نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال چهاردهم شماره 3 (پیاپی 53، پاییز 1389)

An experiment was conducted in order to evaluate the effects of increased concentration of potassium and calcium in hydroponic nutrient solution on the response of safflower to salinity. The experiment was carried out in a glasshouse using a completely randomized design. Four saline treatments (Johnson solution containing 100 mM of NaCl, Johnson solution containing 100 mM of NaCl + 10 mM potassium, Johnson solution containing 100 mM of NaCl + 5 mM calcium, Johnson solution containing 100 mM of NaCl + 10 mM potassium + 5 mM calcium) and Johnson solution without any addition of salt as control. Leaf area per plant, shoot and root dry matter was decreased in saline treatments. The concentration of potassium and calcium in the plants were decreased but those of sodium were increased at salinity. The extent of shoot and root dry mater reduction with salinity was less in saline treatment with additional calcium alone. The addition of potassium into the nutrient solution could not mitigate the negative effects of salt stress on the plants. Increasing the concentration of both potassium and calcium in saline nutrient solution resulted in a greater reduction of shoot dry matter. The results showed that the negative effects of salinity may be alleviated by increasing the concentration of calcium in nutrient solution.

Temporal and spatial distribution of water components in watersheds, estimation of water quality, and uncertainties associated with these estimations are important issues in freshwater studies. In this study, Soil and Water Assessment Tool (SWAT) model was used to estimate components of freshwater availability: blue water (surface runoff plus deep aquifer recharge), green water flow (actual evapotranspiration) and green water storage (soil water), in Hamadan-Bahar watershed. Also, the Sequential Uncertainty Fitting program (SUFI2) was used to calibrate and validate the SWAT model and do the uncertainty analysis. Degree of uncertainty is calculated by R-factor and P-factor parameters. In this paper, results of calibration and validation are given for the river monthly discharge. In most stations, especially in outlet of the watershed (Koshkabad station), simulation of river discharge was satisfactory. Values of R-factor in calibration of monthly runoff were 0.4-0.8. These small values show good calibration of runoff in this watershed.Values of P-factor were 20-60%. These small values show high uncertainty in estimations. For most stations of the watershed, lack of data on river-water withdrawal caused poor simulation of base-flow and therefore the P-factor values were low. Nash-Sutcliff (NS) coefficient was 0.3-0.8 after calibration, which shows good model calibration of outlet.This study provided good information on the components of freshwater availability at spatial (sub-basin) and temporal (monthly) scales with 95% prediction uncertainty ranges. The results of uncertainty analysis of components of freshwater availability show that uncertainty ranges of average monthly blue water are larger than the othercomponents, because of its sensitivity to more parameters.

Climate change has different impacts on extreme events such as flood and drought. However, in Iran there are few researches about the impacts. This research was aimed to investigate maximum annual discharge (magnitude and frequency) that may occur due to climate change in Aidoghmoush Basin during 2040-2069 (2050s). At first, monthly temperature and precipitation data of HadCM3 model under the SRES emission scenario, namely; A2, was provided for the basin. Then, these data were downscaled spatially and temporally to Aidoghmoush basin by proportional and change factor downscaling methods. Results showed that the temperature increases (between 1.5 to 4) and the precipitation varies (30 to 40 percent) in 2040-2069 compared with baseline period (1971-2000). A semi-conceptual model (IHACRES) for simulation of daily runoff was calibrated. Downscaled temperature and Precipitation for 2050s were introduced to IHACRES and daily runoff was simulated for the future. Probability distribution was fitted to maximum annual discharge series and the maximum discharge regime of the future was compared with the baseline. Results indicated that climate change affects Maximum discharge in the regime of the basin. Also, the analysis showed that the intensity of maximum discharges for the time period less than 50 does not show any significant difference; but by increasing the return period, the intensity increases in future periods. Moreover, it was shown that the probability of maximum discharges with constant intensity will decrease in the future compared to the baseline.

The Clark method is one of the most applicable techniques for development of instantaneous unit hydrograph whose efficacy depends upon the accuracy in estimating storage coefficient. The present study was conducted in Kasilian watershed in Mazandaran Province to determine the efficiency of developed hydrograph using Clark's method and to compare the Muskingum storage coefficients obtained through graphical, Clark, Linsley, Mitchell, Johnstone-Cross and Eaton methods. To this aim, the time-area histogram of the study watershed was initially developed. The 3h-unit hydrograph was then derived using the data collected in Sangedeh climatological and Valikbon hydrometric stations. The efficiency of Clark’s instantaneous unit hydrograph developed based on 6 methods for calculation of Muskingum storage coefficient was ultimately compared with the observed average 3h-unit hydrograph of the study area. The results of the study revealed that the Clark’s instantaneous unit hydrograph obtained from graphical method for estimation of storage coefficient with estimation error of less than 33.33% and efficiency coefficient of 83% could suitably simulate different components of the observed average unit hydrograph for the study watershed.

Nowadays in the world, soilless culture as a kind of technique is known to give vegetable crops higher yield and quality. This experiment was conducted at research greenhouse of Agriculture and Natural Research Center of Golestan province in spring 2005. The purpose of this research was to investigate the effects of irrigation frequency and substrates on yield and fruit quality of greenhouse tomato (CV. Hamra). Irrigation was carried out for 4, 8 and 12 times a day. The substrates were Perlite, Leca and Perlite + Leca (1:1, w/w). The experimental design was factorial in the form of randomized complete design with four replicates. The substrates used in the experiment had no effect on most factors. However, TA (0.43 mg/100 l) and fruit set (48%) were increased significantly by perlite and Leca substrates, respectively. The results indicated that higher and lower marketable yields were obtained from plants irrigated 12 (1830.5 g/plant) and four times (1156.7 g/plant) per day, respectively. Also increasing irrigation schedule decreased the Titratable acidity but didnt significantly affect the other factors. According to these results, Irrigation of 12 times per day and Leca substrate increased vitamin C and marketable yields, leading to optimum quality and quantity fruit set and the decreased TA (0.33 mg/100 l) in fruits in this treatment.

Osmotic adjustment is generally regarded as an important adaptation of wheat to drought. Because it helps to maintain turgor and cell volume, osmotic adjustment is often thought to promote growth, yield, or survival, of plants in dry soils. However, a physiological rationale for such views is lacking. This study was conducted to determine the effect of osmotic adjustment and some of its components on the wheat yield. Ten bread wheat cultivars were grown in pots under different watering levels using a split plot design. During grain filling stage, RWC, leaf sugar content, proline content and osmotic regulation were estimated by sampling flag leaf under normal and stress conditions. Main stem was used for measuring sugar content of different parts of stem. Although there were some differences in osmotic regulation in wheat lines, there were no relationships between yield and osmotic regulation. It was shown that these components probably have a little share in wheat osmotic regulation.

In order to classify and determine the plant communities in Karkas mountainsides, central Iran, quantitative data of 46 environmental characteristics including climate (12 characteristics), soil (26 characteristics), geology and physiology (8 characteristics), were analyzed based on partial Euclidean distance indicator using minimum variation method. The results showed the clustered separation of studied sites at 68% similarity level with three different growth places. Of these 46 factors, 24 factors (8 climate characteristics and 16 soil characteristics) were effective in this classification at 95% certainty level. Only 24 of these 46 factors were effective in this classification at 95% certainty level. These 24 effective factors were divided into 8 climate and 16 soil characteristics. In another classification, combinational percentage index of 17 plant species were investigated as an effective factor in separating growth place and determining the plant communities. Result of cluster classification indicated that the studied sites cold be classified to 3 habitats.

The purpose of this study was to compare the physical and chemical characteristics of soils covered with vegetation and soils without vegetation in Dagh-e- Sorkh Ardestan area.To achieve the goal, first the vegetation was classified using physiognomic method, and for each vegetation type, the distinctive area was specified for soil and vegetation sampling. Vegetation sampling was done by stratified random sampling. Alongside pursuing the case, twenty two soil physical and chemical factors were investigated also for each growth type and area without vegetation. In the next step, to investigate the similarities and dissimilarities of the soils of desert areas by means of PC-ORD software, the cluster analysis was performe. After simplifying the one-way ANOVA, the most important soil factors which were effective in causing differences in the area’s soils were identified. Results show that the soils of area covered with vegetation differed much from the soils without vegetation physically in such a way that, the soil texture became heavier and gravel percentage became less in the areas without vegetation. Regarding the chemical characteristics, the frequencies of sodium, magnesium, calcium and chlorines and electrical conductivity were highly different. Because of topographic condition of land without vegetation, runoff is directed to this place and deposits salts there. Also, high groundwater level and capillary flowing salts are the important reasons for the salinity of this place. These are the limiting factors for the vegetation establishment in the desert areas of Ardestan.

In this research, logistic regression analysis was used to create a landslide hazard map for Sajaroud basin. At first, an inventory map of 95 landslides was used to preduce a dependent variable, which takes a value of 0 for absence and 1 for presence of landslides. Ten factors affecting landslide occurence such as elevation, slope gradient, slope aspect, slope curvature, rainfall, distance from fault, distance from drainage, distance from road, land use and geology were taken as independent parameters. The effect of each parameter on landslide occurrence was determined from the corresponding coefficient that appears in the logistic regression function. The interpretation of the coefficients showed that road network plays the most important role in determining landslide occurrence. Elevation, curvature, rainfall and distance from fault were excluded from the final analysis because these variables did not significantly add to the predictive power of the logistic regression. After transferring final probability function into Arc/view 3.2 software, landslide susceptibility map was prepared. The results of accuracy assessment showed that overall accuracy of produced map is 85.3 percent. Therefore, 53% of the area was located in very low hazard, 18.3% in low hazard, 21% in moderate hazard and 7.7 % residual area is located in high hazard regions. Model and then susceptibility map verity was assessed using -2LL, Cox and Snell R2, Nagelkerk R2, and was validated.

Kinetical study on non-exchangeable potassium (NEK) release is necessary for management, optimum use of soil resources, availability and supplying power of potassium. Information about NEK release rate in Golestan soils is limited. The aim of this study was to investigate the NEK release of saturated soil sample by calcium using acid citric and CaCl2 extractants from 2 to 1844 h duration in 12 dominant soil series in Golestan province. Different soils indicated various responses to continuous extraction. The rate of K released in different soils was lower in CaCl2 than that of Citric acid. Potassium release was faster in earlier periods of the extraction in all soils followed by a lower release rate. Due to high coefficient of determination and low value of the standard error of the estimate, the NEK release kinetic by citric acid and CaCl2 were well described by Elovich and Parabolic diffusion equations and Power, First order and Elovich equations, respectively. Therefore, NEK release rate was controlled by K diffusion from weathered surface of soil minerals.

Presence of petroleum contaminants in soil may be toxic to human and organisms and act as a source of ground water contamination; hence, remediation of these compounds from environment is vital. In this study, first the feasibility of remediation of two petroleum-contaminated soil samples around Tehran Oil Refinery (oil refinery landfill and agricultural soils) was assessed using landfarming technique during a four month experimental period. The elimination of total petroleum hydrocarbons (TPHs) from soils treated through landfarming technique was then investigated in the rhizosphere of agropyron and fescue. The results showed that microbial respiration increased due to landfarming processes in both soils. Urease activity in the landfarming treatment for agricultural soil was 21, 45, 26, and 23% higher than the control at the end of first to the 4th months of experiment, respectively. However, no significant differences were observed between the landfarming and control treatments for landfill soil at the end of experiment. Furthermore, about 50 and 57% reduction in TPH-concentration was observed in the landfarming treatment for landfill and agricultural soils at the end of experiment, respectively. In the phytoremediation study, presence of TPHs in both landfarming and control treatments reduced dry matter yield of the studied plants. Urease activity in the rhizosphere of fescue and agropyron was higher than in the unplanted soil. Degradation of petroleum-compounds in the landfill soil under landfarming treatment was more than 20 and 40% in the presence of fescue and agropyron, respectively. The influence of agropyron on TPH-removal from agricultural soil under the landfarming treatment was also higher than fescue.

Heavy metals including cadmium produced as a result of urban, industrial and agricultural activities lead to the water pollution. Also, considering the growing need for silviculture in Iran, it is necessary to conduct a comprehensive research on fast growing and evergreen species of Eucalyptus and their role in heavy metal's absorption. To achieve this goal, Eucalyptus occidentalis seedlings were grown in pots containing silica and irrigated with a mixture of nutrient solution and cadmium chloride in 5, 10 and 15 m M for 10 months. Root and leaf samples were harvested and the amount of cadmium in stem, root and leaf organs was measured. Also, some morphological and physiological characteristics were determined including soluble sugar and praline. The analysis indicated that the cadmium concentrations of 15 mM treatment in the root, leaf and stem were 585, 142 and 87 mg/kg D.W., respectively. Proline content increased with the increase of Cadmium concentration while the content of pigments decreased. The result of this research shows that eucalypt has the potential of cadmium accumulation without any serious damage to its growth. Therefore, the plant can be used to decrease the environmental pollutions.

Overexploitation of groundwater resource may result in lowering groundwater table at a faster rate due to an imbalance in the total recharge and total withdrawal. In order to make a balance between groundwater exploitation and recharge, the major remedial measures suggested are to strengthen groundwater management, adopt water demand policies, raise water use efficiency, and to increase water supply. Because there is a trade off between farmers’ income and sustainability of groundwater based farming, it is essential that a mathematical model be used to study the effects of withdrawal on farmer's income and sustainability of farm. Such a model can determine optimal crop pattern, suitable irrigation strategies and irrigation methods at different levels of available irrigation water. The relationship between farmers’ income and the withdrawal was then examined using multi-objective programming. The data were obtained from a systematic random sampling method through which 112 farmers were chosen. The percentage decrease in the profit was less than that of the withdrawal for all representative farmers, based on the results obtained from multi-objective method. For example, 8% reduction of groundwater pumping could be imposed without a serious impact on the farmer's income (farmer's income falls about 4%). Finally, the results of this study can help farmers to choose crop patterns, irrigation strategies and irrigation methods in such a way that both farmers’ income and withdrawal are simultaneously optimized and lead to a decrease in extracting groundwater compared to the current status.