Journal of Soil Biology
Year:2014 | Volume:2 | Issue:1|Papers Count:8

Soil fungi play an important role in nutrient cycling. They have a significant effect on mineralization of organic matter in soils. Some fungi could decompose organic compound with producing different enzymes. Since soil phosphorus in organic soils exists mostly in organic forms, fungi have a vital role in mineralization of those compounds. In order to study the effect of phytic acid and sodium glycerophosphate on acid and alkaline phosphatase activities of some fungi isolates, an experiment was conducted as a completely randomized design with factorial arrangement with three replications. The first factor included seven fungi isolates (four Aspergillus isolates (A19, A15, A10, A7) and three fungi isolates (Penicillium, Rhizoctonia Solani Trichoderma harzianum) and control (no fungus)) and the second factor included two different organic phosphorus compounds (Phytic acid and Sodium Glycerophosphate). All isolates were grown in PDB at 28 DC and acid and alkaline extracellular phosphatase activities were determined after 7 and 14 days inoculation. The results showed that acid and alkaline phosphatase activity was significantly different among all soil isolates on a 5% significance level. The highest level of acid and alkaline extracellular phosphatase was observed in Trichoderma harzianum (Th) treatment. In this experiment, A15 was the superior among Aspergillus Isolates. Different studies showed that acid phosphatase activity was higher than alkaline extracellular phosphatase among all studied isolates and type of organic phosphorus compound had a significant effect on the phosphatase enzyme activity among all studied isolates. Acid and alkaline Phosphatase activity in sodium glycerophosphate treatment was higher than phytic acid.

Nowadays, safe and secure disposal of agricultural and industrial solid waste such as sawdust and sugarcane bagasse is really important. Improper disposal such as burning or dumping may cause direct and indirect emissions of greenhouse gases. Therefore, substitution of burning or dumping process with biological methods is more advisable. This study was implemented to investigate CO2 emissions and physic-chemical changes of composts derived from cow manure, sugarcane bagasse and sawdust in the presence and absence of Eisenia foetida. A completely randomized design with factorial arrangement and three replications was employed in this experiment. Experimental factors include six different substrates (cow manure, cow manure + sugar cane bagasse, cow manure + sawdust in the presence and absence of Eisenia foetidat and five levels of times (0, 15, 30, 45, 75 and 90 days). The results showed the highest CO2 emissions observed fifteen days after incubation (23.8mg CO2g-1h-1). Nitrogen, phosphorus and potassium in vermicomposts derived from different substrates (cow manure, cow manure + sugar cane bagasse, cow manure + sawdust) were (1.81, 1.47 and 1.53%), (0.50, 0.39 and 0.60%), (1.13, 1.15 and 0.83%) respectively. It seems it is possible to dispose sawdust and sugarcane bagasse during vermicompsting process.

In order to study the spraying of Plant Growth Promoting Bacteria (PGPB) and their metabolites on chlorophyll content, nutrients uptake and yield in Hashemi cultivar of rice, an experiment was arranged based on completely randomized block design with four replications in greenhouse of at the University of Guilan during 2010. In this research, the examined treatments consisted: without spraying and fertilizer (control), without spraying and use of fertilizer, spraying with P fluorescens strain 168, spraying with metabolites of P.jluorescens strain 168, root inoculation with P.jluorescens strain 168, spraying with P.jluorescens strain 136, spraying with metabolites of P fluorescens strain 136, root inoculation with P fluorescens strain 136, spraying with P fluorescens strain 41, spraying with metabolites of P fluorescens strain 41, root inoculation with P fluorescens strain 41. The results of experiment showed the effect of bacteria different levels was significant on leaf greenness content, calcium, magnesium, iron, yield and harvest index, but wasn’t significant on chlorophyll a, band carotenoid contents. Root inoculation with P fluorescens strain 41 was superior to the other treatments regarding all of the studied indices. However, the spraying with P fluorescens strain 41 had lower effect than the root inoculation with P.jluorescens strain 41 and P fluorescens strain 136, but its results was better as compared to the fertilizer and non-sprayed treatments. Spraying effect of metabolites from various bacteria was different that may explain the various bacterial regulator effect on plant growth and development. Results showed that root inoculation with growth promoting bacteria was successful as compared to their spraying in terms of quantitative and qualitative indices of rice. Spraying, however, can be used as complementary to root inoculation with PGPR for crop yield improvement.

The most important limiting factor for mass production of mycorrhizal fungi inoculums and subsequently their use in arable soil is obligate nature of this symbiosis. To overcome this problem, several methods such as hydroponic, aeroponic, and root organ culture have been proposed for spore production of these fungi. Each of these methods has several capabilities and limiting factors. The goal of this research were in vitro production of three species of mycorrhizal spores. In the first stage, attempt was made to produce induced roots by inoculating three strains of Agrobacterumrhizogenesto and using sterile carrot disks. Results showed that, from the inoculated tissues, induced roots developed on carrot. Due to genetic stability, induced roots from carrot disks were used for next stages of this project. Spores of three species of arbuscular mycorrhizal fungi including Glomus intra radices, Glomus etunicatum and Glomus mosseae were prepared by trap culture of Sudan grass, isolated from soil and disinfected by proper antibiotic compounds. These spores were placed near the head of induced carrot roots on M medium in sterile condition. After establishment of symbiotic relationship between these two organisms for spore production, the colonized roots were transferred to 250 ml glass bottle with 100 ml of M medium. After 8 weeks, roots and fungi were isolated from medium. Results of this project showed that ln Vitro culture was an effective method for spore production of Glomus intraradices and Glomus etunicatum. But, Glomus mosseae did not produce any spore by this method and we suggest that other methods, such as aeroponic and hydroponic, be used for spore production of this fungus.

Azospirillum is a well-studied genus of plant growth-promoting bacteria. Phytohormone production by PGPR is considered as one of the effective factor to increase the tomato yield significantly. In order to study the effect of Azospirillum inoculant on on Growth Characteristics and Yields of Tomato, three strain of Azospirillum were isolated, identified, and purified from Tehran suburb soils. Tomato seeds were inoculated by those isolated strains of Azospirillum and tomato seedlings were grown under the greenhouse condition. At the end of grown periodof tomato plant, stem length, root length, leaf and branch fresh weight, root fresh weight, root bulk, leaf and branch dry weight and root dry weight were measured. The results showed that tomato seed inoculation had significant effect on all measured characteristics except the length of root. Inoculation of tomato seed with Azospirillum increased the bulk and dry weight of root and consequently it attributed to increased uptake of plant nutrient. It seems that Azospirillum inoculants have a beneficial effect on tomato growth.

In order to investigate the effects of plant growth promoting Rhizobacteria (PGPR) inoculation on the morphological traits of Tarragon a factorial pot experiment, based on completely randomized design with four replications, were conducted in research field of Horticulture Department of Mohaghegh Ardabili University in 2010 - 2011. Treatments consisted of inoculation with three species of rhizobacteria namel y Azotobacter, Azosperillium, Pseudomonas suspension in single and combination applications of these bacteria which included Azotobacter- Azosperillium, Azotobacter Pseudomonas, Azosperillium-seudomonas, Azotobacter- Azosperillium- Pseudomonas and control (without inoculation), which were applied as rhizome inoculation and foliar spraying. Results revealed that inoculation of tarragon plants with plant growth promoting Rhizobacteria had significant effect on growth parameters. The highest value for traits such as the number of stem branches and rhizome and leaf number were obtained by foliar application of Azosperillium - Pseudomonas combination and combined form of three mentioned Rhizobacteria. Rhizome inoculation of Azotobacter - Azosperillium combination caused increases in plant height and rhizome dry weight in comparison with control. In general, results of this investigation indicated that inoculation with plant growth promoting Rhizobacteria caused increases in growth indices of tarragon plants by enhancing root growth and development by providing favorable conditions for plant growth with respect to supplying better condition for water and nutritional elements absorption from soils.

In order to investigate the physical and chemical properties of some Iranian soils under common bean cultivation, forty-one soil samples were collected from Azna, Zanjan, Aligoudarz and Khomein regions. Root colonization percentage, spore number and infection potentional of arbuscular mycorrhizal fungi in soils were evaluated after sorghum cultivation. The results showed that the soils had a wide range of physical and chemical properties. Soils 3 and 13 (sampled from Khomein and Azena) had the highest number of spores (55) and infection potential (138 Infectant) per 20 g of soil respectively. The highest percentage of root colonization by arbuscular mycorrhizal fungi was observed in the soil No. 38 (prepared from Zanjan) with 38% root colonization. This study revealed that the soil EC, calcium carbonate, organic matter and DTP A- extractable zinc content had positive and significant correlation with the number of spores, infection potential and root colonization percentage. Whereas, there was negative and significant correlation between the amount of phosphorus and three parameters mentioned above.

This experiment was conducted aiming to improve the germination and vigour traits of Asclepias procera by inoculation with PGPR. The study had 8 levels of inoculation including control, Pseudomonas, Azospirillum, Azotobacter, Azospirillum + Pseudomonas, Pseudomonas + Azotobacter, Azospirillum + Azotobacter, Azospirillum + Azotobacter and Pseudomonas in a completely randomized design with four replications. Results showed that inoculation of Calotrope seeds were significantly affected germination traits. The highest germination percentage (72 %) and germination rate (1.8 per day) was observed by inoculation with Pseudomonas putida strain 169 that respectively was 1.8 and 1.63 fold more than control treatment. The greatest root length (19.84 mm) and shortest mean germination time (7.97 days) was belonging to the Pseudomonas + Azotobacter inoculation, that respectively was 1.6 and 7 fold more and less than control. Greatest seed vigor index (17.8) was shown by Azotobacter + Azosprillum that were 1.82 fold more than control. This research revealed that the inoculation of rhizobacterial microorganisms is a new approach that can be effective to improve seed germination in Calotrope shrubs.