Journal of Water and Soil Conservation
Year:2012 | Volume:19 | Issue:3|Papers Count:15

Whereas biological and engineering methods of soil conservation are complementary but pedoturbation by machinery in engineering practices are considered as one of the disadvantages of this method. To investigate the effect of terracing as engineering practices on soil quality attributes, four terracing sites with different aspects, slope, direction, elevation and ages were selected. Soil samples were taken from 0-30 cm depth. The results showed that terracing operation influenced soil physical, chemical and biologic quality indices and have to be considered in land use operation and management. Managers should analyze the effect of this operation on ecosystem health and find the relationships between social and economic aspects. The results of physical soil quality attributes showed that terracing reduced soil aggregate stability from 0.61 to 0.24 mm. Also this operation increased the soil pH from 7.32 to 7.64, EC from 0.347 to 0.808 ds/m, CaCo3 content from 8.96 to 38.69 percent, SP content from 45 to 49 percent, Total N content from 0.124 to 0.176, absorbable P from 1/64 to 5.38 and absorbable K from 71.45 to 159.29 mg/Kg and also reduced OM content from 2.73 to 1.27 percent and CEC from 85.6 to 66.7 cmol+/Kg. Soil respiration as a biological index were measured and based on results of this study, terracing reduced this biologic index. Physical, chemical and biologic soil quality indices were statistically different in four sites.

Water measurements play a pivotal role in the irrigation and drainage networks.Due to effective limitations of simple sharp crested weirs, compound sharp crested weirs have attracted the attention of scientists and civil engineers recently. With this kind of weirs, flow discharge is measured with a reasonable sensitivity over a wide flow range. In this paper, by assumption of flow similarity between compound sharp crested weirs and compound open channels, a new method based on numerical solution of a quasi-two-dimensional mathematical model has been proposed for discharge calculation of compound weir. The numerical results were compared with the experimental data of Jan et al. (2006) and the traditional method (theoretical equations of simple weirs). These comparisons revealed that the proposed method had nearly 1 percent error while the traditional method had more than 8 percent error.

Phytoavailability of copper (Cu) depends on the relative distribution of different chemical forms, which is a function of soil properties. To partition the total Cu into exchangeable (Ex), carbonates-bound (Car), organically bound (OM), Mn-oxidebound (Mnox), amorphous Fe-oxide-bound (AFeox), crystalline Fe-oxide-bound (CFeox) and residual (Res) forms a sequential extraction procedure was conducted in 10 soils of Golestan province that varied in physical and chemical properties.The results revealed that about 0.3, 0.4, 4.5, 1.3, 26, 30.3 and 37.2% of the total soil Cu was present in mentioned forms, respectively. Soil pH was significantly negatively correlated with Cu associated with Mnox and AFeox at 5 and 1% level, respectively. Organically bound Cu did not show significant correlations with any soil properties. Correlation coefficient between calcium carbonate equivalent and carbonate-bound Cu was not significant. DTPA erxtractable Cu was significantly positively correlated with clay content. The Cu concentration in plant was negatively correlated with Cu concentrations in the exchangeable (Ex), carbonatesbound (Car) and organically bound (OM) forms. A negative correlation was observed between total uptake of Cu in plant and Cu concentration in the exchangeable (Ex) form.

The applications of organic and inorganic amendments in saline soils may alleviate salinity effects on soil microbial activity and biochemical characteristics.In order to investigate the effects of different levels of saline irrigation waters, and organic and inorganic amendments on soil respiration, and acid and alkaline phosphatase activities in the rhizosphere soil during vegetative growth of soybean a factorial experiment consisting of five salinity levels (i.e. S1=0.8 S2=1.6 S3=3.2 S4= 4.8 and S5=6.4 dS/m from the sea water source) and five amendment treatments including T1 (control without amendments), T2 (20 ton gypsum ha-1), T3 (20 ton manure ha-1), T4 (10 ton gypsum+10 ton manure ha-1), T5 (15 ton gypsum+15 ton manure ha-1) arranged as randomized blocks design with three replications was conducted using pots under greenhouse conditions. The results showed that with increasing salinity level, soil respiration and enzyme activities of acid and alkaline phosphatases decreased significantly, however, the reductions were not similar and comparable among amendment treatments. Soil respiration and enzyme activities in treatments receiving higher amount of the combined organic and inorganic amendments were greater than other amendment treatments. Increasing the salinity levels in treatment without amendments application caused the reduction of soil enzymes activities and respiration. Whereas, application of manure and gypsum together, as organic and inorganic amendment increased the soil enzymes activities and respiration. Results indicated that the maximum soil respiration occurred in T5 treatments and the greatest soil enzyme activities occurred in T3 treatments relative to the other treatments.

Topography, as a soil-forming factor, influences soil physical characteristics through aspect and slope position. Soil particle size distribution (PSD) is one of the most important soil physical characteristics influencing other soil characteristics directly or indirectly. This study investigates the effect of aspect and slope position on soil particle size distribution, grain-size curves and soil fractal dimension in an area, 35 km distance from Chelgerd, Chaharmahal-va-Bakhtiari province. For this purpose, two slope aspects with the same parent material were selected. Three slope positions (top, middle and base) in seventeen parallel transect along north and south-facing aspects were sampled. Also representative pedons located on three positions of each aspect were classified. Particle size distribution was analyzed by a combination of the sieve and the hydrometer method. The grain-size distribution in all three positions of the north and south-facing aspects were fitted by unimodal and biomodal Fredlund models. The fractal dimension of soil particle size distribution was determined in different aspects and slope positions. Soils in the north-facing aspect are classified as Vertisols, whereas soils in south-facing aspect are classified as Entisols and Inceptisols. Results showed that although the dominant soil textural class in both aspects was the same, the soil particle size distribution in different positions of north-facing aspect and base position of southfacing aspect followed a sigmoidal curve and in top and middle position of south facing aspect followed two sigmoidal curves. Therefore, PSD in north-facing aspect was better described by Fredlund unimodal equation while PSD in top and middle positions of south-facing aspect was better described by Fredlund biomodal equation. Grain size distribution values generally remained similar in north-facing positions but were larger in top and middle south-facing positions. However, coefficient of curvature was independent of aspect and position. In the north-facing aspect, fractal dimension was significantly larger than that of the south-facing aspect and in the base slope position was significantly larger than that of the two other positions. It seems that in mountain area PSD and its shape, PSD-derived values and fractal dimension might better differentiate between the effects of soil forming processes, than some simple texture evaluation.

Local scouring around bridge piers had been considered as an undesirable event and against the bridge safety. In this process, the 3D flow patterns in the vicinity of bridge pier have important role and cause the bed material erosion around bridge pier. Embedment of the foundation in the depth deeper than the maximum local scour depth according to the design flood has been proposed as a conservative solution. However, implementation of the pier foundation in a deep depth from the original bed level is not an economic solution in practical cases. In real cases, the variant stream flow of floods is the main reason of bridge failures. In this study the evolution of local scour depth around circular bridge piers under unsteady flow condition of hydrographs has been numerically simulated using steady flows. The results showed that during the rising period of hydrograph, the scour depth increased steadily and more than 70% of final scour depth occurred at the rising limb of hydrograph. The results also show that by using the SSIIM program, it will be possible to evaluate the local scour depth in the end of rising limb of hydrograph with a satisfying accuracy.

In order to investigate the effects of municipal waste compost application individually and enriched with chemical fertilizers on the micronutrient concentration in soil and lettuce (Lactuca sativa L.) a three years experiment was conducted with randomized complete block design with two factors and three replications at the experimental farm of Sari Agricultural Sciences and Natural Resources University. The Main plot included 6 fertilizers treatments (control, chemical fertilizers, 20 and 40 ton.ha-1 of municipal waste compost individually and enriched with 50% chemical fertilizers). The Sub-plots were considered as one, two and three-years application of fertilizer. The results showed that the effect of different treatments on Zn and Cu Content of soil, root Fe, Zn and Mn concentration and shoot Zn, Cu and Mn concentration were significant. The results also showed that concentration of the microelement in soil and root and shoot of lettuce were affected significantly by one year, two years and three years application of fertilizers. Interaction of two factors had significant effect on avaiable Cu content of soil and Fe, Zn, Cu, Mn concentration of shoot. Municipal waste compost promoted a significant increase in Zn and Cu plant concentrations in relation to chemical fertilizers. These results imply that municipal waste compost could be a suitable source of Zn and Cu for agricultural soils.

In order to prepare the aquifer vulnerability map of Malayer plain which is the water resource of agricultural and industry activities as well as rural consumptive waters of the region, the DRASTIC, SINTACS and SI models were used for exploration of Malayer plain groundwater as following steps: first, by development of aquifer media, vadose zone media, water table, net recharge rate, soil media, hydraulic conductivity, topography and land use maps, the initial layers of the models were prepared. In the second step, the available nitrates layer of the groundwater was also prepared based on 32 measurements of wells during spring 2010. In order to evaluate the performance of the models, the correlation between the initial layers and available nitrates layer was calculated. Based on the calculated coefficient correlation and its significance, DRASTIC, SINTACS and SI models were calibrated and then theirs parameters were modified. Third, using overlap of the and correlated aquifer vulnerability maps, contamination danger map of plain which called agricultural DRASTIC map was produced. At last, by comparing the vulnerability potential map, modified SI map, modified DRASTIC model, agricultural DRASTIC model and neuro fuzzy inference map with the available nitrate layer, the best model was distinguished. The result illustrated that the agricultural DRASTIC method (r=0.81) is identified as the best method to evaluate the vulnerable points of Malayer plain. According to this map, 15.5, 71.66 and 12.84% of the area are located in the less, medium and high vulnerable points, respectively.

Since the measurement of soil moisture retention curve and its index points like field capacity and permanent wilting point are costly and time-consuming using direct methods, one of the quick and low costly estimation methods of these properties is estimating of those properties with respect to soil basic properties including particle size distribution and organic matter content as well as bulk density. In this study, index points of soil moisture retention curve such as field capacity, permanent wilting point and available water were estimated using MLP type neural network with three activate functions and regressions methodology with respect to soil basic properties. In order to conduct the aforementioned issue, 60 soil samples were collected from the case study, the region of Robatkarim of Karaj city, with an area of 24 ha. Then, the moisture content of the index points of soil moisture retention curve was measured by using the pressure plate. Further soil basic properties including the percentages of clay, sand, bulk density and organic matter as well as lime and the moisture content of the index points were measured using the aforementioned methodology. The results of the investigations showed that the artificial neural networks by sigmoid activate function a network with 6 neurons in the input layer and 10 neurons in the hidden layer as well as 3 neurons in the output layer with Performance indicators R2 and RMSE variations of 0.6197–0.8902 and 1.6846–2.0225, respectively was introduced as the efficient network which had the best performance in estimation of wanted outputs in comparison with another activate functions (method of artificial neural network) and regression method. Percentage of lime according to results of sensitivity analysis is considered as an effective factor in the range of soils texture tested.

Zinc deficiency through the reduction in auxin production and photosynthesis, reduces growth, yield components and grain yield of wheat. An experiment was conducted to determine the effect of zinc sulfate on yield, yield components, zinc and protein content of three winter wheat cultivars in Eghlid Agriculture Research during 2007– 2008. The experiment was in a splitplot layout within a randomized complete block design. The main plot consisted of three levels (0, 30 and 60 kgha-1) of zinc sulfate (36% Zn) and the sub-plots were Zarin, Alvand and Shahriar wheat cultivars. The result showed that increasing the Zinc sulfate levels caused meaningful increaseg in the number of fertile heads m-2 (FH), kernel per fertile head (KH), 1000-kernel weight (KW), grain yield (GY), total plant dry weight (TPDW) and harvest index (HI) and zinc and protein, but number of infertile tillers (IT) and infertile heads (IH) reduced. Zarin and Alvand cultivars produced significantly higher FH, KW, GY, HI, ZnC and PP and lower IT, and KH than Shahriar. Cultivars showed no differences in other properties based on the results In this study the highest growth, yield components and grain yield were 10040 and 10030 kg ha-1 by using the 60 kg ha-1 of zinc sulfate in alvand and zarin cultivars respectively. This rate of zinc sulfate application and Alvand and Zarin cultivars might be suitable for wheat production under conditions similar to this study.

Meandering has attracted the attention of scientists and engineers since a long time. In river bend, high variations of flow depth, velocity and shear stress across the river produce a spiral flow and hence, bank erosion in outer bank and sedimentation in inner bank. Such situation is very complicated in rivers with floodplains. In this condition, flood flow enters the floodplains and changes the direction of secondary flow because of momentum transfer between main channel and floodplains. In this paper, using a quasi-two dimensional mathematical model, the lateral distribution of velocity in overbank meandering rivers is simulated. This mathematical model combined with dimensionless relationships for secondary flow term is solved numerically in curvilinear system. The most important result of this research indicates that the maximum and minimum magnitudes of velocity are occurred in inner and outer banks, respectively, which is in the opposite sense with the flow structure at the inbank meandering channels. This finding agrees well with the experimental data in overbank meandering channels. Furthermore, the numerical results have higher accuracy compared with Ervine et. al. method. The mean relative error of proposed and Ervine et al. methods for predicting the main channel velocity are 6 and 10 percents, respectively.

The aim of this study was to assess of land use change effects on soil aggregates stability in marginal lands of Zrebar Lake. Soil samples were collected from the five major land use types including wetland, wetland converted to alfalfa and wheat cultivations, forest and forest converted to vineyard, from the 0-30 and 30- 60 cm depth in each of land use. Soil aggregate stability was measured on soil samples. The amount of large water stable aggregates in 0-30 cm depth of wetland and forest soils was significantly more than cultivated and vineyard soils. The highest amount of mean weight diameter (MWD) was observed in wetland and forest. Conversation of forest to vineyard caused to 20% decrease in soil large macroaggregate amount, whereas amount of soil microaggregate was increased by 11%. Wetland soils converted to alfalfa resulted in 31% decrease of aggregate larger than 2 mm and 15% enrichment of microaggregate in depth of 0-30 cm.Land use change from wetland to wheat cultivation has caused to reduce of large macroaggregate by 23% and 16% increase of microaggregate.

The evapotranspiration (ET) is the one of the most important component of hydrological cycle. Nowadays many researchers presented the valuable relations involving climatic parameters for estimating the potential evapotranspiration of reference plant (ETo), prevent from water stress and water loss. Among them the Hargreaves-Samani (H-S) method is common in the regionS that the measuring of meteorological parameters are limited. This study aims to determine the most accurate correction factor for H-S method to estimate ETo according to the FAOPenman- Monteith (F-P-M) method in Gorgan synoptic station. This coefficient is related to climatic parameters which are available in climatology stations. At first equations were optimized using all parameters in excels environment, then some less effective parameters were omitted and again more equations optimized using the others. For verification of results, the meteorological data were divided to 2 groups namely 80 and 20 percent for calibrating and testing the model respectively.The results showed that the equation which included the maximum and average of daily temperature and max, min and average of relative humidity (RH) data, had the maximum ranking due to statistical investigation (R=0.93, RMSE=0.29). Using the mentioned equation the mean annual evapotranspiration of 1165mm (using H-S method) reduced to 925mm. Moreover there was lower error compared to the F-PM- method which estimated 853 mm of wapo=transpiration.

To solve the problem of water shortages, low-quality waters such as waste water can be used. The present study was accomplished as a completely random block design with 3 water quality levels (6, 8 and 10 ds/m), 3 soil depths levels (0- 15, 15-30 and 30-45cm) and 3 irrigation season (1, 2, 4 months). The soil texture was sandy loam. After 1, 2 and 4 months of irrigation, the hydraulic characteristics of the soils such as saturated hydraulic conductivity, effective porosity and specific water retention of the soils at 0-15cm, 15-30cm and 30-45cm depths were measured. Results indicated that with increasing irrigation water salinity, saturated hydraulic conductivity, effective porosity and specific water retention of soils increased logarithmically. However, with increasing water salinity, the specific water retention increased but was not significant. Also the results of the study showed that with increasing irrigation duration from 2 to 4 months, hydraulic characteristics of the soils increased.