نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال بیستم شماره 1 (پیاپی 75، بهار 1395)

Zinc (Zn) is one of the essential micronutrients for plant growth and its deficiency frequently occurs in calcareous soils. But, a suitable extractant for estimation of plant-available Zn in calcareous soils, amended with sewage sludge, has not been presented yet. The aim of this research was to assess several chemical extractants (7 extractants) for estimation of available Zn in calcareous soils amended (1% w/w) and unamended with sewage sludge. Results showed that Mehlich 3 and Mehlich 1 extractants extracted the highest and the lowest concentrations of Zn in both amended and unamended soils, respectively. All wheat indices (wheat yield, Zn concentration and Zn uptake) increased by sewage sludge addition. Besides, the results indicated that in unamended soils, significant correlations were found (r=0.65*- 0.91**) between extracted Zn using AB-DTPA, DTPA-TEA and Mehlich 3 extractants and different wheat indices. On the contrary, in sewage sludge-amended soils, only the correlation between extracted Zn using Mehlich 2 and Zn concentration was significant (r=0.83**). According to this study findings, the suitable extractant for extracting wheat-available Zn is thoroughly different in calcareous soils amended and unamended with sewage sludge.

Water scarcity forced farmers to use wastewater as water source, without considering its effects on environment and resultant contamination of soils and plants especially with heavy metals. The objectives of this study are to evaluate the application effects of zeolite as soil amendments on the uptake of Cd by spinach (Spinach Oleares L.) irrigated with wastewater (containing 10 ppm Cd). Different levels amounts of zeoilte (0, 1% and 5% w/w) were added to the soil and the experiment was conducted as a completely randomized design in a green house with 3 replications. The results indicated that, the addition of zeolite 1% (w/w) in soil treated with wastewater reduced cadmium concentration in plant, and consequently the percentage of extractable Cd using DTPA was decreased. However, application of zeolite 5% (w/w) increased the soil salinity, and as a result increased Cd concentration in the plant but this increase was not statistically significant, comparing with control. Spinach biomass did not differ significantly under irrigation with wastewater, but the Cd available in wastewater caused a decrease in Spinach biomass yield.

Drought is an extended period of low precipitation which resulted in injuries to consumers of water and reducing their performance, especially in agriculture. Different indices have already been proposed for evaluating drought, based on one of the varieties of meteorological, hydrological and agricultural droughts, but no indices has been identified yet, encompassing all factors. This study has been carried out to assess existing indices for drought monitoring and proposing an integrated index including main factors of drought and is applied to the Zayandehrood river basin as study area, because of its sensitive situation in the central Iran plateau. An integrated index includes various drought factors such as meteorological, hydrological, agricultural, socio - economical and environmental factors. In designing of this integrated index, a combination of static and dynamic layers has been used. Static layers include land use, slope and soil type. Dynamic layers include precipitation, evaporation, temperature, surface water storage, groundwater levels position, and environmental needs. All these layers are analyzed in GIS software and drought zoning maps is prepared. Results showed that based on values of integrated index, water year 1371-72 was a wet year and water year 1378-79 was the most critical, in terms of drought.

In this study, the effect of the secondary flow strength and vorticity on variations of bed shear stress for different positions of spur dike are compared through a mild 90˚ bend along with a T-shaped spur dike in a rigid bed. To carry out these experiments, three dimensional velocimeters (ADV) have been used for measuring velocity. Moreover, a comparison has been made between velocity vectors and variations of streamlines along the bend; the secondary flow strength and vorticity values are estimated for various positions of spur dike, and their effects on bed shear stress variations have been analyzed. It is concluded that the maximum secondary flow strength is evident in a distance of 0.6 of spur dike’s length at upstream under all these different positions of spur dike. Also the maximum vorticity position corresponds to the position of the maximum secondary flow strength, in front of spur dike’s wing. According to these results, it is predicted that the maximum scour occurs near the position of maximum secondary flow strength and maximum vorticity. Besides, the path of sediments motion coincides with the maximum shear stress points locus.

The aim of this study is to prepare the groundwater spring potential map using Weight of Evidence, logistic regression, and frequency ratio methods and comparing their efficiency in Chehlgazi watershed, province of Kurdistan. At first, 17 effective factors in springs occurrence including geology, distance to fault, fault density, elevation, relative permeability of lithological units, slope steepness, slope aspect, plan curvature, profile curvature, precipitation, distance to Stream, drainage Stream density, Sediment Transport Capacity Index (STCI), Stream Power Index, topographic wetness index (TWI) and land use/land cover (LU/LC) were selected. The validation processes of methods were conducted by relative performance characteristic curve (ROC). The area under an ROC curve (AUC) for the weight of evidence, logistic regression and frequency ratio was 85/8%, 79% and 89%, respectively. The results showed that all methods are suitable estimator for mapping the groundwater spring potential in the study area. But the frequency ratio method with the most amounts is the best method to produce and map the groundwater spring potential. Also, validation of the mappings based on the percentage of pilot springs, training springs and all springs showed that the logistic regression, WoE and frequency ratio, with 45, 56 and 45 percent of spring occurrence on the high potential classes respectively, had the highest validation.

This study was conducted to investigate the effects of poultry manure (PM) and its derived biochars on chemical properties of a sample calcareous soil. Poultry manure and its derived biochars at 200(B200), 300(B300) and 400(B400)°C were incorporated with 400 g of soil at 2% level (w/w) and incubated for 150 days. Some chemical properties of soil and bio-availability of some nutritional ingredients such as phosphorous, potassium, iron, manganese, zinc and copper were determined at different times of incubation. Soil nutrients availability, organic carbon (OC), electrical conductivity (EC) and cation exchange capacity (CEC) increased by addition of all these organic substances. Biochars prepared at higher temperatures were more effective in increasing soil OC and its durability. Addition of PM and B200 decreased soil pH, whereas B400 increased it. Although highest soil EC was observed in B300 and B400 treated samples in the early stages of incubation, the rate of increasing in soil EC was higher at PM and B200 treated samples. In general, it was concluded that biochar prepared at 300°C had the highest effect on availability of nutrients and their durability in the soil.

In this study, the impact of some organic matters and a moisture super absorbent were investigated on available water and delay of permanent wilting point in a sample soil of Rasht landscape. In incubation stage, 12 Treatments including control (70% v/v soil with 30% of the composted manure) and various amounts of soil, municipal compost, composted manure, olives and rice wastes along with a super absorbent (A200) were used in a completely randomized design. In order to provide water-release curve and to determine the amount of moisture needed for Field Capacity (FC) and Permanent Wilting Point (PWP), filter paper method was used. Three treatments having more available moisture and further delay in permanent wilting point in incubation stage were being applied in greenhouse stage, along with the control treatment. In greenhouse stage, impact of treatments and irrigation period (36, 72 and 168 hours) were studied on plant growth of Lysimachia, in a factorial experiment based on randomized complete block design. Results showed that the greatest weight of shoot dry matter was obtained in 30% municipal waste compost treatment and rice wastes treatment in 36 hours irrigation period, but at 168 hours period, dry matter decreased and the greatest dry matter was obtained from superabsorbent treatment.

Assessing the root system and its tensile strength is necessary for determine the impact of roots in increasing the soil shear strength. The present study aims to investigate effects of slope and flow of riverbank on root system of riparian POPULOYS trees. In a relatively direct interval, 6 riparian POPULOYS trees were chosen on the slope of Simereh riverbank. To assess the root system, the circular profiles trenching method was utilized. The surface around each tree was divided into four quadrants: upper quadrant, lower quadrant, in slope direction and in flow direction. In every quadrant, number and diameter of roots were measured. The obtained results showed that the highest number of roots were in 90-100 cm depth. 59% of Roots, in the slop direction and 53% of roots in flow direction, were located in the top quadrant. Approximately, 97% of roots had up to 20 mm diameter. The greatest difference in the number of roots in upper, lower, in slop direction and in flow direction quadrants, were seen in diameters up to 5 mm. In slope direction, this difference was almost 2.7 times more than the difference seen in flow direction. The average ratio of root cross-section was 0.26%. The obtained results indicate that the root system of riparian POPULOYS trees on the riverbank is asymmetrical.

This study investigated the effects of climate change on the evapotranspiration amount and water balance in the Zayandeh-Rud river basin. Two important weather stations; Isfahan and Chelgerd stations, located in the East and West of the basin respectively, were selected for investigation in this study. The combination of 15 GCM models were created based on the weighting method and three patterns of climate change including the ideal, medium and critical were defined. Using the proposed patterns, the effects of climate change on temperature and evapotranspiration in Isfahan station and precipitation in Chelgerd station were estimated under the A2 and B1 emissions scenarios. Two indices were considered to determine the sustainability of agricultural water consumption in the study area. Ratio of evapotranspiration in the East part of the basin to precipitation in the West part was defined as EPR index (Evapotranspiration-Precipitation Ratio), and the ratio of maximum agricultural water deficit to the amount of agriculture water need, was considered as maximum deficit index (MD). Results showed that the annual temperature would increase between 0.63-1.13°C in the eastern part of the basin. The west precipitation in the basin would reduce between 6.5-30% in the ideal to critical patterns. Summer season, showed the most amount of increase in the temperature, and winter season, showed the most amount of decrease in precipitation. The A2 emission scenario showed more temperature increase and more precipitation decrease in comparison with the B1 emission scenario and also indicated that the potential evapotranspiration would increase by 3.1 to 4.8% in the basin. The EPR index will increase between 13-52% and MD index will increase between 9-35% in Zayandeh-Rud river basin under different climate change patterns. The results revealed the imbalance between agricultural water use in eastern part and the precipitation in the western part of the basin. In other words, in these conditions, appropriate management strategies and planning should be implemented to ensure the sustainability of water resources in Zayandeh-Rud River Basin.

Soil moisture is one of the main input parameters in many models for monitoring and predicting crop yield. The ability of mathematical models has allowed correct application of brackish water and selection of management options. The purpose of this research was to evaluate the performance of HYDRUS-2D for simulating soil volumetric water content in a heterogeneous heavy soil under field conditions. Three volumes of irrigation water (10, 15 and 20 L) and three salinity levels of irrigation water (1.279, 2.5 and 5 dSm-1) were exerted in a linear drip irrigation system with three replications. In order to check the amount of soil volumetric water content, soil profiles were drilled to 40 cm depth and vertical wall of drip irrigation line was networked. Soil volumetric water content was measured with a TDR MiniTrase kit 6050X3K1B model. The observed soil moisture values were compared with the simulated ones using statistical indices (i.e. nRMSE and CRM). The results indicated that mean soil volumetric water content distribution in irrigation water with different levels of salinities was in the range of field capacity. The range of nRMSE values varied from 0.91 to 2.07 percent in different replications. According to calculated nRMSE values, performance of the simulation model, was ranked as excellent for simulation of soil volumetric water content. Range of CRM values was shown to be from -0.0080 to 0.0170 that was really low. Results of these two statistics indicate high ability of the model in simulating soil volumetric water content using estimating hydraulic parameters by inverse solution.

In this research dense fluid discharge was experimentally investigated under the surface jet in the shallow acceptor. The investigated parameters were depth of the acceptor ambient, flow rate and the concentration of surface jet. In order to investigate the relationship between these parameters, a physical model experiments were performed in the hydraulic laboratory of Shahid Chamran University. The results showed that progressive length of the surface jet core is directly proportional to Froude number of fluid density, and is inversly proportional to fluid density concentration. Besides, the progressive length of the jet core increases with increasing the depth of the acceptor ambient. This length increase is due to the decrease of water surface tension. In average, increasing the depth of acceptor ambient twice, the progressive length will increase 38%, and its increasing three times, will increase progressive length of jet core 62%. Besides, in the relationship obtained for the progressive length of jet core R 2 is 0.94.

Drought is a climatic anomaly that associates with a significant decrease (lack) of precipitation and water resources availability, which spreads on vast temporal and spatial scales, and significantly affects various aspects of life and environment. One of the most common methods of drought assessing and monitoring is calculating drought indices (DIs). Drought areal and temporal extent and its severity are determined by these indices. In this study, an aggregate drought index (Hydro-Meteorological) has been developed for the assessment of hydrological and meteorological droughts in Sarbaz river basin located in southeastern of Iran. The Aggregate Drought Index (ADI) comprehensively considers all physical forms of drought (meteorological, hydrological, and agricultural) through selection of variables that are related to each drought type. In this case, monthly values of Stream flow Drought Index (SDI) and Standardized Precipitation Index (SPI) indicators were used for four similar reference periods with principle component analysis and aggregate hydro-meteorological index was defined based on its first component. The study time span was set between 1981-82 to 2010-11, which begins of October in Iran. Results based on the aggregate drought index (ADI) revealed that a long period of hydro-meteorological drought occurred from 1999-2000 to 2005/06 in southeast of Iran, in which, 2003/04 water year has been extremely a drought year. The ADI methodology provides a clear, objective approach for describing the intensity of drought. This index is appropriately able to represent the behavior of Hydro-Meteorological droughts and recommended as an integrated index for assessing and monitoring of regional droughts. Finally, different states of hydro-meteorological drought have been extracted based on conventional regional thresholds, and have been modeled by Markov chain. This made the estimation of drought state transition frequency possible, and made the prediction of next drought state time more real. State transition frequency matrices, are the main instruments for predicting drought states in real time. Results of validation tests and conforming the predicted results with real data indicate that predicting hydrological drought state transitions in the study area using Markov chain method is valid.

The main objective of this study was evaluation of integrated management and mixing saline/fresh water on soil salinity distribution. For this purpose, a field was selected and 32 plots were made in it with a 6 m×2.5 m size. A split plot experiment was employed with two sunflower varieties (Alstar and Hisan33), four irrigation schemes (CIS) and four replications. Irrigation schemes being applied as treatments are: T1: every other irrigation with saline water (11 dS m-1) and fresh water (2 dS m-1) (every other irrigation), T2: fresh water - saline water, T3: mixed irrigation and T4: saline water - fresh water. Soil samples were collected from depth of 0-20, 20-40 and 40-60 cm in the early, mid and end of the irrigation season. The samples were analyzed for EC, Ca, Mg, Na and Cl. The result showed that soil salinity in depth of 40 cm is greater than salinity in depth of 20 and 60 cm in all treatments and for both sunflower varieties, in all growing stages. The maximum salinity concentration was observed in T2 among all treatments. Increasing irrigation depth has increased the soil extract’s Cl and Na in all treatments during growing season to 50 and 75 meq/L, respectively. The effects of CIS treatments are statistically significant on Ca and Mg in Alstar, and in all regimes affect on different depths. The minimum value of EC and maximum yield was observed in T4, T3, T1 and T2, respectively.

Splash erosion is one of the most important water erosion types, causing initiation of other types of water erosion. The objective of this study is to model the splash erosion using fuzzy logic approach in part of northern Karoon basin. The major land usage in the area are irrigated farming, dry land farming, pasture and degraded pasture. For the purposes of this study, soil properties including organic matter; CaCO3; surface shear strength (SSS); particle size distribution; mean weight diameter (MWD) and soil splash erosion were measured under four different slope conditions (S:%) and rainfall intensity (RI:mm.h-1): 5-50, 5-80, 15-50, 15-80, respectively, using multiple splash sets (MSS) at 80 different locations. Splash erosion was modeled based on combinational rule of inference under five conditions for selection of different operators. The efficiency of the models was evaluated using mean square error (MSE) between observed and estimated values. Results revealed that all models are capable of predicting splash erosion. Also slope, rainfall intensity, MWD, SSS, fine sand and coarse silt attributes were found to be appropriately and precisely using splash erosion.

Knowledge of variation in soil properties from each event to another is very important for the determination of critical periods during which soil is susceptible to erosion processes. This study was carried out to investigate soil loss in sequential rainfall events in Zanjan Province. Toward this, ten soil textures samples were taken and were transported to small plots (60 cm×80cm) with 20-cm depth) on a 8% slope land at three replications. The plots were exposed to ten simulated rainfalls with an intensity of 55 mm h-1 for 30-min and 5-day intervals. A total of 300 simulated rainfall trials were carried out at the plots. Results indicated that soil moisture, runoff production and soil loss were significantly affected by rainfall events (P