JWSS - Journal of Water and Soil Science

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Soil structure maintenance and stability is an important index indicating sustainable soil management. In this regard, components such as soil moisture and organic matter affect soil compactibility during farm machinery trafficking. Soils in Central Iran are commonly very low in organic matter (OM) and thus susceptible to compaction. This study was conducted to measure the effects of soil moisture content and manure application on soil compactibility. A randomized complete block design with four blocks (replicates) with the treatments nested (split-block) into the blocks was used in the soil (Typic Haplargids), located in Isfahan University of Technology Research Farm (Lavark). One-year aged manure treatments 0, 50, and 100 t ha^-1 were incorporated into soil up to the tillage depth (20 cm) by a heavy disc. After five months (July-November), a two-wheel-drive tractor Universal Model U-650 was passed through the field at soil moisture contents of plastic limit (PL), 80% PL (0.8PL), and 60% PL (0.6L), either once (P1) or twice (P2). Bulk density (BD), cone index (CI), and soil sinkage (S) were measured as indices of soil compactibility and trafficability. Adding manure countered the effects of load and wetness on BD and CI, significantly. There was a significant difference between the effects of 50 and 100 t ha^-1 of manure on BD but not on CI. Manure application reduced soil sinkage at high moisture contents (PL) but increased it at low moisture contents (0.6PL). Adding manure also reduced the BD and CI of subsoil. Repeating the passage of tractor (P2) increased compaction significantly. The significant increase in BD and CI did no occur at 0.6PL. When no manure was applied even at 0.6PL, there were limitations for trafficability, whereas this limit for 50 t ha^-1 treatment was reached at 0.8PL. Results from this study indicate that the manure application at a rate of 50 t ha^-1 reduces soil compactibility and increases soil moisture trafficability range.

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Due to high production of organic residues such as sewage sludge and compost, land application is probably the best way to prevent accumulated residues in the environment. However, the risk involved in the land application of organic residues should be evaluated prior to the assessment of their economic and fertilizer values. The objective of this study was to evaluate the effect of organic residues on soil chemical properties, yield and uptake of heavy metals and nutrients by corn (Zea mays L.). The study was a randomized complete block design with three replications with four treatments including cow manure, sewage sludge, municipal compost and inorganic fertilizer.

The organic amendments were applied to the plots at a rate of 50 t ha^-1 and inorganic fertilizer treatment consisted of 250 kg ha^-1 ammonium phosphate and 250 kg ha^-1 urea.

 Organic amendments significantly increased soil organic matter content, EDTA-extractable Fe, Zn, Cu and Pb and plant available P, K, and N. Uptake and concentration of nutrient in corn grain and shoots were significantly affected by treatments, whereas Cd and Pb concentrations were the same among the treatments. Cow manure and sewage sludge treatments had the highest and compost had the lowest corn silage and grain yields. Overall, the results indicated that cow manure and sewage sludge had a high fertilizer value and led to heavy metal concentrations in soil as well as corn tissues which were much lower than the reported standards.

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The effects of 4 different levels of nitrogen (0,120,150, and 180 kg nitrogen per hectare) and one level of poultry manure (10 tons per hectare) on the quantitative and qualitative characteristics of an autumn grown cultivar of cucumber [Cucumis sativus, cv.'super dominos] were studied in DarrehShahr, Ilam. The experiment was conducted in a completely randomized block design with 3 replications. The results showed that treatments affected yield, number of nods and plant fresh weight and the highest yield was 41/287 ton/ha in the plots receiving poultry manure. Also 180 kg of pure nitrogen increased yield compared to control. Effect of treatments on fruit length, diameter, and fruit dry matter was different. Plant length, number of nodes, and plant fresh weight showed a positive and significant correlation with plant yield.

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The objective of this study was to evaluate effects of cow manure on soil hydraulic properties and bromide leaching in a sandy loam soil (coarse loamy mixed, Typic Torrifluvents). Manure was applied at 0, 30, and 60 tha^-1 at three replications in a completely random design. Three months after manure application potassium bromide (KBr) at rate of 300 Kg ha^-1 Br was uniformly applied on the surface. Soil bulk density, porosity, organic matter, and soil moisture at18 levels of matric potentials were determined. Soil samples to the depth of 105 cm at 15-cm increments were collected after 100, 200 and 400 mm of irrigation. Soil bulk density, porosity, organic matter content, and soil moisture at different levels of matric potential increased significantly with manure application. Manure application also significantly affected the hydraulic parameters. Bromide leaching was significantly lower in plots with manure application and the greatest leaching occurred at the zero manure application treatment. The center of mass evaluation indicated a relatively similar result with measured values.

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It is necessary to use organic fertilizers and decrease chemical fertilizers consumption to reach sustainable agriculture. Thus, to study the effects of manure incorporation methods, and integrated effects of poultry manure with chemical fertilizers on the grain yield and yield components of maize, an experiment was conducted in 2004 at the Agricultural Research Farm of Lorestan Weather Department, 30 kms northeast of Khorramabad. The treatments were arranged in a split plot layout based on randomized complete block design with four replications. The main plots consisted of incorporation of fertilizer with soil by furrower or disk. The subplots included T0: control (no consumption of fertilizer and poultry manure) T1: 200, 100, and 100 kg ha^-1 of nitrogen, phosphorus, and potassium, respectively T2: 80% of T1+ 4 ton ha^-1 of poultry manure T3: 60% of T1+ 8 ton ha^-1 of poultry manure T4: 40% of T1+ 12 ton ha^-1 of poultry manure T5: 20% of T1+ 16 ton ha^-1 of poultry manure and T6: 20 ton ha^-1 of poultry manure. The results showed that incorporation of fertilizer by furrower, compared with disk, led to significant increase in plant height, 1000 seed weight and grain and biological yields. However, there were not significant differences in the number of seed per ear and harvest index between the two fertilizer incorporation methods. Fertilizer treatments caused significant increase of the treats mentioned except for the harvest index. The interaction effects were not significant for any traits. T5 treatment produced the highest grain yield, and was significantly different from T0, T1, T3 and T6 treatments. The differences between T1 (chemical nutrition system) and T6 (organic nutrition system) were not significant either. Effectiveness of integrated poultry manure and chemical fertilizers on maize yield components was higher than either poultry manure or chemical fertilizer. The results of this experiment indicated that incorporation of 16 ton poultry manure + 40, 20 and 20 kg ha^-1 N, P and K with furrower might be appropriate for maize prodution under conditions similar to this experiment.

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The increased potential for soil erosion and compaction due to continuous row crop production and intensive tillage is causing some concern and has led to the consideration of reduced tillage techniques as part of the solution. The objective of this study was to investigate the short-term (one-year) influences of different management practices on the physical properties of a sandy loam soil under corn crop. Treatments were the combinations of three tillage systems (no-till, NT chisel plow, CP and moldboard plow, MP) and three composted cattle manure rates [0, 30 and 60 ton (dry weight) ha^-1]. The experiment was carried out in a split-plot design. Three replicates of the treatments were applied in a randomized block design. Saturated hydraulic conductivity (K_s), total porosity (TP), macro-porosity (Macro-P), micro-porosity (Micro-P) of soil and mean weight diameter (MWD) of aggregates, were measured to a depth of 22.5 cm when 100 percent of the tassels appeared. Tillage and manure combination had significant effects on Log[ K_s], TP, Macro-P and Micro-P. The MP system increased pore space and continuity due to complete inversion and loosening, and as a result K_s, TP, Macro-P and Micro-P were higher than NT system. Higher Macro-P observed for CP might have caused higher K_s versus MP. Reduced tillage systems increased MWD and the increment of manure caused an increase in MWD over all tillage treatments. The results indicate short-term positive effects of manure application on soil pore size characteristics and aggregate stability under moldboard and chisel plowings in the region.

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  Organic fertilization has been practiced in Iran due to the shortage of soil organic matter. In recent years, attention has been payed to the organic fertilizers because their commercial production has recently started and demands for their application have increased. The objectives of this study were to investigate the effects of organic fertilizer type, rates and times of application on the N mineralization potential (NMP) in a calcareous soil (fine loamy, mixed, thermic, Typic Haplargid) in Isfahan region. The soil samples were collected from a previousely established field experiment. The experiment design was split plot with three replications. Each main plot was split into subplots receiving 1, 2 and 3 annual consecutive applications of cow manure and sewage sludge at the rates of 0, 25 and 100 Mg ha^-1. The soil samples were taken from 0-15 cm depth, 6 months after the third application of the organic fertilizers. Nitrogen mineralization potential was measured by a long-term leaching-incubation procedure. Results indicated that NMP was similarly affected by cow manure and sewage sludge. Nitrogen mineralization potential in the treatments which received 100 Mg ha^-1 organic fertilizers, was 4 and 1.7 times greater than that of control and 25 Mg ha^-1 treatments, respectively. A significant increase was also observed in NMP in the treatments which received different times of application. The NMP in the three-year applied treatments was 5, 2.5 and 2.1 times greater than that of control, two- and one-year applied soils. Significant correlations were observed between NMP and corn yield (r=0.531**) and corn N uptake (r=0.568***). The product of NMP and N mineralization rate constant was also significantly correlated with corn yield (r=0.710***) and corn N uptake (r=0.734***). Different patterns were observed between the responses of total N and NMP in the treated soils.

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  Understanding nitrogen mineralization from different organic sources should be a key factor in developing efficient prediction of the need for nitrogen fertilization with minimal negative environmental impact. In order to investigate nitrogen mineralization rate in soils amended with compost, vermicompost and cattle manure, an experiment was done as factorial in a randomized complete block design in three replications. Four treatments (compost, vermicompost, cattle manure and soil alone), two temperature levels (8 and 25 ⁰C) and two moisture levels (50% and 85% FC) were used for the 90 - day incubation study. Ammonium and nitrate were measured by spectrophotometer method. Results indicated that the mixed first-and zero-order kinetics model is the best model for our data. Cattle manure treatment had the highest N_min at 25 ⁰C (87.78 mgN/kg equal to 14.54% N_total) and the least value (23.62 mgN/kg equal to 4.62% N_total) was obtained for the compost treatment at 8 ⁰C. N₀k (nitrogen availability index) for treatments was in the following order: Cattle manure>Vermicompost >Compost. With increasing the temperature and moisture, N mineralization increased. Also N_min positively correlated with N₀ (r =0.583*), and N₀k (r =0.834**).

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  Application of slag and converter sludge, major by-products of Esfahan Zob Ahan factory, to enrich two organic amendments for corn nutrition, was investigated. Farm manure and its vermicompost mixed with different rates of slag and sludge were incubated in 3 Kg pots at field capacity moisture and home temperature for three months. The applied rates of slag and sludge were 0, 5 and 10 percent (w/w) of pure iron from these compounds to the organic amendments. Iron sulfate with the above ratios was also examined for comparison. Sub-samples of the incubated materials were taken after 0, 10, 25, 45, 65 and 90 days of incubation and examined for DTPA extractable Fe, Mn, Zn and Cu. After the incubation, the enriched amendments were applied to a soil sample to grow corn. Three Kg soil samples, taken from Chah Anari experimental farm, Esfahan University of Technology, were mixed with 17 gr of the amendments (50 ton/ha) placed in 3 Kg pots. In each pot two corn seeds (single cross 704) were planted and after 70 days crop yield and concentration of Fe, Mn, Zn, Cu in the plant tissues were determined. Results showed that the use of iron sulfate strongly increased DTPA extractable Fe and Mn of the amendments. In enrichment by converter sludge, the best result was obtained in the mixture of 10 percent pure iron with the vermicompost on 60 days of incubation. Treatment of 5 percent pure iron from slag mixed with the manure increased DTPA extractable Fe and Mn with the time, but the 10 percent treatment was not much effective in this regard. The highest rates of iron uptake by the plants occurred in the iron sulfate and 10 percent converter sludge treatments, respectively however, the highest rate of the plant Mn uptake was observed in 5 percent iron from converter sludge mixed with vermicompost. In general, 10 percent pure iron from converter sludge was the most effective enrichment treatment, increasing the plant uptake of Fe, Mn, Zn and Cu micronutrients.

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Organic fertilizers are the sources of many human-pathogenic microorganisms which potentially threaten the human health. This study was carried out to explore the possible effects of soil and manure types on filtration, transport and fate of manure-borne bacteria through undisturbed soil columns. The manure treatments consisted of cow manure, poultry manure and sewage sludge which were distributed at the rate of 10 Mg ha-1 on the surfaces of intact columns of two sandy clay loam and loamy sand soils. The manure-treated soil columns were leached by tap water with similar unsaturated flux of 4.8 cm h-1 up to four pore volumes (PV). The influent and leachate were sampled at different PVs. Gram-negative bacteria concentrations were determined for the influent and the columns’ leachate. Average influent concentration, average effluent concentration, relative filtration, and transported bacteria fraction during the leaching events were determined. Significant differences (P<0.05) were observed between the poultry manure and the other two manures in terms of average influent (i.e. manure-released) bacteria concentration. Stable structure and preferential pathways facilitated the bacteria movement in the sandy clay loam soil columns. The loamy sand soil strained 1.45 times more bacteria than the sandy clay loam soil due to its weak structure and blocked-dead pores. Relative contamination of the effluent was higher for poultry manure when compared with the other fertilizers. The low ionic strength of sewage sludge suspension caused the lower filtration of bacteria through the soil columns. The high concentration of soluble organics in cow manure resulted in a relative transport of the bacteria 1.12 times greater than the poultry manure. In general, management of organic fertilizers especially household poultry manure, as a considerable source of pathogenic bacteria, is important to control the environmental risks of pathogenic pollutions. Moreover, the soil texture and structure significantly affected the fate of manure-borne bacteria.

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Organic matter (OM) and total N (N) are relatively low in majority of the calcareous soils in Iran, and continuous use of N fertilizer would impair the quality of surface and ground water and creates other environmental hazards. Therefore, the combined use of N fertilizer and organic wastes is important to partly supply plant N requirement, improve physico-chemical properties of soil and conservation of environment. The present study was initiated in order to study the effect of two organic wastes with and /or without N enrichment on the growth and chemical composition of paddy rice and some characteristics of the soil in pot experiment. The experiment was carried out in factorial manner in a completely randomized design with three replications. Treatments were two organic matter sources (municipal solid waste compost and cow manure), four OM rates (0, 1, 2, and 4%) and three N levels (0, 75, 150 mg kg-1 soil as urea). Application of compost and cow manure increased top dry weight of rice. The highest growth of rice was obtained with 4% compost and 150 mg kg-1 N. Rice growth increased up to 2 % cow manure and was suppressed with the higher rate, due to build up of soluble salt in soil. Enhancing effect of N on rice growth was only observed with 1% cow manure and at high level of cow manure rice growth was decreased probably due to rise in soil salinity or ammonium toxicity. The mean concentration of N increased by the addition of cow manure, whereas decreased with compost application. Soil N application enhanced the mean concentration of N, and iron (Fe) and magnesium (Mn). Rice plants enriched with either of the two organic wastes accumulated more phosphorus (P), potassium (K), N, Fe, Mn, chloride (Cl) and sodium (Na) than control plants. Post harvest soil sampling indicated that organic matter significantly improved all chemical characteristics. Furthermore, soil treated with cow manure had higher soluble salt (ECe), Cl, K, OM, total nitrogen, available P, Fe and Mn and lower Zn, Cu, lead (Pb), cadmium (Cd) and sodium adsorption ratio.

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Compost and sewage sludge contain high concentration of plant nutrients and, thus, have been used extensively as an inexpensive fertilizer. The objective of this study was to evaluate cumulative and residual effects of compost, sewage sludge and cow manure on nitrogen, phosphorus and potassium in soil and wheat. The experiment included compost, sewage sludge and cow manure, each applied at 3 rates (25, 50 and 100 Mg ha-1), a chemical fertilizer (250 kg ha-1 amonium phosphate + urea) and a control plot with 3 replications. The experimental design consisted in completely randomized blocks with treatments arranged in split plots. To study the cumulative and residual effects of the organic amendments, application was repeated on four fifths of each plot in the second year. Wheat was grown in the plots. The results showed that one application (residual effect) of organic amendments had not significant effect on total N in soil and wheat leaves and stem, but it led to significant increase of available phosphorus and potassium in soil and wheat leaves and stem. Cumulative effects of organic amendments significantly (P≤ 0.05) increased the total N (in 50 and 100 Mg ha-1 Cow manure and 100 Mg ha-1 Compost treatments), available P in all organic treatments and K (in all Compost and Cow manure treatments) in soil. Also, cumulative effects of organic amendments significantly (P≤ 0.05) increased the N (in 100 Mg ha-1 sewage sludge), P (in 100 Mg ha-1 compost) and K (in all organic treatments with the exception of 25 Mg ha-1 Compost) concentrations in leaves and stem.

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Tillage systems and organic manures could affect soil physical and mechanical properties. This study was conducted to investigate the impacts of two tillage systems including conventional tillage by moldboard plowing (plowing depth, 30 cm) and reduced tillage by disk plow (plowing depth, 15 cm) and three rates (0, 30 and 60 ton ha-1) of farmyard manure (FYM) on the soil penetration resistance under corn cropping in a split block design with 3 replications. The cone index (CI) decreased with increase of the tillage depth. It is attributable to soil disturbing and loosening of the deeper layers under conventional tillage compared to reduced tillage. This trend, however, was observed only in the first (after treatments’ application and before cropping) and second (the highest rate of vegetative growth) samplings. In the third sampling (after harvest), there were not significant differences between the CI values under two tillage systems in different soil depths. It might be due to soil re-compaction (approaching the pre-tillage state) as well as disappearance of the tillage effects seven month after commencement of the experiment. In fact, the soil mechanical resistance increased with the time indicating soil re-compaction over the growing season. Adding FYM to the surface layer (i.e. 0-10 cm) of ridge soil resulted in significant decrease of soil mechanical resistance compared to control treatment. The CI decreased significantly in the 30 ton ha-1 treatment up to the stage of highest rate of vegetative grow, but the effect on CI was diminished after harvest. However, the decreasing effects of the 60 ton ha-1 treatment on the CI continued to the harvesting time. There were no significant effects of FYM in the soil deeper than 10 cm from the ridge surface and in all of the layers in furrow. The CI did not decrease significantly in the furrow due to negligible effect of manure application for the inter-row position.

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One important parameter in determining the allowable stress to prevent soil compaction is pre‌compaction stress (σpc). If the stress induced into the soil due to agricultural machinery traffic is lower than the σpc, the possibility of the irreversible (plastic) deformation is low. In this study, plate sinkage test (PST) and confined compression test (CCT) were used to determine the σpc of the disturbed soil samples obtained from the topsoil of a long-term organic amendment experiment. In the organic amendment experiment, organic manures (sewage sludgeو compost, farmyard manure) at three rates (25, 50 and 100 t ha-1) and one inorganic fertilizer combination (250 kg urea ha-1 and 250 kg ammonium phosphate ha-1) were added to a silty clay loam soil for seven years under wheat-corn rotation. The effect of organic and inorganic fertilizers and gravimetrical water contents (17.1 and 20.9% db) on the σpc values was determined using two statistical designs: 1) factorial design and 2) orthogonal contrasts in a completely randomized design with three replications. The σpc values were estimated by the following methods: 1) Casagrande, 2) maximum curvature and 3) intercept of virgin compression line (VCL) with the x-axis at zero strain. The results showed that in both tests, the σpc values for treatments amended with organic manures had over-estimations and the values of the over-estimation were increased as the manure application rate increased. The values of the over-estimations for CCT were higher than for PST. Therefore, it can be concluded that the results of the PST are more reliable. The σpc values estimated by any of the three procedures depend on the manure treatment as well as the initial water content of the soil. For determining the stress at the threshold of the compaction for the un-manure soils (control and inorganic fertilizer) or the treatments amended with low application rate (25 t ha-1) of the organic manures, the PST and the Casagrande procedure can be recommended. In contrast, for the soils amended with high application rates (50 and 100 t ha-1), the PST and the maximum curvature procedure can be used.

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Soil structure and aggregate stability affect soil erodibility. There is a necessity for increasing aggregate stability against erosive factors such as wind and water. This study was conducted on surface soil samples (0-20cm) collected from agricultural land susceptible to erosion located in Chahoo, southeast of Fars province. The experimental design was CRD with 10 treatments and was replicated 3 times as follows: control plot (without addition of soil amendments), pure gypsum, chopped wheat straw, farm yard manure, gypsum+wheat straw, gypsum+ farm yard manure (1% w/w), cement at levels (0.3% w/w), (0.6% w/w), (0.9% w/w), gypsum +cement (0.9% w/w). After one, four and seven months, the amounts of soil aggregates in 53-4000 µm sizes were determined by wet sieving and MWD was calculated. The results of aggregate size distribution in every stage of the experiment showed that application of farm yard manure and wheat straw separately or in combination with gypsum through reduction in aggregates with diameters of <106 µm has caused an increase in aggregates with diameter of >106 µm. Based on the results of this research, the effect of these treatments, which increased MWD of the aggregate, results from the amount of aggregates with diameters larger than 1000 µm. According to the results of this study, it is suggested that these treatments be considered suitable to increase the stability of sensitive silt loam soils.

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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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In agriculture, cow manures are used to enhance soil fertility and productivity. Escherichia coli is the most common fecal coliform in cow manure and considered as an index for microbial contamination of groundwater resources. The objective of this study was to investigate the transport of Escherichia coli (released from cow manure) through the field soil. Lysimeters (with internal diameter of 20.5 and height of 50 cm) were inserted into an in situ clay loam soil. Unsaturated soil water flow was controlled at an inlet matric potential of –5 cm using a tension infiltrometer. When the steady-state flow was established, air-dried fresh cow manure was applied on the lysimeters at a rate of 10 Mg ha-1 (dry basis) and the soil-manure leaching started. Soil solution was sampled at 1, 2, 4, 6, 12 and 24 h after leaching initiation using plastic samplers installed at depths of 20 and 40 cm. Concentrations of Escherichia coli in the soil solution (C) and the influent (C0) were measured using the plate count method. Impacts of soil depth, sampling time, and their interaction on C and C/C0 were significant (P<0.01). In all leaching times, relative adsorption index (SR) was lower when both soil layers were considered and the filtration increased with soil depth. When the concentration was corrected for the second layer (i.e. 20–40 cm), the SR values in this layer were considerable and greater than those in the first layer at 4 and 6 h. The influence of surface layer was substantial in bacterial filtration however, the preferential flows especially in the initial leaching times resulted in bacterial movement towards the second layer. Temperature drop reduced bacteria release from the manure, increased viscosity of the flowing water, and consequently diminished significantly the bacteria concentration in the soil solution at 24 h. Overall, it was found that similar to surface layer, subsurface layer might have great role in bacterial filtration due to its higher clay and carbonate contents

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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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Composting and vermicomposting are two efficient methods to recycle organic wastes. In order to investigate the structural changes in organic matter during the composting and vermicomposting processes, cattle manure and filter-cake of sugar cane were incubated with and without earthworm's presence in a controlled temperature and moisture condition for 16 weeks. Compound samples were taken at 0, 8, and 16 weeks. Carbon, nitrogen and C:N ratio were measured by a CN analyzer apparatus. Solid samples were used for structural analysis using FTIR and solid state CP MAS 13C NMR devices. C:N ratio was decreased with improving decomposition process. The C:N ratio was slightly elevated after 16 weeks of vermicomposting. Structural analysis with both spectroscopic methods showed a decrease of O-alkyl C and increase of aromatic and carboxylic functional groups. The analysis of samples with 13C NMR showed that after 16 weeks, the percentage composition of O-alkyl filter-cake decreased from 41 percent in the first sample to about 33.1 percent. The amount of these compounds in manure samples decreased from 56.7 percent to 43.6 percent. Aromatic compounds in samples of raw filter-cake and manure increased from 12.5 and 13.5 percent to 16.4 and 18.7 percent, respectively. Percentage of carboxyl compounds increased, respectively, from 8.5 and 5.6 percent to 9.7 and 7.2% in the filter-cake and manure sample. Vermicomposts had higher content of aromatic groups compared to composts (In manure samples 18.7 instead of 17.1 percent). After 16 weeks of incubation the aromatic and carboxylic compounds slightly decreased in the vermicomposting process. Analysis of composts and vermicomposts with FTIR and 13C NMR resulted in similar signals with the different frequency intensities. There was a suitable correlation (r=0.897**) among the spectroscopic methods in characterization of composts and vermicomposts

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The incorporation of plant residues in soils of arid and semiarid regions is a major principle of sustainable agriculture. This study was conducted at the research farm of Urmia University (37° 32’N and 45° 5’ E), Urmia, Iran during the 2009 and 2010 growing seasons. Five green manure crops were grown in four replications arranged in a randomized complete block design. The treatments included white clover (T.repens), sainfoin (Onobrychis viciaefolia), pearl millet (Panicum miliaceum), sorghum (Sorghum bicolor) and turnip (Eruca sativa). Changes in soil nutrient elements and nitrogen mineralization were measured during different time periods after plant residues incorporation to soil. The plants were irrigated 50% of field capacity during growing period. The results showed that the total nitrogen and NH4-N were influenced by type of green manure in both years. The lignin and cellulose were the main factors controlling N mineralization and residue decomposition. In the first and second year, the results indicated that pearl millet green residues resulted in the highest amount of soil organic carbon. Nitrate-N content reached the highest amount in sainfoin and white clover. In conclusion, white clover and sainfoin due to increasing total and mineral nitrogen for subsequent plants could be introduced as a proper green manure in water deficit conditions.