بررسی اثر مقادیر مختلف نیتروژن و ازتوبارور بر رشد و عملکرد نخود (Cicer arietinum L.)

Introduction
One of the most important agricultural efforts is to minimize the use of chemicals nitrogen fertilizers and to replace it with biological nitrogen fertilizers to produce healthy productions. In dry conditions the use of industrial nitrogen fertilizers depends on the amount of rainfall and consumed cautiously. Low consumption of nitrogen sources reduce crop growth and yield and higher than optimum applications of chemical Nitrogen sources can cause many environmental disorders. This is while Azotobacter as a soil bacteria also fixes nitrogen, produce vitamins, growth hormones and antibiotics and also increases the photosynthesis, plant growth and grain yield and reduces the need to application of chemical Nitrogen.

Materials and Methods
In order to study the effect of biological and industrial nitrogen fertilizers on growth, yield and yield components of chickpea (Bivanij variety), an experiment was conducted with split plot arrangement based on randomized complete block design (RCBD) with four replications under rainfed conditions in the Telesm village, Dalahoo, Kermanshah, during 2013 agricultural season. Climate of the region is temperate and semi-arid with 535.6 mm of rainfall. Soil texture is clay - loam with 0.02 percent of nitrogen. Basic amount of Nitrogen fertilizer was considered 30 Kg.ha-1 Urea and four levels of chemical nitrogen fertilizers including: %50 of base fertilizer, %100 of base fertilizer, %150 of base fertilizer and no fertilizer (control) were assumed as main plot factors. Similarly, the basic amount of Azotobarvar bio-fertilizer was considered as 100 g.ha-1 and four levels of it including %50 of base fertilizer, %100 of base fertilizer, %150 of base fertilizer and no bio-fertilizer (control) were assumed as sub plot factors. Bio-fertilizers are inoculated to seeds and planting was done manually on 19 March 2013. Density was considered 40 plants per square meter with 25 cm intervals between rows and 10 cm on the row. The yield of chickpea was harvested in 6 July 2013.

Results and Discussion
Results of the experiment showed that the effects of treatments were significant on biological yield, grain yield, harvest index, 100-seed weight, protein content, number of branches, number of pods per branch and number and weight of grains per branch. The highest dry matter and grain yield obtained at %50 nitrogen fertilizer + %100 Azotobarvar with 6730 and 1089 Kg.ha-1, respectively and the lowest in the control treatment with 2420 and 472 Kg.ha-1, respectively. The greatest number of seeds per plant (20.4) were measured in the treatment of %150 nitrogen with Azotobarvar and the lowest (14.4) obtained in the treated %50 of nitrogen and without Azotobarvar. The highest 100-seed weight (46.9 g) obtained in the treatment of %50 nitrogen + %150 Azotobarvar and the lowest nitrogen fertilization (22.5 g) was at %150 of N + non-inoculated Azotobarvar. Also, the highest (26.1%) and lowest (22.7%) protein contents were obtained at the treatments of %50 nitrogen + %150 Azotobarvar and control, respectively. The amount of biomass, grain yield and protein content were in the treatments of no nitrogen and Azotobarvar (control).The application of nitrogen to about %50 of the base amount and Azotobarvar equal the base amount or %150 of the base amount maximized grain yield, total dry matter, 100-seed weight and seed protein content. In other words, taking Azotobavar in this condition (rainfed) was more effective compared to chemical nitrogen (Urea) on the yield. Probably Azotobarvar, because of other mechanisms except the supply of nitrogen, had significant impacts on the growth characteristics of the plant. Finally, based on the results of this experiment, application of the industrial Nitrogen with base dosage, the highest yield is obtained, but its application higher than based amount showed negative reactions. Also increasing the amount of the Azotobarvar (bio-fertilizer) more than basic dosage caused yield reduction.It could be a sign of plant adaptation to Azotobarvar application.

Conclusion
Generally, the study of showed that the application of Azotobarvar biological fertilizer can decrease the amount of industrial nitrogen fertilizer application up to 50 percent in dry climatic conditions.