A. Fallah Nosrat Abad; M. Habibi
Abstract
Introduction: According to WHO and FAO studies, the diseases caused by contaminated foods are of the most widespread threats to human health in developing and developed countries. Therefore, in recent years, researchers have been trying to use soil microorganisms to solve this problem and maintain the ...
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Introduction: According to WHO and FAO studies, the diseases caused by contaminated foods are of the most widespread threats to human health in developing and developed countries. Therefore, in recent years, researchers have been trying to use soil microorganisms to solve this problem and maintain the health of plants and the environment. Phosphorus after nitrogen, is a major macronutrient in plants which controls the growth, seeding and fruit production and involves in basic biological functions such as cell division, nucleic acids synthesis, photosynthesis and respiration and energy transfer. However, high amount of soluble inorganic phosphate is annually applied to the soil as chemical fertilizer but a large portion of it is immobilized rapidly after application due to phosphate fixation by aluminum, calcium, iron, magnesium and soil colloids and becomes unavailable to plants. The use of biological agents especially phosphate solubilizing microorganisms, can play an important role in supplying plant nutrients and improves crop health and productivity without causing any harm in agricultural and natural ecosystems. Bacteria and fungi are the two important groups of phosphate solubilizing microorganisms. Phosphate solubilizing bacteria in soil include Rhizobium, Bacillus, Pseudomonas, Agrobacterium, Achromobacter, Enterobacter and Burkholderia, and the most important ones i.e., Bacillus sp. and Pseudomonas flourescens. Material and Methods: In order to evaluate the effect of Thiobacillus, sulfur and phosphorus applicationon population of phosphate solubilizing bacteria in soil, a field experiment was conducted at Zarghan Agricultural and Natural Resources Research Center of Iran in a factorial, based on complete randomized block design with 3 replications. Treatments consisted of three levels of sulfur fertilizer with biofertilizer containing Thiobacillus bacteria (without sulfur and biofertilizer containing Thiobacillus (S0), application of 500 kg S + 10 kg biofertilizer containing Thiobacillus (S1), 1000 kg S + 20 kg biofertilizer containing Thiobacillus (S2) and 2000 kg S + 40 kg biofertilizer containing Thiobacillus (S3) per hectare), three levels of triple super phosphate (without phosphorus (P0), 100% (P1) and 65% (P2) percent phosphorus recommended based on the soil test) in two corn planted and not planted states. After harvesting, 72 soil samples were collected from each plot and transferred to the biology laboratory of soil and water research institute of Karaj. Soil samples were stored in sterile conditions at 4◦C. In order to isolate phosphate solubilizing bacteria, 10 gram of soil from each sample was suspended in 90 ml of sterilized water to make 1:10 dilution. Then, series of dilution were made (101 – 107) and 0.1 ml of suspensions of the diluted soil sample were transferred to petri dishes containing pikovskaya medium and incubated at 28- 30˚C. To identify PSP from halos surrounding characterized colonies was used and counting was performed 1-14 days after cultivation. The colonies were isolated on the basis morphological characteristics such as shape, color and size and then purified by linear culture. Finally, 60 strains were purified that were used to compare phosphate solubilizing capability. Results and Discussion: The results of this study showed that the main and interaction effects of sulfur fertilizer and biofertilizer treatments of Thiobacillus, phosphorus and plants on the population of phosphate-solubilizing bacteria (cells per gram of dry soil) in Pikovskaya medium were significant at 0.01 level probability. The highest population of bacteria was obtained at the lowest level (S1). Increasing the level of sulfur fertilizer and Thiobacillus biofertilizer decreased the population of phosphate-solubilizing bacteria and the highest level of sulfur and Thiobacillus biofertilizer led to the lowest bacterial population. Also, the study of phosphorus application on the bacterial population showed that phosphorus fertilizer at both levels significantly increased the bacterial population compared to the control (no application phosphorus). The best fertilizer treatment for phosphorus application was P1 which had the greatest effect on bacterial population compared to P2 treatment in Pikovskaya environment. In this experiment, the population of bacteria in corn planted conditions was higher than in non-planted conditions and this population increase was observed in almost all different levels of sulfur and phosphorus fertilizers. The highest bacterial population was observed in combined treatment of S1P2 under corn planted conditions. The results of microscopic, physiological and biochemical tests of the strains showed that all 60 bacterial strains were capable to form clear zone in Pikovskaya medium. Among them, 15 strains (7, 3, 2 and 3 strains belonging to Bacillus megaterium, Bacillus subtilis, Bacillus cereus and Pseudomonas fluorescent, respectively) had higher phosphate solubility than the others.
E. Hashempour; M.B. Farhangi; N. Ghorbanzadeh; M. Fazeli Sangani
Abstract
Introduction: Due to the increasing development of edible oil processing industries, large amounts of wastewater and solid wastes (SW) are inevitable in these industries. Organic wastes can be used as soil conditioners in agriculture due to the high content of organic matter and nutrient loads. Phosphorus ...
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Introduction: Due to the increasing development of edible oil processing industries, large amounts of wastewater and solid wastes (SW) are inevitable in these industries. Organic wastes can be used as soil conditioners in agriculture due to the high content of organic matter and nutrient loads. Phosphorus solubilizing bacteria including Bacillus spp., Pseudomonads and Rhizobium spp. can release phosphorus from insoluble organic and mineral sources in soil. Most soils in the semi-arid regions, including southern parts of Guilan province, have low organic matter content and do not support plant cultivation due to the low fertility and instability of soils. Hence, industrial wastes can be applied as a suitable and low-cost source of organic materials and nutrients in these soils. As phosphorus is one of the most important essential nutrients in plant nutrition which is also present in oil refinery soild wastes and P solubilizing bacteria can release phosphorus from the organic phase of the wastes and make it available in the soil solution, this study aimed to investigate the available phosphorus (Pava) content of soil after simultaneous addition of olive refinery-solid wastes and P solubilizing Bacillus spp.
Materials and Methods: the solid waste obtained from Ganje Rudbar oil refinery plant (located in Rudbar, Guilan province) and a soil sample was collected from a surface layer (0-30 cm) of a pasture, located in Lowshan area (Guilan province). A native strain of Bacillus sp. was isolated from the sampled soil based on its P-solubilizing ability in Sperber medium. An indicator strain, Bacillus persicus was also included in the experiments. P-solubilizing ability of the indicator strain was also evaluated in Sperber medium. The experiment was conducted in a completely randomized design based on factorial arrangement and three replications. Factors included three levels of solid waste (0, 2 and 4%), three levels of inoculated bacteria (no bacteria, native Bacillus sp. and Bacillus persicus) and eleven sampling times (0, 2, 7, 14, 28, 42, 56, 86, 116, 146, and 176 days). Different levels of solid waste were added to the soil, inoculated with bacteria (106 cell/g), and incubated at laboratory condition (~25 ºC) for six months. The moisture content of the soil mixtures fixed around 0.7 FC and kept constant during the incubation period. Sampling was done at desired times. The pH, organic carbon (OC), soil Basal Respiration (BR), available phosphorus concentration (Pava), and phosphatase enzyme activity were measured in soil samples. Data analysis and means comparison were done by Duncans’ test using SAS software package.
Results and Discussion: The studied soil was loam in texture, and had slightly alkaline pH, moderate Pava, and low OC content. The studied solid waste contained considerable OC and total P load. The effect of solid waste (SW), bacteria, sampling time and their interactions were significant on most of the measured characteristics (p < 0.05). SW application decreased soil pH and mixtures inoculated with native Bacillus sp. had lower pH values compared to those inoculated with Bacillus persicus, probably due to the greater effect of Bacillus spp. on SW decomposition compared with B. persicus. The highest average BR was attained in mixtures contained 4% SW which was 1.24 and 1.73 times greater than that in mixtures contained 2 and 0% SW, respectively. While the effect of SW on soil BR was obvious, bacteria inoculation had different impact on soil organic material decomposition and the lowest BR was measured in soil (0% SW) inoculated with Bacillus persicus. OC content of mixtures increased with SW application. The highest OC level (3.21 g 100g-1) was obtained in uninoculated mixture contained 4% SW, which was significantly greater than OC levels in mixtures inoculated with bacteria (p < 0.05). The lowest OC level (3.21 g 100g-1) was observed in uninoculated soil (0% SW). SW application significantly increased Pava. The greatest Pava concentration (142.77 mg Kg-1) was attained in uninoculated mixture contained 4% SW which was not significantly different from Pava concentration in 4% SW-mixture inoculated with native Bacillus sp. (P > 0.05). In control treatments (0% SW), Bacillus persicus was efficient in P release from soil native organic carbon and/or phosphate minerals. However, among the soils contained 2% SW, those inoculated with native Bacillus sp. had the highest Pava concentration. The average Pava concentration in the 4% SW-mixtures was 136.33 mg Kg-1 which was 3.5 times greater than that in control treatment (0% SW). Although soil Pava was related to phosphatase enzyme, this enzyme activity was not affected by treatments. In the P-releasing trend, it was found that 4% SW-mixtures had the highest Pava concentration after 6 months of incubation, and bacteria inoculation made the P-release trend to be flatter compared to control.
Conclusion: The application of oil refinery plant-solid waste improved the basal respiration of the studied soil and increased available phosphorus concentration. The comparison of applied solid waste levels showed that the inoculation of soil with Bacillus bacteria had a positive effect on available phosphorus concentration only at 2% solid waste level.
Mohammad Reza Sarikhani; N. Chalabianlu; S. S. Alavikia
Abstract
Introduction: Phosphorous is one of the essential macronutrients for plant growth and development but its mobility in soil is very low. The utilization of the soil biological potential, in particular phosphate solubilizing bacteria, is an efficient way which can be used for exploiting available sources ...
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Introduction: Phosphorous is one of the essential macronutrients for plant growth and development but its mobility in soil is very low. The utilization of the soil biological potential, in particular phosphate solubilizing bacteria, is an efficient way which can be used for exploiting available sources of phosphorous in the soil. The principal mechanism for mineral phosphate solubilization is the production of organic acid, and acid and alkaline phosphatases play a major role in the mineralization of organic phosphorous in the soil. Presence and distribution of phosphate solubilizing bacteria in the soil and soil phosphatase activities is influenced by soil conditions such as climate, soil type, vegetation and land uses. In order to understand the relationships and considering the importance of the subject, the soil samples were chosen from two different climates; semi-moist (Fandoghlou-Ardabil) and semi-arid (Namin- Ardabil) under culture of legumes, cereals and uncultivated areas, in this experiment.
Materials and Methods: In order to study the effects of different land uses, climate conditions and soil physicochemical properties on phosphate solubilizing microorganism (PSM) distribiution and soil acid and alkaline phosphatase activity, a factorial experiment based on completely randomized design was performed with considering three different land uses (including legumes, cereals and wasteland) and two climate conditions (semi-moist: Fandoghlu- Ardabil and semi-arid: Namin-Ardabil). Four composite soil samples (0-25 cm) were taken from each land uses. Finally, a total number of 24 soil samples were used to enumerate phosphate solubilizng bacteria and evaluate soil phosphatase activities. The enumeration and selection of bacteria in the mineral Sperber medium was done by attention to the clear zone production in the presence of tri-calcium phosphate and in organic sperber (IHP+BCIP) due to blue phenotype of grown colonies. Also, phosphatase activity of soil samples was assessed based on the usual methods for phosphatase assessment. Moreover, after the evaluation of the physicochemical properties of the soil samples and soil enzyme activities and PSB distribution, all data were analyzed by SPSS and MSTAT-C softwares.
Results and Discussion: The Sperber mediums containing mineral and organic phosphates were used in counting the number of PSB. According to the results, the highest total number of bacteria (>6 log cfu/g) was gained in legume land uses in both climate conditions. Furthermore, the highest numbers of organic and mineral phosphate solubilizing bacteria (5.3 log cfu/g) were counted in samples taken from pastures, in other word in soil samples which were collected from uncultured land in semi-moist climate conditions. Enzyme assay showed that acid phosphatase activity (430 µg pNP/g.h) in semi-moist climate conditions were increased three times in comparison to semi-arid climate conditions. Perhaps, this increase can be explained by parameters such as high moisture content and organic matter which can cause an increase in the number of bacteria and soil enzyme content. Our results showed that, alkaline phosphatase activities (APAs) were affectd by interaction effects of land uses and climate, wherein the highest APA (810 µg pNP/g.h) was measured in legume samples in semi-arid climate conditions. The pH of these soil samples and supporting legume rhizospheres from AP producing microorganisms may be the reasons of this increment.
Conclusion: The highest activity of the soil acid phosphatase was observed in soil samples which were taken from uncultivated area under semi-moist climate conditions (namely pastures) (866.59 µgPNP/g.h) while the soil alkaline phosphatase activity had high mean in legume land use soil samples under semi-arid climate conditions (795.15 µPNP/g.h). The total number of bacteria was the highest in semi-arid leguminous land use (14.13×106 cfu/g) but the total numbers of solubilizing bacteria in both mineral and organic media were the highest in semi-moist uncultivated area (respectively 1.9 ×106 and 1.48 × 106cfu/g).
