Effect of nitrogen-fixing asymbiotic bacteria on soil and plant nutrient contents and some agronomical properties in maize farming

More and more fertilizers are being used day by day in order to increase agricultural production. Chemical fertilizers used in increasing rates lead to deteriorate soil quality, pollute the environment and reduce sustainability in agricultural production. This necessitates the development of new strategies in plant nutrition management. Contributing to plant nutrition by increasing the biodiversity in the soil is the most important of these strategies. In this thesis, which is planned for this purpose, the effects of a commercial biological fertilizer consisting of microorganisms (Azospirillum sp., Azorhizobium sp. andAzoarcus sp.) which fixes the free nitrogen (N2) of the air in an asymbiotic way, on maize cultivation, the nutrient contents of the soil and the plant, yield and some agronomic properties of maize were investigated. The experiment was established in the experimental area of Alaşehir Vocational School of Manisa Celal Bayar University, at randomized block design with 3 replications in 2015. In the experiment, biological fertilizer was applied in 2 doses (0 - 0.5 g ha-1) and nitrogen fertilizer in 3 doses (0 - 125 - 250 kg ha-1).Necessary analyzes were carried out by taking soil samples twice, before the application of biological fertilizer and harvest, and by taking leaf samples during tasseling. Yield and some agronomic properties of maize were determined by harvesting at full maturity period. In the statistical analysis of the data obtained at the end of the experiment; the effects of biological fertilizer and different doses of nitrogen applications on soil XII electrical conductivity (EC) and NO3-N in the first period and on Mn, iron (Fe), copper (Cu), maize cob diameter, first cob height and stalk thickness among agronomical properties in the secondperiod were found to be significant. Although not statistically significant, maize grain yield increased with biological fertilizer applications. In addition to nitrogen fixation, microorganisms in the applied biological fertilizer secreted siderophore (microbial siderophor) and provided better utilization of Fe micro nutrients in soil by maize plant. When an evaluation independent of nitrogen doses was made, it was seen that chemical nitrogenous fertilizer was not applied but some agronomic parameters obtained from biological fertilizer applied parcels stood out. Compared to the control plots, the application of biological fertilizer increased the weight of the cob 22.3 g cob-1, the weight of a single cob 21.8 g cob-1, weight of thousand-grain 4 g and the grain yield 183 kg ha-1, respectively. These results demonstrate the effectiveness of biological fertilizer. In the evaluation of the experiment results as a whole, it was determined that biological fertilizer applications had positive effects on nutrient contents of soil and plant, and yield and some agronomic properties of maize plant. In particular, the best results were obtained from the plots where biological fertilizer and half of the recommended nitrogen dosewere applied. Therefore, it was concluded that a dose of 0,5 kg ha-1 biological fertilizer and 125 kg N ha-1 nitrogen could be recommended in order to enhance sustainability in maize production and to enable economical production in Alaşehir region.