JWSS - Journal of Water and Soil Science

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Sewage sludge application on farmland as fertilizer is commonly practiced in many countries. However, high concentration of heavy metals like mercury (Hg) in sludge can cause pollution of soil, plant and the human food chain. In order to examine the risk of Hg transfer into plants a five year field experiment was conducted in which we investigated uptake of Hg from a sludge-amended soil by corn. Sludge application rates were 0, 25, 50 and 100 Mg ha-1. To study cumulative and residual effects of the sewage sludge, applications were repeated on 4/5 of each plot in second year, on 3/5 of plots in third year, on 2/5 of plots in fourth year and in 1/5 of plots in fifth year. After the fifth year, soil samples from the 0-20 and 20-40 cm depths were taken and analyzed for total Hg. Corn plants were harvested and roots, stems and grains were separately analyzed for Hg concentrations. Sludge application significantly increased total Hg concentration in soil. Total Hg concentration in soil ranged from 20 µg kg-1 (in control plots) to 1200 µg kg-1 (in plots with 500 Mg ha-1 sludge application). Sludge application significantly increased uptake of Hg in different plant parts. At the end of the fifth year the average Hg concentrations in root, stem, and grain were 91, 9, and 8 µg kg-1, respectively. Corn yield increased significantly with sludge application and this fertilizer effect was visible five years after a single sludge application.

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The management and application of organic wastes in agricultural lands decreases environmental risks and increases utilization of these matters. The objective of this research was to investigate and compare the effect of polyacryl factory sewage sludge (PSS), municipal compost (MC) and cow manure (CM) on soil properties and on yield and growth of maize (single cross 704, Zea mays L.). The treatments were control (without any organic waste) and application of PSS, MC, and CM at two rates (15 and 45 t ha-1). This research was done in the research farm of Isfahan University of Technology (Lavark-Najafabad). The experimental design was a randomized, complete block with three replications. Treatments were incorporated into the soil before the maize planting (on 23 June 2008) and soil sampling was performed after 132 days (Simultaneously with maize harvesting). Application of the organic wastes resulted in significant increase soil organic matter (SOM), total nitrogen (TN) and saturated hydraulic conductivity (Ks) and significantly decreased bulk density. However, saturated hydraulic conductivity was decreased by application of PSS. Application of 15 and 45 t ha-1 of PSS reduced Ks more than 14% and 42%, respectively, compared with control however, the reduction was significant only in the plots which received 45 t ha-1 of PSS compared with control. The results of plant yield and growth showed that leaf area index (LAI), plant length, biological yield, 1000 seed weight and seed yield increase due to the application of organic wastes.

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The petroleum refinery sludge is an important source of environmental pollution. Burning and burying of the sludge may have adverse effects on environment and human health. Thus, other mechanisms for decreasing the toxic effects of hydrocarbon substances in the sludge must be used. In this study, Isfahan refinery sludge was dewatered, air dried and mixed by 0, 10, 20, 30 and 40% w/w ratio with two calcareous soils, viz., Mahmoud Abad (Typic Haplocalcids with clay texture) and Bagh Parandegan (Anthropic Torrifluvents with silty loam texture). Different mixtures of soil and sludge were farmed for 21 days and irrigated on a daily basis to field capacity. Then, 100 seeds of Tallfescue (Festuca arundinacea) and Agropyron were planted in polluted soils with 3 replicates in 3 kg pots for 5 months. Result showed that Tallfescue and Agropyron yields decreased in sludge contaminated treatments. In the 40% sludge treatment, Tallfescue decreased the total petroleum hydrocarbons content by 65 percent. The highest degradation for agropyron was in the 30% sludge treatment which showed about 55% reduction in total petroleum hydrocarbons. The 40% sludge treatment resulted in the minimum yields of root and shoot plants. The highest degradation of TPHs occurred in the Tallfescue rhizospher of 40% sludge. Maximum degradation of TPHs on the Agropyron rhizospher was in 30% sludge mixed with Bage parandegan soil, but maximum yield of plant was in 20% sludge. Our study shows that Tallfescue rhizospher is most effective for decreasing TPHs, and that the phytoremediation in soils with more clay can adsorb and fix the toxic components and then at higher levels of pollutions can let the plants grow.

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The effects of waterlogging, sewage sludge and manure on the Fe, Mn, Zn, Cu, Pb and Cd uptake and concentrations in roots and shoots of sunflower (Helianthus annuus L.) were investigated in greenhouse conditions. A factorial experiment based on a completely randomized design with three replications including duration of waterlogging at five levels (0, 2, 4, 8, 22 days) and source and amount of organic fertilizer at five levels (0, 15 and 30 grams of both manure and sewage sludge per kg of soil) was conducted. The results showed that by increasing the duration of waterlogging, the Mn uptake and concentration in shoots and Mn concentration in roots increased but Mn uptake in roots did not change significantly. The uptake and concentration of Fe in shoots and Cd concentration in shoots and roots initially increased and then decreased after soil waterlogging, while Zn and Cu concentration of roots increased after an initial decrease. The effect of soil waterlogging on the Pb, Cu and Zn concentrations in shoots was not significant. By application of sewage sludge and manure the uptake and concentration of Fe, Mn, and Zn in shoots and Cu uptake in shoots increased but the uptake and concentration of Pb in shoots increased only by application of sewage sludge. The effect of source and amount of organic fertilizer on the Cd uptake and concentration in shoots, Cd concentration in roots and Cu concentration in shoots was not significant. By application of sewage sludge the root concentration of Fe, Mn, Cu and Zn increased but root concentration of Cd and Pb did not change significantly. The maximum uptake of heavy metals in shoots was obtained by application of 30 g sewage sludge/kg of soil. The effect of soil waterlogging on the heavy metals uptake and concentrations in the roots and shoots was dependent on the source and amount of organic fertilizer. Sunflower plant accumulated Fe, Mn, Zn, Cu, and Pb in roots while the Cd concentration in roots did not differ with shoots significantly.

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Silver toxicity and its fate in the environment are currently being debated and are important as challenging research topics. Even though there are several studies on its total content in soils, fractionation of Ag especially in calcareous soils has not been investigated. Therefore, to provide fundamental information on the chemical behavior of Ag in calcareous and noncalcareous soils, we studied 8-step chemical fractions of Ag (i.e., EXCH, CARB, Me-Org, re-MeOx, H2O2-Org, am-MeOx, cr-FeOx, and RES) after 30 and 60 days of incubation in soils amended with Ag (0 and 15 mg kg-1), sewage sludge (0 and 20 t ha-1) and EDTA (0 and 0.5%). Experimental results showed that redistribution of Ag in spiked noncalcareous soils was EXCH (34%), H2O2-Org (33%) and RES (17%). In calcareous soils, after 30 days, EXCH- and RES-Ag increased but at the end of 60 days H2O2-Org-Ag increased. Based on our data, we could conclude that addition of Ag results in an increase of Ag mobility in soils but incubation and sewage sludge may have adverse effect on its mobility. In contrast to noncalcareous soil, EDTA in calcareous soil resulted in higher Ag mobility. This may have environmental implications in Ag polluted calcareous soils.

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Cow manure and sewage sludge add heavy metals to soil. Organic and inorganic fractions in these compounds can immobilize heavy metals such as lead (Pb) and affect their bio-availability. This investigation was conducted to compare the effects of organic and inorganic fractions of sewage sludge and cow manure on distribution of lead chemical forms in soil as a completely randomized design. Treatments consisted of application of 10% (w/w) enriched sewage sludge and cow manure (6 g Pb kg-1 organic amendments). Another treatment was also used in which soil Pb concentration was increased to 600 mg kg-1 soil using Pb(NO3)2 salt. To compare the effects of organic and inorganic fractions, organic carbon, iron oxide and easily reducible iron and manganese were removed from cow manure and sewage sludge, and were added to the soil by 10% (w/w). The samples were incubated at 23-25ºC for 111 days and their moisture was maintained at 80% water field capacity. More than 50% Pb in Pb(NO3)2 treatment was in exchangeable fraction, while for cow manure and sewage sludge treatments more than 40% Pb was found to be in oxide fraction. Application of cow manure and sewage sludge increased the Pb in oxide fraction by 14.8 and 17.5%, respectively. Removing organic carbon fraction of cow manure and sewage sludge increased the Pb bound to residual fraction by 12% and 14% respectively. Removing iron oxide fraction of sewage sludge and cow manure decreased the Pb bound to oxide fraction by 8% and 13%, respectively. Removing easily reducible iron and manganese decreased the oxide fraction of Pb by 16% and 14%, respectively. It is concluded that, despite relatively high amounts of organic carbon in the sludge and manure, inorganic fractions of these materials have more significant effects on availability of Pb in soil.

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In this study the effects of irrigation with raw or diluted municipal effluents along with foliar micro-nutrients fertilizer spray were examined on the growth, yield and mineral nutrient in foxtail millet plants. The experimental design was a split-plot with three irrigation sources (namely raw sewage, 50% diluted sewage and well water) as main-treatment and four combinations of Mn and Zn foliar spraying as sub-treatments, which were applied with three replications. The experiment was conducted at the Zabol University research farm during 2009. The applied municipal effluents contained higher levels of macro and micro-nutrients than the well water. The experimental results indicated that irrigation of plants by raw or diluted sewage improved the measured growth parameters and productivity of foxtail millet plants. In addition macro and micro-nutrients concentrations were improved. These improvements were attributed to the presence of high levels of essential nutrients such as nitrogen, phosphorus, and organic matters in wastewater. Manganese and Zn supplied through sewage water alone were not able to raise the productivity of millet to the level obtained through fertilizers at the recommended level, which indicated that additional nutrients through fertilizers are required to obtain higher productivity of millet under sewage farming. Despite the differences in nutrients concentration among different irrigation water sources, the micro-nutrients foliar spray did not affect concentration of macro and micro-nutrients in foxtail millet plant. Overall, the results suggest that municipal sewage could be efficiently utilized as an important source of water and nutrients in growing foxtail millet Sewage water irrigation did not have any appreciable harmful effect on crop productivity.

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Application of sewage sludge has been considered as an organic fertilizer in arid and semi-arid regions of Iran. This study was conducted to investigate cumulative and residual effects of sewage sludge on soil inorganic fractions and their relation to phosphorus (P) availability. Two levels of application (50 and 100 Mg ha-1) and three consecutive times of sewage sludge application (1, 3 and 5 years) with a control treatment were studied in a randomized complete block split plot design with three replications. Composite soil samples were collected from 0-30 depth at the end of 5th year of application. Increasing the rate and application year of sewage sludge enhanced dicalcium phosphate (Ca2-P), octacalcium phosphate (Ca8-P), apatite (Ca10-P), aluminum phosphate (Al-P), iron phosphate (Fe-P) and available P but decreased occluded P (OC-P). Residual effect of sewage sludge application resulted in increased inorganic fractions in blocks treated for 1 year compared to control. Positive correlations were observed between inorganic P fractions and Olsen P, wheat yield and P uptake (except OC-P). We concluded that inorganic P fractions and P availability increased in sewage sludge amended soil.

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Improper properties of sewage sludge include odors, trace elements concentration, and presence of pathogens limit its use in agriculture. Composting and using of earthworms in this process is one of the most suitable methods for stabilization and removal of unsuitable properties of sewage sludge. To investigate the effects of kind and mixing proportion of bulking material and sewage sludge decomposition stage on vermicompost quality, an experiment was carried out in a split plot design with three replications. In this experiment, the stage of sewage decomposition (raw sewage, digested sludge in digester, dewatered sludge in lagoons, and final dried sludge in lagoons) was main factor and kind of bulking materials (woodchips, three leaves, and wheat straw) and mixing proportion of bulking materials to swage sludge (0, 15, 30, and 45 %, V/V) were as subordinate factors. Chemical properties of sewage in different decomposition stages and bulking materials were determined. After 5 months of incubation in the controlled moisture and temperature condition, and in the presence of earthworms, the pot's contents were harvested, and nutrients and heavy metal concentration of vermicomposts were measured. Vermicomposts had relatively low pH and EC. Their nutrients content especially N, P, Fe, and Zn were high. These properties showed vermicompost suitability for use as a soil amendment and organic fertilizer. Heavy metals concentrations of vermicomposts, except for Zn, were lower than recommended values by EPA. Despite no significant difference between the kinds of bulking materials, mixing of these materials with sewage sludge decreased pH, N, and Pb content of produced vermicompost. According to the results, 30% (v/v) mixing of bulking material and sewage sludge is recommended

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Studying the distribution of Zn in the soils allows investigating their mobility and bioavailability. In this research, 10 calcareous soil samples were selected, and sewage sludge-amended (1% w/w) and -unamended (control) soils were incubated for 1 month. Before planting, fractions of Zn were determined, three seeds of wheat were planted in each pot and after 8 weeks, they were harvested. Results showed that all Zn fractions were increased by sewage sludge addition. Results of pot experiment indicated a significant correlation between Zn concentration in wheat with exchangeable (r=0.92**) and Zn associated with Fe and Mn oxides (r=0.76*) in control soils. In addition, significant correlation coefficient was found between Zn associated with Fe and Mn oxides and Zn uptake index (r=0.86**). Moreover, wheat responses were significantly correlated with Zn exchangeable (r=0.71*- 0.84**) in amended soils. Yield was correlated with Zn associated with carbonates and Zn associated with Fe and Mn 0.69 and 0.75, respectively. Zn uptake index was correlated with Zn associated carbonates (r=0.64*). Therefore, the exchangeable and Zn associated with Fe and Mn oxides in control soils and the exchangeable and Zn associated carbonates and Zn associated with Fe and Mn oxides in amended soils could be used as available fractions of wheat.

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Zeolites are substances that have been renowned for their remarkable nitrogen adsorption capacity resulting of decrease in leaching rate of soil nitrogen. This research was conducted to study the effect of the zeolite dosage, zeolite particle size and the method of application on the nitrate leaching of the soil irrigated by treated wastewater (TWW). All of the adsorption tests were carried out in a 27 PVC columns with 11 cm diameter and 60 cm length. The experiments were consisted of 9 treatments and 3 replications including 2 zeolite application method (mixed and layered), 2 zeolite’s grain size (63-125 and <63 micrometer) and 2 zeolite dosage (2 and 4 percent). Zeolite powders were added to the soil in mixed or layered fashion. The soil columns were irrigated 13 times with TWW in a weekly period. In the 4th, 9th and 13th irrigation event, three samples were taken from input and output TWW introduced to columns to measure the change in nitrate concentration. The results were shown that nitrate absorption rate was increased by average of 164.3% and 350.7% in mixed and layered treatments, respectively compared to the control. The result showed that zeolite application method, irrigation event, zeolite’s grain size and dosage were statistically significant on nitrate absorption efficiency (P<0.01). It shows that as the zeolite size decrease the soil nitrate adsorption increases significantly. It increases when the zeolite percentage increases. The result show that the soil nitrate adsorption decreases as the irrigation event increase and soil adsorption potential degraded with irrigation events.

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Management of organic and inorganic treatments may have positive or negative effects on soil quality, plant growth and human nutrition. The objectives of this study were to determine the effects of organic and inorganic zinc fertilizer application on soil quality indicators and wheat yield. This research was conducted at Agricultural Research Station Roudasht, Isfahan, Iran. Sewage sludge and cow manure (5 and 10 t/ha), ash rubber (1 t/ha), powder rubber (200 kg/ha), ZnSO4 (40 kg/ha) were applied and wheat was cultivated. Soil samples were collected at tilling and harvest stages. After taking samples and measurements of the soil parameters, we determined the critical limits for each category and class rating for the each soil parameters, and the soil quality index was calculated. The results showed sewage sludge and rubber ash were significantly effective in increasing soil bioavailable Zn compared to other treatments. Application of sewage sludge and cow manure at 10 ton/ha improved soil quality. The expanded soil quality index can help better understand the effect of fertilizers on soil. A positive and significant relationship between soil quality indicators and Zn uptake and wheat yields was also observed. Our results indicate that addition of 10 t/ha sewage sludge as fertilizer can significantly improve soil quality, supplying the necessary amount of Zn for wheat growth.

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Plant parasitic nematodes, especially root knot nematodes, cause damage to most of agricultural products, and many efforts have been done to control them. In recent years, application of industrial waste and wastewater sludge as organic fertilizers in agriculture has been increased. To investigate the effects of sewage sludge on root knot nematode pathogenicity in tomato, different weights of sewage sludge (0, 4, 8, 15 and 25% of sludge in the soil) in soil were added as a completely randomized design with six replications. Analysis variance and mean comparison of growth indices of plants showed significant effects of treatments. For example, means of stem length of plants increased in soil with more amount of sewage sludge. This relationship was also observed in other indices and nutrients elements. So using sewage increased nitrogen, phosphorous, calcium and magnesium in tomato shoots inoculated with nematodes while the change of potassium was very small. Application of sewage sludge decreased the number of galls, egg-masses and eggs in egg-mass of root knot nematode.

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The ability of different soil tests in predicting soil phosphorus (P) is important in soils amended with municipal sewage sludge. The objective of the present study was to evaluate several chemical extractants to estimate available P for bean growing in 10 calcareous soils amended with municipal sewage sludge from Chaharmahal-Va-Bakhtiari province under the greenhouse conditions. For this purpose, the soil samples were incubated with sludge at a rate of 39-ton sludge ha–1. The amount of available P of the soil samples was determined by Olsen, Colwell, ammonium bicarbonate-DTPA, 0.01 M calcium chloride, BrayІ, ІІ, Mehlich І and ІІ methods. A pot experiment in a completely randomized design was conducted to evaluate the bean plant indices. The results showed that the amount of extractable P with the above methods decreased in the following order: Colwell> Bray ІІ> Mehlich ІІ> Olsen> Ammonium bicarbonate DTPA> Mehlich І> Bray І> 0.01M chloride calcium. The extractable P with 0.01M chloride calcium, Mehlich І, ІІ Colwell and Olsen methods correlated significantly with plant indices (P concentration and P uptake). Thus, mentioned methods could be used to estimate plant-available P in the soils amended with sewage sludge.

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Zinc (Zn) is one of the essential micronutrients for plant growth and its deficiency frequently occurs in calcareous soils. But, a suitable extractant for estimation of plant-available Zn in calcareous soils, amended with sewage sludge, has not been presented yet. The aim of this research was to assess several chemical extractants (7 extractants) for estimation of available Zn in calcareous soils amended (1% w/w) and unamended with sewage sludge. Results showed that Mehlich 3 and Mehlich 1 extractants extracted the highest and the lowest concentrations of Zn in both amended and unamended soils, respectively. All wheat indices (wheat yield, Zn concentration and Zn uptake) increased by sewage sludge addition. Besides, the results indicated that in unamended soils, significant correlations were found (r=0.65^*- 0.91^**) between extracted Zn using AB-DTPA, DTPA-TEA and Mehlich 3 extractants and different wheat indices. On the contrary, in sewage sludge-amended soils, only the correlation between extracted Zn using Mehlich 2 and Zn concentration was significant (r=0.83^**). According to this study findings, the suitable extractant for extracting wheat-available Zn is thoroughly different in calcareous soils amended and unamended with sewage sludge.

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The use of organic matter such as urban sewage sludge may help sustainable soil fertility via improving the physical, chemical and biological soil characteristics. The main purpose of this study was to determine the effect of urban sewage sludge on chemical properties, soil basal respiration and microbial biomass carbon in a calcareous soil with silty clay loam texture. Therefore, three levels of water repellency (zero, weak and strong) were artificially created in a silty clay loam soil by adding urban sewage sludge (S0=0:100; S50=50:50 and S80=80:20 sludge weight: soil ratio). Water repellency was determined by water drop penetration time (WDPT) method. Also some chemical properties such as soil acidity (pH) and Electrical Conductivity (EC), Soil Organic Carbon (OC), soluble sodium (Na⁺) and soluble potassium (K⁺) were measured. The samples were incubated at 23-25 ºC for 30 days and their moisture was maintained at 70-80 % under field capacity and soil basal respiration and microbial biomass carbon of incubation period were evaluated. The results showed that the effect of urban sewage sludge on chemical properties was significant (P ≤0.0001). The application of urban sewage sludge led to significant increase in basal respiration (16 and 27 times) and microbial biomass carbon (15.2 and 26.5 times) in the water repellency soils (S50 and S80) compared to control soil. The observed positive effect of sewage sludge might be due to a high content of organic carbon and nutrients in urban sewage sludge and decrease in the labile organic matter and nutrients during incubation period.
 
 

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