JWSS - Journal of Water and Soil Science

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Information about forms of zinc (Zn) is important for the evaluation of its status in soil and also understanding of the soil fertility and chemistry. To obtain such information, amounts and distribution of Zn in different fractions of 20 soil samples of Tehran province, Iran were determined by sequential extraction method and their relationships with each other and with soil characteristics were investigated. Total Zn of soils ranged from 70 to 169.9 mg/kg^-1. The amount of different Zn forms relative to the sum of forms was determined to be as follows: organic less than 0.1, soluble+exchangeable 0.1, manganese-oxide-associated 0.9, carbonate 1.6, crystalline iron-oxide-associated 3.8, amorphous iron-oxide-associated 4.2, and residual form 89.3%. Simple correlation coefficients showed that pH had a negative significant correlation with all forms of Zn except organic. Silt and clay contents had significant positive correlations with total, residual, and crystalline iron-oxide-asociated Zn but CEC had significant correlation only with total Zn. Calcium carbonate equivalent showed a significant correlation with soluble+exchangeable, manganese-oxide-associated and amorphous iron-oxide-associated Zn. DTPA-extractable Zn was significantly correlated with soluble+exchangeable, carbonate, and amorphous iron-oxide-associated Zn. A significant correlation was also observed between the Zn forms themselves, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of an element in soil.

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Improper management of watershed land utilization has many ill effects on the available resources. Land use optimization is one of the proper strategies to achieve sustainable development and to reduce resource dissipation. Focusing on Brimvand watershed in Kermanshah province which comprises an area of 9572 ha, the present study was conducted to find out the most suitable land allocation to different land uses viz. garden, irrigated farming, dry farming and rangeland to achieve soil erosion minimization and benefit maximization. The soil erosion, net benefit and standard land capability maps were supposed as the inputs of the objective functions and to defined constraints. The multi-objective linear problem was then solved using simplex method with the help of ADBASE software package and ultimately the optimal solution was gained. Additionally, the results of the study revealed that the amount of soil erosion could reduce by 7.78% whereas the benefit increases at the rate of 118.62%, in case of implementation of optimal solution. The above mentioned optimization led to dry farming decrease and garden increase over that area. The results of sensitivity analysis also showed that objective functions were strongly susceptible to the variation of maximum constraint of irrigated farming and garden areas.

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A field study was conducted at the Zabol Agricultural Research Center during the years (2003-2004) to investigate the effect of irrigation with treated municipal wastewater on the yield and quality of wheat and some soil properties. Irrigation treatments were: T₁: Irrigation of wheat with well water during entire period of growing season T₂: Irrigation of wheat with well water until the begging of flowering stage, and irrigation with wastewater in every other turns of irrigation T₃: Irrigation of wheat with well water until the beginning of booting stage, and irrigation with wastewater in every other turns of irrigation T₄: Irrigation of wheat with well water until the begging of tilling stage, and irrigation with wastewater in every other turns of irrigation and T₅: Irrigation of wheat with wastewater during entire period of growing season. A complete randomized block design with four replications was adopted for this experiment. The soil was sandy loam with no limitation for internal drainage. Chemical and physical aspects of soil were measured during the experiment. Grain yield, yield components and chemical composition of wheat grain were also measured. The results showed that yield of wheat and total biomass production were statistically significant in T₃, T₄ and T₅ compared with the control treatment. Plant height, width and length of flag leaf, numbers of fertile tillers, length of panicle, numbers of grains per panicle and weight of 1000 grains were also statistically significant with the control treatment. Percentages of protein were statistically different among various irrigation treatments. No significant changes in accumulation of heavy metals in soil and plant grains were observed. The increase of SAR, ECe, O.C% and total nitrogen in the T₄ and T₅ were statistical significant compared with the control treatment. In summary, for sustainable use of Zabol municipal wastewater, the growth stages of wheat should be irrigated with municipal wastewater and other growth stages should be irrigated with nonsalinty water, so that the maximum yield is obtained and soil salinitisation and sodication is prevented.

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Study of phosphorus reactions over time and the role of organic matter in the calcareous soils are important for the development of P fertilizer and manure management practices. The objective of this study was to determine the effect of applied manure on P availability and its chemical forms in the soil, over time. Eight samples were collected from semi-arid calcareous soils of Mashhad plain. The samples were treated with two levels of inorganic P (0 and 300 mg P kg^-1 soil as KH₂PO₄) and two levels of organic matter (0 and 1% cattle manure). The experiment was conducted in a completely randomized design with factorial arrangement. The treated soil samples were incubated for 2, 5, 10, 30, 60, 90 and 150 days, then analyzed for available P (Olsen-P). The result showed that only 17% of added phosphorus was available in P treatment at the end of experiment. In manure treated soils, this figure reached 34% for the same period of time. Application of manure along with P increased the recovery of applied P and CBD-P (Citrate-Bicarbonate-Dithionite). This may be due to the formation of P-organic complexes with Fe oxides. Application of manure in soil increased NaCl-NaOH-P considerably compared with P and P+OM treatments. It can be concluded that P originating from manure compared with inorganic-P may be more available for plants over the time.

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Accumulation of heavy metals (HMs) in cultivated soils is an important environmental problem in many parts of the world. In recent years, HM leaching through preferential paths and also in the form of metal-organic acids complexes has received much attention. For this reason, the effects of plants on creating preferential flow through the soil is important. The objective of this study was to assess the mobility of Cd, Cu, Pb and Zn in a calcareous soil (Typic Haplocalcids) planted with safflower (Carthamus tinctorious). The study was conducted on 12 undisturbed soil columns (22.5 cm in diameter and 50 cm in depth) in greenhouse. The top 10 cm of soil in half of the columns were contaminated with Cd, Cu, Pb, and Zn at the rates of 19.5, 750, 150 and 1400 kg ha^-1, respectively. Half of the contaminated and uncontaminated columns were planted with safflower at a rate of 20 seeds m^-2. Leachate was collected continuously and analyzed for these four heavy metals. After the crop harvest, soil samples were taken at 10 cm intervals and analyzed for DTPA-extractable and water-soluble HMs concentration. Results showed that heavy metal concentrations (DTPA and soluble) of the subsoil in planted columns were more than in fallow columns. The DTPA-extractable Cd, Cu and Zn concentrations in contaminated planted columns were 3.3-, 1.5- and 1.5-times more than in contaminated fallow columns, respectively. The water-soluble Cd, Cu and Zn in planted treatments increased 2.4, 1.2- and 1.1 times more than the fallow treatment. Lead concentrations in both planted and fallow treatments were similar. Metal uptake by safflower increased such that Cd and Zn uptake was more than Cu and Pb. Cd, Cu, Pb and Zn concentrations in the leachate of planted columns increased 32.0-, 2.5-, 6.0- and 2.7- time more than the uncontaminated planted columns. In summary, although topsoil contamination increased metal uptake by safflower, however the presence of safflower increased DTPA-extractable and also soluble metal concentrations in the soil profile and therefore enhanced metal mobility. The order of metal mobility was Cd > Zn >Cu >Pb.

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In order to investigate mineral manganese forms and their relations with plant responses, 22 soil samples from Fars province (0-20 cm) were in a greenhouse experiment filled in 3 liter pots, and soybean (Glycine max (L.) merr.,CV.Williams) was grown for 7 weeks. Chemical forms of manganese were determined in soils by warden and Reisenauer sequential extraction method (readily soluble, weakly adsorbed, carbonate bound and oxide bound extracted with Ca(No₃)₂, Ca DTPA +Na₂B₄O₇, HNO₃ and NH₂OH. HCl, respectively) after harvesting the plants. Results showed that the amount of Mn in different forms was in the following order: Carbonatic Mn >Mn Oxides >Weakly adsorbed Mn > Soluble Mn. Regression equations between soil properties and Mn forms showed a significant correlation between calcium carbonate equivalent and carbonate bound Mn. Significant correlation between Carbonate bound Mn and concentration of Mn in the aerial part of soybean showed that this fraction plays an important role in plant nutrition.

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In order to determine the reciprocal relationship between the important characteristics of soil and the growth of Haloxylon ammodendron (C.A. Mey) plant in segsi plain of Isfahan., ordination method was used. The study was performed through the stratified random sampling and the regions were separated according to the plant age and physical physiognomy, then 10 samples of Haloxylon ammodendron (C.A. Mey) of the same age were selected in each region. Meanwhile, factors such as height, canopy cover area, canopy cover perimeter, canopy cover diameter, and basal area were considered. Also, 30 profiles from viewpoint of growth situations in 10 different regions were dug. Soil characteristics such as : pH, Ec, total soluble Ca²⁺ and Mg²⁺, Cl^-, CO3^--, HCO3^-, SP%, CaCO3%, CaSO4%, organic matter%, total nitrogen percentage, phosphorous, Na⁺, K⁺, SAR, and hardpan depth were measured. Data was analyzed using ordination method. According to the results, samples of the same age showed significant differences in plant features. Other results showed that physical characteristics such as depth of hardpan from soil surface, SP%, and chemical characteristics such as salinity, alkalinity and total nitrogen had the highest effect on qualities of this kind of plant. In other words, the results mentioned above showed the important role of Haloxylon ammodendron (C.A. Mey) in sharp increase of salinity and alkanity in it's stratum.

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Optimal crop water requirement is needed for precise irrigation scheduling. Prediction of crop water requirements is a basic factor to achieve this goal. In this study, maize potential evapotranspiration (ET_p) was prediced by maize simulation model (MSM). Then, it was evaluated and validated using experimental field data obtained in Agricultural Research Station of Shiraz University (Bajghah, Fars province) during 2003 and 2004. Comparison of measured volumetric soil water content with predicted values by MSM model in 2003 and 2004 indicated that this subroutine (prediction of maize evapotranspiration) did not need modification. Also, daily potential evapotranspiration of maize was estimated by using Penman-Monteith equation considering single and dual crop coefficients. Comparison between the results of predicted ET_p by MSM model, calculated ET_p by Penman-Monteith, and measured irrigation water and soil water content indicated that the prediction of ET_p by MSM model was satisfactory. Model prediction of seasonal ET_p, potential transpiration (T_p) and soil evaporation (E) were 831, 536 and 329 mm, respectively, in 2003, and 832, 518 and 314 mm, respectively, in 2004. The values of ET_p, T_p and E calculated by Penman-Monteith method using dual crop coefficients were 693, 489 and 205 mm, respectively, in 2003, and 700, 487 and 213, respectively in 2004. Maximum rate of predicted potential ET_p, Tp and E were 11.1, 8.2 and 5.1 mm d^-1, respectively in 2003 and 13.0, 9.0 and 4.0 mm d^-1, respectively in 2004. The values of calculated seasonal ET_p by Penman-Monteith method using single crop coefficient were 615 and 632 mm in 2003, and 2004, respectively. Comparison between the results of predicted ET_p by MSM model, calculated ET_p by Penman-Monteith equation with single and dual crop coefficients (FAO-56) and measured values of irrigation water and soil water contents of root depth indicated that FAO-56 methods underestimated the ET_p.

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Concentration of soluble fluoride in groundwater, soil, and some crops in Isfahan region was determined by Ion Selective Electrode (ISE) method. The mean fluoride concentration of water samples in the study area was 0.3 and 0.05 mg L^-1 in the spring and summer, respectively. These values are in an acceptable limit for irrigation, whereas for drinking water, they are in deficiency range. The average and maximum concentrations of soluble fluoride in soil samples were 1.0 and 3.2 mg kg^-1, respectively. In general, the spatial distribution of fluoride in soils showed that fluoride content around major industrial centers such as Isfahan Steel Factory, Mobarakeh Steel Co., and Isfahan oil refinery was higher than other sites. The minimum and maximum fluoride contents of crops were observed in alfalfa as 0.2 and in corn as 4.2 mg kg^-1, respectively. Tomato had the highest mean concentration of fluoride as 3.6 mg kg^-1. The fluoride concentration in plants positively correlated with the fluoride concentration in irrigation water and soil (P < 0.01) and negatively correlated with cation exchange capacity of soil (P < 0.05).

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  Soil particle size distribution and bulk density are used for estimating soil-moisture characteristic curve. In this model, soil particle size distribution curve is divided into a number of segments, each with a specific particle radius and cumulative percentage of the particles greater than that radius. Using these data, soil-moisture characteristic curve is estimated. In the model a scale factor, a , is used which may be considered as a constant, or obtained by logistic or linear procedures. F or most conditions, soil particle size distribution curve is not available, but only the percentages of clay, silt and sand could be obtained using soil textural data. In this situation, at first a precise soil particle size distribution must be developed, based on which the soil-moisture characteristic curve can be predicted. According to the previous studies, using particle radius of 999 µ m is more appropriate than radius 125 µ m. Also, adjusted coefficients for estimating soil particle size distribution curve for radii 1 to 20  µ m was obtained. In this study, using the soil textural data of 19 different soils from UNSODA database, soil-moisture characteristic curve of each was estimated with logistic and linear methods based on initial and adjusted soil particle size distribution estimation. The estimated values were compared with the measured data. The results indicated that for most soils, using the combination of logistic and adjusted particle size distribution estimation procedures is more appropriate than the previous methods.

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The effect of overgrazing on vegetation changes in central Zagros has been studied by a few scientists, but there is no detailed information on the impact of such practices on soil properties. The objective of this study was to assess the effect of climate and grazing management on selected soil biochemical properties. Fourteen experimental range sites protected against grazing as well as their adjacent overgrazed sites in Chadegan, Pishkuh and Poshtkuh were selected. In each site, samples were collected from the depths 0-5 and 5-15 cm. Soil organic C (OC), microbial biomass C (MBC), total nitrogen (TN), organic C to total N ratio (C/N), microbial biomass C to organic C ratio (C_mic/C_oc) and metabolic quotient (qCO2) were measured and/or calculated. The results showed that the lowest SOC, MBC, TN and Cmic/Coc occur in Chadegan due to low fresh materials input. The above parameters in Pishkuh and Poshtkuh regions are 2.5 to 3 times greater than those in Chadegan area. Grazing intensity in Pishkuh is less than that in Poshtkuh region and there is no significant difference between grazed and protected sites in Pishkuh. But, there is a significant difference between grazed and protected plots in Poshtkuh due to a higher grazing intensity. Higher C_mic/C_oc and lower qCO2 suggest that the quality of organic matter is better in Poshtkuh and Pishkuh. In conclusion, highly degraded rangelands in Pishkuh and Poshtkuh seem to be able to recover very quickly with proper management, while Chadegan region needs a much longer period of time to restore.

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The present research was intended to alleviate the problems and costs of deep tilling in sugarcane production in Mian-Ab sugarcane farms located in Khuzestan province, Iran. The main objective was to investigate the feasibility of subsoiling operations with bentleg subsoiler (BLS) equipped with shallow tines, a combination expected to increase the critical depth resulting in less power consumption and improved soil physical conditions. Six treatments arranged in a completely randomized block design were used to measure the draft force (except for the bulldozer mounted rippers), disturbed soil cross-sectional area and penetration resistance. The treatments included (1) subsoiling with rippers mounted on bulldozer, (2) BLS without attachment, (3), and (4) BLS equipped with single tine at working depths of ½ and ⅓ of target depth, (5) and (6) BLS equipped with two tines at ½ and ⅓ target depth. The experiment was replicated three times. The results indicated that BLS without attachment had the highest draft requirement as compared with other BLS treatments with shallow tines. In general, tine attachment resulted in less draft mainly due to displacement of critical depth to lower soil zones. Increasing the number and depth of shallow tines resulted in less draft force. The BLS equipped with two tines working at ½ target depth exhibited minimum drawbar power. The inclusion of shallow tines resulted in 21% reduction in drawbar power requirement as compared to BLS without tine attachment. The cross-sectional area of the soil tilled by ripper was minimum. Furthermore, the tilled area was not uniform and subsequent subsoiling operations were needed. The average soil cross-sectional area per unit width was improved by BLS treatments by a factor of 2.3 as compared with that of ripper. The highest cone index was obtained in plots tilled by ripper the BLS reduced this index in a significant manner. The soil worked with subsoiler equipped with tines exhibited the least resistance. The range of wheel slippage for BLS treatments was 12-16% which lies in the upper end of the recommended range for optimum traction efficiency. The proposed idea proved prominent in subsoiling fine textured compact soils.

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To investigate the degree of forest degradation and the effect of land use change on selected soil quality attributes in loess-derived landforms, samples were taken from different land uses including forest, rangeland, degradated rangeland and farmland in Pasang watershed located in the Galikesh area of Golestan province (37°16'N, 55°30'E). The annual average temperature and mean precipitation of study area were 15°C and 730 mm respectively. Organic matter, pH, EC, CaCO₃ and nutrients (N, P, K) as chemical indicators, hydraulic conductivity, bulk density and porosity as physical indicators and soil respiration as biological indicator were measured. The results showed that the amount of organic matter decreased three percent when it was turned from forest to farmland, and increased two percent from farmland to rangeland. The amount of CaCO₃ in surface layer of deforested area was more than in the forest soils. The amount of soil N in forest and soil P and K in rangeland were higher than in other land uses. Bulk density and porosity in forest and MWD in rangeland were higher than in other land uses because of the decrease in organic matter due to farming activities. Soil respiration in forest was highest as compared to in other land uses. Difference of enzymes activities (L-asparaginase and Dehydrogenase) compared to microbial respiration indicates that enzymes activity is related to specific biological processes while soil microbial respiration basically depends on the general activity of soil microbial population. It could be concluded that amount of organic matter, soil N, bulk density, porosity, MWD, soil respiration and enzymes activities are suitable indicators for soil quality evaluation in this area.

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  Soil erosion is one of the most threatening issues for crop production and environmental qualities, especially for soil and water resources. Appropriate knowledge about total soil loss and runoff is valuable in order to perform soil and water conservation practices in watersheds. EUROSEM, "a single event, dynamic and distributed model," was developed to simulate soil loss, sediment transportation and deposition by rill and interrill processes. This study was conducted to evaluate EUROSEM model in order to simulate soil loss and runoff in Sulijan sub-basin, which covered 20 ha, from Charmah-Bakhtari province. The sub-basin was divided in to 19 homogeneous elements using topographic, land use, plant cover, slope and channel properties throughout it. Soil, plant cover, land surface and climate characteristics were measured and evaluated by field observations and laboratory measurements. Actual soil loss and runoff for studied events were determined by direct measurement in the field. After sensitivity analysis, calibration and validation steps were carried out to simulate runoff and soil loss. The results of sensitivity analysis showed that the EUROSEM model for predicting runoff was more sensitive to hydraulic conductivity, capillary drive and initial soil moisture. On the other hand the model for predicting soil loss was more sensitive to Manning's coefficient and soil cohesion. The results showed that the EUROSEM model was able to simulate well the total runoff, peak of runoff discharge, total soil loss and time for the peak of soil loss discharge. But that could not simulate well the peak of soil loss discharge and time for the peak of runoff. Although it seems that EUROSEM is able to predict soil loss and runoff partially well in individual events, it is necessary to evaluate the efficiency of the models for different basins with varieties of soil, plant cover and climatic properties.

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  Phytoremediation is a new technology that employs plants to remediate contaminated soils. This method compared to those that involve the use of large scale energy consuming equipments is an inexpensive method. Phytoremediation models are useful tools to further understanding the governing processes and also to manage the contaminated soils. A thorough literature review indicates that very few models have been developed for phytoremediation due to the complexity of the phenomena. The objective of this study was to develop a simple model for phytoremediation of lead and cadmium. A new formulation of phytoremediation was established based on soil and plant responses to heavy metal pollution. A large quantity of a sandy loam soil was thoroughly mixed to ensure homogeneous different concentration levels by lead and cadmium. These contaminated soils were transferred to some plastic pots. Land Cress (Barbarea verna) and Spinach (Spinacia oleracea L.) seeds were germinated in pots containing 8 kg of contaminated soil. Plants were harvested at five time intervals. The concentrations of Pb and Cd in the plant and soil samples were digested by wet oxidation and 4 M Nitric acid digestion methods, respectively, and were determined by flame and graphite furnace atomic absorption spectrometry methods. Proposed models then were calibrated using the collected data and validated quantitatively. The results indicated that the soil adsorption isotherms followed a linear form for both Pb and Cd concentrations. The results also indicated that the phytoremediation rate of Pb by Land Cress and Spinach are first-order function of Pb concentration in soil. In contrast, a zero-order function of soil Cd contaminations was obtained. Combining these two results of soil and plant responses to Pb and Cd pollution, a simple model with reasonable performance was derived to predict the time needed for remediation of soil Pb (R² > 0.98). However, in the case of Cd, the derived models appeared to be useful to make only some overall estimations of the remediation (R²≈^�0.70).

 

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  Adopting proper agricultural management and conserving soil organic matter are important components of sustainable agriculture. Soil organic matter content is a key attribute in soil quality. Labile organic matter pools can be considered as suitable indicators of soil quality that are very sensitive to changes in soil management practices. This research was carried out to investigate some organic carbon labile pools as an indicator evaluating the effects of different managements on some quality parameters of two calcareous soils. The study was conducted in 2 locations: 1- plots that receiving 0 (C1), 25 (C2), 50 (C3) and 100 (C4) Mg/ha of manure for five years successively with a cropping rotation of wheat –corn every year and plots under three cropping rotations (C5, C6 and C7) at Lavark experimental farm and 2- inquiry research station of Fozveh at different plots with three different cropping rotations (C8, C9 and C10) with a given cropping history recorded for the last 5 years. Soil samples were taken from the center of each plot and the depths of 0-5 cm and 5-15 cm. Their organic carbon, hot water soluble carbohydrate, particulate organic matter (POM), organic carbon and hot water soluble carbohydrate of POM, mean weight diameter of water stable aggregates were determined. Different managements consisting of different levels of manure and types of cropping rotation had significant effects on the soil characteristics measured. The greateast amount of carbohydrate and aggregate stability was obtained in the plots of 100 Mg/ha of manure in Lavak and in alfalfa plots in Fozveh station. Also, the results showed that aggregate stability has a better correlation with hot water soluble carbohydrate in comparison with other soil organic pools. Therefore, the carbohydrate extracted by hot water may be used as an index to assess the impacts of different agricultural management systems on soil quality.

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  Studying soil phosphorus fractions is useful in understanding soil pedogenesis as well as soil fertility. In this reseach, 20 soil samples were taken from different depths of 0-30 and 30-60 cm of upper-slope, mid-slope and lower-slope positions of four toposequences in arid (Jei and Ziar in Isfahan) and semiarid (Farokhshahr and Shahrekord) regions. In each toposequence, the soil depth was relatively low at the upper-slope position and increased toward the lower-slope. The soils in upper-slope and mid-slope were under scarce native vegetation where the soil in lower-slope was under farming activities. Soil phosphorus (P) fractionation was carried out using sequential extraction. The total soil phosphorus was in the range of 302-1135 with an average of 715 mg/kg. About 65-89% of total phosphorus were inorganic, and 11-35% organic. The amount of inorganic and organic P in the soil samples was in the range of 204-897 with an average of 571, and 70-238 with an average of 114 mg/kg, respectively. The amount of total, inorganic and organic P increased from upper-slope toward the arable lands and decreased from topsoil to subsoil in all toposequences. In the studied soils, apatite ( Ca₁₀-P ), aluminum phosphates(Al-P), octacalcium phosphates( Ca₈-P ), iron phosphates (Fe-P), iron oxides occluded phosphates( OC-P ) and dicalcium phosphates( Ca₂-P ) were the major constituents of the soil inorganic phosphates, respectively.

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  Some industrial processes, such as plating and gold mining, utilize cyanide, which entering in their effluents. Because cyanide compounds are toxic contaminants, the waste-containing cyanide must be treated before discharge in the environment. Several methods are available for cyanide removal or detoxification. Natural degradation, alkaline chlorination, and oxidation with hydrogen peroxide are the most common methods in full-scale plants. Because of technical and economical concerns related to these methods, biological treatment processes have recently come under consideration. In phytoremediation, plants potential for pollutant removal is used. The main objective of present study is to investigate feasibility and potential of phytoremediation of cyanide-polluted soils by non-woody plants. The experiments carried out in this study were a completely random factorial design procedure, with three replications. Three non-woody plants: sorghum (as a cyanogenic cereal plant) and fescues with and free of endophyte (as grasses), were examined. Analysis of variance of the data obtained on soil cyanide reduction and cyanide accumulation in plants showed that phytoremediation is a suitable technique for low concentration of cyanide-polluted soils. Besides, it was been found that sorghum has a better soil cyanide removal efficiency than fescues, so that a significant portion of soil cyanide will accumulate in sorghum tissues.

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  Applying of intensive cultivation especially in marginal and sensitive regions, after conversion of rangelands to cropland farms, commonly causes reduction in soil quality, and thus an increase in soil degradation, erosion and runoff. This study was conducted to evaluate the land use change effects on some soil physical and chemical properties such as mean weight diameter (MWD), soil organic matter (SOM), bulk density (BD) and saturated electrical conductivity (ECe). For the experiment, soil samples were collected from 8 regions (rangeland and cultivated range) from west and southwest of Isfahan. Samples were taken from two soil layers 0-15 and 15-30 cm. Results showed that after conversion of range to cultivated lands, in some regions, SOM content was increased about 39% but in some regions decreased about 26%. This is due to the initial conditions of the regions. The ECe also increased by 41% due to this conversion. However, no changes were observed to the MWD, BD and pH in different treatments. Although there were little change to the physical and chemical properties of soil as a result of this conversion, those properties which were changed, could have a degradation effect and lower the soil quality.

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  This study was undertaken to investigate the effects of soil compaction due to wheel traffic on corn growth and yield, in summer 2004 and 2005 at the Badjgah Research Station, Shiraz University located in North West of Shiraz, Iran. The treatments consisted of axial load in two levels and wheel traffic location treatments at four levels, including none, between rows, on rows and on entire plot area. The corn growth rate, root density and yield were not significantly influenced by axial load, but they were significantly affected by wheel traffic in all plots. Corn yield with wheel traffic on entire plot area averaged 3.97 Mg/ha which was significantly lower than the yields with the other treatments which averaged 6.65 Mg/ha with no traffic.