Apr. 18, 2019
By Leonardo Gottems, reporter for AgroPages
The Brazilian Agricultural Research Company (Embrapa) has developed, along with the Emater PR (Paranaense Institute of Technical Assistance and Rural Extension of Paraná), a seed co-inoculation technique using two bacteria: Bradyrhizobium + Azospirillum to protect soybeans. During the 2017/2018 harvest, those growers who used this biological defense saw an increase of 5.6 sacks per hectare, doubling their net profits.
According to researcher Mariangela Hungria from Embrapa Soja, the biological nitrogen fixation process (BNF) occurs through the symbiosis between bacteria of the genus Bradyrhizobium and soybean plants. From this relationship, the root nodules are formed, in which the bacteria harbors and receives protection and food from the host plant. "In exchange, they capture atmospheric nitrogen (N2) and turn it into nitrogen compounds that are exported to the host plant and benefit it," said Hungria.
Hungria noted that for decades, Embrapa research teams have selected elite strains of Bradyrhizobium that are used in the manufacture of inoculants. "Inoculation is essential in first-year areas of soybean cultivation, or where the plant has not been cultivated for a long time because N2-fixing bacteria are absent or in low soil populations," said Hungria.
Hungria emphasizes that even in areas frequently growing soybeans, annual inoculations at each crop yields economic benefits. "The average gain of the annual inoculation of soybean with Bradyrhizobium in traditional areas of cultivation is 8%, that is, a large return on the low cost of the dose of the inoculant", she said.
In the strains of Azospirillum selected by Embrapa, the main contribution occurs during the synthesis of phytoriums that promote plant growth, especially the root system, which favors nodulation and BNF by Bradyrhizobium. Consequently, soybean plants coinoculated with Bradyrhizobium and Azospirillum have a more abundant and precocious nodulation and higher BNF rates.
"Field trials show that, with co-inoculation, there was an average increase of 16% in soybean yield, compared to areas inoculated with Bradyrhizobium only," said Embrapa Soja researcher André Mateus Prando.
Estimates from the National Association of Inoculum Producers and Importers (ANPII) indicate that in the last harvest, about seven million doses of inoculants with Azospirillum, and more than 50 million with Bradyrhizobium, were commercialized in Brazil.
"These results indicate a consistent positive response from the integration of these practices and emphasizes the importance of their annual adoption," said Embrapa Soja (PR) researcher Marco Antonio Nogueira.
Coordinator of Grains Project, Emater PR, Nelson Harger states that, "The most relevant is that productivity gains promote better returns and technology costs little. Despite the benefits of technology, it is not always best used. The application of inoculants directly into the seeder box, for example, hinders the adherence of bacteria to seed and interferes with its efficiency."