نشریه پژوهش های حفاظت آب و خاک
سال نوزدهم شماره 2 (تابستان 1391)

Using direct measurement techniques for estimation of soil hydrological parameters, are time consuming and expensive. One possible solution to this problem is to derive a mathematical relationship between easily measurable soil parameters, such as soil texture, bulk density and organic matter content, and other hard-measurable soil hydraulic parameters. Such a relationship is called pedotransfer function (PTF). In this study, we used 8 point PTFs and 4 parametric PTFs for predicting water content corresponding to different matric potentials for 122 soil samples taken from north and north-east of Iran. Parametric PTFs has been derived to estimate the coefficients of four different water retention functions of van Genuchten, Hutson and Cass, Campbell, and Brooks-Corey. BSS TOPSOIL method (Hutson and Wagenet, 1992; with input variables of soil fractions, Organic Carbon content, and bulk density) with correlation coefficient (r) of 0.75 and root mean square error (RMSE) of 0.033 was the best and Hutson method (Hutson and Wagenet, 1992; with input variables of soil fractions, and bulk density) with R=0.59 and RMSE=0.061 was the worst method in Point PTFs. The best (r=0.90, RMSE=0.037) parametric PTF was due to Campbell (Campbell, 1085) and the worst (r=0.52, RMSE=0.12) one was due to Vereecken (Vereecken et al., 1989). The results showed that including Organic Carbon content as an input variable in PTFs, improves the predictability of soil water content. On overal, the performance of all PTFs increased when the matric potential increased.

Potassium as an essential plant nutrient plays important physiological roles in plants. Q/I relationships present beneficial information for assessment of plant potassium availability and fertilizer application management. The K quantity-intensity relationships and their parameters; labile K, slowly exchangeable K, potassium activity ratio, potassium activity ratio at equilibrium and potassium buffering capacity were compared using four treatments (potassium chloride, potassium chloride + ammonium chloride, potassium chloride + sodium mono phosphate and potassium chloride + ammonium chloride + sodium mono phosphate) on three soils with different specific surfaces. Soil samples obtained from 0-30 cm top-soils of Rahmat Abad soil series (Gorgan University-Pardis), Lavark (Isfahan) and Salehan village (Khomein). The maximum soil PBCk obtained for Gorgan Uneversity (Pardis). Clay type and soil cation exchange capacity control PBCk and its parameters in these soils. Maximum PBCk was obtained by potassium chloride and minimum by potassium chloride + Ammonium chloride in all soils. The PBCk for potassium chloride + sodium mono phosphate was greater than potassium chloride + ammonium chloride + sodium mono phosphate. Increased sodium salt concentration in solution may increase sodium salt concentration in diffuse double layer and hence PBCk. Since the bulk of water and nutrients are held in truncated diffuse double layers with soils of high specific surface area at field conditions, solution potassium concentration and ARKe may more closely estimate plant available potassium relative to PBCk; also suggesting ARKe as a more relevant index when comparing potassium availability for soils of widely differing specific surface area.

In this study, classical statistics and geostatistical methods were used to determine changes in spatial heterogeneity of soil organic carbon (SOC) in relation to topography and different slope positions in loess hillslopes in Toshan region located in Golestan Province. In this investigation, three different geostatistical methods i.e Kriging, Cokriging and Inverse distance weighted have been used and evaluated. Hence, 234 soil samples at regular grid were collected from different parts of a slope. In this research, the evaluation criteria were Mean Error and Root Mean Square Error with the Cross Validation method. The results showed that ordinary cokriging method with clay as covariate estimated better results in evaluation of SOC in whole parts of hillslope with RMSE values of 0.2552 in comparison with Kriging and Inverse distance weighted methods. Interpolation map of organic carbon from whole part of hillslope showed lower SOC concentrations with increasing elevation and slope gradient. Spatial correlation ratio of SOC was different in various slope positions and these patterns were closely related to the structure of topography.

Lateral profile of flow velocity in rivers is the base of stage-discharge rating curve development and also flow and sediment transport calculations. Regarding to high difficulties in measurement of lateral distribution of velocity in natural rivers, especially in time of floods, using the suitable numerical methods is essential. On the other hand, by entering the flood flow into floodplains, flow interaction induced at the main channel-floodplains interface and causes high complexity in flow hydrodynamics. In this research, using finite element method, velocity lateral profiles have been predicted by solving quasi 2-D differential equations of flow in compound channels. Proposed model is based on the depth-averaged Navier-Stocks equation. For evaluation of accuracy, this model has been calibrated and then validated in Minab River at Berentine hydrometric station, in Hormozegan province, based on measured data obtained during 3 flood events. Comparison of measured and predicted profiles of lateral velocity in two phases of calibration and validation shows acceptable accuracy of the proposed mathematical model. Statistical analysis of numerical results shows that the determination coefficients for calibration and validation phases are 0.97 and 0.96, respectively. Also, the root mean square error of these phases are 0.13 and 0.23, respectively. Finally the stage-discharge curve of this river has been predicted with good accuracy.

In this paper by using fuzzy logic and c-mean clustering, different combinations of daily climatic variables including air temperature, relative humidity, wind speed and sunshine hours as input data for predicting pan evaporation were investigated. Therefore, meteorological parameters in years of 1386 and 87 at three synoptic stations (Ahvaz, Abadan and Izeh) in Khuzestan province were used. The results showed that the Takagi-Sugeno fuzzy model and c-mean clustering were able to predict pan evaporation, so that fuzzy models with cluster number of 2 and 3 estimated pan evaporation parameter by correlation coefficients varying from 0.86 to 0.91.

In order to investigate the effect of compost, vermicompost and sewage sludge application on some of the soil physical properties, an experiment was carried out in split plot based on complete randomized block design in three replications in the field of the University of Agricultural Sciences and Natural Resources of Sari. Seven levels of fertilizer treatments (T1=control, T2=compost 20 tons per hectare, T3=compost 40 tons per hectare, T4=vermicompost 20 tons per hectare, T5=vermicompost 40 tons per hectare, T6=sewage sludge 20 tons per hectare, T7=sewage sludge 40 tons per hectare) and four levels of fertilizer years, one year fertilizer (1385), two consecutive years fertilizer (1385 and 1386), three consecutive years fertilizer (1385, 1386 and 1387) and four consecutive years fertilizer (1385, 1386, 1387 and 1388), respectively. Physical properties in this study were as, bulk density, particle density, total porosity, water holding capacity, field capacity, permanent wilting poit and available water capacity in soil. The results of the study showed that the application of compost, vermicompost and sewage sludge in soil were significantly effective in increasing the total porosity, water holding capacity, field capacity, permanent wilting point, available water capacity and in decreasing the bulk density and particle density compared to control. Where as, years of consumption of fertilizer did not have a significant effect on the physical properties of the soil except on the amount of FC, PWP and AWC. The interaction between years of consumption of fertilizers were significantly different only in particle density and field capacity.

Wastewater can be used effectively in irrigation to provide some portion of the water required for agriculture purposes. But for using of the wastewater, the accurate monitoring on their quality should be done. In order to know the quality and suitability of waste water of coal cleaning factory of Vatani for irrigation purpose, the sampling from wastewater ponds and groundwater have been done during winter 2009. According to the hydrochemistry facies of Piper diagram, the wastewater and groundwater types in the studied area belongs to Ca-SO4 type and Ca-HCO3 type respectively. Sodium absorption ratio (SAR) (class S1), sodium percent (%Na), magnesium hazards and chloride potential are less than 10%, 60%, 50% and 20% respectively. The residual sodium carbonate (RSC) (1.25 meq/l) and kelly's ratio (1) for all the studied samples. Indicate that they meet acceptable quality for agricultural purposes. Wastewater studies are based on U.S. Laboratory's Salinity diagram, is in the range C3S1 in respect to ground water (C2S1) and shows high salinity. Wastewater studied samples on the Wilcox’s diagram lies in the area of permissible waters for irrigation. The Gibb's model shows that anions and cations of all the type of waters are of lithological origin. The positive chloroalkaline index of waters indicates that base-exchange reaction occurred between Na+ and K+ of the groundwater with Ca2+and Mg2+ of coal and coal tailings. The permeability index (PI) of all samples are permissible for irrigation.

Bioavailability, toxicity, and mobility of potentially toxic element (PTEs) in soils depend on their partition between solution and solid-phase and their further redistribution among solid-phase components. The wetting-drying consequence cycle is one of the most important factors in controlling the behavior and fate of PTEs in contaminated soils. The aim of this study was to assess the distribution of different applications of lead (Pb) in three soils, with different calcium carbonate contents, after incubation under a wetting-drying (WD) soil moisture regime using sequential extraction procedure. To quantify the binding intensity and to assess the mobility and availability of applied Pb, the reduced partition index (IR) and the percentage or absolute concentration of Pb in soluble + exchangeable fractions were used, respectively. This trail was conducted as a factorial experiment based on randomized complete block design with three factors, soil (in 3 levels), Pb concentration (in 4 levels) and drying-wetting cycles (in 5 levels) in three replications. Results showed that, the binding intensity of Pb significantly increased by WD, however, decreased as the Pb application quantities to soils increased. However, in different soils, no significant differences were recorded. Although, the first WD cycle significantly decreased the soluble + exchangeable fraction of Pb, the further WD cycles had no significant effect. However, mobility and availability, and consequently the potential environmental risks of Pb, increased by increasing Pb applications to soils.

Soil properties are influencing the amount and bioavailability of heavy metals in soil. Therefore, determining soil characteristics affecting cadmium (Cd) solubility and its uptake by plants are of great importance. The objective of this study was to evaluate the relations between main soil properties and Cd concentrations in soil and wheat grains in 4000 km2 wheat farms. A number of 255 pair soil and grain coordinate samples were taken in an weighing sampling scheme. Some soil characteristics including pH. EC, CEC, organic carbon (OC), clay content, lime content (TNV), available P, soil Cd and grain Cd concentrations were measured. The results indicated that the average TNV in the studied soils was more than 46 percent. Average total and DTPA-extractable soil Cd and grain Cd concentrations were 1.47, 0.085, and 0.7 mg kg-1, respectively. In the studied calcareous soils, total Cd concentrations had significant correlation with TNV (P≤0.01), available P (P≤0.01), CEC (P≤0.05), and OC (P≤0.05). The DTPA-extractable Cd had significant correlation with OC (P≤0.01), pH, and clay content (P≤0.05). Significant correlations were also found between grain Cd concentrations with OC (P≤0.05), CEC (P≤0.01), and DTPA-extractable Cd (P≤0.05). However, the total Cd, soil pH and lime content (TNV) had no significant (P≤0.05) correlations with wheat grain Cd in the study area. However, the correlations between soil properties and two wheat cultivars (Bread and Durum) were different. A significant (P≤0.01) correlation was obtained between durum grain Cd and OC, CEC, and DTPA-extractable soils Cd. For bread Cd in grains, a significant (P≤0.01) correlation was found between more soil properties, including OC, CEC, and DTPA-extractable Cd, TNV and clay content. The Pearson coefficient values for durum wheat cultivar shows that, the OC, CEC and Cd-DTPA had more effects on durum wheat than bread wheat cultivar. It could be concluded that plant-availability of soil Cd as effected by soil properties and wheat cultivar

Study of soil erosion process and assessment of the control factors are the most important prerequisite for proper management of soil and water resources. This research was carried out to investigate effects of slope and soil properties on runoff and soil loss using rainfall simulator in Chehel-chai watershed, Golestan province. Also, considering the land unit map of the area, three land units were selected in the farm lands. In each land unit, three slope classes of 0-10%, 10-30% and highes than 30% were determined. Then four 10×10 m plots were selected in each slope class. Runoff and erosion were measured in each plot randomly using rainfall simulator with 2 mm/min intensity and 15 min duration in 4 replicates. Soil samples were taken in each plot as well. Results showed that there was a weak correlation between runoff and slope and there was no significant relationship at 0.05 confidence level but there was a significant and positive correlation between soil loss and slope at 0.01 confidence level. Based on the results of the Pearson correlation matrix, the contents of the fine sand in 1% confidence level and lime and silt at 5% confidence level had positive correlation with runoff and soil moisture content had positive correlation and soil surface resistance had negative correlation with soil loss. However, runoff volume and soil loss increased 8% and 100%, respectively in slope class of more than 30% in comparison with 0-10% slope class. With increasing slope, soil resistance decreased and soil loss increased.

Many approaches with different assumptions have been developed for designing compound channels and prediction of their stage-discharge curves. Most of these methods have satisfactory results in laboratory compound flumes but extending them to all hydraulic and geometric conditions such as natural rivers is very limited. In this study, using nearly 400 laboratory and field stage-discharge data sets of 30 compound channels with different geometric and hydraulic conditions, a new method has been presented for calculation of flow discharge in compound channels, based on Genetic Algorithm. This proposed stage-discharge relation with sufficient accuracy (R2=0.91, MSE=0.01) in comparison with divided channel method (R2=0.27, MSE=0.11) can be used for all types of compound channels (laboratory and field). Therefore, this approach is suitably applicable in flood control projects, river flood routing and design of conveyance canals.

As a fact, the soil properties are affected by geology, topography, climate and biology of areas. Therefore, soil properties are the important factors that influence plant distribution specially, in saline areas. To develop an efficient management it is necessary to have precise information on soil and vegetative cover relations in all areas. For this propose the relationship between soil physico-chemical properties and plant community characteristics in arid lands of Ghareh Tappeh, Saveh have been studied. The sample plots for data collection have been selected by random-systematic method. In this way ten number lines with five sample plots over all areas have been selected. The list of species, canopy cover, plant density, diversity and frequency of species were recorded. Also on each line soil sampling have been done in two depths; 0-30 cm. and 30-60 cm. Then soil texture, acidity, EC, PSW, OC, CaSO4, CaCO3 and SAR were determined in laboratory. Two plant communities have been recognized in the area; Salsola crasa and Salsola-Tamarix. The study showed that, the canopy cover and plant diversity were highly affected by soil properties. The amount of clay and EC were the most effective factors on plant characteristics.

In this study, experimental tests have been conducted in intake by feeding the sediments from the upstream of intake by a constant rate in three different flow depths and Froude numbers in the range of 0.2-0.45. During each test, three components of flow velocities were measured using ADV. The results showed that as Froude number increases, the ratio of sediment entry ratio to the discharge ratio () reaches to a minimum value at Froude number of 0.36. From analysis of velocity vectors and angle of stream line entering the intake, it was found that as Froude number and increase, the lateral velocity component and angle of entry stream line in lower layer that provides a large amount of sediment and the most important layer in sediment entry, increases as well.

The purpose of this study was to use a venturi injector in a linear irrigation system in order to investigate nitrate distribution uniformity compared with a traditional fertilization method. This study was conducted in a corn field with an area of 11.4 hectares under linear sprinkler irrigation system and a corn field with the area of 8 hectares under furrow irrigation system. A water tank and a venturi injector was installed on the linear irrigation system and the soluble fertilizer (urea 46% N) was applied to the system in the rate of 0.11 l/s by the fertigation method during seasonal growth. The urea fertilizer was implemented with the traditional method in the furrow irrigation. Results showed that the average fertilizer distribution uniformity coefficient on the soil surface was 92% in the linear irrigation method. The average nitrate distribution uniformity coefficient in soil profile at both the venturi injector and the traditional methods were 80 and 58% respectively. Moreover the fertilizer consumption use in the linear irrigation method was 67% less than furrow irrigation and the water use efficiency in the linear irrigation method was double compared to the furrow irrigation method.