farshad kiani; Behroz Behtari nejad; Ali Najafi nejad; Abdolreza Kaboli4
Abstract
Introduction: population growth, urbanization and land use changes cause negative effects in natural ecosystems and water resources. Soil erosion is one of the most important problems in agriculture and natural resources of Golestan province. Using low cost and accurate methods for planning and proper ...
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Introduction: population growth, urbanization and land use changes cause negative effects in natural ecosystems and water resources. Soil erosion is one of the most important problems in agriculture and natural resources of Golestan province. Using low cost and accurate methods for planning and proper management of land and water resources are essential for estimating consequences of soil erosion and providing appropriate solutions to reduce soil losses.
Materials and Methods: The study area is located in eastern part of Golestan province with an area of 1524 square Kilometers. The average annual precipitation of the region is 496 millimeters. In this watershed, rainfall decreases from south and south west to north and north east (due to the remoteness from the Caspian Sea), while evapotranspiration, temperature and the number of dry months increase in the same direction. Also the average annual temperature of the watershed and its relative humidity and evaporation are 17.8°C, 68.5 % and 1398.34 millimeters, respectively. Tamer watershed was divided into 15 sub-watersheds by adding an outlet in the site of Tamar gauging station. In this study, the SWAT model was used to simulate erosion and sedimentation. To compare the measured and simulated data and evaluation of the SWAT performance in terms of simulating flow and sediments, daily flow (cubic meters per second) and sediment (tons per day) data at the Tamar gauging station located in Tamar’s watershed outlet was collected from the studies of water resources organization (Tamab). Simulated values were generally consistent with the data observed during calibration and validation period. At this stage of calibration, the SUFI-2 model was used to optimize the parameter values. In this study, daily rainfall and temperature data recorded during an 8-year period by the stations within the watershed were imported into the model. The daily discharge data and daily sediment data of Tamar station recorded during 1999- 2006 were selected. Then model was run using runoff and sediment parameters, and ranges of parameters were adjusted at each iterations, and therefore SWAT model was calibrated using SUFI-2 model. After calibration, model must be validated and its ability to predict future events must be determined. Validation was performed using the runoff and sediment data recorded in Tamar gauging station from 2007 to 2010.
Results and Discussion: NS, R2, R-factor and P-factor were estimated for runoff calibration about 0.76, 0.77, 0.06 and 69 and for runoff evaluation 0.72, 0.75, 0.05 and 69 respectively. The same parameters were also measured for sediment calibration about 0.54, 0.62, 0.15, and 16 and sediment evaluation 0.55, 0.61, 0.35, and 12 respectively. The results showed that irrigated agriculture 24.95 and 15.56 t ha -1y-1 respectively, with average erosion and sediment ha of agriculture by an average of 20.23 and 12.33 t ha -1y-1 respectively erosion and sediment erosion and deposition are tons per hectare maximum value. Results also showed that the soil loss caused by erosion in this watershed is average 6.49 t ha -1y-1 in sediment and 10.28 t ha -1y-1 in erosion.
Conclusion: The assessment factors showed that model has successfully simulated the daily runoff discharge during calibration and validation phases with a Nash-Sutcliffe coefficient of 0.76 and 0.72. A Nash-Sutcliffe coefficient above 0.5 could be acceptable for sediment simulation. However, sediment load simulated for rainy seasons has been lower than actual value while this value has been higher than actual value during dry seasons. In most months of the year, model results are higher than measured values and this issue is more pronounced in the peak runoffs. This issue is due to limitations in spatial distribution of rainfall, so when a small area in watershed experience a severe rainfall, model considers the impact for the entire watershed and therefore overestimates the total runoff. The results showed that SWAT model can be a useful tool for the simulation of flow and sediment basins in the loess land.
Simulation results showed that land use changes have resulted in corresponding increases in surface runoff and sediment. Rates were highly variable both spatially and temporally, and the agricultural lands were most significantly affected. These land use changes have negative implications for the ecological health of the river system as and local communities.
Sona Azarneshan; farhad khormali; fereydoon sarmadian; farshad kiani; kamran Eftekhari
Abstract
Introduction: Assessing the soil quality of agricultural land is essential for the economic success and sustainability of the environment in developing countries. Recently, there are many types of methods for assessing soil quality, each of them uses different criteria. Considering that Qazvin plain ...
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Introduction: Assessing the soil quality of agricultural land is essential for the economic success and sustainability of the environment in developing countries. Recently, there are many types of methods for assessing soil quality, each of them uses different criteria. Considering that Qazvin plain is one of the most important regions of agricultural products in Iran as well as Middle East, so the assessment of the soil status using quantitative models of soil quality can be used as an indicator of the status of soils in relation to sustainable agriculture, optimal utilization of resources Natural and better land management. Among the quantitative models of soil quality index, cumulative model integrated quality index (IQI) and Nomero (NQI) index can be mentioned. Therefore, this study intends to evaluate the best quantitative and quality index model by examining and comparing two methods of selecting the appropriate criteria, Total data set (TDS) and Minimum (MDS) and the second order soil quality index, integrated quality index(IQI) and Nomero (NQI) index in Qazvin plain lands.
Material and Methods: The study area with 25220 hectares is located in east of Qazvin Province. The average annual precipitation is 275 mm and the soil moisture and temperature regimes are Thermic, Dry xeric and Weak Aridic, respectively. A total of 76 samples from the depth of 0-20 cm of the soil surface were studied and based on uniformity, soil type and land use. In this study, four types of criteria that affect the quality of soil in terms of their performance, including: upper limit, lower limit, optimal limit and descriptive function were selected. To qualify (normalize), the upper limit, lower limit and peak limit were selected. In the following, the Total Data Set (TDS) and the Minimum Data Set (MDS) set of data were used. In the TDS method, all of the measured characteristics (a total of 19 physicals, chemical and biological properties of the soil) were considered. Then, the degree of soil quality indices was determined based on the combination of TDS and MDS criteria and the final NQI and IQI quality indices.
Result and Dissection: Comparison of soil types in the region showed that the Aridisols had good, moderate and poor quality (19.35% of soil with good quality, 67.76% with moderate quality and 12.94% with poor quality), Entisols have good and medium quality (53.21% of the soil with good quality and 46.79% with moderate quality) and Inceptisols have very good, good, moderate and poor quality (96.9% Soils with very good quality, 66.73% with good quality, 15.85% with moderate quality and 13.44% with poor quality).
According to the TDS standard and the NQI model, the soils with qualities I, II and III were 30.67%, 66.86%, 47.2% of the total soils of the area (lands with poor quality soil quality were not observed in TDSNQI method). Therefore, according to this method, Aridisols has a very good, good and medium quality (13.26% of the soil with a very good quality rating, 73.88% with a good quality and 12.84% with a moderate quality grade), Entisols with The good quality (100% of the soil with good quality degree) and Inceptisols have a very good and good quality (28.11% of the soil with a very good quality grade, 71.88% with a good quality grade). The results of quantitative soil quality by using the MDS standard method and IQI model were showed, soils with very good, good, moderate and poor degree are 2.45, 16.45, 48.93 and 46.3 percent of total land area respectively.
The results of the combination of the MDS and the NQI model also showed that the soils with a very good, good and average grade are 30.67%, 66.86% and 47.2% of the total land, respectively. Also, the results of the combination of the MDS and NQI model showed that the soils with very good, good and average quality are 30.67%, 66.86% and 47.2% of the total land area respectively. The results of the evaluation based on 4 indicators showed that good quality (II) was prevalent in the studied soils and accounted for about 47% of the total area studied in Qazvin plain lands. The map of distribution of soil quality degrees, the distribution of soil degrees is relatively similar to all of four combination methods, the choice of criteria and model. By examining the linear relationship between the indices obtained from TDS and MDS criteria and the IQI and NQI indexes, it is observed that the correlation coefficient is more and more reliable than the NQI model when used in the IQI model (R2 = 0.77). So the highest correlation coefficient we observed two methods for selecting the TDS and MDS criteria when using the IQI model. In general, the results of this study indicate a better performance of the MDS criteria than TDS.
Conclusions: Therefore, the main results of this study suggest using the IQI model with the MDS selection method as the starting point in the global standard path for future studies. Special attention should be paid to the criteria chosen by the MDS. In addition, conducting a series of research into the future in order to modify the MDSIQI model can make it more relevant to international standards.
Hanifeh khormai1; farshad kiani; Farhad khormali
Abstract
Introduction: Globally, Soil erosion is a principal degradation process resulting in negative impacts on different soil functions (food and other biomass production, water storing, filtering and transformation, habitat and gene pool, physical and cultural environment for mankind, and source of raw materials) ...
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Introduction: Globally, Soil erosion is a principal degradation process resulting in negative impacts on different soil functions (food and other biomass production, water storing, filtering and transformation, habitat and gene pool, physical and cultural environment for mankind, and source of raw materials) which ultimately causes irreversible effect on the poorly renewable soil resource. Determination of the soil erodibility factor (K-factor) is a cumbersome and expensive undertaking in the effort to predict the soil loss rates. Soil erodibility (K-value) is a key parameter in erosion prediction and is important for conservation planning in the face of a rising need for protecting the limited land resources. The technique proposed by Wischmeier& Smith for estimating the soil erodibility factor is among the most important methods in this regard.
Materials and Methods: Given the high amounts of silt and lime content in loess soils of eastern parts of Golestan province, the purpose of this study was to evaluate the ability of Wischmeier& Smith index to estimate the soil erodibility of this region. In this study, soil erodibility was obtained by Wischmeier’s nomograph and then was compared with the actual values obtained by selecting three plots and then performing physical and chemical tests on these samples. The Universal Soil Loss Equation (USLE) developed by Wischmeier and Smith (1978) is the most frequently used empirical soil erosion model worldwide. Soil erodibility is one of six factors affecting soil erosion in the USLE that reflects the ease with which soil is detached by splash during rainfall, surface flow or both. To check soil erosion,three plots of 15 meters long and three meters wide with a slope of 16 percentwere selected in the next sites of the station. The plots were separated by metal fences to a height of 30 cm,.To measure the soil profile parameters, the sampling was performedin one stage from depth of0-30 cm in the middle of July 2010 and the samples were transported to the laboratory. The erosion Wischmeier& Smith Index (A), as well as those obtained by SWAT model and two obvious erosion indices of (R) and Fournier was Carefully evaluate based on the half-hour rainfall intensity.
Results and Discussion: The analysis of soil profile parameters showed that the soilsweremostly silty loamwith 20.29%sand, 66.54% silt and 13.66% clay, with 2% organic matter and 16.6% CaCO3. The soil aggregate stability expressed as MWDwas about 0.8 mm. Overal, 74 rainfallsoccurredin 2010-2011. The minimum and maximum intensities of deposit-producing rainfalls were 2.98 and 73.589 mm h-1, respectively. Using the nomograph, Wischmeier index was calculated to 0.05-0.092 Mg h MJ−1 mm−1. The results showed that Wischmeier index was 182 times the actual value of erosion obtained from plots and half-hour rainfall intensity and 4.11 times that value while considering Fournier index (R); this parameter was also 6 times the value obtained by SWAT model and half-hour rainfall intensity and 0.35 times that value while considering Fournier index. According to the results,there was a negative correlation between clay and soil erodibility factor in USLE, so the rates of erosion in loess soils increases with the decrease in the clay content. Aggregate stability was affected by organic matter content and there was a negative correlation between aggregate stability and the K-factor. The results showed that the soil mostly contained silt and had a medium texture. This is due to the presence of loess parent materials in the soils of the study area. Based on the laboratory results, the actual soil erodibility was0.35 to 182 times smaller than the value estimated by USLE nomograph. The results showed that the parameters used in determining soil erodibility index have shortcomings for use in the soils of the study area. Therefore, corrections must be done according to soil characteristics or other indicators should be used. The particle size and the amount of lime in the soil are two factors that affect the index.
Conclusions: The obtained results showed that the erodibility estimated by Wischmeier& Smith index was higher than the actual measured value. Also,Wischmeier &Smith’snomographhas been proposed by assessing the erodibility of almost non- calcareous soils with limited amount of silt. While in arid and semiarid loess soils of Golestan province, limestone and siltstone have key roles in erodibilityand aggregate stability. On the other hand, the nomograph is based on rainfalls of semi-humid areas of Central America that are different from rain characteristics (intensity and duration) of the study area. Poor performance of this index in loess soils indicates the need for further research in this field.
S. Tajari; mojtaba barani; F. Khormali; F. Kiani
Abstract
Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to ...
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Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to a large degree, determine the fate and transport of P in soils. Fractionation schemes using different chemical sequential extractions have been used in order to describe the many different forms in which P can be found in the soil. The reason for fractionating and studying P forms in the soil is usually to allow a more precise description of the potentials for P release from the soil. The forms and dynamics of soil P can be greatly affected by agricultural management practices. Since inorganic P is the preferred source for plant uptake, knowledge of the inorganic form within soils is fundamental to understanding bioavailability of P and sustainability of agricultural practice. The aim of this study was to investigate the effect of land use change on the form and distribution of inorganic P using a sequential extraction procedure.
Materials and Methods: In order to study the impact of land-use change from forestland to cultivated land, composite samples in four replicates from the upper 10 cm of the different land use systems (natural forest, pasture, bower olive, farmland) were collected. We collected five subsamples from each land use in a radial sampling scheme. The five subsamples were then bulked into one sample. The spacing between the subsamples on the radii ranged from 5 to 10 m. The soil samples were transferred to polyethylene bags and transported to the laboratory where they were slightly crushed, passed through a 2 mm sieve prior to fractionation and chemical analysis. Soil texture, cation exchange capacity, organic carbon (OC), electrical conductivity, pH and calcium carbonate equivalent (CCE) were measured with standard methods. Total P and total inorganic P (Pi) contents were measured by the ignition method, for which P in the ignited (550 °C) and unignited soil samples were extracted by 0.5 M H2SO4. A modified version of the sequential extraction of Olsen and Sommers (1982) was used to fractionate inorganic P. Phosphorus was measured in the extracted supernatants by the molybdate–ascorbic acid method.
Results and Discussion: The results showed that clear-cutting of the indigenous forests and their conversion into agricultural fields significantly decreased total P and total organic P levels. Land-use changes from natural forest to farmland decreased the total P by 23% (from 644 to 495 mg per kg). Clearing and subsequent cultivation of the native woodland resulted in a marked depletion of total organic P. In addition, the land-use conversion from the natural forestland to an agroecosystem (cultivated land) led to increases in total inorganic P and inorganic P forms levels (labile P, P non-occluded, occluded in oxides of iron and aluminum, soluble calcium phosphate and sparingly soluble calcium phosphate). Labile inorganic P (NaHCO-Pi) showed the greatest changes, such as labile inorganic P in the amount of change from 1.75 in the forest land to 13.01 mg per kg of cultivated land, which represent an increase of approximately 8-fold compared to control (natural forest). The results also revealed that the refractory inorganic P fractions (HCl-Pi) were the major inorganic P pool, comprising 50-70% of the total inorganic P pool, indicating CaCO3 control over phosphorus availability in the studied soils. This study indicated that forestland degradation and cultivation caused chemical changes of P dynamics.
Conclusion: Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Toshan region, has greatly impacted the forms and content of P in the soils. Generally, the conversion of natural ecosystem to agroecosystems, decreased the proportion of organic P (Po) in the top-soils at depth of 0 to 10 cm. The depletion in organic P from the cropped fields could be attributed to the enhanced mineralization of soil organic P caused by cultivation and removal of P in the crops. However, the conversion of natural forest to farmland led to increases in inorganic P (Pi). About 50% to 70% of the TP was bound to CaCO3, and thus this solid phase is critical to P fate in the soils and ecosystem of the Toshan Region, Golestan province
Z. Naghizadeh Asl; E. Dordipour; A.L. Gholizadeh; F. Kiani; H. Emami
Abstract
Abstract
In order to assess the availability of phosphorous (P), different methods have been proposed in the last decades. The results of these methods in soils with various pH, calcium carbonate, organic matter, Al and Fe oxides and hydroxides and other properties especially in Iranian soils can not ...
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Abstract
In order to assess the availability of phosphorous (P), different methods have been proposed in the last decades. The results of these methods in soils with various pH, calcium carbonate, organic matter, Al and Fe oxides and hydroxides and other properties especially in Iranian soils can not be used. In addition, knowledge about transformation of P forms is necessary for perception of P behavior. The objective of this research was to study the relationship between P extracted by some extract ants and soil properties and, different forms of inorganic P. Therefore 20 soil samples were collected from 0-30 cm depth of Glosetan province soils. Soil P was extracted and measured by sodium bicarbonate at pH = 8.5 (NaHCO3), DTPA- Ammonium bicarbonate (NH4HCO3-DTPA), DTPA- Sodium bicarbonate (NaHCO3-DTPA), and 0.01 M CaCl2. Also, different forms of inorganic P in the studied soils were measured by Jiang and Gu sequential fractionation method. The results showed that the amount of P extracted by different extract ants was in the order NaHCO3 > NaHCO3-DTPA > NH4HCO3-DTPA > CaCl2. There was a significant correlation between P extracted by different extract ants and determination coefficient between P extracted by NaHCO3 and NaHCO3-DTPA, NaHCO3 and NH4HCO3-DTPA, and NaHCO3-DTPA and NH4HCO3-DTPA were 0.91**, 0.85**, and 0.82** respectively. P extracted by NaHCO3, NH4HCO3-DTPA, and NaHCO3-DTPA with pH, EC, clay and Calcium carbonate percentage had a negative and significant correlation, but with Organic matter it was significant and positive. Also among the P forms only di, octa and Al oxides P had a significant correlation with P extracted by studied extract ants. In general the distribution of inorganic P forms in these soils was as below: Ca10-P > Al-P > Ca8-P > Fe-P > Ca2-P > Fe- Occluded-P. According to significant correlation between P extracted by studied extract ants with some P forms it seems that, some P forms can be transferred to available form of plants.
Keywords: P Extract ants, Sequential fractionation, Inorganic P forms
