Iranian Soil Research Articles

Isolation and Identification of Phenol-Degrading Bacteria from Iranian Soil and Leaf Samples.

By considering the importance and role of soil in the health of humanity, it is important to remove the presence of harmful compounds, such as phenol. In this study, four types of soil and leaf samples were collected from Kerman, Iran, and the amounts of heterotrophic and degradation bacteria were determined using the serial dilution and most probable number (MPN) methods. The amount of removed phenol was investigated using the Gibbs method with different concentrations of phenol. Then, an isolate with the highest percentage of phenol degradation was identified as the superior strain using 16 sRNA sequencing. The effects of the different factors, such as the carbon source (1% molasses and 1 g glucose), nitrogen source (0.1 g yeast extract), mixed culture, and time (14 and 28 days), on the biodegradation ability of the superior strain was investigated. A total of 18 bacterial strains were isolated from the samples. Isolate B3 had the highest rate (75%) of phenol degradation, at a concentration of 1000 ppm, meaning it was identified as the superior strain. The molecular analysis results identified this isolate as the Comamonas testosteroni strain F4. This bacterium can degrade 89% of the phenol at 30 °C, 180 rpm, and 800 ppm over 28 days. C. testosteroni did not show a favorable phenol degradation ability in the presence of the investigated carbon sources, while this ability was also reduced in mixed cultures. C. testosteroni bacterial strain isolated from soil samples of pistachio orchards in Kerman, Iran, has a favorable ability to biodegrade phenol.

Ecological risk assessment of trace elements (TEs) pollution and human health risk exposure in agricultural soils used for saffron cultivation

Contamination of farmland soils by trace elements (TEs) has become an international issue concerning food safety and human health risks. In the present research, the concentrations of TEs including cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), zinc (Zn) and iron (Fe) in soils of 16 farmlands were determined in Gonabad, Iran. In addition, the human health risks due to exposure to the TEs from the soils were assessed. Moreover, the soil contamination likelihood was evaluated based on various contamination indices including contamination factor (mathrm{CF}), enrichment factor (EF), geo-accumulation index (Igeo), and pollution load index (PLI) calculations. The soil mean concentrations for Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and Fe ranges as 0.102, 6.968, 22.550, 29.263, 475.281, 34.234, 13.617, 54.482 and 19,683.6 mg/kg in farmland soils. The mean concentrations of the TEs decreased in the order of Fe > Mn > Zn > Ni > Cu > Cr > Pb > Co > As > Cd. Levels of all metals in this study were within the FAO/WHO and Iranian soil standards. The HQ values from investigated elements for adults and children in the studied farms were less than the limit of 1, indicating no health risks for the studied subpopulations. The results of the present research indicated no significant carcinogenic health hazards for both adults and children through ingestion, skin contact and inhalation exposure routes. mathrm{CF} values of Ni and Zn in 100% and 6.25% of farmlands were above 1, showing moderate contamination conditions. EF values of metals in farmlands were recorded as “no enrichment”, “minimal enrichment” and “moderate enrichment” classes. Furthermore, it can be concluded that the all farms were uncontaminated except Ni (moderately contaminated) based on Igeo. This is an indication that the selected TEs in the agricultural soils have no appreciable threat to human health.

Isolation and Molecular Identification of Streptomyces spp. Producing Antibacterial Compounds from Iranian Soil

Isolation and Molecular Identification of Streptomyces spp. Producing Antibacterial Compounds from Iranian Soil

Peace at Home, a Minor Intervention Abroad? Explaining the Turkish-Iranian Border Revision of 1932

Although historians of Turkish foreign policy have emphasized Turkey’s pro-status-quo stance during the interwar period, the international and regional political context of the time sometimes offered states the opportunity to make revisions to the existing order. Cross-border rebellions represented one such opportunity. Turkey was among the countries which saw border amendments as an option, despite a nation-state discourse and ideology emphasizing the ‘inviolability’ of the existing borders. This article shows how Turkey, unable to suppress the cross-border Ararat Rebellion in the late 1920s and early 1930s, opted for a military operation on Iranian soil and successfully demanded a revision to its supposedly well-established ‘Qasr-e Shirin borders.’ The article identifies three major factors that conditioned Turkey’s exceptional approach to its Iranian border in the 1930s: the historical factor of Ottoman-Iranian relations, the new territoriality of nation-states, and the Soviet Union’s influence on the region. It critically employs the memoirs of key Turkish political elites active in the resolution of this dispute, Turkish newspapers, and archival documents. It contributes to our understanding of early republican Turkish notions of territoriality while building on recent scholarship which questions the assumption of early republican Turkey’s strict non-revisionism and disinterest in the Middle East.

THE POSITION OF THE UNITED STATES OF AMERICA ON THE POLITICAL DEVELOPMENTS IN IRAN (1939-1955)

The features of Iran’s importance in the American strategy emerged during the first stage of World War II, after Nazi Germany invaded the Soviet lands and turned it into an important transit point for weapons, materiel, foodstuffs and logistical support from the allies of the Soviet Union. Thus, the latter, along with Britain, had to issue more than one warning to the government of Reza Shah Pahlavi in order to expel the Germans on Iranian soil. When the Shah refused the Soviet-British warnings, he was removed from the throne and his son was installed in his stead. The British and Soviet forces occupied large areas of Iran, and the American war effort joined them to make Iran one of the countries under foreign occupation. and by virtue of its importance, a conference was held in it Known as the (Tehran) Conference in 1943 which attended by the leaders of the United States of America, represented by President Franklin Roosevelt, President of the Soviet Union Joseph Stalin, and British Prime Minister Winston Churchill. Key words:

Origins of the Pentecostal Movement in Iran

This article aims at providing an analysis of the roots and the early development of the Pentecostal movement among the Assyrians in Iran. It is focused on the autobiographical narratives delivered by Andrew Urshan, Benjamin Alexander and Thomas Nasseri. Although produced in different times and for different purposes, their narratives refer to the beginnings of Pentecostalism on the Iranian soil. The description of the spread of the Pentecostal ideas provided in the narratives has been contextualized in reference to the social and political changes occurring in Iran at the beginning of the twentieth century, before and during the First World War. Special attention has been paid to the migratory experiences of the early Assyrian Pentecostals as well as to the transformation of the Church of the East tradition. The article discusses the problem of cultural adaptation of Pentecostalism among Assyrians and emphasizes the fact that the movement was perceived as a factor for unifying the whole Assyrian community. This is mainly due to the fact that the movement was initiated and narrated by native Assyrian Christians rather than American missionaries. This makes Iranian Pentecostalism a rather special case in the Pentecostal history of the non-Western world.

The Assassination of Fakhrizadeh—A Major Iranian Counterintelligence Failure?

The assassination of Iranian top nuclear scientist Mohsen Fakhrizadeh is one of numerous assassinations in Iran conducted by foreign powers ever since 2007. In the past six months, assassins have in addition to Fakhrizadeh also been able to kill Al-Qaida’s no. 2 on Iranian soil. The three most important organizations in the Iranian intelligence community are the Ministry of Intelligence, as well as the Intelligence Organization and Intelligence Protection Organization of the Islamic Revolutionary Guard Corps. There is no doubt that the assassination of Fakhrizadeh is a counterintelligence failure; however, there are indications that the Iranian intelligence community have been compromised. The assassins of Fakhrizadeh had accurate information about Fakhrizadeh and his security details. Because of this breach, Iran will conduct serious reforms in its intelligence community and may also eliminate individuals it suspects work on behalf of foreign powers and may have leaked information.

Growth optimization and identification of an \u03c9-transaminase by a novel native PAGE activity staining method in a Bacillus sp. strain BaH isolated from Iranian soil

ω-Transaminases’ (ω-TAs) importance for synthesizing chiral amines led to the development of different methods to quickly identify and characterize new sources of these enzymes. Here we describe the optimization of growth and induction of such an enzyme in a wild type strain of Bacillus sp. strain BaH (IBRC-M 11337) isolated from Iranian soil in shaking flasks by the response surface methodology (RSM). Optimum conditions were set in a multiplexed bench-top bioreactor system (Sixfors). ω-TA activity of obtained biomass was checked by an innovative efficient colorimetric assay for localizing ω-TAs in crude extracts on acrylamide gel by using ortho-xylylenediamine (OXD) as amino donor. The application of the established OXD assay is thereby expanded from high-throughput activity screenings and colony-based screenings of heterologously expressed mutants to a direct identification of ω-TAs in wild-type strains: This assay can be used to detect the protein band of the respective enzyme in crude extracts of novel isolates by visual inspection of native PAGEs without any upstream protein purification, thus enabling subsequent further investigations of a newly discovered enzyme directly from the crude extract.

A survey of intact low-density polyethylene film biodegradation by terrestrial Actinobacterial species.

Low-density polyethylene (LDPE) polymer is mainly used in the production of plastic bags and food packaging making up the largest volume of plastic pollutions. These polymers are potential substrates for bacteria in the bioremediation process. In this study, soil samples were collected from different plastic landfills in Iran and subsequently enriched in specific media (polyethylene as carbon source) to increase the population of LDPE-degrading bacteria. Seventeen PE-degrading bacteria, some novel, were isolated from Iranian soil samples and identified using 16S rDNA gene sequencing. These isolates were capable of degrading PE in a limited incubation period without the need for physicochemical pretreatments and comprise mostly of Actinobacteria which include the three genera of Streptomyces, Nocardia, and Rhodococcus. The isolates belonged to 17 different species of gram-positive Actinobacteria. In all, 11 species of the genus Streptomyces, 3 species of the genus Rhodococcus, and 3 species of the genus Nocardia were identified. The isolates with less than 99% 16S rRNA gene similarity to previously known species were suspected to be new species. Various analyses (weight loss, SEM, FTIR, and tensile strength test) to determine polyethylene biodegradation rate were carried out after a 60-day incubation period. Analysis of polyethylene biodegradation elucidates that Actinobacteria have a high ability for biodegradation of polyethylene-based plastics. Streptomyces sp. IR-SGS-T10 showed the highest reduction in weight of the LDPE film (1.58mg/g/day) after 60days of incubation without any pretreatments. Rhodococcus sp. IR-SGS-T11 shows the best reduction in the tensile property of LDPE film, while results from FTIR study for Streptomyces sp. IR-SGS-Y1 indicated a significant change in structural analysis.

Application of exploratory and Spatial Data Analysis (SDA), singularity matrix analysis, and fractal models to delineate background of potentially toxic elements: A case study of Ahvaz, SW Iran

It is essential to study spatial distribution of Potentially Toxic Elements (PTEs) in surface soil, and separate PTEs geochemical background from their human sources, and also determine their correlation with other environmental factors in order to assess their impacts on humans, provide realistic environmental geochemical maps, and carry out soil management. For this purpose, this study was designed to investigate the surface soil in Ahvaz, Southwest of Iran. The applied methods were exploratory data analysis (EDA), including boxplot, Q-Q plot, probability plot (PP), concentration-area (C-A), number-size (N-S) fractal model, and singularity index (SI) model. The obtained results revealed that the fractal models led to a more realistic distinction among the geochemical population compared to the EDA methods such as probability plot. Furthermore, the C-A model was found to be more effective on the separation of subpopulation compared to the N-S and PP models. The studied elements exhibited a similar pattern implying that pollution is a function of geochemical dispersion regarding the surface soil in Ahvaz (Zn ≫ Pb > Cu > As). The studied metals-major elements plot also indicated that there was no meaningful relationship between Pb, Zn, Cu, and major elements in the study area. Plots of association of Pb, Zn, Cu, and As distinctly showed two general geogenic and anthropogenic populations. Moreover, the results of SI revealed that the highly contaminated area was consistent with the main defined hotspots and anthropogenic sources of elements as well as places affected by the contaminated area that have not been reported in previous studies. Furthermore, a combination of geochemical and geographical model comprising different statistical models was developed to more effectively separate geogenic from anthropogenic sources. Also, the geochemical background for the studied elements (Pb 180 mg/kg; Cu 200 mg/kg; Zn 90 mg/kg; As 65 mg/kg) was shown to be higher than the Iranian soil quality guideline with Pb, Zn, Cu, and As of 100, 80, 200, and 18 mg/kg, respectively.

Screening and Comparative Characterization of Microorganisms from Iranian Soil Samples Showing ω-Transaminase Activity toward a Plethora of Substrates

In this study, soil microorganisms from Iran were screened for ω-transaminase (ω-TA) activity based on growth on minimal media containing (rac)-α-methylbenzylamine (rac-α-MBA) as a sole nitrogen source. Then, for the selection of strains with high enzyme activity, a colorimetric o-xylylendiamine assay was conducted. The most promising strains were identified by 16S rDNA sequencing. Five microorganisms showing high ω-TA activity were subjected to determine optimal conditions for ω-TA activity, including pH, temperature, co-solvent, and the specificity of the ω-TA toward different amine donors and acceptors. Among the five screened microorganisms, Bacillus halotolerans turned out to be the most promising strain: Its cell-free extract showed a highly versatile amino donor spectrum toward aliphatic, aromatic chiral amines and a broad range of pH activity. Transaminase activity also exhibited excellent solvent tolerance, with maximum turnover in the presence of 30% (v/v) DMSO.

How Can Organic Amendments Help to Bind Sulfadiazine in the Soil? – An Iranian Soil Study

ABSTRACTVeterinary antibiotics can enter the environment especially agricultural soils via animal manure application in which Sulfadiazine (SDZ) is considered as one of the most used antibiotic. After soil application, it may be transported into subsurface water. The sorption behavior of SDZ is not only influenced by the soil type but also by soil organic matters as well. Hence, an experiment was executed aimed to study sorption/desorption processes of SDZ under experimental conditions in three various soils treated by different bio fertilizers including rice husk compost (RHC), rice husk biochar (RHB) and Micrococcus yunnanensis (My) bacterium. Sorption/desorption data of soils with and without bio-fertilizers were well fitted with Freundlich model (R2 = 0.97). Results showed that bio-amended soils had higher values of kd sorption ranged from 1.16 to 52.4 without and with bio-fertilizers application respectively, proposing low sorption of SDZ with substantial risk of leaching without bio-fertilizers application. Also for the desorption cycle values of Kd increased from 1.03 to 39.1 without and with bio-fertilizers application, respectively. Furthermore, there was a hysteresis effect using organic matter. As a result of bio-fertilizers application, a significant value of SDZ was strongly adsorbed on the soil particles which was not desorb through desorption process.

Evaluation of some heavy metals contaminated soils around the Shahid Salimi power plant, Neka, Mazandaran Province, Iran

<p><span style="font-family: TimesNewRomanPS-ItalicMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"><em></em><span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">One of the most important problems threatening the health of natural resources and, in<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> turn, the food safety of societies is environmental contamination. Heavy metals are considered as<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> the environmental pollutants. The entry of heavy metals into the soil is done through the atmospheric sources and mostly via melting plants, oil refieries and power plants. Due to the mazut<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> consumption in some seasons, power plants are considered as a threat to the soil. This study was<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> conducted with the aim of evaluating contamination of some heavy metals including copper, zinc,<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> cadmium, lead, and nickel in the soils around the Shahid Salimi power plant, Neka located in<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> Mazandaran province, north of Iran. One of the greatest threats is the possible contamination of<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> cultivated paddy by pollutant elements. A number of 50 samples from the soil around the power<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> plant were taken from a depth of 0–20 cm within the form of a regular grid and the concentration<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> of the corresponding metals was measured in each of them. The mean background concentration<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> of copper, nickel, lead, zinc, and cadmium was 36.2, 339.8, 90.8, 13.8, and 0.20 mg∙kg, respectively. The maximum mean contamination factor belongs to nickel, lead, copper, zinc, and cadmium, respectively. The frequency of the obtained contamination evaluation classes indicates that<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> the majority of the analyzed samples have a medium level of contamination. Copper, nickel, and<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> lead belong to the class of very high contaminants. By comparing the concentrations of the heavy<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> metals of studied region with quality standard of Iranian soil resources, presented by the Depart<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">ment of Environment Protection of Iran, it was observed that the concentrations of cadmium, zinc,<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> and copper have been signifiant at the level of 5% based on the standards determined by the<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> agency for agricultural uses, environmental standard and groundwater level. In other words, they<span style="font-family: TimesNewRomanPSMT; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;"> do not have conflct with the determined standard at any of the three levels.</span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /><br class="Apple-interchange-newline" /></span></span></span></span></span></span></span></span></span></span></span></span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /></span></span></p>

Allocating soil profile descriptions to a novel comprehensive soil classification system

Previous work has been put into the creation of a comprehensive soil classification system (CSCS) using a harmonised dataset of 23 soil properties at 18 depth intervals. The classification consists of selected soil taxa from the US Soil Taxonomy, World Reference Base for Soil Resources, the Australian Soil Classification, and the New Zealand Soil Classification. In this paper, the CSCS was tested for allocation using data for from 44 soil profiles collected in Iran. A distance-based algorithm was used to allocate and name the soil profiles according to the CSCS. It was found that 36 Iranian soil profiles are close to the existing taxa of the CSCS in the taxonomic space. Three Iranian profiles with distances between 25 and 30 taxonomic units to the closest CSCS taxa were added to the CSCS and assigned with new systematic names. Allocating the remaining 5 Iranian taxa would require regenerating the nomenclature system. The CSCS has shown advantages for allocating soil profiles from other regions of the world other than the USA, Australia and New Zealand. It also enables cross-referencing with existing soil classification systems. In the future, the CSCS can be further improved by adding taxa from other global or regional soil classification systems.

Distribution and health risk assessment of heavy metals in soil surrounding a lead and zinc smelting plant in Zanjan, Iran

ABSTRACTOne of the problematic issues in soil pollution studies is heavy metal particles which are produced by mines and smelting units and spread through wind action and/or runoff. Pollution and health risk assessment of cadmium, lead, zinc, copper, and nickel in soil around the lead and zinc smelting factory was carried out in Zanjan City, Iran. Contamination factor (Cf), pollution load index (PLI), geoaccumulation index (Igeo), hazard quotient (HQ), hazard index (HI), and carcinogenic risk were pollution and human health risk assessment metrics in this study. Based on the Iranian soil guideline value, soil samples in the studied areas were contaminated the least by copper and nickel and the most by cadmium. PLI results showed that soils near the production line were heavily or extremely heavily polluted. The results of Cf and Igeo showed that lead and zinc were the most important contaminants. Health risk assessment indicated that lead and cadmium in soil were the main contaminants, which pose both carcinogenic and non-carcinogenic risks to human health; carcinogenic risk levels were unacceptably high (above 1 × 10−4). It can be concluded that mining and smelting activities degrade soil quality in this region and the soil pollution might be extended to farming areas.

Impact of monovalent cations on soil structure. Part II. Results of two Swiss soils

AbstractIn this study, we investigated the impact of adding solutions with different potassium and sodium concentrations on dispersible clay, water retention characteristics, air permeability, and soil shrinkage behaviour using two agricultural soils from Switzerland with different clay content but similar organic carbon to clay ratio. Three different solutions (including only Na, only K, and the combination of both) were added to soil samples at three different cation ratio of soil structural stability levels, and the soil samples were incubated for one month. Our findings showed that the amount of readily dispersible clay increased with increasing Na concentrations and with increasing cation ratio of soil structural stability. The treatment with the maximum Na concentration resulted in the highest water retention and in the lowest shrinkage capacity. This was was associated with high amounts of readily dispersible clay. Air permeability generally increased during incubation due to moderate wetting and drying cycles, but the increase was negatively correlated with readily dispersible clay. Readily dispersible clay decreased with increasing K, while readily dispersible clay increased with increasing K in Iranian soil (Part I of our study). This can be attributed to the different clay mineralogy of the studied soils (muscovite in Part I and illite in Part II).

Impact of monovalent cations on soil structure. Part I. Results of an Iranian soil

AbstractThis study investigated the impact of monovalent cations on clay dispersion, aggregate stability, soil pore size distribution, and saturated hydraulic conductivity on agricultural soil in Iran. The soil was incubated with treatment solutions containing different concentrations (0-54.4 mmol l−1) of potassium and sodium cations. The treatment solutions included two levels of electrical conductivity (EC=3 or 6 dS m−1) and six K:Na ratios per electrical conductivity level. At both electrical conductivity levels, spontaneously dispersible clay increased with increasing K concentration, and with increasing K:Na ratio. A negative linear relationship between percentage of water-stable aggregates and spontaneously dispersible clay was observed. Clay dispersion generally reduced the mean pore size, presumably due to clogging of pores, resulting in increased water retention. At both electrical conductivity levels, hydraulic conductivity increased with increasing exchangeable potassium percentage at low exchangeable potassium percentage values, but decreased with further increases in exchangeable potassium percentage at higher exchangeable potassium percentage. This is in agreement with earlier studies, but seems in conflict with our data showing increasing spontaneously dispersible clay with increasing exchangeable potassium percentage. Our findings show that clay dispersion increased with increasing K concentration and increasing K:Na ratio, demonstrating that K can have negative impacts on soil structure.

Reza Shah’s journey into exile

On September 16, 1941, three weeks after British and Soviet troops invaded Iran in the Second World War and occupied the country, Reza Shah abdicated the throne in favor of his son, quit Iranian soil and boarded a British ship to go into exile. The British refused to allow Reza Shah to choose his own place of exile (South America) and sent him to the island of Mauritius. This article examines British thinking that resulted in the choice of Mauritius as the place of exile. It traces Reza Shah’s journey across Iran as he prepared to leave the country; details the composition of the large party of family and staff that accompanied him; provides an account of Reza’s Shah’s reminiscences and reflections at this difficult and emotion-laden moment when he was forced to surrender power, and describes the ‘stooped and aged man’ he had become. It ends with the arrival of the ship carrying Reza Shah and the royal party in Mauritius.

Available alkalinity and N mineralization are key factors regulating soil pH value of an organically amended Iranian agricultural soil

ABSTRACTThis study was conducted to evaluate short- and long-term effects of poultry and sheep manures, as well as sunflower, canola, and potato residues, which commonly are being used as organic amendments (OAs) in agricultural soils, on the pH value, buffering capacity, and nitrogen (N) turnover of a sub-alkaline agricultural soil using laboratory incubation. The tested OAs had pH values ranging from alkaline (manures) to acidic (plant residues), and their effects of the short- and log-term on soil pH value were assessed by fractionation of the OAs alkalinity and evaluating the contribution of OA-borne N mineralization to soil acidity. On average, 45% of potential alkalinity in tested OAs was available for acid-base reactions, soluble alkalinity accounted for 58, 80, 32, 50, and 50% of the excess cations for poultry manure, sheep manure, sunflower, canola, and potato residues, respectively. Buffering capacity of the tested OAs was higher for sunflower residues, potato residues, and poultry manure and lower for canola residues and sheep manure. The tested OAs showed different N mineralization potential, and during the 100 days of incubation, soils amended with sheep manure, poultry manure, and potato residues released 107, 118, 129, and 240 mg N kg−1 soil, respectively, more than double than that released from unamended soil. Our results demonstrated that long-term impact of OAs on the soil pH value is not related to the initial OAs pH value and soluble alkalinity and that available alkalinity and N mineralization are key factors regulating the soil pH value on the long-term.

The Ability of Streptomyces spp. Isolated from Iranian Soil to Solubilize Rock Phosphate

Many agricultural soils are deficient in plant available phosphate and hence not able to sustain optimal crop productivity. The problem is due to the ability of many soils to fix phosphate in a wide range of soil pH and ecological conditions. There is a need to search for more environmental friendly alternatives to improve soil fertility and crop production in phosphate deficient soil. The aim of this study was to isolate, screen, and characterize phosphate solubilizing actinomycetes found in different types of soil with varied pH from various sites in Iran. Phosphate solubilizing ability of the actinomycetes was evaluated both on modified Pikovskaya's (PVK) agar and into broth media containing Christmas Island Rock Phosphate (CIRP). The abilities of each isolate to solubilize phosphorus was evaluated from day 1 to day 14 after inoculation. Streptomyces spp. were identified morphologically under scanning electron microscope (SEM). About 31% (22/70) isolates of actinomycetes were found to have the ability to solubilize (CIRP). Isolates IA15 and IA31 showed high solubilizing index (SI) on agar medium whereas isolates IA61, IA59, IA38, IA35, and IA31 were determined to have high CIRP solubilizing ability in broth medium. Isolates IA11, IA31, IA10, and IA61 had high pH decrease in broth medium after 14 days of inoculation. A gradual decrease in pH was observed over a 14 day period of incubation, suggesting a slow release of phosphate from CIRP. The mechanism of solubilization was related to pH decrease in broth medium. In general, majority of phosphate solubilizing actinomycetes revealed superior ability to solubilize CIRP. Key words: rock phosphate; solubilizing phosphate; Streptomyces spp