Journal of Soil Biology
Year:2020 | Volume:8 | Issue:2|Papers Count:8

One of the best ways to reduce the adverse effects of chemical fertilizers on soil physicochemical properties and plant growth is to use biological fertilizers such as plant growth-promoting fungi. Biological fertilizers could be used as a supplement or alternative to the chemical fertilizers in sustainable agriculture. Accordingly, to investigate the effect of Trichoderma fungi on the nutrition and growth of pistachio trees, an experiment was conducted in a randomized complete block design, in which each block contains four treatments, control (T0) (no inoculation), Trichoderma harzianum (T1), Trichoderma viride (T2) and treatment of an equal mixture of T1 and T2 (T3) in three replications under common garden conditions. The results showed that all three fungal treatments significantly increased growth parameters including branch length (up to 60%), the number of vegetative buds (up to 30%), leaf area (up to 50%), and chlorophyll index (up to 171%) in pistachio trees in comparison with control. The use of fungal treatments significantly increased the concentration of potassium and zinc in pistachio leaves up to 20 and 70%, respectively, compared to the control. T2 treatment significantly increased the phosphorus concentration by 14% and the calcium by 40% in pistachio leaves. The application of T1 and T3 treatments significantly increased the magnesium concentration up to 25%, in pistachio leaves compared to the control. T1 treatment significantly increased the leaf iron concentration by 28% compared to the control. The application of T1, T2, and T3 treatments significantly increased the content of total chlorophyll up to 73. 2, 171, and 59. 2% of and carotenoids up to 77. 6, 3. 80, and 64. 8% in pistachio leaves respectively, compared to the control. According to the results of this study and after further field experiments, it can be expected that the studied fungi can be used as biofertilizers (alone or in combination) to reduce the utilization of chemical fertilizers in the future.

Plants have difficulty living in hard habitats such as heavy metal contaminated soils that the application of plant growth-promoting bacteria can be beneficial to reduce this difficulty. This study was designed to investigate the autecology and synecology of Pseudomonas fluorescens CHAO-Rif in a heavy metal contaminated soil. This research was a factorial experiment with a completely randomized design with three replications in greenhouse condition. The first factor was plant species (sunflower and hemp plants) and the second factor was soil sterilization, in which the treated soils were inoculated with Pseudomonas fluorescens CHAO-Rif bacterium purchased from the Plant Pathology Group of the Institute for Integrative Biology (IBZ) in Zurich, Switzerland. The plants were harvested at the beginning of the flowering stage. The population of the applied Pseudomonas was significantly higher (more than 1. 5 times) in sterile soil planted with sunflower compared to that in unsterile soil planted with cannabis. In sterile soil, the inoculated Pseudomonas could colonize in the inner tissues of the sunflower root. Here the natural log of the number of the bacterium was 4. 02± 0. 06, but it was not found in the cannabis root. The bacterium was found in the rhizosphere and non-rhizosphere soils and on the root surface (rhizoplane) of both plants. However, it was not found in aerial parts of the plants. In unsterile soil, the inoculated bacteria were found only in the rhizosphere and on the root surface of the plants, but not seen in the shoots and roots of the plants. Although soil native microorganisms reduced the abundance of applied Pseudomonas in unsterile soil, the application of this bacterium did not have a significant negative effect on the studied soil native microorganisms.

Soil phosphorus availability is mostly dependent on acid and alkaline phosphatase activities. The present experiment was carried out in a completely randomized design with four treatments and three replications in Qazvin soils under wheat cultivation. Treatments included: application of 100% phosphorus fertilizer based on soil test (TSP), municipal solid wastes compost (MSWC): 20 tons per hectare, sheep manure (SM): 20 tons per hectare, and control (without fertilizer). The results showed that the application of organic fertilizers significantly increased the activity of alkaline and acidic phosphatase compared to the TSP treatment. When MSWC and SM applied to the soil, alkaline phosphatase activity increased by 29. 5% and 26. 1% compared to the TSP treatment, respectively. All three fertilizer treatments increased the activity of alkaline phosphatase compared to the control. MSWC, SM, and TSP treatments increased activity of alkaline phosphatase by 62. 6%, 58. 5%, and 25. 7% compared to control, respectively. The application of TSP fertilizer increased phosphorus uptake by 5. 9 kg/ha compared to the control. These values were 8. 7 and 9. 2 kg/ha for MSWC and SM treatments, respectively. According to the data, the application of organic fertilizers increased phosphatase activity and improved phosphorus uptake by wheat.

Climate is the most important factor that determines the plant yield and soil microbial activity. Therefore, this study aimed to investigate the soil biological properties in three different climate zones including Eyvan (humid), Ilam (semi-humid), and Syrvan (semi-arid) under seed-origin and coppice oak trees. To this purpose, three plots (100 × 100 m dimension) randomly prepared in less undisturbed forest consist of both growth types. Soil sampling took place randomly at 0-20 cm of soil depth under each seed-origin and coppice oak trees in three regions. The results showed that growth type had no significant effect on microbial biomass carbon in the Ilam and Syrvan climates. However, in Eyvan forest soils, the amount of microbial biomass carbon under seed-origin was 1. 71 times higher than the coppice trees. The highest amount of microbial biomass nitrogen (5. 32 mg. kg-1) was observed in the Eyvon climate, which did not have a significant difference with the Ilam climate and it was the lowest (2. 90 mg. kg-1) in the Syrvan climate. The highest metabolic quotient (qCO2) was observed in coppice type in the Eyvan and Syrvan climate and the least amount was observed in the Ilam climate. Growth type had no significant effect on the metabolic quotient of the soil in the Ilam climate. The highest basal and substrate-induced respiration was obtained in the Eyvan climate, while the Syrvan soils showed the least amount of these parameters. The highest amount of organic carbon and nitrogen were observed in the Ilam forest soils and the least amount was obtained in the Syrvan forest soils.

Fluorescent pseudomonads are one of the most effective microorganisms among the plant growth-promoting bacteria. They have attracted many researchers attention due to their unique properties such as motility in the rhizosphere, high growth rate, and potential for the root colonization of various plants. In most studies, rhizospheric soils were used for isolation but Pseudomonas bacteria also have been isolated from various organic fertilizers. Therefore, the present study was conducted to evaluate plant-growth promotion and biocontrol characteristics of fluorescent pseudomonads isolated from vermicompost. Then, the ability of isolates was evaluated for auxin and siderophore production, tricalcium phosphate dissolution, and secretion of growth inhibitor metabolites. Total of 43 fluorescent pseudomonads isolates were isolated and purified based on irradiation under a UV lamp and fluorescence properties. Results of the PGP characteristics revealed that all the isolates were able to produce auxin and solubilize inorganic phosphorous. The average of auxin production was 2. 51 mg/l. The highest (708 mg/l) and lowest (203 mg/l) amount of soluble phosphate belonged to P15 and P43 isolates, respectively. P35 isolate showed the most efficient in terms of siderophore production in which the ratio of halo zone diameter: colony diameter was 2. 04 mm (after 48 hours) and 2. 12 mm (after 72 hours). The results of the hydrogen cyanide production test showed that 88. 35% of isolates could secrete this metabolite. In this research, all isolates were not able to produce protease enzymes. In terms of production of this enzyme, the P17 isolate showed the highest ratio of halo zone diameter: colony diameter (2. 7 mm), was the most efficient one. None of the isolates were able to produce cellulase enzymes.

The aim of this study was to recognize the transformation of soil organic matter fractions in burned and unburned pasture lands. The study area was a pasture land located in Alvand hillslope (toposequence), near the village of Haidara, Hamadan. The low-intensity wildfire occurred in the hillslope in autumn (October) 2015, in such a way that half the toposequence was burned up to the bottom symmetrically. Soil samples were gathered from three locations (up, mid, and down) of burned and unburned parts of toposequence 2 (December, 2015-autumn) and 9 months (June, 2016-spring) after wildfire occurrence. In each location, soil sampling was carried out in two parts; between the bushes and under their canopies and in two depths; 0-5 (upper) and 5-10 cm (lower) layers, respectively. Litter samples were also gathered in a 30*30 cm2 plot for each burnt and unburnt parts of toposequence. All sampling was carried out in three replications. The light fraction of organic matter (LF), cold and hot water extractable organic carbons (CWEOC and HWEOC), biomass carbon (BC), total organic carbon (TOC), and basal respiration (BR) were measured. The data analyzed in split-split plot design for each layer (upper and lower) and each season (autumn and spring) of sampling separately. In the mentioned statistical design, sampling location on toposequence (up, mid, and down) was regarded as the main plot, fire impacted area (burnt and unburnt) as a subplot, and sampling location related to bushes (between and under canopy) as sub-sub plot. Soil OC and BR were higher in the upper layer and under the bush's canopy rather than the lower layer and between bushes. In general wildfire increased TOC (42%), LF (41%), and BC (52%) in the sampled soils. In contrast, CWEOC, HWEOC, and BR in burnt soils were 61, 52, and 48% lower compared to those in unburnt soils, respectively. Although in autumn the litter content was lower on burnt soils compared to those in unburnt soils (50%), in spring it significantly increased on burnt soils. The increases in litter on burnt and unburnt soils were 4. 5 and 2 times, respectively. The study showed that wildfire and burning of plant cover by producing biochar on the pastures can improve carbon sequestration in soil.

Soil salinity is the main factor in reducing crop yield, especially in arid areas. The availability of Phosphorous (P), is low in salt-affected soils. The purpose of this study was to isolate and identify the phosphate solubilizing fungi from saline-sodic soils and also to investigate phosphate solubilization in the presence of different salt concentrations. For this purpose, twenty soil samples were collected from the rhizosphere of Salicornia persica. Isolation of phosphate solubilizing fungi was done by plate culture technique on National Botanical Research Institute’ s phosphate growth medium-Bromo Phenol Blue (NBRIP-BPB) solid media. Phosphate solubilization was tested in the presence of 0, 50, 100, 200, 400, 600, 800, and 1000 mM NaCl during 15 days of incubation on solid media. Thereafter, the phosphate solubilizing potential of isolates was tested in 6-day experiments in broth, and the phosphate solubilizing capability was evaluated in the presence of different concentrations of NaCl. The results showed that all strains produced halo zone until NaCl concentration reached to 200 mM, but with increasing salinity, only KARFUN 1 and KARFUN 2 could solubilize phosphate. Results of the 6-day experiment in broth culture were showed that KARFUN 1 had the highest phosphate solubilization potential, so it was selected for further investigation. Molecular identification indicated that KARFUN 1 isolate had a similarity of 100% with Aspergillus. niger and A. tubingensis species. The results showed that with increasing NaCl concentration, the phosphate solubilization increased and pH decreased. The lowest and the highest phosphorous concentration was observed in 1000 and 0 mM NaCl, respectively. Irrespective of NaCl concentration, results showed that there was an increase in phosphorous solubilization during the incubation time. The maximum phosphate solubilization was achieved (549 mgL-1) after 12 days of incubation and pH reached to 1. 19. However, the KARFUN1 strain was able to solubilize inorganic phosphate in different NaCl concentrations as it could release 224 mgL-1 phosphorus at 1000 mM NaCl in broth medium.

Due to the problems of salinity and heavy metals in agricultural soils, this study was designed to reduce the adverse effect of salinity and cadmium stresses when wheat inoculated with pseudomonas. The experiment was designed as a factorial arrangement with three factors including salinity levels (3 and 10 dS m-1), cadmium concentration (0, 25, and 50 mg kg-1), and Pseudomonas inoculation (inoculated and non-inoculated) in a completely randomized design with three replications. After harvesting, some soil biological properties (soil respiration and soil microbial biomass) and some plant growth were measured. The results showed that basal respiration (14. 6 mg CO2 100g-1 day-1), substrateinduced respiration (93. 2 mg CO2 100g-1 day-1), soil microbial biomass (13. 4 mg 100g-1), dry weights of shoot and root (7. 65 and 2. 30 mg pot-1 respectively), Ca concentration of shoot and root (3. 12 and 5. 92 mg kg-1 respectively), and Mg concentration of shoot and root (3. 16 and 6. 75 mg kg-1 respectively) decreased with increasing the salinity and cadmium concentrations. Inoculation of Pseudomonas encouraged those parameters compared to non-inoculated treatments. Cd concentration of shoot and root (1. 63 and 7. 13 mg kg-1, respectively) increased with increasing the salinity and cadmium stress but inoculation of Pseudomonas lessened the Cd concentration of shoot and root. Therefore, the negatives effect of saline and Cd stress might be condensed if wheat is inoculated by Pseudomonas.