Development Of Plant Growth Promoting Rhizobacteria (PGPR) And Their Inoculum On Maize Growth

In present paper, the use of selective medium isolated and screen out the plant growthpromoting rhizobacteria(PGPR) from three major maize growing areas in Wuwei,Baiyin andDingxi city of Gansu. The PGPR strains were selected based on the measurement of nitrogenfixation capacity, phosphate-solubilization capacity(organic phosphorus and inorganicphosphorus) and IAA secretion capacity. The potential PGPR were developed into a specialfertilizer of maize and used for in vitro inoculation experiment and field trial in2013. Theresults were obtained as follows：1. There were262strains of PGPR were isolated from the rhizosphere of maize, consist of48strains nitrogen fixing bacteria,108strains soluble inorganic phosphorus strains and106strains dissolving organic phosphorus strains. The number of bacteria was presented as RS(root soil)> NRS (soil away from roots)> RP (rhizoplan or surface of roots)> HP (histoplanor interior of roots), having an obvious rhizosphere effect.2. The phosphorus-solubilizing activity and IAA secretion capacity of214strains weremeasured and screened base on phosphate-solubilizing ring method, molybdenum bluemethod, Salkowski colorimetry method,while the nitrogen fixation ability of48azotobacterstrains were determined by using the acetylene reduction assay method (ARA). The resultsshowed that10strains had excellent nitrogenase activity, which varied from2.65to178.94nmol C2H4·h-1·mL-1;14strains have excellent ability of dissolving inorganic phosphorus, theamount of dissolved phosphorus in3.10-514.28μg·mL-1while14strains can dissolve organicphosphorus, the amount of dissolved phosphorus in4.66-39.88μg·mL-1;15strains have theability to secreting IAA, its secretion was in1.36-17.80μg·mL-1. The result of determinationof interaction,7strains both have dissolved phosphorus, nitrogen fixation and the ability tosecrete IAA strains.The serial number: P2-1,P4-4, P4-12, P4-15, P4-17,4N4and2N2.3. A pot experiment was conducted for the7strains were used for mixed inoculants (liquid),inoculation experiment the results indicated that the height and underground biomass of maizetreated by PGPR inoculants were significantly higher than that of control (CK), The effects ofroot average diameter,total root length, root surface area, root volume on two differentvarieties of maize in different growing media difference was different.The carrier substrate forthe cultivation of Xian Yu No.335, compared with the control,the effect of root length androot surface area of PGPR difference is not significant, the average diameter of root and rootvolume were significant differences; Cultivated in sand matrix, effect on root length of PGPR is significantly different, the root surface area, root volume and root mean diameter ofthe impact was not significant. The carrier substrate for the cultivation of Jin Sui No.4,compared with controls, effect on root length, root surface area, root volume and averageroot diameter were significantly different; with sand as growing media,the impact on rootlength, root volume and root mean diameter were not significant, effect on the root surfacearea significantly different.4. Development maize special fertilizer comply with―Microbial Fertilizer‖(NY227-94)standard. Dressing biofertilizer and chemical fertilizer reduction with field trials reduction,results show that the effect on plant height, dry matter accumulation,leaf area withbiofertilizer with chemical fertilizer reduction is obvious;On grain yield and hay yieldsignificant differences, among the treatments, biofertilizer+85%chemical fertilizer was thebest; the biofertilizer+70%chemical fertilizer and the local best fertilizing standard was notsignificant, while biofertilizer on maize maturity CP also significantly improved, comparewith the full amount of fertilizer increase rate of3.8%to4.2%. The cost of fertilizer reduceand increase efficiency1135.5CNY·hm-2and1076CNY·hm-2.5. Different fertilizer treatments on soil phosphorus content of maize effective than the wholeamount of fertilizer significant difference to the optimal treatment B,available phosphorusincrease the range of6.3%to9.9%, compared with no fertilizer (E) treatment were71%to73%. Biofertilizer impact on four enzymes in soil are more obvious,for catalase biofertilizerwith chemical fertilizer reduction is better than the full amount of fertilizer, better than thewhole amount of fertilizer applied fertilizer treatment, and treatment B works best; later fromthe jointing stage fertilizer with chemical fertilizer to improve soil invertase activity wassignificantly higher than the full amount of fertilizer;on soil alkaline phosphatase and ureaseactivity were increased in varying degrees, and the activity peaks appeared at jointing andflowering.Effects of applied fertilizer on maize rhizosphere microbial population of bacteriais most significant.In summary, excellent PGPR P2-1,P4-4, P4-12, P4-15, P4-17,4N4and2N2strains ofcorn can be used as an excellent dedicated PGPR bacterial fertilizer, and use them to developa special fertilizer not only improves crop yields,and reduce the amount of fertilizer inputs,and to some extent, improved the physical and chemical properties of crop rhizosphere soilhas good potential for development and application.