Soil science
H. Hatami; H. Parvizi; A. Parnian; Gholamhassan Ranjbar
Abstract
IntroductionThe availability of phosphorus (P) is a limiting factor for the production of crops due to its reactions with soil components. Furthermore, there are concerns about the depletion of non-renewable global rock phosphate (the main source of P) reserves because of the high demand for P fertilizers. ...
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IntroductionThe availability of phosphorus (P) is a limiting factor for the production of crops due to its reactions with soil components. Furthermore, there are concerns about the depletion of non-renewable global rock phosphate (the main source of P) reserves because of the high demand for P fertilizers. Therefore, it is essential to revisit existing agricultural practices to determine new resource management practices that utilize renewable resources. The application of sewage sludge could be an alternative P source; contrary to inorganic fertilizers, sewage sludge is cheap, contains nutrients, and improves soil quality due to contained organic matter. The total P content of sewage sludge may vary from less than 0.1% to over 14% on a dry solid basis, depending on the nature of the raw sewage being treated and the treatment process under consideration. However, the use of organic P resources can affect the soil chemistry, leading to changes to the P fractions and their quantities. Hence, the objective of this study was to compare the effect of the application of municipal sewage sludge and triple superphosphate on the distribution of soil-P fractions under saline and non-saline conditions.Materials and MethodsTo investigate the effect of municipal sewage sludge and triple superphosphate on changes in P fractions an incubation experiment was conducted in a completely randomized factorial design with three levels of triple superphosphate (0, 75, and 100 Kg ha-1 which were named T0, T1, and T3, respectively), three levels of municipal sewage sludge (0, 0.25 and 0.5% w/w which were named M0, M1 and M3, respectively), two levels of salinity of irrigation water (2 and 12 dS m−1, which were named saline and non-saline, respectively) and three replicates. The total number of samples was 54. The treated soils were incubated for three months and maintained at field capacity by adding the appropriate amount of saline and non-saline waters. P fractionated to KCl-P (soluble and exchangeable P), NaOH-P (Fe- and Al bound P), HCl-P (Ca-bound P), Res-P (residual P), and organic-P by sequential extraction method. Moreover, P percentage recovery for Olsen-P at each treatment was calculated. P concentration in samples was determined by the molybdate method. Data analysis was performed by MSTAT-C software, and the means were compared at α꞊5% by Duncan test. Results and DiscussionThe results showed that although the relative distribution of fractions followed the order of HCl-P < Organic-P < KCl-P < NaOH-P <Res-P, the changes in each fraction were dependent on the type of treatment and fraction. The amounts of KCl-P for application of municipal sewage sludge and fertilizer TSP combined, especially, T2M2 were 3.1 and 2.3 times higher than T0M0 in non-saline and saline conditions, respectively. The same result was obtained for NaOH-P. The combined and separate application of municipal sewage sludge diminished the relative distribution of HCl-P compared with triple superphosphate and control treatments in both salinities. However, the HCl-P in all treatments was more than 57% of the total P, suggesting that most of the soil P was in the carbonate phase. The treatments did not have a considerable impact on Res-P. The relative distribution of Organic-P increased by increasing levels of salinity and municipal sewage sludge. Therefore, it seems that municipal sewage sludge addition along with fertilizer P can reduce the negative effects of salinity and increase soil P availability compared with alone use of P fertilizer through growing the contents of KCl-P, NaOH-P, and organic-P fractions and, consequently, decreasing P entry into HCl-P fraction. Moreover, the application of municipal sewage sludge plus triple superphosphate increased P recovery as Olsen-P compared to a separate application of triple superphosphate which confirmed the advantage of the combined use of these sources.ConclusionThe findings of this study indicate that the simultaneous application of municipal sewage sludge and triple superphosphate can effectively improve phosphorus (P) availability in saline conditions. This enhancement is attributed to the alteration of the relative distribution of non-stable P fractions, such as KCl-P and NaOH-P, which increase, while stable P fractions like HCl-P decrease. Moreover, the addition of municipal sewage sludge into soils led to a significant increase in organic C as well as the relative distribution of organic-P. Therefore, application of municipal sewage sludge can improve the physico-chemical properties of saline soil along with increase of P availability. Hence, further research on the growth response of halophyte plants as affected by these treatments is recommended.
Akbar Karimi; abdolamir moezzi; Mostafa Chorom; Naeimeh Enayatizamir
Abstract
Introduction: Zinc is a key micronutrient which takes part in plant physiological functions. One of the extensively wide range abiotic stresses arises from Zn shortage in agricultural calcareous soils. Zn is one of the most prevalent disorders among various crops. Zinc deficiency is very common in most ...
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Introduction: Zinc is a key micronutrient which takes part in plant physiological functions. One of the extensively wide range abiotic stresses arises from Zn shortage in agricultural calcareous soils. Zn is one of the most prevalent disorders among various crops. Zinc deficiency is very common in most calcareous soils. Different mechanisms are involved in the deficiency of Zn In calcareous soils. The presence of calcium carbonate, lack of organic matter and high pH lead to Zn deficiency. Knowledge on the total Zn contents of in soil gives little information for their bioavailability. In order for better understanding availability of Zn to plant, knowledge about their mobility, and distribution in soil fractions is necessary. Biochar is a carbon-rich material produced by pyrolysis of biomass under oxygen-limited conditions and relatively low temperature. Biochar as a valuable soil amendment has received much attention due to its beneficial effects on carbon sequestration, soil physiochemical properties, soil microbial activity as well as soil fertility. Pyrolysis temperature has a significant influence on biochar physicochemical properties. Furthermore, biochar may alter the distribution of Zn fractions in calcareous soils. The impact of produced biochars at different pyrolysis temperature on distribution of Zn fractions in calcareous soils has been less studied. Therefore, the objective of this research was to evaluate the changes in distribution of Zn fractions in a calcareous soils treated with sugarcane bagasse derived biochars at different pyrolysis temperature.
Materials and Methods: An incubation experiment was carried out in laboratory condition as a factorial experiment based on a randomized complete design with two factors: (1) biochar type in four levels including control (without biochar) and biochar produced at 200 (B200), 350 (B350) and 500 ˚C (B500), (2) biochar application rate in two levels including 1 and 2% (w/w), and in three replications. Biochars were produced at 200, 350 and 500˚C pyrolysis temperatures under slow pyrolysis conditions with a heating rate of 5 °C min−1. Heating at this temperature lasted for 2 h. Then biochars were sieved to pass through 2 mm sieve and some properties were measured using the standard methods. The soil used in this study was sampled from the surface layer (0 to 20 cm depth), then, air-dried and sieved through 2 mm. Biochars produced at 200, 350 and 500˚C were mixed at 1 and 2% (w/w) with the 300 g of soil sample and incubated in ambient temperature at laboratory conditions (25 ± 2°C), for 90 days. Soil moisture content was maintained at 80% of field capacity. The samples were weighted every day and the required amounts of distilled water were added. At the end of incubation period, soil samples were air-dried and soil chemical parameters such as pH, cation exchange capacity (CEC), total organic carbon (TOC) and dissolved organic carbon (DOC) were measured.Chemical fractions of Zn in the incubated soil were determined according to the Tessier fractionation method. The Tessier sequential extraction method categorized Zn into 5 different fractions including: the exchangeable (Exch), bound to carbonate fraction (Car), bound to organic matter (OM), bound to Fe and Mn-oxides (FeMnOx) and residual fraction (Res).
Results and Discussion: Result indicated that application of different biochars significantly increased soil CEC and TOC. Maximum CEC and TOC were measured in B200 and B350 treatments, respectively, while their minimum values were observed in control treatment. In B200 treatments (B200, 1% and B200, 2%), pH significantly decreased compared to control, while this value significantly increased in B350, 1% , B500, 1% and B500, 2% treatments. B350 1% treatment did not have a significant effect on the soil pH. Application of 1 and 2% B200 significantly enhanced DOC (23.9 and 38%, respectively), compared to the control, but increase of DOC in B350 and B500 treatments was not significant compared to the control. Results showed that concentration of exchangeable Zn fraction decreased by 9.3, 19.5 and 9.5 % in B350, 2%, B500, 1% and B500, 2% treatments, respectively, compared to the control. However, B200 treatments (B200, 1% and B200, 2%) caused a significant increase in concentration of exchangeable Zn fractions (12.5 and 21.6%) compared to the control. The concentration of OM and Car Zn fractions increased in all biochar treatments compared to control. The highest concentration of OM and Car Zn fractions was observed after application of 2% B200 and 2% B500, respectively. Results showed that application of B350 and B500 had no significant effect on concentration of FeMnOx Zn fraction, while, this concentration significantly increased after B200 was applied. There were no significant (P ≤0.05) differences in concentration of residual Zn fraction among all the biochar treatments. The mean comparison results showed that the concentration of residual Zn in B200 treatments was significantly (P ≤0.05) lower than B350 and B500 treatments. There were no significant differences in this concentration among B500, B350 and the control treatments. Results revealed that in all treatments, different Zn fractions in the soil were distributed in the following order: Res > FeMnOx > Car > OM > Exch. The largest effect of biochars on the change in distribution of Zn fractions of soil was observed at 2% application rate.
Conclusion: It can be concluded that biochar B200 application could be an effective amendment for improving chemical properties and conversion of Zn from less available fractions to fractions with more bioavailability in the calcareous soil. Moreover, the biochar produced at 350 and 500˚C is better suited for enhancing soil organic carbon and Zn stabilization in calcareous soil.
leila tabande; M. R.Bakhshi
Abstract
Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, ...
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Introduction
Among essential plant microelements, iron (Fe) exert the highest restriction of crop production in Fars Province. Trace elements in the soil is composed of forms into 5 groups. These are the water-soluble and variable, adsorbed, chelate creating with complex compounds, secondary clay minerals, forms insoluble metal oxide minerals, and primary minerals. Water-soluble, changeable, adsorbed or form in chelates to be present as balance in the soil is noted and to be important for plants in nutrition.
Materials and Methods
In a greenhouse experiment was done with Soybean planting, the effects of Fe chelate (FeEDDHA) fertilizer levels on William cultivar of soybean (Glycine max L.) growth and chemical composition were studied by using a completely randomized design with 3 replications. Treatments were consisted of 10 soil samples and 3 levels of Fe applications (control, 5 and 10 mg.kg-1 as Fe EDDHA). Beside some physical and chemical soil properties and Extractable iron content with DTPA and EDTA were determined. By sequential extraction methods of Singh & Sposito ( 1982), chemical forms of Iron, exchangeable iron (Exch-Fe), organic bounded iron (OM-Fe), amorph iron oxides bounded iron (AFeOX-Fe), crystal iron oxides bounded iron (CFeOX-Fe) contents of soils were determined. Then, Concentration and uptake of Fe, Mn, Cu and Zn in plant were calculated.
Results and Discussion
carbonate, organically, amorphous oxide, crystalline iron oxide bounded and residual forms of iron were 0.0053, 0.0016, 0.44, 21.1 and 78.6% of the total iron as average, respectively. Therefore, content of carbonate, organically bound iron of soil, represented only a small fraction would not be considered as important as the total iron. In other words, crystalline iron oxide bound iron and residue iron forms constitued an important part of total iron.
Considering the average iron content of the soil related to chemical forms of iron was arrenged such as:
Res-Fe>CFeOX-Fe>AFeOX-Fe>Car-Fe> OM-Fe > Exch.-Fe
Applications of Fe had significant effect on dry matter, concentration, and uptake of Fe, Zn, Cu and Mn, extractable forms via extracting DTPA, EDTA, organic and exchangeable forms in soybean compared to control. Among chemical forms of iron, organic form with the amount of available iron plant (extraction by DTPA) had significant positive correlation. Also, many of the physical and chemical properties of calcareous soils studied, were significantly correlated with some chemical forms and amount of iron uptake by plant. DTPA extractable iron had negative correlation with pH ( R2= 0.514*) and EDTA extractable iron had positive correlation with organic matter (R2= 0.428*).
Conclusions
Application of Fe EDDHA, was leaded to significant increase organic and plant available (DTPA) forms of iron and due to significant regression equation (r=0.435*) between two chemical forms of iron (organic and DTPA extracted), it can be inferred that, the bulk of available iron plant was in form of organically bound. One reason for the positive reaction to the use of Fe EDDHA, subjected to a significant increase absorbable forms of iron in the studied soils.
Keywords: Chemical and Physical properties of soil, DTPA, EDTA, Iron, Sequential extraction
Ahmad Farrokhian Firouzi; Mohammad javad Amiri; Hosein Hamidifar; Mehdi Bahrami
Abstract
Introduction Some methods of contaminated soils remediation reduces the mobile fraction of trace elements, which could contaminate groundwater or be taken up by soil organisms. Cadmium (Cd) as a heavy metal has received much attention in the past few decades due to its potential toxic impact on soil ...
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Introduction Some methods of contaminated soils remediation reduces the mobile fraction of trace elements, which could contaminate groundwater or be taken up by soil organisms. Cadmium (Cd) as a heavy metal has received much attention in the past few decades due to its potential toxic impact on soil organism activity and compositions. Cadmium is a soil pollutant of no known essential biological functions, and may pose threats to soil-dwelling organisms and human health. Soil contamination with Cd usually originates from mining and smelting activities, atmospheric deposition from metallurgical industries, incineration of plastics and batteries, land application of sewage sludge, and burning of fossil fuels. Heavy metal immobilization using amendments is a simple and rapid method for the reduction of heavy metal pollution. One way of the assessment of contaminated soils is sequential extraction procedure. Sequential extraction of heavy metals in soils is an appropriate way to determine soil metal forms including soluble, exchangeable, carbonate, oxides of iron and manganese, and the residual. Its results are valuable in prediction of bioavailability, leaching rate and elements transformation in contaminated agricultural soils.
Materials and Methods The objective of this study was to synthesize magnetite nanoparticles (Fe3O4) stabilized with sodium dodecyl sulfate (SDS) and to investigate the effect of its different percentages (0, 1, 2.5, 5, and 10%) on the different fractions of cadmium in soil by sequential extraction method. The nanoparticles were synthesized following the protocol described by Si et al. (19). The investigations were carried out with a loamy sand topsoil. Before use, the soil was air-dried, homogenized and sieved (
Mohaddese Savasari; Mostafa Emadi; Mohammad Ali Bahmanyar; Puria Biparva4
Abstract
Introduction: Increases in pollution of water resources due to the contaminants have made researchers to develop the various methods in the remediation and the reuses of polluted resources contamination of soils with heavy metals is one of great environmental concerns for the human beings. Cadmium (Cd) ...
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Introduction: Increases in pollution of water resources due to the contaminants have made researchers to develop the various methods in the remediation and the reuses of polluted resources contamination of soils with heavy metals is one of great environmental concerns for the human beings. Cadmium (Cd) as a toxic heavy metal is of significant environmental and occupational concern. Contamination of soils with heavy metals is one of great environmental concerns for the human beings. The numbers of sorbents that have been used for Cd (II) reductive removal are biopolymers, fly ash, activated carbon, metal oxides, clays, zeolites, dried plant parts, microorganisms, and sewage sludge. However, most of the mentioned sorbents had limitations of cost and durability that call a needed approach by cost effective remediation technique with high efficiency. Application of zero valent iron nanoparticles (ZVINs) as a promising technique for remediation of heavy metals are being increasingly considered by researchers. This study was conducted to synthesis and characterize the ZVINs stabilized with ascorbic acid (AAS - ZVIN) in aerobic conditions and to assess their ability for removal efficiency of cadmium (Cd) from the soils and changes in different fraction of Cd in three spiked soils including sandy, acidity and calcareous soils were also studied.
Materials and Methods: The stabilized ZVINs were prepared in cold distilled water by reducing Fe (III) to Fe0 using sodium borohydride in the presence of ascorbic acid as stabilizer and reducing agent. The freshly synthesized AAS-ZVIN washed three times and then used for the subsequent analysis. Characterization of the synthesized AAS-ZVIN was carried out by scanning electron microscope (SEM). X-ray diffraction (XRD) was performed using a Philips D500 diffract meter with Ni-filtered Cu ka radiation. To determine the availability of Cd, the DTPA-extractable amounts of Cd in the spiked soils so sandy, acid and calcareous soils with three replications was studied were studied in an experiment of randomized completely design with a factorial arrangement of treatments consisting of AAS-ZVIN dosage (0, 0.5, 1 and 2 w/w %), Cd contamination levels (15 and 45 mg kg-1) in two time periods of 1 and 4 weeks in the three spiked soils. Moreover, the distribution of the chemical forms of Cd was determined using the sequential extraction method.
Results Discussion: The results of this study show that zero valent iron nanoparticles can be sustained in the future by ascorbic acid under aerobic conditions in a laboratory that is to reduce the cadmium as a useful method, simple, fast and high performance in the decontamination of soils contaminated with lead that require further research to investigate other heavy elements. The results from the obtained SEM and XRD analyses indicated that AAS-ZVINs had the mean size of less than 50 nm, the maximum 2θ peak at 44.8°. Therefore, the particle size of ZVINs produced in this study, measured by SEM images, are less than 100 nm. Chain structure formations have been attributed to the magnetic interactions between the adjacent metal particles. Furthermore, there was an apparent separation between these ZVIN with a little aggregation. Results also showed that the DTPA-extractable Cd in three sandy, acid and calcareous spiked soils decreased with increasing of AAS-ZVIN dosages at both level of contaminations. The availability of Cd in sandy, acid and calcareous spiked soils at 15 and 45 mg kg-1 of contamination were 71 and 49.5 % and 47.52 and 49.47; and 36.05 and 61.3 percentages, respectively. Availability of Cd after four weeks application at two contamination level was also decreased significantly. The results of sequential extraction of sandy, acid and calcareous soils showed that with increasing the level of AAS-ZVIN application from 0 to 2 %, the soluble, exchangeable and carbonate-bound of Cd decreased but organic matter-bound, Fe/Mn oxides bound and residual Cd were increased. Over four weeks after application of AAS-ZVIN in three spiked soils the soluble, exchangeable and carbonate-bound were decreased but organic matter-bound, Fe/Mn oxides bound and residual Cd increased.
Conclusions: The results of this study show zero valent iron nanoparticles can be sustained in the future by ascorbic acid under aerobic conditions in a laboratory that is, To reduce the cadmium as a useful method, simple, fast and high performance in the decontamination of soils contaminated with lead that require further research to investigate other heavy elements. Moreover, the high resolution transmission electronmicroscopy, energy dispersive X-ray analysis, x-ray diffraction spectrophotometer measurements are potentially needed to reveal the accurate morphology, composition, crystal structure, functionality and stability of the prepared stabilized-ZVINs. Moreover, these synthesized ZVINs can also possibly applicable for remediation of soils and wastewater.
Ali Afshari; H. Khademi; shamsollah Ayoubi
Abstract
Introduction: Heavy metals are found to be one of the major environmental hazardous contaminants, for human health, animal life, air quality and other components of environment. They can affect geochemical cycles and accumulate in animal tissues since physical processes are not able to remove them, so ...
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Introduction: Heavy metals are found to be one of the major environmental hazardous contaminants, for human health, animal life, air quality and other components of environment. They can affect geochemical cycles and accumulate in animal tissues since physical processes are not able to remove them, so they are consistent in long term. The analysis of the total concentration of heavy metals in soil may provide information about soils enrichment but in general, it is widely used to determine the potential mobility of heavy metals in environmental behavior under chemical forms of metals in soils. Heavy metals existat several phases including water-soluble, exchangeable, bounded to organic matter, bounded to carbonates, bounded to Fe-Mn oxides, secondary clay minerals and residual fraction within primary minerals network. There is a dynamic equilibrium between different fractions of elements in soil. The main objectives of the present study were a) The analysis of the total concentration of heavy metals such as Fe, Mn, Ni, Cr, Co, Pb, Zn, Cd and Cu and b) The fractionations of heavy metals and identification of controlling factors to distribution and behavior of heavy metals in soils at different land uses.
Materials and Methods: The study was performed at central area of Zanjan province (Iran). The study area was over 2000 km2 in coordinates 20´ 36° to 41´ 36° E and 19´ 48° to 53´ 48° N. The average altitudes were over 1500 meters above sea level. The major land uses of the study area included agriculture (AG), rangeland (RA) and urban (UR). Sample collection was done based on the random grid method in August 2011. Surface soil samples (0-10 cm depth) were taken from grid centers included 137, 77 and 27 samples from AG, RA and UR land uses, respectively. The samples were digested in Nitric acid 5 normal (Sposito et al., 1982) and total concentration of Pb, Zn, Ni, Mn, Cu, Cr, Fe and Co were measured by Perkin-Elmer: AA 200 atomic absorption instrument and cadmium was measured by atomic absorption equipped with Rayleigh: WF-1E graphite furnace. 75 soil samples were selected, DTPA-extraction and sequential extraction were performed and physiochemical characteristics of these samples analyzed. To extract the metals by DTPA, the method developed by Lindsay and Norvell, (1978) was used and sequential extraction was done by Tessier et al., (1979) method. All statistical parameters were calculated using SPSS 16.0 software, and mean comparison (mean separation) was carried out using Duncan test at probability level of 5%.
Results and Discussion: The results indicated that heavy metals concentrations and patterns were evidently affected by different land uses. Co concentration was between 17.0 – 35.7 mg/kg and had the lowest total coefficient of variation (14%). The maximum total Cr and Ni values were measured in AG land use (26.1 and 52.6 mg/kg, respectively) and lowest was in UR land use (17.0 and 37.2 mg/kg, respectively). The highest total average value of Mn was found in RA (698.9 mg/kg) and the lowest in UR (629.1mg/kg) land use. The highest Fe concentrations were measured in AG and RA land uses (17.2 and 17.0 g/kg, respectively) and the lowest in UR land use (14.0 g/kg). The maximum Concentration of total Cd was observed in UR land use (2.47 mg/kg) and its minimum values were found in RA and AG (0.83 and 0.75 mg/kg, respectively) in the study area. In UR land use, Cu and Zn were more significant than AG and RA land uses. Pb variation was the same as Zn so that its increased concentration was found in urban land use (90.2 to 1357.5 on average 220.1 mg/kg). The highest Pb values were measured in UR land use (220 mg/kg) while the lowest concentrations were found in RA and AG land uses (80.6 and 69.0 mg/kg, respectively).
Different elements showed various fractional distribution in different land uses. The highest Co percentage was related to residual fraction at all land uses, with values up to 48.4%, 54.0% and 48.1% in AG, RA and UR land uses, respectively. Ni fractionation had approximately the same pattern with Co in all factions and land uses, except exchangeable fraction of Ni that showed the lowest percentage in all land uses. The dominant fraction of Cu was residual fraction with the amounts of 73.3% 76.0% and 61.9% in AG, RA and UR land uses, respectively. The second dominant fraction in UR and AG land uses was related to that was bounded to OM, with 16.5% and 10.1%, respectively. Zn distribution in the AG and RA land uses had the same trend: Residual>bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction. Whereas, Zn distribution showed different trend in UR land use as bounded to Fe-Mn oxides>residual>bounded to carbonate>bounded to OM>exchangeable fraction. Pb distribution was different in each land use. Pb showed similar distribution to Zn in UR. In AG and RA land uses residual fraction of Pb was measured as highest value while other fractions of Pb had these distributions: Pb bounded to carbonate>bounded to Fe-Mn oxides>exchangeable >bounded to OM fraction in AG land use and Pb bounded to Fe-Mn oxides>bounded to OM>bounded to carbonate>exchangeable fraction in RA land use.
Conclusion: Based on the results of this study, Cr, Co, Ni, Mn and Fe magnitudes are uneven in soils. The total heavy metal concentrations fractionation can provide information on the contaminant metals sources. High levels of exchangeable fractions, acid soluble and easily reducible perhaps indicates anthropogenic activities. Naturally, Chemicals are associated to resistant soil fractions such as oxy hydroxides, organic matter and sulfides. In soil fractionation, the contribution of each fraction in soil was a function of metal type and land uses. Those metals were affected by anthropogenic activities such as lead, zinc, and partly copper, showed the highest percentage in the fraction that influenced by external input sources. Those were characterized by lithogenic origin (cobalt and nickel) was mainly found to be highest in residual fraction. However, in all metals, those fractions affected by anthropogenic activities (non-resistant fractions) were much more in urban land use than agriculture and rangeland ones.
abolfazl azadi; M. Baghernejad; N. A. Karimian; S. A. Abtahi
Abstract
Introduction: Phosphorus (P) is the second limiting nutrient in soils for crop production after nitrogen. Phosphorus is an essential nutrient in crop production. Determination of forms of soil phosphorus is important in the evaluation of soil phosphorus status. Various sequential P fractionation procedures ...
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Introduction: Phosphorus (P) is the second limiting nutrient in soils for crop production after nitrogen. Phosphorus is an essential nutrient in crop production. Determination of forms of soil phosphorus is important in the evaluation of soil phosphorus status. Various sequential P fractionation procedures have been used to identify the forms of P and to determine the distribution of P fractions in soils (Chang and Jackson, 1957, Williams et al., 1967; Hedley et al., 1982), but are not particularly sensitive to the various P compounds that may exist in calcareous soils. A Sequential fractionation scheme has been suggested for calcareous soils by which three types of Ca-phosphates i.e. dicalcium phosphate, octacalcium phosphate, and apatite could be identified (Jiang and Gu, 1989). These types of Ca-phosphates were described as Ca2-P (NaHCO3-extractable P), Ca8-P (NH4AC-extractable P) and Ca10-P (apatite type), respectively. In this study, the amount and distribution of soil inorganic phosphorus fractions were examined in 49 soil samples of Fars province according to the method described by Jiang and Gu (1989).
Materials and Methods: Based on the previous soil survey maps of Fars province and According to Soil Moisture and Temperature Regime Map of Iran (Banaei, 1998), three regions (abadeh, eghlid and noorabad) with different Soil Moisture and Temperature Regimes were selected. The soils were comprised Aridic, xeric, and ustic moisture regimes along with mesic, and hyperthemic temperature regimes. 49 representative samples were selected. The soil samples were air-dried and were passed through a 2-mm sieve before analysis. Particle size distribution was determined by hydrometer method (Gee and Bauder 1996). Also, Cation exchange capacity (CEC; Sumner and Miller 1996), calcium carbonate equivalent (Loeppert and Suarez 1996), organic matter content (Nelson and Sommers 1996), and pH by saturated paste method (Thomas 1996) were determined . Inorganic phosphorus sequential fractionation scheme was preformed according to the method described by Jiang and Gu (1989). Olsen-P fraction that was extracted by NaHCO3 (Olsen and Sommers 1982) was regarded as P-availability index. Also, Total-P by perchloric acid (HClO4) digestion (Sparks; 1996) and organic P were determined.. All of the extraction procedures were performed in duplicate and the amounts of P were colorimetrically measured in the supernatants by the ascorbic acid method of Murphy and Riley (1962).The relationships between forms of P and some of the soil properties were established using correlation method.
Results and Discussion: The chemical data of the soils showed that soils were calcareous with CCE range between 9.94 to 74.27 % ( average 51.10%) and pH range between 7.02 to 8.36 (average 7.85). Also, the amounts of CEC were between 5.35 to 29.39 cmol (+) kg-1(average 16.68 cmol (+) kg-1). The results showed a wide range in content of Phosphorus fractions. The amount of total Phosphate ranged from 301.87 to 1458.68 mg kg-1 with an average of 626.63 mg kg-1 . Calcium Phosphate ranged from 147.83 to 666.90 mg kg-1 with an average of 324.79 mg kg-1, that comprised 85 and 52 percent of inorganic and total Phosphorus, respectively. The amount of Fe-P ranged from 0.38 to 59.18 mg kg-1 with an average of 7.56 mg kg-1 that comprised 13.64 and 8.34 percent of inorganic and total Phosphorus, respectively. Also, the amount of Al-P ranged from 20.49 to 123.09 mg kg-1 with an average of 52.28 mg kg-1that comprised 1.97 and 1.21 percent of inorganic and total Phosphorus, respectively. The results of correlation study showed that available Phosphorus was significantly correlated with Ca2-P, Ca8-P, Al-P, Ca10-P, and Pt (total phosphorus). So, in calcareous soils, awareness of soil properties and phosphorus fractions and their relationships are important for evaluation of phosphorous status in soil and understanding of soil chemistry that influence soil fertility.
Conclusion: The relative abundance of inorganic P forms were in order of Ca10 – P > Ca8- P > Al –P> Ca2-P> Fe-P. Among the inorganic P fractions, Ca-P had the highest value and varied from 147.83 to 666.90 mg kg-1, which accounted for 53 percent of the sum of P fractions, occurred in H2SO4 extractable P fraction, which is attributed to primary Ca–P minerals, indicating their weak weathering nature. Also, correlation study showed that available Phosphorus was significantly correlated with Ca2-P, Ca8-P, Al-P, Ca10-P, and Pt. This result indicate that these fractions probably can be used by plant.
S. Tajari; mojtaba barani; F. Khormali; F. Kiani
Abstract
Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to ...
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Introduction: P in soils exists in many complex chemical forms, which differ markedly in their behavior, mobility and resistance to bioavailability in the soils. The total P content of a soil provides little information regarding the behavior of P in the environment. The various forms of P present to a large degree, determine the fate and transport of P in soils. Fractionation schemes using different chemical sequential extractions have been used in order to describe the many different forms in which P can be found in the soil. The reason for fractionating and studying P forms in the soil is usually to allow a more precise description of the potentials for P release from the soil. The forms and dynamics of soil P can be greatly affected by agricultural management practices. Since inorganic P is the preferred source for plant uptake, knowledge of the inorganic form within soils is fundamental to understanding bioavailability of P and sustainability of agricultural practice. The aim of this study was to investigate the effect of land use change on the form and distribution of inorganic P using a sequential extraction procedure.
Materials and Methods: In order to study the impact of land-use change from forestland to cultivated land, composite samples in four replicates from the upper 10 cm of the different land use systems (natural forest, pasture, bower olive, farmland) were collected. We collected five subsamples from each land use in a radial sampling scheme. The five subsamples were then bulked into one sample. The spacing between the subsamples on the radii ranged from 5 to 10 m. The soil samples were transferred to polyethylene bags and transported to the laboratory where they were slightly crushed, passed through a 2 mm sieve prior to fractionation and chemical analysis. Soil texture, cation exchange capacity, organic carbon (OC), electrical conductivity, pH and calcium carbonate equivalent (CCE) were measured with standard methods. Total P and total inorganic P (Pi) contents were measured by the ignition method, for which P in the ignited (550 °C) and unignited soil samples were extracted by 0.5 M H2SO4. A modified version of the sequential extraction of Olsen and Sommers (1982) was used to fractionate inorganic P. Phosphorus was measured in the extracted supernatants by the molybdate–ascorbic acid method.
Results and Discussion: The results showed that clear-cutting of the indigenous forests and their conversion into agricultural fields significantly decreased total P and total organic P levels. Land-use changes from natural forest to farmland decreased the total P by 23% (from 644 to 495 mg per kg). Clearing and subsequent cultivation of the native woodland resulted in a marked depletion of total organic P. In addition, the land-use conversion from the natural forestland to an agroecosystem (cultivated land) led to increases in total inorganic P and inorganic P forms levels (labile P, P non-occluded, occluded in oxides of iron and aluminum, soluble calcium phosphate and sparingly soluble calcium phosphate). Labile inorganic P (NaHCO-Pi) showed the greatest changes, such as labile inorganic P in the amount of change from 1.75 in the forest land to 13.01 mg per kg of cultivated land, which represent an increase of approximately 8-fold compared to control (natural forest). The results also revealed that the refractory inorganic P fractions (HCl-Pi) were the major inorganic P pool, comprising 50-70% of the total inorganic P pool, indicating CaCO3 control over phosphorus availability in the studied soils. This study indicated that forestland degradation and cultivation caused chemical changes of P dynamics.
Conclusion: Large-scale conversion of indigenous forests to cultivated land, driven by long-term agricultural development in the Toshan region, has greatly impacted the forms and content of P in the soils. Generally, the conversion of natural ecosystem to agroecosystems, decreased the proportion of organic P (Po) in the top-soils at depth of 0 to 10 cm. The depletion in organic P from the cropped fields could be attributed to the enhanced mineralization of soil organic P caused by cultivation and removal of P in the crops. However, the conversion of natural forest to farmland led to increases in inorganic P (Pi). About 50% to 70% of the TP was bound to CaCO3, and thus this solid phase is critical to P fate in the soils and ecosystem of the Toshan Region, Golestan province
ghodsie hoseinian rostami; Ahmad Gholamalizadeh Ahangar
Abstract
Adding heavy metals to soils leads to change of their original distribution pattern. Heavy metals distribution in soils depends upon heavy metal, application level, application time and soil characteristics as well. This investigation was conducted to assess the time effect on distribution of different ...
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Adding heavy metals to soils leads to change of their original distribution pattern. Heavy metals distribution in soils depends upon heavy metal, application level, application time and soil characteristics as well. This investigation was conducted to assess the time effect on distribution of different fractions of Lead in soils. The experiment conducted as a factorial in a completely randomized design with three replications and two levels of cow manure (0 and 5%) and two levels of Lead using Lead nitrate (0 and 200 mg kg-1). Samples were incubated at 250C and 60% of field capacity for 120 days with different time intervals (0-30, 0-60, 0-90 and 0-120 day) to determine Lead fractions using sequential extraction methods. The results showed that Lead concentration decrease in exchangeable, carbonated and residual fractions during the time. Also the interactions between cow manure and time cause of decreases in the exchangeable and residual fractions and increases in the carbonated, Fe-Mn oxides-bound as well as organic matter-bond fractions. The interactions between time and Lead concentration lead to decrease in the exchangeable, carbonated and residual fractions and increase in the Fe-Mn oxides-bound and organic matter-bond Lead fractions. Since the most availability and toxic potential of lead is in the exchangeable-solution, the advantage of the this study is to reduce potion of this section during the time.
Hadis Hatami; Ali reza Karimi; A. Fotovat; H. Khademi
Abstract
Aluminosilicates such as K-feldspar and micaceous minerals are the main source of potassium in soils. The objectives of this study were to investigate the release of K from micaceous minerals (biotite, phlogopite, muscovite) and K-feldspars (Zanjan and Yazd) using sequential extraction by 0.05 M BaCl2 ...
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Aluminosilicates such as K-feldspar and micaceous minerals are the main source of potassium in soils. The objectives of this study were to investigate the release of K from micaceous minerals (biotite, phlogopite, muscovite) and K-feldspars (Zanjan and Yazd) using sequential extraction by 0.05 M BaCl2 and determine the effect of mineral grain size and application of kinetic models to describe K release. For this purpose, sequential extraction with BaCl2 was conducted on two sizes of 50-100 and less than 50 micron for the periods of 2-600 hours. The amount of K released into the solution was measured by flame photometer. The results indicated that after 13 times of extraction, in the both sizes, biotite and muscovite had the highest and lowest values of K release, respectively. Meanwhile, the released K increased by decreasing the mineral size. The kinetics of K release from minerals consisted of two phases, the first phase was relatively rapid and then continued with a slow rate to end of the experiment. Regarding the high determination coefficient (R2) and low standard error of the estimate (SE), parabulic diffusion and exponential function equations could reasonably describe the K release kinetics. Therefore, it may be concluded that the release of K is controlled by diffusion process from the surface of the study minerals.
A. Golestani Fard; H. Mirseyed Hosseini; Gholam Reza Savaghebi; Gh.R. Savaghebi
Abstract
In this research chemical forms of lead and zinc in bulk and rhizosphere soil of different cultivars of maize and canola were determined by sequential and single step extraction methods. Some factors affecting chemical transformation of the two elements such as pH, dissolved organic carbon (DOC), their ...
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In this research chemical forms of lead and zinc in bulk and rhizosphere soil of different cultivars of maize and canola were determined by sequential and single step extraction methods. Some factors affecting chemical transformation of the two elements such as pH, dissolved organic carbon (DOC), their uptake by plant and also cation exchange capacity in the rhizosphere and bulk soil were also assessed. Rhizosphere was obtained with gentle shaking and separating the soil around plant roots. Results showed that zinc uptake was more than lead in both plant cultivars. Zinc and lead accumulation in all cultivars roots were also more than shoots. Translocation index (The ratio of element concentration in shoot to root) in the corn cultivars was higher than canola cultivars (significant correlation= 1%) while the ratio was higher for lead in canola cultivars. Metal concentration in shoots to total metal concentrations in soil (Accumulation factor) showed a similar trend like the translocation index. In total, the corn ability in zinc and lead absorption and extraction in soil was higher compared to canola. There weren’t any significant changes in rhizosphere pH compared to bulk soil. Dissolved organic carbon in the rhizosphere of different cultivars was more than bulk soil and the amount of it in canola was significantly more than corn cultivars. Among each plant cultivars, the absorption rate increased with increasing root exudates. The results of sequential and single step extraction methods showed that the general trend and the soil system tendency (Root-Soil interface) is toward zinc availability in the rhizosphere. The amount of lead in rhizosphere showed no significant changes to bulk soil with none of the extractants in single step extraction method but with regards to the results of sequential extraction method, rhizosphere processes tend to reduce the availability of this element in both plant cultivars.
