Abstract
The use of plant growth-promoting diazotrophic bacteria as an alternative to increase nitrogen (N) availability and contribute to its use by corn can be a less costly and ecologically more viable option. Thus, this study aimed to evaluate the effects of the inoculation with Azospirillum brasilense and Herbaspirillum seropedicae in association with N fertilization on the N use efficiency and its biological fixation by corn, in field conditions, using the 15N-isotope technique. A randomized-block design was used, with nine treatments and six replicates. The following parameters were evaluated: grain productivity, dry matter production, accumulated N in plant, percentage of N from the fertilizer, total N from the fertilizer, use efficiency of N applied as fertilizer and percentage of biological N fixation. Results show that N fertilization associated with A. brasilense and H. seropedicae inoculations influences positively grain productivity in corn. The inoculation with A. brasilense and H. seropedicae combined with 30 and 120 kg ha-1 of N promotes a reduction of N percentages in corn grains and shoot. The increase in N dose associated with the inoculation of A. brasilense and H. seropedicae promotes an increase in the N from the fertilizer in corn grains and shoot and reduces the N use efficiency by the crop. Using the 15N natural abundance technique, it was found that the inoculation with A. brasilense and H. seropedicae contributed, respectively, with in average 19.40% and 9.49% of the N required for the development of corn plants. Key words: Zea mays L., Azospirillum brasilense, Herbaspirillum seropedicae, 15N, biological nitrogen fixation.
Highlights
Corn cultivation has a high demand for nitrogen fertilizers, making necessary the application of this nutrient to obtain high productivities (Bastos et al, 2008; Fidelis et al., 2007)
The highest corn grain productivities were obtained in the treatment fertilized with 120 kg ha-1 of N, which did not differ statistically from that inoculated with H. seropedicae and supplied with 120 kg ha-1 of N and that inoculated with A. brasilense and supplied with 30 and 120 kg ha-1 of
The treatment inoculated with H. seropedicae and supplied with 120 kg ha-1 of N and that inoculated with A. brasilense and supplied with 30 and 120 kg ha-1 of N promoted increases in grain productivity of about 6.78, 6.82 and 3.25%, respectively, they had not shown any significant difference compared to the control
Summary
Corn cultivation has a high demand for nitrogen fertilizers, making necessary the application of this nutrient to obtain high productivities (Bastos et al, 2008; Fidelis et al., 2007). Due to the high economic and environmental costs of the industrial process for nitrogen fixation, combined with the increase in food demand, there arises. The need to incorporate new technologies into agricultural activities, aiming to rationalize the use of nitrogen fertilizers. One option is using the benefits provided by the association between diazotrophic bacteria and crops of great economic interest, since these microorganisms are capable of promoting plant growth and increasing plant development and productivity (Baldani et al, 1997)
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