JWSS - Journal of Water and Soil Science

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Soil organic matter and clay minerals adsorb and immobilize extracellular enzymes of microorganisms and increase soil enzymes stability. This study aims to clarify the relative importance of soil organic matter and clay minerals on the cellulolytic activities of soils. Fluca prepared cellulase was immobilized on some agricultural residues and clay minerals, avicel and a sample of soil. Immobilized exoglucanase and endoglucanase were assayed at different times. Activities of the immobilized enzymes were strikingly dependent on the kind of sorbent. After 20 days of storing in refrigerator at 4^oC, the deactivation of immobilized enzymes on the organic substances (as avicel) was very low but deactivation of immobilized enzymes on the soil and clay minerals was relatively high. On the other hand, the activities of immobilized enzymes on the agricultural residues and avicel were significantly higher than the soil and clay minerals. So it may be concluded that a large part of cellulolytic activity of soil is related to immobilized enzymes on agricultural residues. Coating of the clay minerals, soil and avicel with 4 mmol of Al (OH) x per mg of them significantly increased their immobilization capacity and activities of immobilized enzymes. Activities of immobilized exoglucanase and endoglucanase on the Ca- homoionized soil and clay minerals were significantly higher than the K- homoionized soil and clay minerals. However, these effects may be related to the specific effects of cations on the method of enzyme assay or enzymes activities. These homoionizing-cations effects on the activity of immobilized enzymes on avicel were not significant.

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Excessive application of sewage sludge leads to the accumulation of potentially toxic elements in soils. The objective of this greenhouse study was to examine the DTPA–extractability of Fe, Zn, Cu, Mn, Pb, Cd, Ni, and Co in relation to soil pH and to investigate the concentrations of these metals in corn (Zea mayz). The study was conducted using a factorial experiment in a completely randomized design with three replications. Sewage sludge was applied at 0, 50, 100, and 200 t/ha on four soils [Langaroud (pH= 4.8), Lahijan (pH= 5.7), Rasht (pH= 6.8), and Isfahan (pH= 7.9)]. Application of sewage sludge significantly increased DTPA-extractable Fe, Zn, Cu, Pb, Cd, and Ni in all soils. The increasing effect was in accordance with sludge level. Langaroud soil had the highest and Isfahan soil the lowest levels of DTPA-extractable metals. Application of sewage sludge increased plant growth and metals in the foliage of corn plants. The metal concentration in corn tissues also increased with decreasing soil pH. Overall, the application of sewage sludge as an organic material, particularly in acid soils, may increase availability of heavy metals, which may, in turn, result in soil pollution. Therefore, addition of sewage sludge to soils should be managed on the basis of the changes in soil heavy metal concentration.

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Cation exchange capacity (CEC) is one of the most important chemical characteristics which influences soil quality from different aspects. At the same time, CEC is an input parameter of many computer models being applied in soil science and agriculture. Methods of CEC determination are always time-consuming and laborious. Therefore, developing a model for CEC estimation from other soil properties is essential. The objective of this study was to understand the associations between CEC (as a dependent variable) and sand, silt, clay, organic matter and pH (as independent variables). In this study 464 soil samples from A, B, and C horizons of different soils were used. Results revealed that CEC is negatively correlated with sand (r=-0.389***) and is positively correlated with organic matter (r=0.772***), clay (r= 0.391***) and silt (r= 0.233***). No significant correlation was observed between CEC and pH. Stepwise regression analysis showed that both organic matter and clay enter the model and that coefficients of determination (r²) for the multiple models are higher than those of simple linear correlations. Other parameters could not increase the r² considerably. Correlation analysis on data from A, B, and C horizons revealed that the CEC of organic matter in different horizons are not the same. Separation of Aridisols could not increase the r² of the model and the accuracy of the estimations. Correlation studies in acid soils showed that the contribution of organic matter in CEC is much higher than that of clays.

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A factorial experiment with two levels of Zn (0 and 1.5 mg Zn kg^-1), five salinity levels of irrigation water (0, 60, 120 and 180 mM NaC1, and 120 mM NaNO₃) in three replications was conducted. Wheat (Triticum aestivum cv. Roshan) was seeded in pots. After plant harvesting, zinc and cadmium concentrations were determined in the shoot. Activities of metal species in the soil solution were predicted using the computer program MINTEQA2. Treating the soil with NaC1-salinized water increased total concentration of cadmium (Cd_T) as well as Cd²⁺, CdC1⁰₂, and CdCl⁺ species whereas, NaNO₃ treatment had no significant effect on Cd_T. Shoot Cd concentrations were positively related to Cd_T and soil solution Cl^- but negatively related to Zn_T. Application of Zn-fertilizer decreased Cd and increased Zn concentrations in shoot, significantly. The results of this experiment showed that Cl^- has an effective role in increasing mobility of soil Cd and its uptake by plant.

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The ability of earthworms in recycling a wide range of organic solid wastes is well established. Only a few earthworm species are suitable for commercial vermicomposting. Two species, Eisenia foetida and Lumbricus rubellus, are common in temperate regions. Samples of earthworms were collected from manure pills and forest litter in North and Northwest of Iran. The samples were maintained in pots under greenhouse conditions. External morphological characteristics of mature worms were used in identifying earthworm species. These characteristics included: total number of body segments, numbers of clitellum and tubercula pubertatis (TP) segments, dorsal and external body color, body size, prestomium and prostomium shape, number of first segment with dorsal pore and patterns of clitellum and TP. All collected samples belonged to the species Eisenia foetida. Under incubation conditions in manure substrate (a moisture of 70% saturation at 24±2^oC), each worm produced 1-2 cocoons daily and each cocoon contained 2-7 worm embryos. The collected earthworm samples showed a good ability in vermicomposting of manure, plant residues, and some organic industrial refuses. The C:N ratio decreased during the vermicomposting process, which indicates the improved stage of decomposition and the vermicompost stability.

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The possibility of using a steel plant by-product (converter sludge) as an iron fertilizer was investigated. This compound consists of 64% Fe oxides. Considerable amounts of elements such as Ca, Si, Mn, P, and K are also present in the sludge. To study the converter sludge, an incubation experiment was carried out on three calcareous soils. Treatments were 0, 4, and 8 percent of converter sludge mixed with soils plus mixtures of 4% converter sludge with elemental sulfur, thiobacillus inoculum and sulfuric acid. Soil samples (400 g) were kept at field capacity and room temperature in capped, aerated plastic containers for two months. Sub-samples were taken at 1, 10, 30, and 60 days of incubation and analyzed for Fe, Mn, Zn, P, and K contents as well as EC and pH. Results showed that converter sludge increased significantly extractable Fe proportional to the rate of sludge used. Sulfuric acid application increased Fe availability significantly, but the availability of this nutrient generally decreased with the incubation time. Application of the sludge also increased the pH slightly at the beginning of incubation. Elemental sulfur and sulfuric acid application increased Fe and Mn availability significantly. Application of the sludge without and with elemental sulfur and sulfuric acid slightly increased availability of P. The results of this study revealed that converter sludge might be used as an iron fertilizer. However, further investigation in greenhouse and field experiments is needed.

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Lintz-Donawitz (LD) converter slag, a by-product of the iron and steel-making industry is produced in large quantities in Isfahan, Iran. The slag contains 52.8 and 2.2% (w/w) CaO and MgO, respectively. To determine the influence of LD slag on the chemical characteristics of three acid soils from Gilan, an incubation study was conducted. The soil samples were collected from 0-30 cm of rice and tobacco fields and a tea garden. Treatments were 0, 0.5, 1, 2, 4, 8 and 16 % (w/w) of converter slag/kg soil. The slag was thoroughly mixed with 500g soil in plastic pots. Soil moisture content was adjusted to near field capacity and changes in pH, EC and AB-DTPA-extractable Fe, Mn, Zn, P and K were determined at 1, 10, 30 and 60 days. Results showed that soil pH increased with increasing slag rates. Slag increased AB-DTPA-extractable P and Mn, the magnitude increase depend on the amount of slag applied. However, the effect of slag on AB-DTPA-extractable Fe depended on initial pH, initially decreasing at the pH range of 7.4 - 8.5 and then increasing at higher pH levels. Slag decreased AB-DTPA-extractable K especially in highly acid soil. In the present study, soil pH and AB-DTPA-extractable Fe decreased with time, though the effect of incubation time on pH was not significant. The effect of incubation time on AB-DTPA extractable Mn and P was different. Time effect on EC and AB-DTPA-extractable K was not significant. In general, soil chemical characteristics were more affected by slag rates than by incubation time. In conclusion, it seems that converter slag is a suitable amendment for acid soils. It is suggested that the effect of LD converter slag on plant growth and chemical characteristics of acid soils be studied under field conditions.

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To investigate drought tolerant isolates of rhizobial symbioant of lentil (Lens culinaris L.), 12 soil samples were collected from cultivated and non-cultivated area of Golestan, Chaharmahal-O-Bakhtiari and Isfahan provinces. Local cultivars of lentil including Binam Dorosht, Ghazvini and Faridani were planted in each soil sample. After 10 weeks, a total of 324 rhizobial isolates were recovered from root nodules of the lentil plants. Evaluation of the ability of the isolates to grow at different concentration of salt showed that all isolates grew normally on 200 mM NaCl and only 20% was determined as salt tolerant isolats(>400mM). Among the isolates RL249 was classified as superior salt tolerant strain due to growing on 600 mM salt. The drought tolerance of the isolates was also examined, using PEG6000. In general, the salt tolerant isolates were also drought tolerant, however their tolerance to salinity and drought is not related to their geographical origin. In a randomized split factorial design with three replications, the effectiveness of tolerant isolates(RL249 and RL211) and a sensitive strain (RL 77) was compared on two cultivars of lentil (Binam Dorosht and Faridani) under water stress treatments with the consumptions of 50, 75,90 and 98% of soil available water. Although nodulation rate was reduced in both cultivars as the consequence of drought stresses, plants of Binam Dorosht cultivar showed high nodulation rate due to the increased fresh weight of the roots. Despite the fact that RL249 was identified as a superior nodulating and salt/drought isolate, however nodulation efficiency was decreased significantly under water stress treatments with more than 50 % of soil available water.

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Sewage sludge and effluents, as cheap sources of irrigation water and fertilizer, can supply plants with water and nutrients however, contamination of these sources with heavy metals and the possibility of human food chain contamination using these sources should be considered. In this research, the effects of industrial sewage sludge and effluents on concentration of some nurtients, heavy metals and sodium and dry matter yield of wheat (Triticum aestivum), barley (Hordeum vulgare) and corn (Zea mays) were investigated. The experiment was carried out in a greenhouse using a complete randomized design with four replication. The treatments comprised well water, well water + sewage sludge(50 tons/ha), and three industrial effluents from Iran Polyacryl factory including the cooling tower, the over flow and the factory outlet effluents. Chemical analysis showed the following results: The concentration of the elements in the sludge and the effluents were below the critical contaminating levels. The application of the treatments did not supply enough nitrogen for corn the cooling tower effluent could not supply enough nitrogen for wheat and barley all the treatments supplied enough P for wheat. None of the treatments could supply enough P for corn. The cooling tower, over flow and the factory outlet effluents could not supply enough P for barley, the micronutrient and heavy metal concentrations in the plant tissues using the effluents and the sewage sludge were higher than those for well water the dry matter yield of plants’roots and shoots was highest using well water + sludge and in comparison with the well water, effluents could increase the shoot dry matter yield.

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Hamadan province is one of the most important alfalfa (Medicago sativa) producing regions in Iran. However, little is known about P status in this region and no suitable extraction method has yet been introduced. This experiment was carried out to determine the available phosphorus by nine chemical extractants in some soils of the Hamadan region. The treatments consisted of 15 soils and 2 P levels (0 and 200 mg P kg^-1 as Ca(H₂PO₄)₂.H₂O ) in a factorial experiment in a randomized design with three replications. Alfalfa plant were harvested in three cutting. The results indicated that the amount of extractable phosphorus decreased in the following order: Collwell>Bray 2>0.1 N HCl>Bray 1>Olsen>AB-DTPA>Mehlich 1>Mehlich 2 > 0.01 M CaCl₂ The amounts of P extracted by all methods except that by 0.01 M CaCl₂ method, showed significant correlation. The results of correlation studies showed that in the first cutting, Collwel method, in the second cutting AB-DTPA, Olsen, Collwel, Bray 1, Bray 2 and Mehlich 2 and in the third cutting, AB-DTPA, Olsen, Collwel, Bray 1, and Mehlich 2 methods seems to be suitable extractants for assessing available P of soils in Hamadan province.

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Application of sewage sludge on the farmland as a source of crop nutrient had recently received considerable attention. Some management practices may be required to control the accumulation of toxic elements including Pb, Ni and Cd. Sequential extraction gives useful information on plant bioavailability of the elements. The objective of this study was to investigate the cumulative and residual effects of sewage sludge application on the chemical forms and mobility factor of Pb, Ni and Cd. Zero, 25, 50 and 100 Mg ha-1 of sewage sludge were applied for 1, 2 and 3 consecutive years in a split plot design, with three replications. Soil samples were taken from 0-20 cm at the end of the third year of application. Different chemical forms of Pb, Ni and Cd were measured. Results revealed that the soluble form (SOL) of Ni and Cd increased whereas Pb soluble form decreased with increasing levels and years of application. Exchangeable (EXC), carbonate (CAR) and organic (ORG) forms of the three elements increased as levels and years of application increased. Occluded (OCC) form decreased for Pb, Ni and increased for Cd. Residual form (RES) of Pb increased while that of Ni and Cd decreased. A gereral increase was observed for available (DTPA-extractable) concentration of Pb, Ni and Cd. Relative distributions of different chemical forms were in the following order: Pb: OCC > RES> ORG> CAR> EXC> SOL, Ni: RES> ORG> OCC> CAR>EXC> SOL and Cd: OCC> CAR> RES> ORG> EXC> SOL. The comparison of different forms of the metals showed the following orders: soluble Ni>Pb>Cd, exchangeable, carbonate and occluded Pb>Ni> Cd, organic and residual Ni> Pb>cd. Increasing the available (DTPA-extractable) concentration of the elements in such a calcareous soil showed that consecutive application of sewage sludge may increase the available (DTPA-extractable) concentration beyond critical levels. A significant corretation was observed between organic form and available (DTPA-extractable) concentration of the elements.

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Sewage sludge application on farmland as fertilizer is commonly practiced in many countries. Sewage sludge is rich in macro- and micro- nutrients. However, high concentration of heavy metals in sludge may cause pollution of soil, groundwater and human food chain because of uptake of toxic metals by crops. The objective of this study was to determine residual and cumulative effects of sewage sludge on concentration of Pb and Cd in soil and wheat. Different levels of 0, 25, 50 and 100 Mg ha^-1 of sewage sludge were applied to the soil for four years. To study the cumulative and residual effects of the sewage sludge, applications were repeated on three fourth of each plot in the second year, on one half of plots in the third year and in one fourth of plots in the fourth year. Wheat grown in the plots, after the fourth year, soil samples from the 0-20 cm depth of the different parts of the plots were taken and analyzed. Wheat was also harvested roots, stems and grains were separately analyzed for the heavy metal concentritons. Cumulative sewage sludge application increased OM, CEC, ECe, total and DTPA-extractable concentration of Pb and Cd in soil significantly (P≤ 0.05). Residual sewage sludge in the soil also increased CEC, total and DTPA-extractable concentration of Pb and Cd significantly. Single sludge applications at different rates increased the DTPA-extractable concentrations of heavy metals. In subsequent years with no further sludge application, DTPA–extractable metal concentrations in soil decreased continuously approaching the levels in the control. However, even after four years, DTPA-extractable concentration of Pb and Cd, were still significantly higher in plots which received more than 50 Mg ha^-1 sludge than control. DTPA-extractable concentrations of Pb was closely correlated with total concentrations. Sewage sludge increased concentration of Cd in roots and stems and Pb in grains significantly. Cumulative effects on concentrations of Pb in grains, and Cd in stems were more than residual effects. The results of this study show that cumulative and residual effects of sewage sludge application increased concentrations of heavy metals in soil and wheat.

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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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Iron deficiency is most widespread among plant nutrients. Nowadays, different materials such as inorganic salts, organic chelates, soil acidifying materials and industrial wastes are used to correct iron deficiency. Slag and convertor sludge of steel factories are among the industrials wastes for this purpose. These materials contain considerable amount of iron produced in large quantities every year. Application of slag and convertor sludge to soil may affect bioavailability and chemical forms of iron in soil. Sequential chemical extraction technique has been widely used to examine these chemical forms, and thus to better understand the processes that influence element availability. It was, therefore, the objective of this study to investigate the application effect of slag and convertor sludge of Esfahan Steel Mill on the chemical forms of iron, distribution of these forms and bioavailability of iron in surface (0-20cm) and subsurface (20-45cm) soil of three research fields. The results showed that more than 99% of the applied Fe occurred in residual, Fe oxide and hydroxide and free forms. Application of slag and convertor sludge for three consecutive years increased chemical forms and DTPA extractable iron in surface and subsurface soil of three fields.

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In Iran, no research has yet been performed on potassium release from feldspar in comparison with that from muscovite. The objective of this research was to compare potassium release kinetics of these minerals as influenced by organic and inorganic extractants using successive extraction method. The experiment was carried out in a completely randomized design with a factorial combination. Treatments consisted of three kinds of K-bearing minerals (Muscovite, and Yazd and Ward feldspars), three extractants including CaCl2, oxalic and citric acids of 0.01 M concentration and 6 times of extraction (1, 2, 8, 24 and 48 hours). The results indicated that the potassium release from muscovite was 6-8 times higher than that from feldspars. The type of extractant significantly affected potassium release. Potassium release by organic extractants was 2.5-3 times higher than that by CaCl2 as an inorganic extractant. Different kinetic equations showed that power function, parabolic diffusion and first order equations adequately described K release whereas Elovich equation did not. Among the three equations, power function equation was selected as the best model describing K release from the minerals. Based on the selected kinetic equations, it seems that potassium release from K-bearing minerals is controlled by diffusion process.