Results of research conducted by Embrapa Soja (PR) over the last ten years show that the inoculation of corn seeds with the bacteria Brazilian Azospirillum (strains Ab-V5 and Ab-V6) allows the 25% reduction of nitrogen fertilization, considering a dose of 90 kg per hectare of N-fertilizer.
“The use of microorganisms that promote plant growth - capable of replacing, partially or completely, chemical fertilizers - represents a key strategy for Brazil, which imports the majority of fertilizers used in agriculture”, argues Embrapa researcher Mariangela Hungary.
The economic and environmental benefits of this technology will be presented by researchers Marco Antonio Nogueira and Mariangela Virgínia, from Embrapa Soja, during online event to be held on November 25th, starting at 10:30 am, on Radar da Tecnologia, Embrapa Soja's YouTube channel.
According to Mariangela Virgínia, the technology for inoculating corn with the bacteria Brazilian Azospirillum provides a reduction in nitrogen top dressing and also allows an average increase of 3,1% in grain productivity.
“All the experiments carried out confirm these benefits, in different yield levels, tropical and subtropical conditions, clayey and sandy soils, with high and low organic matter content”, highlights the scientist.
For ten years, Embrapa Soja conducted 30 field trials (26 of them in the first harvest) to evaluate the inoculation of 12 commercial genotypes (hybrids and varieties) of corn with the Ab-V5 and Ab-V6 strains of A. brasilense. Researcher Marco Antonio Nogueira explains that the plants received the same base fertilizer with macro and micronutrients and the inoculation was carried out at sowing, when 24 kg/ha of nitrogen (N) were also applied.
According to him, around 35 days after corn emergence, 0%, 50%, 75% and 100% of N were supplied in coverage, with 100% corresponding to 90 kg/ha of nitrogen, to the inoculated and non-inoculated treatments. .
“The grain yield of inoculated plants with 75% nitrogen fertilization in top dressing was equal to that of non-inoculated plants that received 100% nitrogen fertilization, which indicates that it is possible to reduce nitrogen fertilization in top dressing by 25%, without loss productivity”, celebrates Nogueira.
For researchers, these results are a reflection of two complementary microbial processes, coordinated by plant growth-promoting bacteria (BPCP). One of them is biological nitrogen fixation, which, although modest, is generally capable of meeting 5 to 20% of the plant's needs. The other process favors corn root growth, via the synthesis of phytohormones, mainly indoleacetic acid, which allows improving the exploitation of soil for water and nutrients.
“The inoculant increases the efficiency of using nitrogen fertilizer, which, in Brazilian conditions, is rarely more than 50%, with much of it lost through leaching, contaminating river waters, groundwater and the emission of greenhouse gases”, he reports.
Embrapa launched the first commercial strains of Azospirillum brasilense for corn and wheat crops and the first commercial inoculants were launched in the 2009/2010 harvest. According to a market survey, the use of inoculants with these bacteria already exceeds ten million doses annually.
Mariangela Hungary also highlights that the technology of inoculating corn during sowing with Azospirillum brasilense (strains Ab-V5 and Ab-V6) provides a significant reduction in the emission of greenhouse gases. Considering a dose of 90 kg/ha of N in coverage, the 25% reduction in N implies a mitigation of 236 kg/ha of CO2 equivalents (considering the conversion rate of 1 kg of N = 10,5 kg of CO2 equivalents of CO2022). In economic terms, considering the average price of urea on the Brazilian market in July 260, the savings were around R$XNUMX/ha.
Despite the benefits of inoculating maize with the Ab-V5 and Ab-V6 strains of A. brasilense, the researchers call attention to the need to adopt good inoculation practices, which involve care from purchasing to using the inoculant in the field.
“It is important to make sure about the origin and quality of the inoculant, especially if it contains the strains recommended by research in the indicated concentration, if the product is registered with the Ministry of Agriculture, Livestock and Supply for this purpose, as well as if the product it was kept in appropriate transport and storage conditions, with a maximum temperature of 30º C”, emphasizes the researcher.
“As the inoculant contains living beings, sensitive to heat, after acquisition it is necessary to store the product in a place protected from the sun and ventilated until use”, he recommends.
Mariangela Hungary explains that BPCP correspond to a group of beneficial microorganisms capable of colonizing tissues of roots, stems, leaves, fruits, seeds and nodules of legumes. BPCP can stimulate plant growth through several processes, such as biological nitrogen fixation (which contributes to nitrogen nutrition), the synthesis of phytohormones (which impacts root growth), and increased phosphorus (P) availability. ) and potassium (K), tolerance to biotic stresses that can be caused by living organisms (insects and microorganisms) or abiotic (such as temperature, high irradiation and water restriction), among other functions.
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