Intercropping and plant growth-promoting rhizobacteria improve sustainability of agro-ecosystems. To evaluate the effect of Azotobacter (Azotobacter chroococcum) inoculation on productivity of a peanut /maize intercropping system, a two-year study was design as a randomized complete block in a factorial arrangement with three replicates at Astaneh-ye Ashrafiyeh, Guilan province. Factors were Azotobacter inoculation [control (non-inoculated) and inoculated with Azotobacter chroococcum) and intercropping pattern (Sole cropping of peanut and maize, additive intercropping pattern at three levels (100% peanut + 100% maize, 100% peanut + 50% maize, and 50% peanut + 100% maize), and replacement intercropping pattern at three levels (50% peanut + 50% maize, 67% peanut +33% maize, and 33% peanut + 67% maize). Results showed that gain yields of maize and peanut were significantly affected by Azotobacter inoculation and intercropping pattern. Inoculation with Azotobacter chroococcum significantly increased grain yields of peanut and maize by 10% and 16%, respectively. Maximum and minimum of land equivalent ratio (LER) were observed at 100% peanut + 50% maize and 50% peanut + 50% maize, respectively and inoculated intercropped plots with Azotobacter chroococcum had 12-16% grater LER that non-inoculated ones. Regards to impossibility of mechanical weed control by machines in additive intercropping patterns, to obtain the highest productivity in maize/peanut intercropping system, intercropping pattern of 100% peanut + 50% maize along with Azotobacter application will be suitable in fields with low weed density. Otherwise, based on LER and grain yield of peanut, the intercropping pattern of 67% peanut + 33% maize along with Azotobacter application will be suitable.

The potential of three Azotobacter chroococcum strains for whey degradation and alginate production were investigated. After dilution, samples were spread plated on isolation agar and Manitol agar and incubated at 30 °C for 24 h. Microorganisms were screened for their ability to whey degradation and alginate production based on colony morphology, negative and capsule staining, ability to decrease the apparent turbidity of the fermentation broths in batch and semi continuous culture by spectrophotometer assay at 400 nanometer and tensiometer assay. Of the three strains tested for whey degradation, only Azotobacter chroococcum 1723 produced significant apparent growth on whey broth and could decrease about 70% of turbidity in fermentation broth during 6 days in batch culture. Colonies of this strain was characteristically yellow, large, moucoid and slimy on whey agar than Manitol agar after 24 h at 30°C. Transmission electron microscopy assay and Carbazole reagent were used to recognize the alginate biopolymer. After optimizing environmental factors such as pH, salt concentration and temperature, this strain was able to produce exopolysaccharide greater than 5 mg/mL. Optimum results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35 °C and pH 7. Increasing inorganic and organic nitrogen sources (yeast extract and NH4NO3) reduced whey degradation at least 30%. Transmission electron microscopy assay showed a net-structured polysaccharide capsule around the cells. Semi-continuous culture results demonstrated that, alginate production as well as whey degradation was decreased (1 mg/mL and 30 %).

A field experiment was conducted at Rasht, in 2014, to investigate controlling weeds in native Hashemi cultivar paddy fields by different methods of herbicide applications and inoculated withAzotobacter chroococcum. The factorial experiment based on a randomized complete block design with three replicates was performed.Factors were Azotobacter application with two levels (inoculation with or without Azotobacter chroococcum) and weed management regimes with six levels (pretilachlor plus a supplementary hand weeding, bensulfuron methyl plus a supplementary hand weeding, and pretilachlor+bensulfuron methyl plus a supplementary hand weeding, hand weeding during rice growing period+no herbicide, un-weeded during rice growing period+no herbicide). Results indicated that paddy rice yield was significantly increased by 16% afterAzotobacter chroococcum inoculation. Rice paddy yield was significantly reduced in un-weeded plots compared to hand weeded and herbicide treated plots. ANOVA also revealed that there was no interaction effect between Azotobacter chroococcumapplications and weed management regimes on paddy and biological yields, indicating that the herbicides had no adverse effect on Azotobacter efficiency in promoting growth and paddy yield of rice. Weed dry weight was reduced by 88, 91, 92, and 94 percentages in weeded plot and plots treated with pretilachlor, bensulfuron methyl, and pretilachlor+bensulfuron methyl, respectively, compared to un-weeded plots.Azotobacter chroococcum inoculation had no significant effect on weed biomass. Overall, the result of this experiment confirmed the feasibility of chemical weed control in paddy fields inoculated withAzotobacter chroococcum.

In order to evaluate effect of Azotobacter chroococcum strains on yield, yield components and qualitative indices of winter rapeseed (Brassica napus L.), an experiment was conducted during 2009-2010 growing season at Research Institute of Rice in Rasht. The experimental design was completely randomized block, with three replications. Investigated treatments were including control (without seed inoculation), seed inoculation with Azotobacter chroococcum strains 6, 9, 11, 12, 13, 14, 15, 16, 19, 21, 23, 25, 28, 35 and 38. Results showed that Azotobacter chroococcum significantly affected on all traits. The highest of seed oil yield and K, P, Mg content caused by A. chroococcum strain 14. A. chroococcum strain 12 caused the highest of seed yield with average of 3532.43 kg/ha that hadn’t significant difference with strains 9 and 14. As A. chroococcum strain 12 caused the highest of seed yield components and N, Ca, oil seed content. Growth promoting hormones production, N2 fixation, mineral nutrients dissolubility such as phosphorus, siderophore production and kinds of antibiotics are the effect of Azotobacter chroococcum mechanisms that seems to be using at least one of these mechanisms is increased plant yield. Generally, A. chroococcum strain 12, A. chroococcum strain 14 and A. chroococcum strain 9 had more positive effect on traits compared with other strains. Results of this experiment showed the use of A. chroococcum increases yield and qualitative characteristics of rapeseed and therefore can be used as supplementary of chemical fertilizers.

Azotobacter is a bacterium belongs to gamma-proteobacteria class and Pseudomodaceae family with 7 species. It cannot produce spores but forms cyst. Azotobacter is able to fix molecular nitrogen non-symbiotically. It can synthesize plant growth hormones. Azotobactercan stimulate the growth of plants through different mechanisms which include nitrogen fixation, production of phytohormones such as auxins, ability of solubilizing phosphorous from the soil. In this research the soil samples from fields under cultivation of wheat in Azerbaijan-e Sharghi, Azarbayjan -e Gharbi, Kordestan, Gloestan, Fars and Khorasan provinces of Iran were collected and evaluated for isolation of Azotobacter chroococcum. The capability of auxine (Indole Acetic Acid) and hydrogen cyanide (HCN) production of selected strains was assessed. The ability of these strains for solublizing insoluble phosphates based on the ratio of corona halo to colony diameter on Sperber medium was investigated as well. The greenhouse experiment was conducted to examine the effects of inoculation of native Azotobacter in a complete factorial randomized block design on wheat growth. From 362 soil samples, 217 strains of Azotobacter isolated. One hundred two strains were selected for further investigations. The selected strains synthesized auxine (IAA) between 0-4 mgr.ml-1.24h-1. The selected strains did not show HCN production. Based on the ratio between corona halo to colony diameter in these strains the ability of solublizing insoluble phosphates was zero up to 1.3. Based on the above measurements, 37 strains were selected for greenhouse investigations. The greenhouse results showed that inoculation increased significantly the shoot dry weight and nitrogen uptake of wheat but inoculation had no noticible effects on phosphorous and potasum uptake. Based on the greenhouse results, 11 strains were selected for further investigation and field experiments.

In order to study the effect of Azotobacter chroococcum and Bradyrhizobium japonicum on soybean [Glycine max (L.) Merr] cultivar seed characteristics produced under water stress, a factorial test was conducted in form of completely randomized design with four replications. Treatments were water stress [Irrigation after 50 mm (normal irrigation), 100 mm (mild stress), and 150 mm (severe stress) evaporation from pan of class A], Cultivar [Manokin, SRF×T3, Williams] and inoculation [Bradyrhizobium japonicum, Bradyrhizobium japonicum co-inoculated with Azotobacter chroococcum, control]. The result showed that stress has significant effect on time, speed and percent of germination. Seedling inoculated with Bradyrhizobium japonicum, had higher length compared to seeding not inoculated. The dry weight of Seedling grown from seeds produced under mild stress was 10% higher the one that in normal irrigation. Bradyrhizobium japonicum, co-inoculated with Azotobacter chroococcum, increased mean time of germination and root dry weight. Seeds produced under mild stress as compared to normal irrigation, had further seedling and stem length. Therefore, bacteria couldn’t compensate severe stress effects and just increased seed characteristics of mild stress condition.

To evaluate the effect of manure and Azotobacter application on yield and yield components of maize, an experiment was carried out in Ecological Research Station of Khorramabad in 2007. Four plant densities (75, 85, 95 and 105 thousand plants per ha) and manure at 80% and 100% (24 and 30 ton.ha-1) and two levels of Azotobacter chroococcum (inoculation and uninoculation), were arranged in a split split plot design based on randomized complete block design with three replications. Results showed that plant density had significant effect on biological yield, grain yield and number of ears per unit area. Increasing of plant density from 75000 to 105000 plants.ha-1 increased 42% of biological yield, 65% of grain yield and 42% of the number of ears per unit area. Totally, results from current research showed that under climate conditions of Khorramabad, the autumn crops are harvested in early summer next year. Therefore, corn plant can be considered in rotation cycle as the second culture. Also, the plant density of 95000 plant.ha-1 and application of 24 ton.ha-1 manure for supplying plant nutrition are suitable for corn as second culture. It seems that there is not the suitable conditions to show the beneficial effects of bacteria in rich soils of nutrients (manure application).

Copolymer Polyhydroxyalkanoat (PHAs) is the most well known degradable product of Poly-beta-hydroxybutyrate (PHB). In this research, for producing this kind of polyesters, Azotobacter was separated from soil, and then purified. By changing culture media conditions such as saturated and unsaturated oils (palmitic acid, Olive oil, Castor oil, Sesame oil, Sprout wheat oil, Almond oil, Sweet almond oil, Coconut oil, Snake oil, Nigella seeds oil, Myrtles oil, Walnut oil, Paraffin, Stearic acid, Oleic acid, Chamomile oil, Glycerin), nitrogen, temperature and air blowing, optimum biopolymer growth condition inside the cell was evaluated. With using quantities and qualities methods like spectrophotometer assay and percentage counted by using gas chromatography (GC), and rate of PHB production were investigated. Result shows that among 10 separated Azotobacter strains, AZ7 was capable to produce 80.793% amount of PHB. Maximum amount of this biopolymer (84.48%) in 2% Almond oil as carbon source, 1% yeast extract as nitrogen source, 200 rpm air blowing and 33°C were observed. It seems that AZ7 strain accumulated 80-90% of their cellular dry weight of PHB in different media and in competitive of foreign strain is a native candidate for production of PHB.