نشریه آب و خاک
سال بیست و هفتم شماره 5 (پیاپی 31، آذر و دی 1392)

By paying attention to the increasingly development that we observe in accuracy and correctness of short term predictions and also by consideration to the development of tool and instruments and methods of safeguarding plants against frost we can revise about determining length of growing season period. So in this study it has taken an action to extract 3 indexes: the length of potential growing season period and the length of risk management. The length of growing season period consists of chronological space between the occurrence of the last frost in spring and the first frost in autumn that is zero centigrade degree according to the threshold. The length of potential growing season was identified as chronological space between the last prolonged 3 days period having zero or under zero centigrade degree in autumn and it''s last prolonged 3 days period in winter or the beginning of spring. The risk management was identified according to the space between the first or last frost days with the first or last prolonged 3 days frost. In continuation، for determining these 3 indexes in Iran، the data of minimum daily temperature of 62 synoptic stations for a 15 years period (1991-2007) during the month October to May was received from meteorology station. The result has shown that the length of growing season period in Iran varies from 161 to 365 day. So that Saghez، Ardabil and Shahr kord stations each with 161،167 and 169 day has the shortest length of growing season in Iran and the stations of southern coast like Chabahar، Khask، Bandar Abbas port، Lengeh port and Booshehr is 365 day. But using the index of length of potential growing season period instead of index of length of development period shows that the length of development period will increase from 4 days in Dogonbadan station to 58 days in Gorgan station. The station of Saghez، Ardabil and Shahr kord that had shortest length of growing season period in Iran، have again the shortest length of growing season in Iran by this new index. But with the difference that the length of growing season period is 198، 202 and 211 days in order، it means that in proportion to the length of growing season period، 35،34،41 days was added to their development period. The length of risk management period after southern stations that don''t have frost، the stations such as Dogonbadan، Dehloran and Bam with 4،8،9 days are 3 stations that have the shortest period of risk management. Tehran، Dushan، Rasht، Gorgan with more than 40 days have devoted the longest period of risk management in Iran.

Soil erosion prediction models are of great significance for soil and water conservation management. Rill erosion is the most important component of hillslope soil erosion processes. Therefore، predicting hillslope erosion requires that rill erosion is well understood and predictable. The study was conducted to empirical quantification of rill development in the hillslopes. Rill characteristics consist of width، depth، cross section area، length، volume and soil loss، density of the rills and soil erosion rate along with slope characteristics (steepness and length) and soil properties were determined in 27 rills occurred on 9 hillslopes in marl formations of the Zanjanroud watershed، north west of Zanjan، Iran. All rill characteristics except the length showed significant correlation with both slope steepness and some soil properties including particle size distribution، sodium adsorption ratio، aggregate stability and saturated hydraulic conductivity. Rill depth as compared to other rill characteristics was reliably quantified in the hillslopes. This parameter had the highest relationship with slope steepness and saturated hydraulic conductivity (R2= 0. 67، p< 0. 001). Rill erosion rate contrary to the slope characteristics significantly related to clay content (R2= 0. 56). This result revealed that in order to develop a model to predict rill erosion، it is vital that investigate all hillslope characteristics a long with soil properties in the watershed surface.

Conversion of forest and pasture lands into agricultural lands، which is triggered by the rapid population growth، causes serious soil degradation، especially in the hilly regions with undulating topography. The objective of this study was to explore the slope position and land use change effects on some soil properties in hilly region of west of Isfahan province، Feryduhahr district. In the two mentioned dominant ecosystems، four slope positions including summit، shoulder، backs lope and foot slope were identified and in each land use and slope position، three cores were selected to collect 72 soil samples from three depths (0–10، 10–20، 20–30 cm). The results showed that soil organic matter (SOM) in pasture land (2. 1%) was approximately 40% higher than cu1tivated land (1. 2%). Overall، SOM، total nitrogen، available potassium، clay and sand content significantly in pasture land were higher than cu1tivated land. In consequence of land use change from pasture to cultivated land، some soil properties in surface soils including calcium carbonate، bulk density and soil acidity showed increasing tendency as compared to pasture soils. The pasture soil with lower soil erosion and higher fine materials (clay)، indicated higher magnetic susceptibility as compared to cultivated land. Variability of most of measured soil properties showed significant differences in different slope positions. Improper management practices and consequently water soil erosion was identified as the most possible process which has affected soil properties in different slope positions. In overall، it is conc1uded that slope positions and land use significantly influenced soil physical، chemical and magnetic properties in steep slopes of the study area.

Nowadays، modeling and prediction of climatic parameters due to climate change، global warming and the recent droughts is inevitable. Maximum and minimum temperatures are including climatic parameters that are important in water resources management and agriculture. In order to model the maximum and minimum monthly temperatures of Mashhad plain، the long- term data of Mashhad and Golmakan were used for the joint period from 1987 to 2008. The SARIMA (0،0،0) (0،1،1) 12 model for maximum monthly temperature and the SARIMA (0،0،0) (2،1،1) 12 model for minimum monthly temperature were determined as the final models using time series. High correlation coefficientsindicate acceptable adaptation of modeling and actual values in the calibration and validation of models. Finlay، predictions were performed based on models fitted for the next 10 years (2009-2018). Comparison of results for future period (2009-2018) and the base period (1987-2008) represents maximum temperature mean 1 °c increase and minimum temperature mean 1. 4 °cincrease.

Precipitation is a key input to different crop and hydrological models. Usually، the rain gauge precipitation data is applied for the most management and researching projects. But because of non-appropriate spatial distribution of rain gauge network، this data does not have a desirable accurate. So estimation of daily areal rainfall can be obtained by spatial interpolation of rain gauges data. However، direct application of these techniques may produce inaccurate results. In the last years، applying the remote sensing for estimation of rainfall have got so popular all around the word and many techniques have been developed based on the satellite data with high temporal and spatial resolution. In this paper، CMORPH model was validated for precipitation estimation over the northeast of Iran. Results showed that this model could not estimate precipitation accurately in daily scale، but in monthly and seasonal scale the estimation was more accurate. Farooj and Namanloo station had the highest correlation equal to 0. 31 in daily scale. The highest correlation in monthly scale was equal to 0. 62 for Barzoo، Namanloo and Se yekAb station. In Seasonal scale Gholaman station had the highest correlation which was equal to 0. 63. Also، the probability of detection has been estimated accurately by CMORPH. But this technique did not have an accurate estimation for wet and dry days، mean annual precipitation and the number of non-rainy days.

In most civil projects، such as irrigation and drainage networks constructions، soil stabilization has an important role. Achieving maximum durability against wet-dry cycles is one of the soil stabilization objects. Therefore، depend upon project type and its importance; various hydraulic binders with different amounts are tested to obtain desirable results from technical and economical view. In this research، the effect of dry-wet cycles on engineering properties of clayey soils (low plasticity) was studied and lime، cement and lime-cement binders، with (2-6) percent of soil weight، were used. The results showed that with changing type and percent of binders، various sample durability against dry-wet cycles is different so that without binder samples did not have durability and the samples stabilized by 4% cement and 4% lime tolerance 12 wet-dry cycles. The results also showed that after dry-wet cycles، the mass and volume of sample were changed and its unconfined compressive strength was decreased so that the decrease of the unconfined compressive strength was between 40% and 60%. The present study showed that dry-wet cycles significantly cause to change the soil geotechnical properties.

Soil biota such as earthworms and arbuscular mycorrhizal fungi (AMF) play an important role in the stability of ecosystem، and the bioavailability of soil elements، in particular heavy metals، in soils. To examine the effects of these organisms، a 3×2×3 factorial experiment arranged as randomized complete design was set up to study the individual and combined influence of earthworms (Lumbricus rubellus L.) and AMF (Glomus mosseae and Glomus intraradices) on soil organic matter (OM)، dissolve organic carbon (DOC)، soil respiration، microbial biomass carbon (MBC)، soil enzyme activity and glomalin production in a calcareous soil contaminated with 0، 10، 20 mg of Cd kg-1 soil cropped with sunflower (Helianthus annuus L.) with three replications. Both earthworms and mycorrhizal fungi were able to survive in all the treatments with added Cd. Results showed that Cd pollution decreased all the measured microbial activities and properties in soil. Earthworm treatment increased DOC by 4-10% at all Cd levels. The amount of soil MBC in mycorrhizal treatments was greater (1. 9-2. 4 times) than that in non-mycorrhizal treatment، and AMF inoculation increased MBC/TOC ratio from 23% to 53% in Cd-polluted soils. Earthworm and AMF enhanced soil enzyme activity/MBC ratio، 10-18 and 40-54% for soil alkaline phosphatase and 4-9 and 40-55% for soil urease، respectively. The glomalin production increased at 20 mg kg-1 and was about 15% greater in G. mosseae than in G. intraradices species. Although soil respiration was decreased substantially with Cd pollution، inoculation of either earthworms or AMF enhanced soil respiration when compared with the corresponding controls.

Land cover/use changes and soil and forest degradation influence on emission of greenhouse gases effectively and lead to global warming. This research was done with objective of investigation of relationships between soil organic carbon density (SOCD) and primary terrain attribute in two depths 0-20 cm and 20-40 cm in Deylaman region، Giulan province. Stratified Random sampling method was used for determination of sampling plot location in uniform unit. A Walkely-Black method was used for content of soil organic carbon measurement. Finally، statistical and correlation analysis were used to understand the relationship between SOCD and primary terrain attributes. This research showed the primary terrain attributes had different roles on each land use/covers. Slope has significant impact on SOCD in forest land while has no significant role in cultivated land and rangeland. Aspect has not significant impact in different land covers/uses in 0-20 cm soil layer. Elevation has significant role on SOCD in cultivated land and rangeland while it has no significant impact in forest land. Exist of enough information about of impact of primary terrain attributes on increasing carbon sequestration process could be effective for land sustainable management in different land use especially in north of country.

The existence of bridge pier in streamflow causes a complex 3D flow formation، which also causes the scouring around bridge pier. Since rivers are usually curved، it is necessary to investigate the impact of change in flow patterns caused by passage of flow through the curve on the scouring around bridge pier. By developing Computational Fluid Dynamics (CFD)، there is a possibility to simulate the flow pattern around the bridge piers. Therefore، the purpose of this research is modeled a 3D flow stream near the bridge piers in a curved channel. For this purpose a fluent model software was employed، and solved by stream equations using finite volume method of centralism. For discretization of Navier Stocks equation، three turbulence models of K-ε، K-ω، and RSM were used. In order to consider free surface، Fluid Volume Method was applied. The numerical model was validated with measured experimental data around the bridge piers in the meandering flume with 5 sequential curve paths. The results showed that the RSM turbulence model performed well compared to the other two models. When comparing the flow of upstream to downstream of bridge piers it can be observed that the placement of bridge piers in the middle of curved shape channel may lead secondary flow towards the inner curve of a channel. Also، the resulted vortex continues with a 150 degree curve.

The objective of this study was to evaluate the effect of soil salinity on the availability and uptake of cadmium (Cd)، lead (Pb)، nickel (Ni)، zinc (Zn) and copper (Cu) in a soil treated with municipal sewage sludge (MSS). Soil was salinized (2، 4، 8 and 12 dSm-1 soil paste extract) with NaCl + CaCl2 (1:1ratio)، and incubated at soil field capacity (FC) for 1 month. The soil was treated with a 1. 5 percent of MSS and incubated again at FC for 1 month. Before planting،soluble and DTPA-TEA extractable of heavy metals and soluble Chloride (Cl-) were determined. Then barley seeds were planted and، plants were harvested 10 weeks after germination. The plant indices (dry weight، heavy metal concentration and heavy metal uptake) were measured. The results showed that all salinity levels significantly increased soluble and availability of Cd، Pb، Ni، Zn and Cu. Soil salinity had a significant effect on concentrations and absorption of Cd and Pb in plant (P)

Change in microorganism activity and chemical properties can be affect on availability and fractionation of Copper (Cu). This research was conducted to investigate the availability and fractionation of Cu in the bean rhizosphere and bulk soils in 10 calcareous soils using rhizobox at greenhouse. Total organic carbon (TOC)، dissolved organic carbon (DOC)، microbial biomass carbon (MBC)، pH، available Cu (by using 7 chemical extractants) and Cu-fractions were determined in the rhizosphere and bulk soils. The results indicated that in the bean rhizosphere soils، TOC، DOC and MBC increased significantly (p)

Gas diffusion ratio in the soil in compare to diffusion in the atmosphere (DP/D0) and air permeability in the soil (Ka) is a function of soil physical characteristic، including pore size، continuity and air porosity. The results showed that with increase in soil moisture and Se، DP/D0 and Ka decreased as a logarithmic function. Maximum and minimum value are obtained، at low and high humidity (near saturation)، respectively

Drought can affects by reduced water resources، agricultural productivity، change in vegetation cover، and accelerate the desertification of areas. In order to drought monitoring، we need to quantify drought effects by using drought indices. These indices based on type of available data are divided into two general categories of ground- and satellite- based indices. The aim of this study was to compare the capability of detection and classification of vegetation changes occurred due to the drought، between one ground-based drought index (Standardized Precipitation Index (SPI)) and four satellite drought indices derived from AVHRR-NOAA (normalized difference vegetation index (NDVI)، temperature condition index (TCI)، ratio vegetation index (RVI)، standardized vegetation index (SVI) in the Kermanshah province. To do this، the change vector (CV) analysis was used as one of the important change detection algorithms. In this method، the change occurred in vegetation has been shown by two components، change magnitude and change direction. The results of implementation of the CVA on the maps of drought indices during the growing season (March to August) in selected years (two normal years، one wet year، and one drought year) showed the best response to the drought in the study years (except the wet year 1992)، obtained by SVI. The lowest similarity was obtained between the SPI and TCI، for wet and normal years. Finally، the study suggests mostly the satellite indices based on the vegetation conditions، rather than the temperature indices، for assessing the effect of drought on vegetation cover.

To investigate the long-term effect (13 and 23 years) of wastewater irrigation on soil physical quality indices in Taqanak، Shahrekord، four homogenous fields but with long and different history of treated municipal wastewater application were selected. The changes in conventional soil physical indicators (organic carbon، bulk density، mean diameter of aggregates) as well as retention-curve derived indices: Dexter’s S index، Macro pore porosity (MacPOR)، air capacity (AC)، plant available water content (PAWC) and relative water capacity (RWC) were investigated in these farms. Irrigation with wastewater significantly increased (p)

Adding heavy metals to soils leads to change of their original distribution pattern. Heavy metals distribution in soils depends upon heavy metal، application level، application time and soil characteristics as well. This investigation was conducted to assess the time effect on distribution of different fractions of Lead in soils. The experiment conducted as a factorial in a completely randomized design with three replications and two levels of cow manure (0 and 5%) and two levels of Lead using Lead nitrate (0 and 200 mg kg-1). Samples were incubated at 250C and 60% of field capacity for 120 days with different time intervals (0-30، 0-60، 0-90 and 0-120 day) to determine Lead fractions using sequential extraction methods. The results showed that Lead concentration decrease in exchangeable، carbonated and residual fractions during the time. Also the interactions between cow manure and time cause of decreases in the exchangeable and residual fractions and increases in the carbonated، Fe-Mn oxides-bound as well as organic matter-bond fractions. The interactions between time and Lead concentration lead to decrease in the exchangeable، carbonated and residual fractions and increase in the Fe-Mn oxides-bound and organic matter-bond Lead fractions. Since the most availability and toxic potential of lead is in the exchangeable-solution، the advantage of the this study is to reduce potion of this section during the time.

Simulation of rainfall-runoff process in the watershed has a significant importance from various points of view، such as better understanding of hydrological issues، water resources management، river engineering، flood control structures and flood storage. Therefore in this study، the river flow and surface runoff are simulated using the distributed hydrological model، WetSpa. In the WetSpa model runoff process of the basin is simulated using diffusive wave approximation method based on gradient، flow rate and distributed features along the flow routes. Atrak watershed with about 11639 km2 area is one of the largest watersheds of Iran and average annual precipitation is about 283mm. Meteorological data from 1383 to 1390 consisting of rainfall in 25 stations، temperature and evaporation measurements in 5 stations were used as model input data. To run the model three base maps including DEM، land use and soil type with cell size of 100m were provided. Simulation results show a relatively good agreement between calculated hydrographs and measurements at the basin outlet. The model estimates daily hydrographs، with an accuracy of over 60% and 53% based on Nash-Sutcliff criterion، for calibration and validation periods، respectively. And based on Nash-Sutcliff criterion adapted for the maximum flow rate، the model accuracy was evaluated as 77%. According to model output and hydrological factors with spatial distribution at each time step، the model has the ability to analyze topographic effects، soil texture and land use in hydrological behavior of basin.