils over the region in the future.

Mycorrhizal fungi are important symbionts in plants and play key roles in nutrients acquisition and enhancing plant tolerance against environmental stresses. A factorial experiment was conducted with maize plant in a completely-randomized design with four replications in greenhouse conditions. The factors were NaCl salinity with three levels (1.34, 4 and 8 dS/m) and mycorrhizal fungi with four levels (non mycorrhizal, Glomus versiforme, G. intraradices, and G. etunicatum). Shoot and root dry weights, root colonization percentage, and concentrations of P, K, Ca, Mg, Na and Cl were measured. The results showed that the interaction of salinity and mycorrhizal fungi on shoot and root dry weights, root colonization percentage, contents of P, K, Ca, Mg and concentration of Na was significant at p£0.01. The highest shoot and root dry weights were obtained at the salinity level of 1.34 dS/m in the presence of mycorrhizal fungi. Statistical analysis showed that shoot and root dry weights, and contents of P, K, Ca, and Mg in mycorrhizal plants were significantly higher than those in non-mycorrhizal plants. Also Na and Cl concentrations decreased in shoot of mycorrhizal plants but not in their roots. At the 8 dS/m salinity level, root colonization percentage decreased significantly compared to the non-saline control.

Sediment deposition in reservoirs is inevitable and the turbidity current is one of the most important factors that affects sediment distribution in reservoirs. Knowledge about the turbidity currents properties can help to manage and release these currents from dam reservoirs. The Sefidroud dam reservoir has many problems on water storage due to sediment deposition. In this study, the properties of these currents including head velocity, plunge point depth and its distance from the dam are simulated by TCM model, in different discharges and water elevations of the Sefidroud reservoir. The results show, depending on the discharge and water elevation, plunge point depth changes from 2.2 to 8.3 m, its distance is between 6-11 km from the dam structure and the head velocity variation is up to 0.48 m/sec.

One of the most important parameters in designing surface and subsurface drip irrigation systems is the advance velocity of the wetting (moisture) front in soil, which enormously affects the performance of these systems. In this study, experiments were carried out in a transparent plexy-glass tank (0.5m*1.22m*3m) using three different soil textures (fine, heavy and medium). The drippers were installed at 4 different soil depths (surface, 15cm, 30cm and 45cm). The emitter outflows were considered 2.4, 4 and 6 lit/hr with irrigation duration of 6 hr. Then, using the-p theorem of Buckingham and Dimensional Analysis, equations were developed to estimate the advance velocity of the wetting front (horizontal, downward and upward). The results of the comparisons between the simulated and measured values showed that these equations were very capable of predicting the advance velocity of the wetting front in different directions. The average Standard Error (SE) values at all depths and in all directions (horizontal and vertical) for clay, loam and sandy soil textures were estimated as 0.18, 0.21 and 0.23, respectively which were the evidence for the relative superiority of the developed equations in clay soil texture. Also, the average SE values at all depths and in all soil textures (0.28, 0.20, 0.23 and 0.15, respectively) showed the increase of equation accuracy with the increase of soil depth. Using these equations in designing surface and subsurface drip irrigation systems could improve system performance.

Drought is a natural disaster that affects the human life due to its significant effects on agricultural and economic sectors. Using the remote sensing technique, drought can be studied through its effects on plants, and it is possible to gain a more accurate and effective modeling of drought. In this study, the efficiency of vegetation condition index in analyzing the agricultural drought was evaluated using the remote sensing facilities for East Azarbaijan province. The data included the MODIS sensor images from Terra satellite between 2000-2011 and the rainfalls from synoptic and climatic stations of the province. To gain the vegetation condition index (VCI) values, the normalized vegetation index (NDVI) values were used. The NDVI derived from the information of the bands 13 &16. According to the VCI values the drought covered more areas in the years 2001, 2008, 2000 & 2009 while it covered less areas in the years 2010 & 2003. To assess the efficiency of the study, the Standardized Precipitation Index (SPI) were calculated from the data of the years 2001, 2008, 2010, 2003, in 9 weather stations and compared with the data collected from VCI maps. According to the SPI index, the years of 2008 & 2001 encountered the highest drought and also the years of 2010 & 2003 had the lowest drought. The results indicate that using the VCI index is an excellent method for evaluating the agricultural droughts through the Remote Sensing. Furthermore, in areas with or without sporadic weather stations this index can be used for estimating drought since the number of sampling points on satellite images exceeds the number of the weather stations.

Artificial recharge is the well known method for controlling the degradation of groundwater quality and quantity. The artificial recharge is substantially dependent on the identification of a suitable recharge location which plays the main role in the success of the project. In this research, quantity of precipitation, land slope, surface infiltration, geology, hydraulic conductivity of the aquifer, depth of water table, transmissivity and land use information were used to find the most appropriate location for artificial recharge and the weight of each layer was determined based on the importance of its role in surface water infiltration into aquifer. The AHP technique was used to identify the most appropriate weight for various parameters in site selection for artificial recharge. Results showed that 1.4% of the studied area was very suitable for artificial recharge, while 10.39% and 13.33% were suitable and to some extent suitable, respectively, and 75.14% was unsuitable for artificial recharge. In eight different locations which were classified in suitable group, four locations had suitable situation regarding to the drainage system and roads. Regarding the accordance of these four alluvium sites with the resulted maps by Ground Water Model in GMS environment, three suitable sites were selected for the long-term and one site was proposed for the short- term recharge programs in the Boushkan region. In this watershed, the artificial recharge in alluvial deposits was much more suitable than that in karst environment.

Study on the reduction of flow energy intensity in order to reduce damage of the downstream hydraulic structures, always has been one of the potential interesting issues. One of the most important topics in this field is the study on hydraulic jump and its control method. Like other structures, in energy dissipaters considering economic and ease of construction is an essential issue. Therefore, in this study, the effects of the roughness and negative bed slope on water level and velocity profiles of hydraulic jumps for upstream flow in Froude numbers ranges of 4.9-7.8, with three different bed roughnesses and slopes of 0%, 3.1%, 60%, and % 2 were studied. The results indicated some similarities between the measured velocity profiles and some differences between the profiles of water jets as compared with those on smooth beds. Also, the thickness of the dimensionless boundary layer was calculated to be 0.66, which was significantly different in comparison with its value for the flat bed (0.16). Moreover, the bed shear stress on the rough negative sloping bed was at least 10 times greater than the shear stress on the smooth flat bed. Also, the energy and momentum correction coefficients were higher relative to the classic mode.

Because of the importance of canola as a major oil plant and its compatibility with different climatic conditions, an experiment was conducted in the Agricultural Research Station of Tabriz University to determine its lysimetric evapotranspiration. Lysimetric evapotranspiration was measured 583.6 mm in the study region. Results showed that there was 23.36 percent difference between lysimetric evapotranspiration and potential evapotranspiration resulting from FAO Penman-Monteith method. A relationship for crop coefficient was obtained based on the days after planting and radiation absorbed by plants and was corrected with temperature and leaf area index. The durations of growing stages of spring Canola including initial, development, middle and end stages based on percentage of land cover and LAI were obtained equal to 25, 35, 20 and 20 days, respectively. Also the mean values of crop coefficients were determined for the initial, middle and the end stages of growth equal to 0.72, 1.45 and 0.66, respectively. There was significant difference between crop coefficients resulting from this study with the recommended values in the FAO 56. In this study, changes in the ground cover percentage, LAI, plant height and evapotranspiration were investigated on different days after planting.

Knowledge of the chemical forms of heavy metal pollution in soil, plants and groundwater is important. This study was done to investigate the effect of leonardite in changing the chemical forms of heavy metals in soils derived from different parent materials including Syenite, Schist, Gabbro and Calcite. Analyses of the physico-chemical properties and clay mineralogy of soils were carried out. Chemical forms of the lead (Pb) and cadmium (Cd) in presence of the leonardite (0, 2, and 5%) were evaluated using sequential extraction method. The results showed that the quality and quantity of the clay minerals were different and the smectite mineral was dominant at different ratios of the leonardite. However, the vermiculite (42%) and hydroxy interlayer vermiculite (HIV) (82%) minerals were observed in the schist and calcite-derived soils, respectively. Leonardite application decreased the pH value in the derived soils from Syenite. The result showed that the chemical form of heavy metals in different soils was significantly affected by the leonardite levels. Pb and Cd chemical species were different in each soil type. The maximum amounts of the exchangeable Pb and Cd were observed in the syenite and gabbro, and the syenite soil, respectively. Leonardite decreased the elements related to the oxides Fe- and Mn, whereas the organic carbon based section was significantly increased by the leonardite application. Also leonardite reduced the amounts of the residual fraction of heavy metal in soil. Accordingly, leonardite behavior varied in different soils and its application should be based on the physico-chemical properties of soil.

Considering the importance of preserving spatial correlation between neighboring stations in many of the studies in the fields of agriculture and water resources on a daily time basis, in this research, a weather generator model (WG) was developed to simulate climatic variables in neighboring stations while preserving spatial correlations between these stations. This model uses an extended Markov model to generate precipitation occurrence series which is capable of simulating spatial correlations between neighboring stations with an acceptable performance. In order to simulate precipitation amounts on wet days and other climatic variables, a nonparametric algorithm was proposed. The performance of this algorithm was assessed in relation with the generation of daily mean and standard deviation, daily correlation and lag-1 autocorrelation of climatic variables and also spatial correlation between neighboring stations using Coefficient of Determination (R2), Standardized Root Mean Square Error (SRMSE) and Standardized Mean Absolute Error (SMAE) statistics. The results showed that this model was capable of reproducing statistical properties of historical time series with an acceptable accuracy, while the model underestimated the values of lag-1 autocorrelation coefficients. Moreover, climate change scenarios can be simulated by modifying model parameters while preserving spatial correlations between neighboring stations.

In deep reservoirs the turbidity currents are usually the reason of transport and deposition of sediment. If the turbidity current is completely stopped in the middle regions of the reservoir; sediment deposition reduces near the dam wall and as a result the main tasks of the dam are not disrupted. Roughening up the bed is a technique for changing the density current hydraulics or slowing of its velocity. Therefore in the present research the head velocity of the density current on the bed with cylindrical roughness is studied and a relationship for head velocity is presented. A series of gravity currents experiments are performed in a flume with 35 cm width, 70 cm height and 9 m length. The experiments are developed as salinity fluid flow with three salt concentrations of 10, 15 and 20 g/L in bed slopes renge of 0.5, 1.25 and 2% and three roughness height of 2.5, 4 and 5.5 cm. The result indicates that head velocity is almost constant during passage from smooth bed while it reduces significantly in rough bed. The bed slope and fluid concentration have direct relation with the head velocity. Roughening up the bed has reduced the gravity current head velocity. Also, increasing roughness height reduces the velocity of the current head to a certain extent. Finally, a relationship is developed to estimate the head velocity.

In order to assess the effects of organic and inorganic nitrogen sources on yield of some winter rapeseed (Brassica napus L.) varieties, soil physicochemical properties and available nutrient elements such as nitrogen, potassium, phosphorus, iron, manganese, zinc, copper and sulphur, two field experiments were carried out during 2008 - 2010 cropping seasons as factorial arrangement in randomized complete blocks design in three replications at the Agricultural and Natural Resources Research Center of Markazi Province, Arak, by using two factors of nitrogen sources at three levels of Azocompost, 50% Azocompost plus 50% urea, 100% urea and three rapeseed varieties including Okapi, Modena and Licord. Nitrogen sources were utilized such that a net quantity of 150 kg N/ha was added to the soil. The results showed that there were significant differences between the nitrogen sources for seed yield and soil properties including moisture weight, bulk density, soil electrical conductivity, pH, organic matter, saturation percentage, porosity percentage and infiltration velocity at 1% probability level. The rapeseed varieties had significant differences for seed yield and soil properties such as bulk density, electrical conductivity, organic matter, porosity percentage and also for the availability of nitrogen, potassium, iron, zinc, manganese and sulphur elements in the soil. In these experiments, the Licord variety showed a greater yield (3847 kg/ha) at integrated nutrition system compared to the other treatments. In addition, the availability of Fe, Mn, Zn and S in soil solution were increased, but the availability of K was decreased. In this research, the integrated application of Azocompost and Urea fertilizers, increased seed yield of Licord cultivar and improved the most of soil properties. Therefore, the integrated nutrition (50% Azocompost plus 50% urea) and extension of Licord variety cultivation area could be recommended for the rapeseed yield enhancement.

River flow accurate forecasting is so important in design, operation and planning of water resources systems. In this study, the performances of the non-parametric nearest neighbor method, adaptive neuro- fuzzy (ANFIS) and support vector regression (SVR) approaches were evaluated for streamflow forecasting. In order to derive the model, monthly streamflow observations of 36 years time period at Dizaj hydrometric station located in the Baranduz-Chay River (in monthly time scale) were used. Different combinations of the recorded data were used as the input pattern of streamflow forecasting. The results indicated that all of the applied models had reasonable performances in prediction of the monthly river flow. By adding the seasonality coefficient of streamflow to input pattern, performances of the intelligent models increased considerably. In general, the SVR model using the suitable input pattern was selected as the best method. The values of the three different evaluation criteria, namely correlation coefficient (R), root mean square error (RMSE), mean absolute relative error (MARE) were equal to 0.88, 3.63 (m3/s) and 78.45, respectively. Furthermore, evaluation of the performances of the models for streamflow forecasting revealed that in the cases of high discharges all of the models underestimated the streamflow comparing with the observed values.

Prediction of flow distribution is necessary in open channels junctions at irrigation and conveyance water systems in order to design suitable plans and protect them in emergency situations. In this study, a one dimensional analytical model of subcritical flow distribution using mass - energy and momentum conservation laws was presented for a four-branch junction of open channels and compared with experimental results. The results showed that as the inlet discharge ratio and bed elevation of the lateral channels increased, the outlet discharge of the main channel increased. Furthermore, as the Froud number at the inlet of the main channel decreased, the outlet discharge of it increased. Changes in the height of the weirs at the end of the outlet channels had no considerable effect on the flow distribution. The maximum and minimum deviations of the flow amounts to the outlet lateral channel occurred at the angles of 60 and 90 degrees, respectively. Comparison of the analytical and experimental results showed a good agreement between them so that the maximum error was less than 10%.

Soil salinity and compaction are probably the most prevailed limitations for crop growth and yield. This research was performed to investigate the combined effect of soil salinity and soil compaction on several aspects of corn (Zea mays cv. single cross 704) growth. For this purpose a factorial pot experiment on the basis of completely randomized design with three replications was performed. The experimental factors were soil salinity at three levels (saturated extract electrical conductivity of 1.5, 2.5 and 4.5 dS/m) and soil compaction at three levels (bulk density of 1.30, 1.55 and 1.75 g/cm3). For creating salinity in the soil different amounts of NaCl dissolved in required volumes of distilled water to raise the mass water content to 16% were added to the pots, soil. For soil compaction a mass of 4.5 kg was allowed to fall from a 45 cm height over the soil surface in the pots. Increasing the soil salinity from 1.5 to 4.5 dS/m resulted in significant decline (from 10 to 24%) in plant height, shoot and root dry weight, leaf area and chlorophyll index. Increasing the soil compaction from 1.3 to 1.75 g/cm3 significantly decreased (from 11 to 63%) the mentioned growth indices. In the applied range of soil salinity and compaction, soil compaction caused more decline and suppression than soil salinity in the corn growth. Combined effect of the salinity and compaction became more significant than their individual effects and reduced drastically (22 to 73%) the growth indices specially chlorophyll index. In other words, soil compaction intensified the negative effects of salinity on corn growth.