نشریه پژوهش های حفاظت آب و خاک
سال هجدهم شماره 3 (پاییز 1390)

Potassium is essential plant macronutrients. According to the conceptual approach soil potassium (K) can be classified into four forms: soil solution K, exchangeable K, fixed K and structural K. In this research, potassium forms were determined in loess and loess like derived soils of Golestan Province and in the silt and clay fractions of them. The objective of this research was to determine the contribution of soil separates in release of potassium and to be fertilizer management in the soils. Mean extracted potassium content in clay particles of all soils was more than that of soil and silt fraction. The quantity of K extracted by HNO3, NH4oAc and HF in soils varied from 632 to 1200, 103 to 476 and 12000 to 17800 mg/Kg, respectively. The mean of exchangeable, nonexchancheable and total potassium contents were 160.6, 1155.1 and 19100 mgKg-1, respectively in clay fraction. The quantity of non exchancheable K extracted from silt fraction was a half of its quantity in clay fraction.

Drought is one of the significant problems that has situated in the first rank from the perspective of intensity, duration and damages among the other natural disasters. Some times for compensating this defect, users attack to wards ground waters. if this condition continue, water resource excessively reduce, so The Farsan-Jonaghan and Shalamzar hydrologic units were selected to examine the effect of drought on the Ground Water Resource and agriculture in the Behesht Abad basin(Sub Basin of north karoon Basin), respectively. 30 years records of hydrometery station of Darkesh-Varkesh and Koohe Sookhteh located in the outlet of Jonaghan and Behesht Abad River was used to monitoring of drought effect in the Farsan-Jonaghan and Shalamzar plains, respectively. Normal percentage index was used to determine of wet, normal and dry years. WEAP model as water resources allocation model was utilized to evaluate of agriculture status. The model was calibrated and validated using data for 10 (1995-2004) and 30 (2005-2034) years, respectively. Then, some scenarios were considered. Condition of ground water level and agriculture was examined in the limited extract of an aquifer. The results showed that the highest effect of drought was on the groundwater level of aquifer (in some of dry years the volume of aquifer reduce 30%). In the other scenario, the fluctuation of groundwater level of aquifer was controlled during dry years. In this condition, there was a significant different between the percentages of meeting demands of dry and wet years. The level of normal cultivation with regard to the kind of climate was modeled with consideration of normal demand supply percent in total wet and dry years. Finally, using the results of model, a graph was prepared that it can be used for measuring of the cultivation area changing for each degree of drought.

Land suitability evaluation is the fitness of a given tract of land based on its potential for a defined use. The objective of this study were to define the qualitative, quantitative and economical land suitability evaluation of Zarrinshahr and Mobarakeh located at the west of Isfahan province and assessment the environmental impacts of the questioned land utilization types. The economical evaluation included collecting the economical data, comparison of inputs and outputs and analysis of gross income. Potential yield was calculated using the method proposed by F.A.O. The result of potential yield analysis showed that the potential yields were determined 9.01 and 11.01 t/ha for wheat and rice production, respectively. The quantitative land evaluation and their classes were defined according to incorporating observed yield and marginal yield with the qualitative evaluation results. The predicted yield varied from 1.3 to 6.7 and from 0.7 to 4.6 t/ha for wheat and rice, respectively. High correlation between the observed yield and predicted yield indicated the appropriate selection of the factors and evaluation approach. Based on the quantitative evaluation, most of the land unit’s wheat was identified that had more suitability in the study area. The cultivation of rice is not recommended in the study area, because of negative environmental impact including soil physical destruction, non-efficient water consuming, arising of ground water surface and increasing soil salinity.

To determine the appropriate depth of leaching water requirement for Saline-Sodic soil reclamation, some field experiments are recommended. Having the results of such field experiments, the so-called leaching curves will be obtained. These empirical curves will enhance determining the amount of leaching water to reduce the soil salinity and sodicity to desirable levels. The objectives of this study were to conduct such experiments in order to obtain soil Desalinization & Desodification curves and to compare the obtained results with some empirical models. Furthermore, it was supposed to determine a new empirical model for the saline-sodic soils in central part of Khuzestan province. In this study, the field experimental results of a heavy texture, Saline-Sodic soils, which was carried out by cylinder infilterometer are presented. In this regards three different sites were selected in the most saline-sodic parts of the study area for which 1.0 meter depth of leaching water were applied intermittently. The field salt leaching data and calculated valves were used to verify a newly proposed empirical model obtained by curve estimation technique. The results indicated that the empirical relationships proposed by Revee, Dielman and Verma and Gupta can not resemble to the field conditions. However, the empirical relationships introduced by Laffelar and Sharma, Hoffman, Pazira and Kawachi and Pazira and Keshavarez could estimate the depth of required reclamation water 1.5 times more than the newly proposed empirical model. The theoretically calculated values with the proposed exponential model, could well simulate the real experimental data.

Time domain reflectometry (TDR) is used for determining soil water content nowadays. Amount and type of clay minerals in heavy soil can affect soil dielectric constant and cause the error in soil water content. The effect of the amount of clay minerals on soil water content was the subject of many researchers, but they did not work on the effect of the type of clay minerals. The aim of this research was the effect of type and amount of clay minerals on dielectric constant in heavy soils. For this purpose soil samples with different textures including clay, clay loam, loam, silty clay and sandy clay were taken. The results showed that with increasing the clay content, due to bound water and delay time, the soil dielectric constant decreased and consequently soil water content has been shown less than the real amount. The results also showed that Smectite group increased soil dielectric constant. Our results showed that the presented model with four phases including solid, air, bound water and free water in non saline soils presents acceptable results for volumetric water content. But in saline soil this model did not show accurate results. Consequently, soil salinity and clay type can affect on soil dielectric constant and water content.

It is necessary to recognize the critical growth stages of date palm to water deficit for Irrigation scheduling and management. This study was carried out in a randomized complete blocks design with five treatments and four replications. The treatments of irrigation: namely 50, 100, 150 and 200 mm with irrigation depth equal to 100% net irrigation requirement and 200 mm with irrigation depth equal to 50% net irrigation requirement after evaporation from class A pan during flowering and fruit set stages. The yield of each palm was determinated in harvest season. Also the fruits quantitative and qualitative characteristics such as weight, length, diameter, volume, pH, moisture, acidity, TSS, total sugar, N, P and K were measured. The results showed that irrigation treatments have significant effect on fruit weight, fruit diameter and yield. There was no significant differences between length, volume and qualitative characteristics of fruit. The highest water productivity and fruit weight, diameter and yield was obtained with irrigation after 50 mm evaporation from the class A pan.

Lower atmosphere. The global concentration of these gases is increasing, mainly due to human activities, such as the combustion of fossil fuels (which release carbon dioxide) and deforestation (because forests remove carbon from the atmosphere). Projections of future climate change are derived from global climate model or general circulation model (GCM) experiments. Climate model projections show an increase in the global mean air temperature by 1 to 3.5˚C by 2100. One of the most important problems in the management and planning of water resources is forecasting of precipitation. This research explored the issues of downscaling the outputs of GCMs using an artificial neural network (ANN) approach. This data used in daily precipitation forecasting. This study focuses on the impact of climate changes on precipitation in the karimisaha (humid climate) and Robat gharebil station (semi-arid climate) in Golestan dam basin in Golestan. GCM model in this research is CGCM3. These data are derived from two scenarios, A2 and B1 for two periods: 2021-2050 and 2071-2100. Precipitation data for 1979 to 2000 period selected for base period. Result showed that Increase monthly average precipitation in winter and autumn to 43 mm in karim ishan station and 32mm in robat gharbil station and decrease in spring and summer to 23 mm in Karim ishan station and 11 mm in robat gharbl station.

Determining the exact value of bed load is concerned with investigators. In this study the performance of 13 bed load sediment transport formula developed for use in steep gravel-bedded armored ChehelChay River, Iran is tested. The formulas are applied in the manner intended by the original authors. The results have been expressed in terms of a discrepancy ratio (r) defined as the ratio of the predicted and measured transport rate. The method of Ackers and White yields the best results for field data with 64% of the predicted transport rates in the range of 0.5≤ r ≤2. The Meyer-Peter and Mueller and Van Rijn equations yields approximately good results with 43%, and 36% of the predicted transport rates within a factor 2 of the measured values, respectively.

Study of soil quality indicators were considered as a useful method in the land use management. Population growth tends to high pressure to nature resource and change of the forest to other land uses and building in Golestan Province. Therefore this study to evaluate the effects of land use change and Villa building on some selected indicators of soil quality in the four land uses forest, pasture, cultivated and the urban, in two North and West geography aspect. Soil samples were taken of 0 to 30 cm depth and analysis of data taken by the method of completely randomized split-plot design with six replications. Soil quality indicators were containing physical, chemical and biological important parameters. Analysis data showed that the amount of organic carbon in both urban and cultivated land uses decreased 70 and 52 percent with respect to forest land use, and also bulk density from 13 to 35%; mean weight diameter from57 to 87%; total nitrogen from 39 to 60%; and microbial respiration 22 to 26% respectively in the urban and pasture land uses. The amount of carbonates increased in both urban and cultivated land uses 80 to 88%; electrical conductivity 42 to 84% with respect to forest and soil reaction in cultivated and pasture13 to 17 with respect to forest. Water infiltration of soil in the forest showed that decrease of soil and water quality because the high pollution in this resourced in the Gorgan the main city province. If this changing will be continued, the health of the ecosystem and especially human life in the cities will be changed.

An application of a spatially distributed hydrologic model WetSpa working on a daily time scale is presented in this paper. The model combines elevation; soil and land use data within GIS, and predicts flood hydrograph and the spatial distribution of hydrologic characteristics through a watershed. WetSpa model uses a modified rational method to calculate runoff. The runoff is routed through the basin along flow paths using a diffusive wave transfer model that depending upon slope, flow velocity and dissipation characteristic along the flow lines. The Chehel-chai basin is located in the east of Golestan Province with an area of 254.9 km2. Elevation rangs from 194 to 2547 m and a mean slope is 34%. The mean annual precipitation in the catchment is 766.5 mm. Daily hydrometeorological data from 2002 to 2006, including precipitation data from three stations (Lazoreh, Dozin, and Narab), temperature and evaporation data from two stations (Lazoreh, Dozin) were used as input to the model. Three base maps, i.e. DEM, land use and soil types are prepared in GIS form using 90×90 m cell size. Simulated hydrographs are compared with measured hydrographs which are available for the same 2 and 3 year periods. Results of the simulations show a rather good agreement between calculated and measured hydrographs. The model predicts the daily hydrographs with a rather good accuracy, more than 50 and 57% for calibration and validation periods respectively according to the Nash-Sutcliff criterion.

Soil erosion posses play a key role in organic matter loss from watershed. Therefore, study of the organic matter on suspended sediment is very important for watershed management and soil and water conservation planning. The present study was conducted in Kojour Watershed to determine loss of the suspended sediment associated organic matter. The suspended sediment and organic matter sampling was made via depth integration. The results of this study showed that 57 ton organic matter loss from 8 rainfall events and 48gr om in 1 kg sediment loss in each rainfall this period.

Various researches on assessing and mapping of desertification have been carried out which have lead in development of regional and local models. In this study the MEDALUS method have been applied to assess and map the current status of desertification in the Sofikam – Mangali plain, the northwest of the Golestan province, Iran. The criteria and indices model were re-defined before the model application, whereas in the revised model 5 criteria, 20 indices were used to assess the condition of the study area. The criteria included were water erosion, vegetation, climate, soil and management. Then several sub-indicators affecting the quality of each main criterion were identified. Similar to the original version of the MEDALUS method, each sub-indicator was quantified according to its quality. ArcGIS 9 software was used to analyze and prepare the layers of quality maps using the geometric mean to integrate the individual sub-indicator maps. In turn the geometric mean of all five criteria quality maps was used to generate a desertification map of the study area. The results showed that 54.12 percent of the area is classified as severe, 43.7122 percent, moderate and 2.17 percent as low affected by desertification process. Further analysis indicated that the soil and vegetation indicators were the most important factors affecting desertification process in the Sofikam – Mangali plain, the northwest of the Golestan province.