Abstract
A successful application of humic acids and diazotrophic bacteria in corn represents a potential that collaborates to break the current energetic consumption paradigm, which is based on unsustainable fossil sources. Thus, this study aimed to quantify the contribution of diazotrophic bacteria in association with humic acids and nitrogen (N) in corn, in an experiment conducted under controlled conditions in a greenhouse. The experiment was carried out at the Federal Institute of Rondônia, Campus of Colorado do Oeste-RO, Brazil. The experimental design was completely randomized with four replicates and the treatments consisted of: control; inoculation of Azospirillum brasilense; 80 kg ha-1 of N; inoculation of A. brasilense + humic acid; inoculation of A. brasilense + 80 kg ha-1 of N; and inoculation of A. brasilense + 80 kg ha-1 of N + humic acid. At 40 days after emergence, plants were collected, divided into shoots and roots, and the variables were analyzed. According to the results, the joint use of plant growth-promoting bacteria and humic acids increased in plant height, stem diameter and root length and volume. Inoculation of A. brasilense combined with 80 kg ha-1 of N and humic acid increased N use efficiency in corn plants by 60%, while inoculation of A. brasilense combined with 80 kg ha-1 of N increased shoot N contents in corn plants. Key words: Zea mays L., Azospirillum brasilense, humic substances, biological nitrogen fixation (BNF).
Highlights
Brazil occupies the third position in the ranking of corn grain production, after UAE and China
There was significant difference (p≤0.05) for plant height, stem diameter and root length and volume in response to A. brasilense inoculation associated with humic substances and N (Table 1)
Plant height and stem diameter of corn showed the highest values in the treatment with A. brasilense inoculation associated with humic acids, statistically differing from the control (Table 1)
Summary
Brazil occupies the third position in the ranking of corn grain production, after UAE and China. Corn planted area in the 2014/2015 season is estimated at 15,769 million hectares with production of 78,554 million tons of corn (Conab, 2015). Despite its high photosynthetic rate, corn is influenced by problems of environmental stress, such as those related to low fertility of soils, which mostly have nitrogen (N) deficiency (Araujo et al, 2014). Identifying, selecting and using corn genotypes more tolerant to N deficiency and more efficient to absorb this nutrient constitute an important strategy (Reis Junior et al, 2008). The search for genotypes that form more-efficient associations with diazotrophic bacteria must be considered.
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