نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال دوازدهم شماره 4 (پیاپی 46، زمستان 1387)

In this research the effect of Super Absorbent Polymer (SAP) on the crop growth, wilting point, sunflower survival, water holding capacity, and irrigation interval was investigated. The experiment was conducted with different concentrations of absorbent hydrogel (Igeta): 0% (control treatment), 0.05%, 0.1%, 0.2%, and 0.3% (w/w). The soil textures were sand, loam, and clay. The experiment was a completely randomized design with three replications. The results of this research are: 1- Adding of Igeta to the soil changed solid, liquid, and gas phases. Application of 0.05%, 0.1%, 0.2%, and 0.3% (w/w) of Igeta increased the volume of clay, loam and sand soils between 10-40% , 5-32% and 9-37%, respectively. 2- With application of Igeta, absorption of nutrients (N, P, and K) was increased. Maximum absorption nutrients occurred at the level of 0.05%, 0.1%, and 0.3% with confidence level of 90% for clay, loam, and sandy soils, respectively. 3- Igeta increased water holding capacity and irrigation intervals. Increasing in irrigation interval was between 30-130% in clay, 60-120% in loam, and 150-300% in sandy soils. Water saving in clay, loam, and sandy soils was 30%, 40%, and 70%, respectively. 4- at the level of 0.3% Igeta, starting time of temporary wilting point was delayed from 4 to 10 days (150%) in clay and loam soils, and from 4 to 12 days (200%) in sandy soil. The starting time of permanent wilting point was delayed from 8 to 12 days (50%) in clay, 7 to 12 days (71.4%) in loam, and 9 to 14 (55.5%) days in sandy soils. Therefore, application of Igeta delayed starting time of permanent wilting point between 50-71% and temporary wilting point between 150-200%.

Iran, with an average annual precipitation of about 252 mm (413 BCM) and renewable freshwater resources of 130 BCM, has irregular distribution of water resources. With a high population growth rate, agriculture remains the greatest water user in Iran but its production still does not meet the total food demand of the country. Due to unreliable water availability, the competition for water from other sectors and the increasing demand for food and better diets, Iran will experience water stress. In this study, virtual water trade in relation to water resources availability has been assessed as a way of relaxing water stress in Iran. The results showed that from the 21 food products, cereals, pulses, nuts and oilseeds are water-intensive crops according to their estimated virtual water content, while fruits, vegetables and industrial crops are not water-intensive. Considering the volume of virtual water entering the country through food imports, more water will be available for other essential uses. However, the virtual water trade has been developed rather unconsciously regarding water use and crop water productivity during the past two decades. For instance, wheat with a share of 58.5% in the virtual water import to Iran, was the dominant imported crop during 1983-2003. By importing 10.4 Mt of wheat, 11.6 BCM of water has been saved within the country during 1999-2003. However, Iran became self-sufficient in wheat production in early 2005. Consequently, this latest drive for self-sufficiency in the production of wheat, as a water-intensive crop, put tremendous pressure on domestic water resources. The trend in crop trade in terms of quantity and virtual water for other groups of crops has also been shown in the study. Seemingly, crop production and import have been greatly influenced by the weather conditions. With the increasing water scarcity, the role of virtual water in food security is expected to rise continuously in Iran. Thus, conscious virtual water trade as a policy measure in water management and judicious adjustment in agricultural structure will ensure sustainable food security and water availability in Iran.

Tracer experiments are very important in the studies related to aquifer contamination for determination of dispersion coefficient. In this study, the effect of sampling method on the dispersion coefficients of two simulated sandy aquifers was examined. The physical model was made from Plexiglas material with inner length, width and height of 72, 10 and 120 cm, respectively. A solution containing 9 g/l sodium chloride (Ec = 14 ds/m) was used as the non - reactive (conservative) contaminant. Homogeneous sands with coarse and medium particle sizes were used as media for the simulated aquifers. The experiments were carried out in the aquifers with various thicknesses from 20 to 100 cm with 10 cm thickness increment. Point and mixed samples were taken through all experiments. The results of the study showed that (1) for both simulated aquifers, the dispersion coefficient values obtained by point sampling method were close to the values obtained by other researchers from laboratory experiments (2) In all the experiments, the dispersion coefficient values obtained by mixed sampling method were higher than those obtained by the point sampling method (3) with increasing the aquifer thickness, the dispersion coefficient values obtained from the mixed samples varied but did not have a uniform trend which could be due to the unavoidable experimental errors and (4) there was no difference between the breakthrough and pore volume curves of various aquifer thicknesses obtained from point and mixed samples. Overall, based on the results obtained from this research, in studies related to aquifer contamination, it is recommended to take point samples instead of mixed samples to obtain more precise results.

Dates of start and end of frost based on minimum shelter temperature equal to or less than 0°C were studied in Zanjan, Ghazvin and Tehran during 1961-2000. The cause of these frosts was determined by weather parameter values at observation hours and the aid of synoptic maps. Frost series based upon last spring or first fall advection are defined and found to be random and normally distributed. The "potential growing season", defined as the interval between spring last and first fall advection frosts, is found to be 29 days in Zanjan, 23 days in Ghazvin and 10 days in Tehran longer than the "growing season" defined by the interval from last spring to first fall occurrences of minimum shelter temperature of 0°C or less. The numbers of radiation frosts in the interval between first radiation frosts in fall or last radiation frost in spring and related advection frost were counted and found that this parameter is greater in Zanjan. Frostless days between the first two fall frosts and last two spring frosts show that the lengthening of spring season with one night protection is possible for 4 days in Zanjan, 6 in Gazvin and 4 in Tehran, providing that first fall and spring last frost is radiation. Results of this study permit estimating the practicality of frost protection for specialized crops in the area of study.

Overtopping is one of the main factors responsible for dam failure. To avoid overtopping, dam is equipped with one or some spillways to release the water impounded in the reservoir. The number and size of these spillways are determined on the basis of design flood. Determination of design flood of dam spillway can be formulated as a multiobjective risk problem. This problem can be solved by Quantitative Risk Analysis Methods. Here, four economical design methods which are based on risk analysis including, United States National Research Council (NRC), US Civil Engineering, Unit Curve and Partitioned Multiobjective Risk (PMR) were studied. In order to compare these methods, Risk Analysis was performed for re-determining design flood of Pishin Dam Spillway. This Dam has been constructed on the Sarbaz River. Owing to the fact that the integrals of the expected damage relations in the two methods, i.e., Civil Engineering, and Partitioned Multiobjective Risk are analytically unsolvable, Romberg numerical integration technique and Excel software were utilized for the related calculations and drawing graphs. Also, in order to select suitable distribution, the flood analysis was done using Smada software. The findings of the study indicated that design flood determined by the three methods, i.e., Civil Engineering, National Research Council and Unit Curve was almost the same, and that the amount of flood was less than the 10,000-year-old flood while design flood determined by Partitioned Multiobjective Risk Method, was larger than the 10,000- year-old flood.

The Madden–Julian Oscillation (MJO) known as the dominant mode of tropical and extratropical intraseasonal variability has an important role in the coupled ocean-atmosphere system. This study investigates the eastward propagation of the MJO and its impact on monthly (February-April) maximum and minimum precipitation in Fars Province. The positive and negative phases of MJO were categorized for the period 1979-2002. The maximum and minimum values of monthly precipitation was then determined for each phase as well as for the entire length of records. The given results have indicated that, in February, both maximum and minimum precipitation during negative phase were significantly greater than the corresponding values during the positive phase. This implies that the enhanced February precipitation and flood events are associated to the negative MJO phase. On the other hand, severe water shotage in February was linked with prevalence of the positive phase. The results for April were mostly found to be similar to February except that minimum precipitation was not significantly associated to the positive phase. In contrast to February, minimum monthly precipitation in March was found to coincide with the negative MJO phase. Maximum precipitation, however, could coincide with neither of extreme phases of MJO.

Global solar radiation (Rs) has wide applications in several disciplines. The data of measured or predicted Rs are widely applied by solar engineers, architects, agriculturists and hydrologists. Due to the importance of Rs, several empirical models have been developed to predict its values all over the world. In this study, Angstrom model was calibrated based on the ratio of actual and possible sunshine hours n/N by using measured daily data of Rs at Bajghah meteorological station in Fars province during 2003-2004. The model was modified by using air temperature for considering the effect of cloudy conditions as well as n/N ratios. The results showed that using both the air temperatures and the ratios of n/N led to a higher accuracy. In regard to estimation of the Rs values, the results showed that mean air temperatures have a higher accuracy compared with differences between maximum and minimum air temperatures. Also, a new local model with higher accuracy was developed based on a number of daily meteorological parameters such as deficit vapor pressure, relative humidity, precipitation, mean air temperature, maximum and minimum air temperatures difference and n/N. This new local model that used different meteorological parameters had the highest accuracy in comparison with the other models. Also, a number of models developed by other investigators for estimation of Rs were calibrated for the study area. Finally, different selected models were validated by using the measured data of Rs in 2005. The results showed that the developed local multi-variable model provided higher accuracy results in comparison with the other radiation models.

In this research, using geographic information system (GIS) and different geostatistical methods including the kriging and co-kriging (ordinary, simple and universal) as well as the radial basis functions, the spatial distributions of runoff coefficient were evaluated in Hamedan province. To this end, the annual runoff were calculated in 18 existing hydrometery stations and another 11 auxiliary points, using digital elevation model (DEM) and 11 years available data of the stations. The performance criteria for evaluating the methods were mean absolute error (MAE), mean bias error (MBE), root mean square error (RMSE), and general standard deviation (GSD) along with the cross validation examination. A high regression between the runoff coefficient and watershed average slope was selected as auxiliary variable. The results showed that the runoff coefficient of the region changes between 3.5 and 85%. The findings also indicated that the universal co-krigings with spherical semi-variogram model had better performance with the values of MBE (-0.0014), MAE (0.036), RMSE (0.054) and GSD (20.152). The universal and simple kriging with spherical model were equal in runoff estimation of the region and were ranked as the second methods to this propose.

Soil erosion is an important economical, social and environmental problem requiring intensive watershed management for its control. In recent years, modeling has become a useful approach for assessing the impact of various erosion-reduction approaches. Due to limited hydrologic data in mountainous watersheds, watershed modeling is, however, subject to large uncertainties. In this study, SWAT2000 was applied to simulate runoff and sediment discharge in Beheshtabad watershed, a sub-basin of Northern Karun catchment in central Iran, with an area of 3860 km2. Model calibration and uncertainty analysis were performed with SUFI-2. Four indices were used to assess the goodness of calibration, viz., P-factor, d-factor, R2 and Nash-Sutcliffe (NS). Runoff data (1996-2004) of six hydrometery stations were used for calibration and validation of this watershed. The results of monthly calibration p-factor, d-factor, R2 and NS values for runoff at the watershed outlet were 0.61, 0.48, 0.85 and 0.75, respectively, and for the validation, these statistics were 0.53, 0.38, 0.85 and 0.57, respectively. The values for calibration of sediment concentration at the watershed outlet were 0.55, 0.41, 0.55 and 0.52, respectively, and for the validation, these statistics were 0.69, 0.29, 0.60 and 0.27, respectively. In general, SWAT simulated runoff much better than sediment. Weak simulation of runoff at some months of the year might be due to under-prediction of snowmelt in this mountainous watershed, model’s assumptions in frozen and saturated soil layers, and lack of sufficient data. Improper simulation of sediment load could be attributed to weak simulation of runoff, insufficient data and periodicity of sediment data.

Tamarix sricta plant grows in riversides of Karun river. Outer body plant in the flood times causes decrease in water velocity, preventing erosion. One of the factors by which the hydraulic resistance is expressed is the roughness coefficient. Measurement of roughness coefficient of the existing plants in these riversides and floodplains, and surveying their effects on the velocity decrease and shear stress of the flow are important. The present research studies roughness coefficient of the plants manning existing in the riverside. Tamaix sricta was studied in non-submerged and sub-critical conditions in a flume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in different velocity, discharge and depth ranges. The height of plants in this study was 35 cm with a natural arrangement in a bench of 2.8 m in length put in the bed of the flume. The total number of the experiments is 22. The results of this study show that roughness coefficients of plants are functions of velocity, depth, hydraulic radius and type of plants. Roughness coefficients in non-submerge condition change nonlinearly with changes in velocity, depth, Reynolds number, submerge depth and (VR) in natural conditions.

The increasing cultivation of corn in Ahwaz and the direct relation between the increase of the summer corn yield and its perfect irrigation in sowing period all together have made the research regarding this crop necessary. Deciding over the suitable irrigation scheduling of corn (hybrid SC.704) in summer by utilization of class A evaporation pan is the focal point of this research. Accordingly, a project was conducted in the form of stadistical perfect accidendal block in four repetitions and four treatments in 1383 on Ahwaz Azad university research land situated in Choneibeh. The irrigation treatment had four levels of T1,T2,T3 and T4 in class A evaporation pan containing of four levels of 50,75,100 and 150 mm, carried out in split plot. The suitable irrigation period was chosen according to the best treatment performance and its components, and the total amount of water in the taking period defines the depth of irrigation. The soil texture is clay lomy silty and the internal soil is silty clay. According to the amount of the accumulated evaporation from class A evaporation pan and taking the plant coefficient (Kc) into consideration, the amount of needed evapotrans piration was calculated and the amount of needed water for plot was measured by water counter. Then a comparison between the means by the use of Donken multi domains test was made and in this way the superior treatment was selected. Accordingly, the most suitable time for irrigation of summer corn in Ahwaz was after 50 mm of accumulated evaporation from class A evaporation pan which equals ten irrigation in the growing period. So in order to acquire 12 tons of seed yield in each hectare, at least 9600 m^3 of water for every hectar is needed. However, given the equal amount of water, with 3 times decrease in irrigation in treatment T2 in comparison with T1, a performance near 11 tons and with five times decrease in irrigation and ten tons in treatment T3 a performance near 10 tons can be attained.

After construction of a dam across a river, sediments settle behind the dam. It is important for dam designers to estimate the rate and distribution of sediments in the reservoir. In this study, the accuracy of area-increment and area-reduction empirical methods to predict the sediment distribution of Dez, Dorudzan and Shahid Abbaspour reservoirs is evaluated. The last measurement of sediment in these reservoirs was in 2003 (Dez), 2005 (Dorudzan) and 2005 (Shahid Abbaspour). The comparison between actual sediment distribution and predicted sediment distribution by using area-increment and area-reduction methods showed the maximum error at the depth of sediment behind the dam. At higher elevations, the error decreased and reached zero when the elevation was maximum. For Dorudzan reservoir, which has the least sediment volume (31 Mm3), the area-reduction method is less accurate, as compared to the area-increment method (81% vs. 37.5%). For Dez and Shahid Abbaspour reservoirs, where their sediment volume is high (608 and 737 Mm3, respectively), the error of the two methods is relatively equal (in Dez, 29% for both methods, and in Shahid Abbaspour, 22% for area-reduction and 25% for area-increment methods). After long-time sedimentation, the shape factor decreased and reservoir type of all three reservoirs changed to 2.

Water and fertilizer applications management should be improved due to scarce resources and environmental protection aspects. An analysis of crop yield production and profit maximization was conducted to determine the optimal water and nitrogen allocation. In this study, maize grain yields were predicted for 25 different amounts of irrigation water (350-1700 mm) and 46 different rates of nitrogen application (0-450 kg N/ha) were predicted using MSM (Maize Simulation Model) model. Irrigation water was distributed in growth period based on maize evapotranspiration. 30% and 70% nitrogen fertilization was used 19 and 50 days after planting date, respectively. Based on field operational costs and present market value in Fars province, optimal amounts of applied water and nitrogen were determined in different conditions of maximum yield (Wm and Nm, respectively), maximum profit under limited land (WL and NL, respectively) and maximum profit under limited water (Ww and Nw, respectively). At present market value ( 88 Rls m-3 for water, 1946 Rls kg-1 for nitrogen and 1570 Rls kg-1 for maize grain), the amounts of Wm, WL and Ww were 1336, 1008, 844 mm, respectively, and the amounts of Nm, NL and Nw were 450 kg N ha-1. Because of the low price of nitrogen, the optimum amounts of nitrogen in the analyzed conditions were similar. If the price of nitrogen and water are increased (i.e. 30000 Rls kg-1 N and 1000 Rls m-3 water), the optimum amounts of applied nitrogen and water in the analyzed conditions are changed to 450, 120 and 210 kg N ha-1, and 1336, 899 and 874 mm, respectively.

Under different climatic conditions of Iran, the evaluation of evapotranspiration (ETo) models sensitivity to meteorological parameters, prior to introducing the superior performance model, seems quite necessary. Using a 35-year (1971-2005) climatological observations in Hamedan, this study compares the sensitivity of different commonly used evapotranspiration models to different meteorological parameters within the IPCC recommended variability range of 10 to 20% during the growing season (April-October). The radiation and temperature-based ETo models include: Penman-Monteith -FAO56 [PMF56], Jensen-Haise [JH1,2], Humid Turc [TH], Arid (semi) arid Turc [TA], Makkink [MK], Hansen [HN], and Hargreaves-Samani [HS]. Results indicate that all the above-mentioned ETo models show the highest sensitivity to radiation and temperature parameters. This implies that special care is required when we apply model-generated radiation and albedo parameters in such ETo models. It is predicted that by 2050, as a result of global warming, the cold semi-arid climates of Iran will cause an average evapotranspiration rise of about 8.5% in crop reference during the growing season.

The forms and dynamics of soil phosphorus can be greatly affected by land use changes, which often involve changes in vegetation cover, biomass production and nutrient cycling in the ecosystem. Present research evaluates the impact of land use change on the amount of total organic and inorganic P, labile, moderately labile and nonlabile P pools in semiarid soils of central Zagros. Samples were collected from surface soils (0-10 cm) of i) of moderately degraded pasture (20-25% plant cover), ii) highly degraded pasture (5-10 % plant cover), and iii) cultivated field (10 years) in Soolegan sub watershed and i) moderately degraded pasture (25-30 % plant cover) and ii) highly degraded pasture (5-10 % plant cover) in Sadat Abad sub-watershed. Significantly (P<0.05) low amounts of total organic P were found following cultivation (23.9%) and overgrazing (18.2 and 40.8 %) in Soolegan and Sadat Abad, respectively. The largest depletion of labile organic P (NaHCO3-Po) (72.3%) and moderately labile organic P (H2SO4-Po plus NaOH-Pi) (24.3%) were observed in cultivated rainfed land in Soolegan. Overgrazing led to decrease in labile organic P (42.1 and 64.4%), moderately labile organic P (13.9 and 35.7%) and nonlabile organic P (NaOH-Po) including moderately resistant and resistant organic P (12.9 and 44.4%) in Soolegan and Sadat Abad, respectively. Our results showed that degradation of natural plant cover cause to depletion in the soil P pools. Decreasing the amounts of moderately resistant and resistant P pools led to a decline in soil productivity and fertility.

Understanding distribution of soil properties at the field scale is important for improving agricultural management practices and for assessing the effects of agriculture on environmental quality. Spatial variability within soil occurs naturally due to pedogenic factors as well as land use and management strategies. The variability of soil properties within fields is often described by classical statistical and geostatistical methods. This research was conducted to study what factors control the spatial variability of soil nutrients using an integration of principal component analysis and geostatistics in Appaipally Village, Andra Pradesh, India. 110 soil samples were randomly collected from 0-30 cm and prepared for laboratory analyses. Total N, available P, Ca, K, Na, Mg, S, B, Mn, Fe, Zn were measured using standard methods. Statistical and geostatistical analysis were then performed on raw data. The results of PCA analysis showed that 4 PC's had Eigen-value of more than 1 and explained 71.64 % of total variance. The results of geostatistical analysis revealed that three PC's had isotropic distribution based on surface variogram. Spherical model was fitted to all PC's. Ranges of model were 288 and 393 m for PC1 and PC3 respectively. On the other hand the range for PC2 was significantly different (877m). The most important elements in PC2 such as Fe, Mn, and Zn probably had similar range of effectiveness (700-900m). The comparison of PC's distributions indicated that PC1 and PC3 including total N, available Mg, K, Cu, Ca and P, were in accordance with farming plots dimensions and management practices. Therefore, it is necessary to improve the appropriate fertilizers used by farmers. The pattern of PC2 distribution was not consistent with farmer's plots, but had the best concordance with soil acidity. Therefore, the most correlated elements with this PC including Fe, Mn, and Zn are mainly controlled by soil acidity and not affected by management practices. However, spatial variability of these elements in areas lower than critical values should be considered for site-specific management.

Successive cropping of potassium-demanding crops like sunflower leads to depletion of soil potassium (K). This study was conducted to investigate the different forms of K and quantity–intensity (Q/I) relationship for sunflower growing soils in Khoy region, West Azarbaijan province. Twenty composite soil samples were collected from different soil series. Different forms of K, including solution K (Kso), exchangeable K (Kex) and non-exchangeable K (Knex) were determined. The results showed that Kso values varied from 0.061 to 0.54 (mmol L-1), with an average of 0.28 (mmol L-1), Kav values ranged from 55 to 699 (mg kg-1), 265 mg Kg-1 on average, and Kex values ranged from 54 to 694 (mg Kg-1) with an average of 261 (mg kg-1). Furthermore, Knex values varied from 160 to 612 (mg kg-1), 261 (mg kg-1) on average. Available K (NH4OAc- extraction) was less than 250 mg Kg-1 in half of the soils indicating the depletion of potassium from these soils. The Q/I curves were predominantly located in the adsorption regions. The Q/I curves were linear and lacked the curvature part relating to loss and gain of potassium present in the specific sites. The PBCK values varied from 11 to 108 (cmolc kg-1)/ (mol L-1) 0.5 and an average of 38 (cmolc kg-1)/(mol L-1)0.5. There was a linear significant relationship between PBCK and CEC (r2=0.82***). The AReK values ranged from 0.0014 to 0.027 (mol L-1) 0.5 and 0.0076 (mol L-1)0.5 on average. There was a significant relationship between the values of AReK and those of the soil solution K (r=0.68**). The Ko values varied from 0.0050 to 0.49 cmolc kg-1and an average of 0.21cmolc kg-1. Additionally, there was a high significant relationship between the values of Ko and ARoK (r= 0.95***) in the soils under study.

Sewage sludge application on farmland as fertilizer is commonly practiced in many countries. Sewage sludge is rich in macro and micronutrients. However, high concentration of heavy metals in sludge may cause pollution of soil, groundwater and human food chain because of toxic metals uptake by crops. The objective of this study was to determine residual and cumulative effects of sewage sludge on concentration of Zn and Cu in soil and wheat. Different levels of 0, 25, 50 and 100 Mg ha-1 of sewage sludge were applied to the soil for four years. To study the cumulative and residual effects of the sewage sludge, applications were repeated on three fourth of each plot in the second year, on one half of plots in the third year and on one fourth of plots in the fourth year. Wheat was grown in the plots. After the fourth year, soil samples from the 0-20 cm depth of the different parts of the plots were taken and analyzed. After harvesting the wheat, roots, stems and grains were separately analyzed for the heavy metal concentrations. Cumulative sewage sludge application significantly (P≤0.05) increased the total and DTPA-extractable concentration of Zn and Cu in soil. Residual sewage sludge in the soil also increased the total and DTPA-extractable concentration of Zn and Cu. Single sludge applications at different rates increased the DTPA-extractable concentrations of heavy metals. In subsequent years with no further sludge application, DTPA–extractable metal concentrations in soil decreased continuously, approaching the levels in the control. However, even after four years, DTPA-extractable concentration of Zn in plots receiving more than 50 Mg ha-1 and Cu in plots receiving more than 25 Mg ha-1 sludge, were still significantly higher than control. DTPA-extractable concentrations of metals were closely correlated with total concentrations. Sewage sludge had a significant effect on concentration of Zn and Cu in stems and grains. Cumulative effects on Zn and Cu uptake by stems were more than residual effects. The results of this study show that cumulative and residual effects of sewage sludge application increased concentrations of micronutrients in soil and wheat.

Iron deficiency is a worldwide nutritional constraint in agricultural lands especially in calcareous soils. Cultivation of crops tolerant to Fe-deficiency is an approach to combat Fe deficiency. The aim of this investigation was to evaluate Fe-efficiency of selected important crops in Iran. A completely randomized block design in triplicates was conducted at IUT research greenhouse in fall 2006. Sweet corn (Hybrid K.S.C. 404), grain corn (Hybrid S.C. 500), safflower (cvs. S3110, S-411), sunflower (Hybrid Hyson) and durum wheat (cv. Shuga) were grown in a nutrient solution at two Fe levels (1 and 10 µM Fe-EDTA). The results showed significant (P < 0.01) variation among the studied crops in Fe-efficiency. Corn hybrids were more sensitive to Fe deficiency (FeE = 26%) as compared to other studied crops, and the greatest reduction was observed in their shoot dry matter at 0.1 mM Fe- EDTA treatment. In contrast, the lowest decrease in root and shoot dry matter weight under Fe-deficient condition was found for durum wheat (FeE=94%). Comparing the calculated Fe-efficiency using different indices showed that Fe concentration and content in the whole plant, shoot and root had no relationship with crop tolerance to Fe deficiency.

Many researchers have reported positive effects of converter sludge and slag, two by-products in Isfahan iron melting factory. In this work, the optimum rate of application and the availability of some essential elements (for plant growth) in the converter sludge and slag for corn were investigated. The converter sludge contains about 64% Fe ІІ and ІІІ oxides and some other essential elements for plant growth. The slag also contains 17% iron oxides, 52.8% calcium oxide as well as considerable amounts of some other elements. Treatments included a control, Fe-EDTA foliar spray with 5 in 1000 concentration, application of sludge in 4 levels (L1, L2, L3 and L4 equal to 5.83, 13.33, 20.83 and 26.67 ton/ha, respectively) and application of slag in 4 levels (S1, S2, S3 and S4 equal to 3.20, 7.28, 11.36 and 15.44 ton/ha, respectively) which supply 1, 2, 3 and 4 times as much as soil test recommends, based on AB-DTPA extractable Fe in the soil. Corn (Zea mays) single cross 704 was planted for the experiment. Applications of the two compounds increased the soil extractable Fe and Mn, decreased Mg but the treatment did not change the soil-extractable Zn, Cu and Ca. The corn yield also increased due to the applications of the two compounds and the maximum yield was related to L3, L4, S3 and S4 treatments. The foliar application treated the leaf chlorosis and increased the silage, grain and leaf + stalk yields however, this was not as efficient as sludge and slag application. Also applications of the two compounds increased the Fe, Mn, Zn, Cu, Ca and Mg uptake by corn. The L3 and S3 treatments can be recommended as the proper levels of these compounds as iron fertilizer.

Salinization and alkalization are considered spatiotemporal dynamic soil degradation processes. In order to investigate the effects of agricultural activities on land degradation and soil salinity, Shamsabad area in Qom province was selected. Aerial photos (1955) and satellite images (1990-2002) were used to examine the changes in land use. Soil samples were collected from 25 locations in the study area from 0-50 cm and 51-100 cm depth at each location. For comparative purposes, sampling locations in this study were similar to locations used for salinity study in 1983. For each sample, pH, electrical conductivity (ECe), base saturation percentage, exchangeable sodium, lime and texture were measured. Land use and salinity maps were created by using geographic information system (GIS) softwares. Results revealed an increase of 9.5 times in cultivated lands in 47 years. Increase in agricultural activities in the study area has also intensified the pressure on water resource in the area, lowering ground water tables and degrading water quality. In the 0-50 cm soil depth, the average soil ECe was 6.5 dS/m in 1983, which increased to 10.7 dS/m in 2005. If soil salinity trend and pressure on water resources continue, large part of Shamsabad area is expected to change to desert in near future years.

Organic fertilizers are the sources of many human-pathogenic microorganisms which potentially threaten the human health. This study was carried out to explore the possible effects of soil and manure types on filtration, transport and fate of manure-borne bacteria through undisturbed soil columns. The manure treatments consisted of cow manure, poultry manure and sewage sludge which were distributed at the rate of 10 Mg ha-1 on the surfaces of intact columns of two sandy clay loam and loamy sand soils. The manure-treated soil columns were leached by tap water with similar unsaturated flux of 4.8 cm h-1 up to four pore volumes (PV). The influent and leachate were sampled at different PVs. Gram-negative bacteria concentrations were determined for the influent and the columns’ leachate. Average influent concentration, average effluent concentration, relative filtration, and transported bacteria fraction during the leaching events were determined. Significant differences (P<0.05) were observed between the poultry manure and the other two manures in terms of average influent (i.e. manure-released) bacteria concentration. Stable structure and preferential pathways facilitated the bacteria movement in the sandy clay loam soil columns. The loamy sand soil strained 1.45 times more bacteria than the sandy clay loam soil due to its weak structure and blocked-dead pores. Relative contamination of the effluent was higher for poultry manure when compared with the other fertilizers. The low ionic strength of sewage sludge suspension caused the lower filtration of bacteria through the soil columns. The high concentration of soluble organics in cow manure resulted in a relative transport of the bacteria 1.12 times greater than the poultry manure. In general, management of organic fertilizers especially household poultry manure, as a considerable source of pathogenic bacteria, is important to control the environmental risks of pathogenic pollutions. Moreover, the soil texture and structure significantly affected the fate of manure-borne bacteria.

Organic matter (OM) and total N (N) are relatively low in majority of the calcareous soils in Iran, and continuous use of N fertilizer would impair the quality of surface and ground water and creates other environmental hazards. Therefore, the combined use of N fertilizer and organic wastes is important to partly supply plant N requirement, improve physico-chemical properties of soil and conservation of environment. The present study was initiated in order to study the effect of two organic wastes with and /or without N enrichment on the growth and chemical composition of paddy rice and some characteristics of the soil in pot experiment. The experiment was carried out in factorial manner in a completely randomized design with three replications. Treatments were two organic matter sources (municipal solid waste compost and cow manure), four OM rates (0, 1, 2, and 4%) and three N levels (0, 75, 150 mg kg-1 soil as urea). Application of compost and cow manure increased top dry weight of rice. The highest growth of rice was obtained with 4% compost and 150 mg kg-1 N. Rice growth increased up to 2 % cow manure and was suppressed with the higher rate, due to build up of soluble salt in soil. Enhancing effect of N on rice growth was only observed with 1% cow manure and at high level of cow manure rice growth was decreased probably due to rise in soil salinity or ammonium toxicity. The mean concentration of N increased by the addition of cow manure, whereas decreased with compost application. Soil N application enhanced the mean concentration of N, and iron (Fe) and magnesium (Mn). Rice plants enriched with either of the two organic wastes accumulated more phosphorus (P), potassium (K), N, Fe, Mn, chloride (Cl) and sodium (Na) than control plants. Post harvest soil sampling indicated that organic matter significantly improved all chemical characteristics. Furthermore, soil treated with cow manure had higher soluble salt (ECe), Cl, K, OM, total nitrogen, available P, Fe and Mn and lower Zn, Cu, lead (Pb), cadmium (Cd) and sodium adsorption ratio.

Modeling plant response to salinity and nitrogen deficiency is very important for estimating optimum yield in arid and semi-arid regions. For this purpose, the models of Leibig-Sprengel (LS) and Mitscherlich-Baule (MB) originally proposed to explain plant response to nutrients only were modified to evaluate plant yield response to combined nitrogen and salinity stress conditions. Afterwards, in order to model canola (Brassica napus L.) response to combined salinity and nitrogen stress, an experiment was designed with different nitrogen and salinity levels. The water salinity treatments consisted of non-saline water, 3, 6, 9 and 12 dS m-1. The nitrogen treatments were 0, 75, 150 and 300 mg kg soil-1 added as ammonium nitrate. The results indicated that both modified models can satisfactorily predict canola yield. However, the modified MB model (R2=0.94) provided better estimation than the modified LS model (R2=0.87). The calculated statistics including Maximum Error, Root Mean Square Error, Modeling Efficiency, Coefficient of Determination and Coefficient of Residual Mass for the modified models indicated that the estimated relative grain yield for soil nitrogen, salinity and each rate of soil nitrogen in salinity levels by modified MB model compared with those by modified LS model is closer to the measured relative yield. Therefore, the use of modified MB model for estimating canola relative grain yield in salinity and nitrogen stresses is recommended. Using modified LS model showed that the salinity threshold value changes with the applied nitrogen. In this case, by application of each 75 mgN kg-1 soil, the salinity threshold value decreased 4 dS m-1 in saline conditions. Application of nitrogen decreased chloride concentration in grains under saline conditions. Nitrogen uptake also augmented with increasing canola transpiration, because nitrogen was carried over from soil to the uptake sites mainly by mass flow.

At present, soil surface characteristics (SSC) are recognised as key parameters controlling infiltration rates, runoff generation and erosion. Microtopography of surface among SSC is the main one. The work presented in this paper is based on a set of digital elevation models (DEMs) supplied by two different methods Laser roughness-meter and photogrammetry method. We used two maquettes. The used maquettes correspond to varying roughness (rough and soft roughness). These methods were compared using different statistical parameters of SSC such as heights and slopes histograms. In addition, we studied estimation of Random Roughness (RR) coefficient and Maximum Depression Storage (MDS). RR is considered as an indicator of microtopography and it is one of the main parameters influencing erosion and runoff-infiltration processes. The obtained RR by photogrammetry method showed, on average, 10 percent difference from laser method for soft maquette and 5 percent for the rough maquette. The range of this difference for the MDS varies from 2 to 34 percent, i.e., maximum 0.17 millimetres. In this study, photogrammetric method gives the DEMs with a lower slope for the rough maquette (on average 40.5 versus 46 for the laser method) and higher slope for the soft maquette (about 23.5 versus 20.7 for the laser method). The results showed the DEMs provided by photogrammetric method is able to perform accurate estimation for RR and provides good estimation for the MDS. Therefore, it can be useful in erosion and hydraulic studies.

Crop yield, soil properties and erosion are strongly affected by terrain parameters. Therefore, knowledge about the effects of terrain parameters on strategic crops such as wheat production will help us with sustainable management of landscape. This study was conducted in 900ha, of Ardal district, Charmahal and Bakhtiari Province to develop regression models on wheat yield components vs. terrain parameters. Wheat yield and its components were measured in 100 points. Points were distributed randomly in stratified geomorphic surfaces. Yield components were measured by harvesting of 1 m2 plots. Terrain parameters were calculated by a 3×3 m spacing from digital elevation model. The result of descriptive statistics showed that all variables followed a normal distribution. The highest and lowest coefficient of variance (CV) was related to grain yield (0.36) and thousand seeds weight (0.13), respectively. Multiple regression models were established between yield components and terrain parameters attributes. The predictive models were validated using validation data set (20% of all data). The regression analysis revealed that wetness index and curvature were the most important attributes which explained about 45-78% of total yield components variability within the study area. The overall results indicated that topographic attributes may control a significant variability of rain-fed wheat yield. The result of validation analysis confirmed the above-stated conclusion with low RMSE and ME measures.

Magnetic susceptibility (χ) measurements are widely used for the evaluation of soil profile development. Fourteen soil profiles were studied in a relatively wide range of climatic conditions in Fars Province. Citrate-bicarbonate-dithionite (CBD) extraction and micro CT-Scan images were used to evaluate the source of magnetic susceptibility. The results showed that soil samples lost 23 to 91 percent of their magnetic susceptibility after CBD extraction (χCBD), reflecting differences in the source (pedogenic or lithogenic) of magnetic susceptibility. Greater values of the decrease were noticed mostly in well developed soil profiles as well as in soil surface. 22 to 89% of the decrease was observed in frequency dependence of magnetic susceptibility (χfd) after CBD extraction. A significant positive correlation (P<0.01) was obtained between χCBD and χfd in the soil studied. Micro CT-Scan images with a spatial resolution of 33 µm showed lithogenic magnetic Fe oxide (magnetite) grains.

Organic manures can affect phosphorus (P) sorption characteristics (PSC) and its availability in soils. Information about effect of sewage sludge (SL) on PSC in calcareous soils of Hamadan province is limited. The objective of this research was to study the effect of SL on PSC and available P in 10 calcareous soils. The soil samples were incubated with and without 1.5 % SL for 5 months at field capacity at 25 ±1 סC . After incubation, available P was determined by Olsen method. Furthermore, 2.5 g samples were shaken with 25 mL 0.01 M CaCl2 containing 0 to 30 mg P L-1 as KH2PO4. After equilibration, suspensions were centrifuged and P concentration was determined in clear extracts. The results showed that SL application increased available P. The mean available P value increased by 37.6 %. Available P in untreated and SL-treated soils ranged from 8.1 to 22.1 and 14.8 to 28.0 mg kg-1, respectively. Sorption data in the all samples were well described by Freundlich and linear isotherm, whereas sorption data in all SL-treated soils did not adequately fit to the Langmuir isotherm. The constants of sorption isotherms were lowered by SL application. The mean sorption maxima, binding energy and maximum buffering capacity values decreased by 38.85, 21.34 and 38.90 % respectively. The mean distribution coefficient, Freundlich n and the mean buffering capacity (slope of linear model) values decreased by 21.7, 16.0 and 6.1 %, respectively. The results of this study showed that application of SL decreases standard phosphorus requirement. Moreover PSC results indicated that use of sewage sludge might increase the risk of P transfer to surface water.

Compost and sewage sludge contain high concentration of plant nutrients and, thus, have been used extensively as an inexpensive fertilizer. The objective of this study was to evaluate cumulative and residual effects of compost, sewage sludge and cow manure on nitrogen, phosphorus and potassium in soil and wheat. The experiment included compost, sewage sludge and cow manure, each applied at 3 rates (25, 50 and 100 Mg ha-1), a chemical fertilizer (250 kg ha-1 amonium phosphate + urea) and a control plot with 3 replications. The experimental design consisted in completely randomized blocks with treatments arranged in split plots. To study the cumulative and residual effects of the organic amendments, application was repeated on four fifths of each plot in the second year. Wheat was grown in the plots. The results showed that one application (residual effect) of organic amendments had not significant effect on total N in soil and wheat leaves and stem, but it led to significant increase of available phosphorus and potassium in soil and wheat leaves and stem. Cumulative effects of organic amendments significantly (P≤ 0.05) increased the total N (in 50 and 100 Mg ha-1 Cow manure and 100 Mg ha-1 Compost treatments), available P in all organic treatments and K (in all Compost and Cow manure treatments) in soil. Also, cumulative effects of organic amendments significantly (P≤ 0.05) increased the N (in 100 Mg ha-1 sewage sludge), P (in 100 Mg ha-1 compost) and K (in all organic treatments with the exception of 25 Mg ha-1 Compost) concentrations in leaves and stem.

In this study, the flow characteristics have been investigated by measuring separation zone, surface and velocity profiles over the circular crested side weirs. An equation was proposed for the length of the separation zone using dimensional, statistical and regression analysis. The dimensional analysis showed that the length of separation zone depends on the upstream to the downstream water depth over the side weir, channel width to the downstream water depth and the Froude number. Comparison of the longitudinal and sectional surface profiles showed that the surface profiles at the vicinity of the side weir are non-uniform, due to separation zone close to the side weir. Therefore, the suitable place for measuring the characteristics of flow is along the centre line of the channel. It was observed that the maximum velocity occurred below the surface water which might be due to the secondary flow around the side weir. By increasing the distance far enough from the side weir, the effects of secondary flow were minimized and the velocity profiles tended to be uniform.