Investigating the Interaction of Azotobacter and Nitrogen Application on the Remobilization, Yield and Yield Components of Grain Barley (Hordeum vulgar L.)

Nitrogen is a vital and important element for the plant and is available by chemical or biological process. The contribution of nitrogen fertilizer to performance improvement in various studies has been reported to be between 30-50%. Koocheki et al. (2017) reported that the levels of nitrogen fertilizers used in experiments for wheat in the range of 20-250 kg.ha-1 increased wheat yield by 2477 kg.ha-1 compared to control treatment. Biodegradable fertilizers (especially Azotobacter) has been reported positive because they have great potential to improve the nutrition of plants and replace chemical fertilizers, and can minimize or completely eliminate the use of chemical fertilizers and reduce environmental hazards, improve soil structure in cereal, dissolve phosphate and increase growth via absorption of mineral elements. Azotobacter, one of the most reputed free-living bacteria that stabilizes nitrogen in the air, which by using different mechanisms, increases the production of auxin hormone and the development of the plant's root system (increasing root area with more growth), and ultimately helps increase the yield of crops and orchards. The amount of nitrogen consolidated by 20 to 40 kg.ha-1 per year is estimated for cereals such as wheat, corn, sorghum, millet and rice, with a yield increase of 7-12% and a maximum of 39% in these plants.

This experiment was conducted on irrigated barley (Hordeum vulgar v. Bahman) in a farm in the Songhor town, Kermanshah Province, as factorial based on completely randomized block design (CRBD) with three replications during 2014-2015. Factors including Azotobacter chroococcum (0, 100 and 200 g.ha-1) and nitrogen fertilizer from urea source (0, 50, 100, 150 and 200 kg.ha-1). In this test were studied LAI, number of tillers, shoot dry weight, hectoliter weight, protein content, biological yield, grain yield, harvest index, number of spikes.m-2, number of seeds per plant and thousand-seed weight traits. Sowing date was 19 November, 2014. Azotobacters used as inoculate with seed treatment and urea fertilizer at planting time just one-third and two-thirds were stem elongation.

Analysis of variance showed that the effects of azotobacter and nitrogen as well as interactions between them were significant on all traits. The maximum amount LAI, tillers, shoot dry weight, hectoliter weight, protein content (12.5%), biological yield, harvest index, number of spikes, number of grains per spike, thousand seed weight and grain yield (871 g m-2) were obtained in treated with 200 g.ha-1Azotobacter and 200 kg.ha-1 N With the increase the amount of inputs also increased attribute values. Considering the cost of the inputs and amount of grain yield and protein, the consumption of 100 g.ha-1Azotobacter and 100 kg.ha-1 N about 834 g.m-2 and 26%, respectively, had the most economic output and did not significantly different with maximum consumption of them. Generally, the results showed that the effect of industrial nitrogen on all traits was more than Azotobacter, but optimal use of biological and chemical fertilizers combined treatment with low doses (100 g inoculated with 100 kg.ha-1 N), also had the significant and positive effect on morphological traits and yield. So it may be partly replaced urea fertilizer consumption with Azotobacter.

The results of this experiment showed that the highest grain yield (871 g.m-2) was obtained from the combined application of 200 g.ha-1 biomass with 200 kg.ha-1 N. In general, with increasing amount of nitrogen from type of urea, the grain yield was between 20 and 71% and the grain protein content was between 20 and 32%, but with the increase of azotobacter (alone), the grain yield increased between 17 and 42%, and the grain protein was between 5 and 10 Percentage.