DTPA Soil Research Articles

Pollution assessment, ecological risk and source identification of heavy metals in paddy soils and rice grains from Salem, South India

The present study investigated concentrations of metals (Cu, Zn, Fe, Mn, Ni, Pb, and Cd) in paddy soils and rice tissues of nine different widely used indica rice varieties in Salem district, India. The order of DTPA soil available metal contents (mg kg-1) were Fe (33.50) > Mn (8.86) > Cu (2.58) > Pb (1.99) > Zn (1.67) > Ni (1.48) > Cd (0.13). Pollution load index (PLI) levels for Cd (1.28) were ‘moderately polluted’, contamination factor (CF) and enrichment factor (EF) values for all metals showed ‘medium contamination’ and ‘less enrichment’ except for Cu and Pb. Ecological risk factor (ERF) and potential ecological risk index (PRI) values of Cd (31.94 and 287.50) showed ‘moderate risk’ and ‘strong ecological risk’. Bio-accumulation factor (BAF) levels of Cd (48.12) and Pb (27.89) are classified as ‘high concentrators’. Translocation factor (TF) values of Pb (2.9), Cd (2.5) and Ni (1.7) were greater than one for roots to plants. Children had higher target hazard quotient (THQ) and hazard index (HI) values for Cd, Pb and Ni than adults. Principal component analysis (PCA) revealed with all parameters that they fell within the two primary factors 1 and 2, with an eigenvalue of 4.69 (33.52% variation) and 3.73 (26.66% variation), respectively. However, cluster analysis (CA) revealed three distinct groups between the metals studied. Although the soil metal contents were within the permissible levels, the grain Cd (6.07 mg kg-1), Pb (56.20 mg kg-1), and Fe (116.11 mg kg-1) contents in all the rice varieties exceeded the prescribed limits of 0.4, 0.2, and 15 mg kg-1, respectively. Our findings will provide important data for metal enrichment in soils to implement more effective measures to reduce the contamination of metals in paddy fields.

Potential to Ensure Safe Production of Water Spinach in Heavy Metals-Contaminated Soil by Substituting Chemical Fertilizer with Organic Fertilizer

Organic fertilizers are widely used to improve soil quality. However, their potential for ensuring the safe production of vegetables in soils with varying levels of heavy metals pollution remains inadequately explored. Here, we conducted a pot experiment to investigate the effects of substituting chemical fertilizers with organic fertilizer on the HMs accumulation in water spinach by simulating soils with different levels of HMs pollution. The results showed that the organic fertilizer significantly increased the soil pH, cation exchange capacity (CEC), and organic matter (OM). Furthermore, it led to a reduction in the soil DTPA–Cd and DTPA–Pb levels by 3.3–20.6% and 22.4–47.3%, respectively, whereas the DTPA–As levels increased by 0.07–7.7 times. The organic fertilizer effectively reduced the Cd and Pb content in water spinach below the safety limits when the added Cd content in the soil was less than 2 mg/kg and the Pb content was equal to or less than 90 mg/kg. However, its efficacy in reducing As accumulation in water spinach was limited, emphasizing the need for caution when using organic fertilizers in As-contaminated soils. Our results provide valuable insights for the scientific and precise utilization of organic fertilizers, thereby contributing to the safe production of vegetables.

Varietal responses to a soil amendment: Balancing cadmium mitigation and mineral biofortification in wheat production

The application of soil amendment (SA) and the cultivation of low Cd-accumulating varieties have been a widely favored strategy to enable the safe utilization of Cd-contaminated arable land. However, little has been reported on the reciprocal effects of SA on the Cd mitigation and nutritional quality of different wheat varieties. In this study, we evaluated the impact of an SA on agronomic traits, Cd accumulation, translocation and mineral nutrition of 12 wheat varieties in an acidic field with a Cd concentration of 0.46 mg/kg. The results showed that the SA significantly reduced soil DTPA Cd (42.3 %) and resulted in a slight decrease in wheat grain yield (4.24–9.72 %, average 7.62 %). Similarly, the SA significantly reduced grain Cd concentrations (average 61.65 %) while increased the concentrations of beneficial elements such as Mo and Se in all wheat varieties. However, this intervention also led to a reduction in the concentration of essential mineral elements (such as Ca, Fe, and Mn) in whole wheat grain and starchy endosperm, as well as a reduction in their proportion in the bran. Based on genotypic differences, Huaimai 33, Zhenmai 168, Sumai 188 and Yangmai 28 were considered to be the relatively most promising wheat varieties for achieving a balance among food safety, nutritional quality, and economic yield in this region. Taken together, this study highlights the varietal differences in Cd mitigation and mineral accumulation in different wheat varieties in response to the SA, offering new perspectives for phytoremediation and biofortification strategies for Cd-contaminated farmland.

Accumulation of livestock manure–derived heavy metals in the Hexi Corridor oasis agricultural alkaline soil and bioavailability to Chinese cabbage (Brassica pekinensis L.) after 4-year continuous application

Hexi Corridor is one of the most important base of vegetable producing areas in China. Livestock manure (LM) applied to agricultural field could lead to soil heavy metal (HM) pollution. Previous studies have focused on HM pollution following LM application in acidic polluted soils; however, fewer studies have been conducted in alkaline unpolluted soils. A 4–year field vegetable production experiment was conducted using pig manure (PM) and chicken manure (CM) at five application rates (0, 15, 30, 45, and 60 t ha−1) to elucidate potential risks of HMs in an alkaline unpolluted soil in the Hexi Corridor oasis agricultural area and HM uptake by Chinese cabbage. The results showed that LM application caused a significant build–up of Cu, Zn, Pb, Cd, and Ni content in topsoil by 30.6–99.7%, 11.4–51.7%, 1.4–31.3%, 5.6–44.9%, 14%–40.8%, respectively. The Cd, Cu, Zn could potentially exceed the soil threshold in next 8–65 years after 15–60 t ha−1 LM application. Under LM treatment, the soil DTPA–extractable Cu, Zn, Fe, the acid–extractable fraction of Cu, Zn, Fe, Cd, Ni, and the Oxidable fraction of Cu, Zn, Fe, Mn, Cd, Ni significantly increased, but the DTPA–extractable Pb, Cd, the acid–extractable fraction of Pb, and the reducible fraction of Cd significantly decreased. Cu and Zn could migrate to the deeper soil and relatively increase in DTPA–extracted Cu, Zn were found in 20–40 cm soil depth after LM application. The pH and SOM could influence the bioavailability of HMs in soil. The bioaccumulation factor and transfer factor (TF) values were <1 except Mn (TF > 1). HMs in leaf did not approach the threshold for HM toxicity due to the “dilution effect”. Recommend the type of manure was the PM and the annual PM application rate was 30 t ha−1 to ensure a 20–year period of clean production in alkaline unpolluted Fluvo–aqiuc vegetable soils.

Endophytic Bacteria in Ricinus communis L.: Diversity of Bacterial Community, Plant−Growth Promoting Traits of the Isolates and Its Effect on Cu and Cd Speciation in Soil

Ricinus communis L. shows certain tolerance to and good accumulation ability with heavy metals. Endophytic bacteria−enhanced phytoremediation is an effective method to improve heavy metal extraction efficiency. Here, for better application of castor in phytoremediation, the Illumina high−throughput sequencing was carried out to reveal the endophytic bacterial community in the tissues of castor grown in two locations, and traditional microbial cultivation was used to isolate endophytic bacteria from castor. The dominant bacterial phyla were Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes and Acidobacteria, and Proteobacteria was absolutely dominate in all castor tissues. There were significant differences in the composition of endophytic bacterial communities between castor grown in two sites, with obvious variation in the relative abundance of the dominant phylum. The samples from two sites also had their own unique dominant bacterial genera. The analysis of alpha diversity illustrated that the diversity and species richness of endophytic bacteria community in different parts of castor sampled in Tonglushan mining area were lower than those in Gangxia village, Yangxin county. In total, there were 44 endophytic bacteria strains isolated from the tissues of castor, of which 42 strains possessed three or more growth−promoting properties. Most of these isolates were tolerant to Cu or Cd to varying degrees. Eight isolates were selected for further Cu mobilization and soil incubation experiments. Strains TR8, TR18, TR21, YL1, YS3 and YS5 could well solubilize Cu2(OH)2CO3 in medium. Strain YS3 had the best effect on increasing soil DTPA−Cu and DTPA−Cd contents by 8.4% and 6.9%, respectively. Inoculated endophytic isolates were conducive to the conversion of heavy metal forms from insoluble to relatively unstable, and could increase available phosphate content in soil (10.8–29.2%). Therefore, the plant growth−promoting endophytes screened from castor have great application prospects and can provide important support for the microbial−assisted phytoremediation of heavy metal−contaminated soil.

Influence of Nutrient Management Practices on DTPA Soil Micronutrients and Its Relation with Soil pH and Cation Exchange Capacity in Pearlmillet (Pennisetum glaucum L.) Cultivated Soils of Western India

A field experiment was conducted during kharif, 2019 at Anand Agricultural University, Anand, Gujarat, India. The effect of nutrient management practices on soil pH, cation exchange capacity, DTPA micronutrient and their inter relationship were studied. The result of present study showed that relationship between available micronutrients and soil pH was significantly and negatively correlated for DPTA Fe, Mn and Zn. In case of DTPA Cu and soil pH relationship was positively correlated. The highest R2 value for the relationship between DTPA micronutrients and soil pH was for the available Fe (0 79). The relationship between available micronutrients and cation exchange capacity of soil was reverse of soil pH. Available Fe, Mn and Zn were positively correlated with cation exchange capacity and reverse for DTPA Cu. The lowest R2 value for relationship between DTPA micronutrients and soil cation exchange capacity was for DTPA Cu (0.008).

Status and Distribution of Micronutrients in Vertisol for Teff and Nitisol for Wheat Growing Area of West Showa Zone

The study was conducted to evaluate soil micronutrients status and to investigate soil–plant nutrient relationships, in West Showa Zone, during 2018/2019 GC. A total of 30 samples randomly taken from each field of wheat and teff-growing fields were used for soil and plant sample collection. The extractable micronutrients were determined using DTPA soil test extraction procedure. The study shows that mean values micronutrients were in the order of Fe&gt;Zn&gt; Mn&gt; Cu at both study area of soil types. Descriptive statistics was carried out to reveal the soil - plant relationships. The soil was low Fe (201.06ppm) at Welmera and medium (191.19ppm) at Adaberga and sufficient in Zn (76.8ppm at Welmera) and (76.29ppm) at Adaberga, while, Mn was found in deficient categories. The concentration of extractable micronutrient was found in the order of Fe&gt;Zn&gt;Mn&gt;Cu. The concentration of Fe (318.29ppm), Zn (6.73ppm), and Mn (53.27ppm) were recorded from wheat tissue. High concentration of Fe (ppm) at both site and sufficient in Zn, Mn and Cu concentration was recorded from plant tissue of wheat. The soil will not require supplementary application of Fe nutrient. Since concentration of Fe were above critical limits of arable land and a supplementary application of Zn, Mn and Cu nutrient were not strongly recommended to enhance the soil fertility status and soil productivity of the area. Keywords: concentration; micronutrient; nitisoil; vertisol; soil–plant relationship DOI: 10.7176/JEES/11-12-01 Publication date: December 31 st 2021

Zincated Nanoclay Polymer Composite (ZNCPC): Effect on DTPA-Zn, Olsen-P and Soil Enzymatic Activities in Rice Rhizosphere

ABSTRACT Zinc (Zn) is the most deficient micronutrient globally resulting in malnutrition and requires improved mode of delivery for increased nutrient use efficiency. An innovative fertilizer formulation, Zincated nanoclay polymer composite (ZNCPC), containing a total 6.59% Zn was evaluated in a pot experiment in comparison with ZnSO4 using rice (Oryza Sativa L.) (PRH 10 variety) as a test crop. The ZNCPC was applied in two doses [5.0 mg Zn kg−1 (T1) and 2.5 mg Zn kg−1 (T2)] whereas ZnSO4. 7 H2O was applied at single dose (5.0 mg Zn kg−1) (T3) in Zn deficient soil along with a control (without application of Zn) (T4). Effects of two modes of Zn application were evaluated under maximum tillering (MT) (55 days after transplanting) and panicle initiation stage (PI) (70 days after transplanting) on DTPA Zn, Zn uptake, Olsen-P, P uptake and soil enzymatic activities in rhizosphere and non-rhizosphere soil. Treatment T1 increased DTPA-extractable Zn content in rhizosphere soil to 157% in PI stage in comparison with T3. Stimulation of soil enzymes activity namely, dehydrogenase, acid and alkaline phosphatase was recorded in rhizosphere soil. Our study demonstrates that ZNCPC could potentially to be novel and innovative fertilizer formulation to increase Zn uptake in rice.

Impact of Continuous Fertilization on Heavy Metals Content in Soil and Food Grains under 25 Years of Long-Term Fertilizer Experiment

ABSTRACT In the present investigation, an attempt was made to determine the direct effects of fertilizers on various soil properties like acidification, organic matter content, the content of essential and toxic trace metals in soils and food grains under long term (>25 years) fertilizer experiment. Soil and plant samples were collected from Bengaluru center of All India Coordinated Research Project on Long-Term Fertilizer Experimental site in the sub-regions AESR 8.1 of India, with the treatments e.g. control, 100% N, 100% NP, 100% NPK, 150% NPK, 100% NPK + Lime, 100% NPK+ farmyard manure (FYM) at 0 to 60 cm depth with an interval of 15 cm. Laboratory analysis was conducted to know the vertical distribution of heavy metals and micronutrient cations in soil and plant produce by following the standard method. The DTPA soil Zn remained unchanged with the higher rates of N application, i.e. 100% N. There was very little effect of N, NP, and NPK application on the buildup of DTPA-able Zn, Fe, Mn, and Cu content in both the soils. However, the application of NPK + FYM showed a buildup in comparison to control for Fe 10 mg kg−1, Mn 18 mg kg−1, Zn 1.23 mg kg−1, and Cu 0.84 mg kg−1 in soil. Continuous fertilizer application contributed a meager amount accumulation of Cd, Pb, Ni, Co, and Cr in the soil under the finger millet – maize cropping sequence. The estimation of heavy metals in food grains, supposed to come from fertilizers, lime materials applied in soil was also of our concern. All the cited heavy metals were present in the maize and finger-millet grains. Risk assessment to human health (Hazard Quotient, HQ) for the intake of heavy metals through consumption of contaminated food grains was computed and observed that the values of ‘HQ’ for all the crops were far less than unity (<1) and safe for the consumers.

Effects of composited organic mobilizing agents and their application periods on cadmium absorption of Sorghum bicolor L. in a Cd-contaminated soil

Organic mobilizing agents have been advocated for phytoremediation of heavy metals contaminated soils, while the effects of application period of such agents remain unclear. A pot experiment was conducted, with two composited organic agents (oxalic acid or citric acid + dissolved organic fertilizer (OA + DOF and CA + DOF)) and four application periods (seeding, jointing, flag leaf and heading stages) of sorghum (Sorghum bicolor L.), to investigate their impacts on Cd bioavailability in soil. Results indicated that application of the two composited agents increased soil dissolved organic carbon (DOC) and DTPA extractable Cd by 7.31–49.13%, Cd contents in roots and shoots by 21.49–72.10%, bioaccumulation factor (BCF) and translocation factor (TF) of shoots by 4.44–71.99%, while reduced soil pH by 0.25–0.53 units, respectively. Most of these indices increased with the application periods, and largely peaked with their application during the flag leaf to heading stages. Meanwhile, the maximum sorghum biomass (132.84 g pot−1) and Cd bioaccumulation quantity (BCQ, 0.71 mg pot−1) in shoots were obtained for the CA + DOF applied at the heading. The DTPA extractable Cd was closely related to soil pH and DOC. Similar close relationships were observed between the Cd contents in shoots and soil DTPA extractable Cd, pH and DOC. The BCQ of Cd was positively related to the shoots biomass rather than their Cd contents. Therefore, the sorghum combined with the CA + DOF may be advocated as an alternative phytoremediation mode in Cd-contaminated soils, and the mobilizing agent should be primarily applied at the heading stage.

Effect of nano iron oxide application on iron availability in calcareous vertisols

Incubation studies on dynamics of applied nano iron oxides in calcareous Vertisol was conducted for a period of 60 days at department of Soil Science and Agricultural Chemistry, University of Agricultural Sciences, Dharwad. The results revealed that, DTPA iron in soil decreased with advancement in period of incubation. Highest DTPA extractable iron (6.87, 5.97, 4.89 and 4.74 mg kg-1 at 15, 30, 45 and 60 DAI, respectively) and water soluble iron (1.59, 1.81, 1.92 and 1.72 mg kg-1 at 15, 30, 45 and 60 DAI, respectively) was recorded in the treatment receiving nano Fe2O3 @ 2.5 mg kg-1mixed with FYM. The water soluble iron increased in all the treatments up to 45 DAI and thereafter, decreased. The treatments which received iron oxide formulations chelated with FYM recorded higher DTPA extractable and water soluble iron than their respective unchelated ones at all the concentration levels. Between the sizes, the nanoparticles having the size < 50 nm were found better than the size range of particles between 50 - 100 nm in maintaining soil DTPA iron and water soluble iron status at all concentration ranges throughout the incubation period.

Zinc nutrition of rice as influenced by crop establishment methods, rates of nitrogen and phosphorus fertilization and inoculation with microbial consortia

Zinc (Zn) fertilization in rice is important to enhance productivity and increase Zn concentration in rice grain to improve its nutritional status. A field experiment was conducted in wet seasons of 2013 and 2014 to study Zn nutrition of rice in three different crop establishment methods (CEMs) viz. puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS), under three different rates of nitrogen (N) and phosphorus (P) viz. 0, 75 and 100% of recommended dose of fertilizer (RDF) (120 kg N ha−1 and 25.8 kg P ha−1) and two different sources of N and P viz. chemical fertilizer and microbial inoculation (MI). Concentration and uptake of Zn at different growth stages and in straw and milled rice was significantly higher in PTR and SRI than ARS. Soil DTPA–extractable Zn content of soil was increased by 1142.4, 1140.3 and 755.8 g ha−1 in PTR, SRI and ARS after two year of Zn fertilization (soil application of 5 kg Zn ha−1). Zinc nutrition increase its Zn concentration in straw and milled rice and improvement in total uptake was 38.1, 40.3 and 40.8 g ha−1 when Zn was applied with RDF, 75% RDF + Anabaena sp. (CR1) + Providencia sp (PR3) consortia (MI1) and 75% RDF + Anabaena-Pseudomonas biofilmed bio-fertilizer (MI2), respectively. Positive correlation between milled rice yield and Zn concentration (R2= 0.95 and 0.97) showed the importance of Zn nutrition in improving rice yield. Zinc concentration at 70 days after sowing (DAS) and 100 DAS was also found positively correlated with dehydrogenase activity and microbial biomass carbon in soil.

Simulation of soil heavy metal pollution environmental stress on plant growth characteristics in the presence of wastewater

&lt;p&gt;Soil pollution was simulated by means of artificial heavy metal enrichment, in the presence of treated wastewater, and its effect on the growth characteristics of Beta vulgaris L. (red beets) i.e. on the dry matter yield, and on beet quality expressed in terms of dry matter heavy metal, nitrogen and crude protein content, was investigated in a greenhouse pot experiment. Twelve treatment combinations of heavy metals mixtures composed of Zn, Mn, Cd, Co, Cu, Cr, Ni, and Pb, with each one metal participating in the mixture at 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 mg.kg-1 were applied, respectively. It was found that the increase of soil DTPA extractable heavy metal concentrations reflecting high soil pollution, decreased statistically significantly the beet dry matter (dm) yield, but increased the metal and the , the nitrogen concentrations, and consequently, contributed statistisically significantly to the increase of beet crude protein yield.&lt;/p&gt;

Signs for secondary buildup of heavy metals in soils at the periphery of Athens International Airport, Greece.

Emissions from civil airports are similar to those observed in industrial and urban areas. While air pollution and noise levels are regularly monitored and assessed, information on the status of heavy metals in soils close to airport facilities is limited. In this study, we monitored and assessed heavy metal distribution in soils close to Athens International Airport (AIA) in Attica, Greece. Following a grid sampling scenario, topsoil samples were collected from 86 sites at the periphery of AIA and total and available forms of Cu, Zn, Fe, Mn, Ni, Cr, Pb, and Ba concentrations were determined in aqua regia and DTPA soil extracts, respectively. Median concentration values for both metal forms are not considered as particularly high. However, 90th percentile concentration values for some metals are high, indicating soil enrichment. Evaluation of enrichment factor (EF) and availability ratio (AR) values and EFs spatial distribution have led to consistent conclusions of secondary and ongoing metal accumulation in the soils of the studied area. Tessier sequential extraction procedure was applied to 10% of the soil samples and the results showed high potential availability of Pb, Mn, Cu, and Ni, further supporting the continuous metal accumulation in the studied soils.

Visible near infrared reflectance spectroscopy prediction of soil heavy metal concentrations in paper mill biosolid- and liming by-product-amended agricultural soils

Continuous assessment of soil heavy metal concentrations in agricultural soils is critical for ensuring ecosystem health and minimizing potential adverse effects. However, conventional laboratory determinations are time-consuming, expensive and involve hazardous chemicals. We evaluated the potential of visible near infrared reflectance spectroscopy (VNIRS) to rapidly and simultaneously predict total, Mehlich-3 (M3), DTPA, and water-soluble (H2O) soil heavy metal concentrations. Soil samples were collected from a loam soil (n=64) and a loamy sand (n=32) after repeated annual applications (3–9years) of paper mill biosolids (PB) and liming by-products. Models were developed using modified partial least squares regression on 75% of the total sample set and also for each soil, after removal of the spectral outliers (n=3), with the remainder used for validation. The coefficient of determination in validation (R2V) and the ratio of performance to deviation (RPD) were used to assess model accuracy. Predictions for the total set were excellent for total Zn and Cd, M3-Cu and -Cd, and DTPA-Cd (R2V>0.90, RPD>3.0), good for total Cu, Ni and Mo, M3-Ni, DTPA-Cu and -Ni, and H2O-Cu and -Ni (R2V=0.70 to 0.90, RPD=1.70 to 3.0), but poor for M3-Zn, DTPA-Zn, and H2O-Zn, -Cd and -Mo (R2V<0.70, RPD<1.70). Except for one case, site-specific models were either more accurate or provided similar results with the model of the total set in predicting site-specific concentrations. The relationship with soil organic matter (SOM) was the major predictive mechanism for Cd in our dataset, while the prediction of other soil heavy metals was due to the combined influence of SOM and Fe oxides. We conclude that VNIRS has the potential to predict total, M3, DTPA and to a lesser extent water-soluble soil heavy metals, especially when developed using site-specific samples.

The Study of Changes in Tomato Herbaceous Species Using Municipal Composts of Mashhad City

While environmental and economic adversities in waste disposal and the decrease of organic soil have caused the enhancement of municipal composts' production and application, it is of great importance to choose and utilize an appropriate fertilizer in order to amend the soil. Therefore, the effects of using three types of municipal composts (powdered compost, sulphur granular compost, and sulphur granular compost with thiobacillus inoculum amounting 2% of sulphur) and their amounts were assessed through the application of complete randomized block design with a 35 factorial experiment in five rates of zero (control), 15, 30, 45, and 60 tons per hectare to plant tomato. These experiments were started in 2008 and repeated three times during the following years. The achieved findings indicated that applying municipal composts is useful in planting tomato. The comparison of various types of composts proved that scholars should place more priority on sulphur granular compost, rather than two other kinds. In developing countries, a decline in organic matter of arable soils and the process of decays in soil performance, and also residues which are returned to the soil are all caused by disregarding new technical advantages and knowledge, soil and water limitations, high density plantation, small surfaces of planted soil and increased rate of subsistence farming. A good supply of soil organic matter can prevent from soil decays. Organic matter is the key factor of chemical, physical and biological soil properties which indicates soil fertility and productivity. Iran, especial Khorasan province, is located in an arid and semi-arid region consisting of the soil with low organic contents due to the dry climates. Keshavarz stated that the amount of organic carbon is less than critical level in all regions of Khorasan Razavi province. However, high level of PH in the soil and presence of bicarbonate ion in the water have redoubled problems of plant nutrition. The obtained results of various researches indicated that sulphur can deplete PH in calcareous soil, and increase the solubility of micronutrients such as phosphorus, and also amend halomorphic and sodic soils in inappropriate waters. Some soil properties such as moisture and organic matter can enable thiobacillus bacteria to oxidize the sulphur and make it sulphuric acid, but in Iran, owing to the low rate of organic matter in arable soils, the aforementioned process does not appropriately occur. On the other hand, different environmental and economic problems in waste disposal can cause the enhancement of municipal composts' production and application; therefore, lots of composts have been produced in different European, American and other countries by applying advanced facilities and machineries with high efficiency and capacity to control the process of soil productivity. Utilizing compost is beneficial in many ways, for instance it can amend the soil organic matter to provide useful bacteria such as sulphur- oxidizing bacteria. Improving the status of soil productivity is subject to increasing the rate of sulphur and municipal composts as sources of organic soil, and applying calcareous soil with a suitable level of PH, and also enhancing the amount of nutrients' solubility such as phosphorus, iron, manganese, and zinc. So, the current study aims to investigate the effectiveness of various municipal composts in tomato. II. Review of literature In many conducted researches, sulphur is considered as an acid-generating material which is capable of amending calcareous and sodic soils (2). Sulphur is of great importance due to its beneficial effects when acidifying the local soil and increasing the capability of solubility in nutrients. Kalbasi et al. (21) conducted a field experiment and investigated the effect of sulphur treatments on yield and uptake of Fe, Mn and Zn by corn, sorghum and soybeans. The results of their study indicated that elemental sulphur (powder sulphur) decreased the soil PH and increased soil DTPA - extractable Fe, Mn and Zn. Iron and Zn uptake increased while Mn uptake decreased significantly by corn, sorghum and soybeans for almost all the treatments. The main problem of applying sulphur in arable soils is its oxidation after being used. This process can be appropriately done by

A Survey of Heavy Metals content of Soil and plants As Affected by Long-Term Application of Sewage Water. A Case Study

As part of a four year study evaluating the practicability and value of sewage sludge use in Egypt, soil and plant surveys were carried out on a citrus plantation, irrigated with Cairo sewage since the 1920s, in order to evaluate the long-term accumulation of trace elements and heavy metals and their bioavailability. While total and DTPA soil concentrations correlated well, no relationship could be found between soil and plant tissue concentrations, despite elevated levels of heavy metals in the soil. Study of long-term contamination of soil with potentially toxic elements (PTEs) has not demonstrated a potential risk to crop quality and yield or human health from the slow accumulation of PTEs in sludge-treated agricultural soil. PTE concentrations in plant tissues remained low and within normal ranges despite significant increases in soil content after long-term irrigation with sewage effluent. Concentrations of PTEs in plant tissues were not related to total or DTPA extractable metals in contaminated soil. DTPA may not be a sufficiently reliable indicator of actual phytoavailability of trace elements in sludge-treated soil, although it is accepted that DTPA is widely used in nutrient diagnosis assessment. These data provide assurance about the minimal risk to the environment from trace elements and PTEs in sludge-treated agricultural soil, but a more detailed dietary analysis of Cd intakes under Egyptian conditions is recommended, following the approaches adopted in the UK and US for setting Cd soil limits or loading rates for this element.

Effect of biosolids from municipal sewage sludge composted with rice husk on soil functionality

Two different biosolids were obtained compost- ing anaerobic (A) and aerobic (B) municipal sewage sludge (SS) with rice husk. Higher amounts of SS (1:1 v/v) could be used in this composting process than in conventional ones. The two biosolids were characterized by chemical analysis and compared with a conventional green manure plus mu- nicipal solid waste and municipal SS compost. The effect of these products on soil functionality was studied in a 14- week incubation experiment by their addition to two different soils (silty clay—Ustic Endoaquert—and sandy loam—Aquic Xeropsamment). The total organic C ranged from 20 to 26 % and total N from 1.6 to 2.5 % in the two biosolids. The most relevant difference was due to dissolved organic C that was lower in the anaerobic biosolid (1 mgCkg −1 ) than in the other prod- ucts (5- 6m gCkg −1 ). The total trace elements (Cd, Cr, Cu, Ni, Pb and Zn) contents were under the limits fixed by the European legislation for soil application of SS (EC Directive 86/278/EEC, 1986). The three biosolids did not show strong negative effects on soil functional- ity during the incubation experiment, although some significant differences were found. The aerobic biosolid B mainly increased cumulative N release, microbial activity, basal respiration rate, microbial biomass-C-to- total organic C ratio, β-glucosidase, alkaline phospho- monoesterase and aryl-sulphatase activities. The anaero- bic one (B) decreased basal respiration rate, microbial biomass-C-to-total organic C ratio and aryl-sulphatase activity. DTPA soil bioavailable heavy metals were not affected by biosolids additions.

Kinetics of zinc release from ground tire rubber and rubber ash in a calcareous soil as alternatives to Zn fertilizers

Ground rubber contains 15–20 g Zn kg−1 but very low levels of Cd and could serve as an inexpensive byproduct Zn fertilizer. The aim of this investigation was to test Zn release in a soil treated with ground tire rubber and rubber ash compared with commercial Zn fertilizer and a laboratory grade zinc sulfate. A Zn-deficient soil was chosen from wheat fields in Isfahan province, central Iran, and the ground rubber, rubber ash and fertilizer-Zn and laboratory ZnSO4 were added at 0.5 and 2 mg Zn kg−1; 0.5 kg ha−1 would usually correct Zn deficiency in such pot tests. The soil DTPA-extractable Zn was then measured with time and the results were described examining first order, Elovich, power function and parabolic diffusion kinetics models. In the pot experiment, corn (Zea mays L.) plants were exposed to three rates of Zn (0, 20, 40 mg Zn kg−1) from two different sources (ZnSO4 and ground rubber). Ground rubber was applied as 2–3 mm and <1 mm diameter particles. Zinc treatments were mixed with the soils before planting. At harvest, concentrations of Zn, Pb, and Cd in roots and shoots of corn were measured. Results showed that ground rubber and rubber ash significantly increased the concentration of DTPA-Zn in the soil and this increase was higher than achieved with the commercial Zn fertilizer. At the lower Zn application rate, Zn release followed parabolic diffusion, while at the higher rate the kinetics of release followed power function and Elovich models. There was an increase in Zn concentration of corn shoot and roots by adding of Zn regardless the source of applied Zn. With increase in the rate of rubber used, the shoot Zn uptake increased. The Pb concentration of shoot and Cd concentrations of shoot and roots were low (less than 0.02 mg kg−1) in all treatments. The results showed that the soil DTPA Zn decreases over time if the soil is amended with a soluble form of Zn whereas the reverse was observed if the Zn is added as ground rubber which only gradually transforms. Thus ground rubber and rubber ash offer strong value as Zn fertilizer for Zn deficient soils.

Long-Term Residual Value of Zinc Fertilizer for Pasture Legumes Using Yield of Dried Herbage and Critical Concentration of Zinc in Young Tissue

ABSTRACT The zinc (Zn) requirements of subterranean clover (Trifolium subteraneaum L.) are well known for the predominantly marginally acidic to neutral sandy soils of southwestern Australia, but the Zn requirements of French serradella (Ornithopus sativus Brot.) and biserrula (Biserrula pelecinus L.), now also grown on these soils, is not known and were investigated in a glasshouse pot experiment. Soil was collected from field plots never treated with Zn or treated once only with 0.5 and 1.0 kg Zn/ha as Zn oxide either in 1983, 1984, 1986, 1990, 1992, 1996, 1997, or 2000. In the pot experiment, six levels of Zn were freshly-applied to samples of soil collected from each Zn treatment of the field experiment, and pots were sown either with subterranean clover cv. ‘Dalkeith’, French serradella cv. ‘Margurita’, or biserrula cv. ‘Casbah’. The pasture species were defoliated by cutting pasture herbage 3 cm above the soil surface for up to 4 consecutive defoliations. The approximate linear relationship between the level of freshly-applied Zn in the pot experiment required to produce 90% of the maximum yield of dried defoliated herbage (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 or 1.0 kg Zn/ha treatments applied in the field to require the same level of freshly-applied Zn to produce 90% of the maximum yield of the nil-Zn treatment in the field. This was 18–19 years for the 0.5 kg Zn/ha treatment and 32–35 years for the 1.0 kg Zn/ha treatment. The range in values was due to differences between legume species and the defoliation treatments, which were not significant. When yields were measured, samples of young growth (YG) were separated from the rest of the defoliated herbage (ROH) and the concentration of Zn in YG and ROH was measured. The concentration of Zn in YG that was related to 90% of the maximum yield of defoliated dried herbage (critical tissue test value) was (mg/kg) 13 for subterranean clover, 17 for French serradella, and 19 for biserrula; respective critical tissue test values for ROH were 19, 24, and 21 mg/kg. The approximate linear relationship between critical Zn concentration in YG (y-axis) and the number of years since Zn was applied in the field (x-axis) was used to project the number of years it took for the 0.5 and 1.0 kg Zn/ha levels applied in the field to reach the same critical tissue test value as the nil-Zn treatment of the field experiment. This was 17–20 years for the 0.5 kg Zn/ha treatment and 31–37 years for the 1.0 kg/ha treatment, which was similar to the 18–19 and 32–35 years projected using yield data. Before sowing the legumes in the pot study soil samples were collected to measure soil test Zn using the DTPA procedure. The critical DTPA soil test Zn, the soil test value that was related to 90% of the maximum yield of defoliated dried herbage, was about 0.20 mg Zn/kg for the 3 pasture legume species and all Zn treatments in the field and pot studies.