An economic evaluation carried out by Embrapa Arroz e Feijão on the use of biological products in coinoculation, replacing nitrogen fertilizers in bean production in the states of Goiás and Minas Gerais, showed return rates on investment that varied between 190% and 214% for commercial crops; and 113% for family farming. The study also showed that the total cost of production when using nitrogen fertilizer was 5% higher for commercial crops and 8,5% higher for family farming compared to treatments carried out with coinoculation.
The research was conducted in a cultivation system irrigated by central pivot in the Goiás municipalities of Cristalina, Itaberaí and Santo Antônio de Goiás; and in Paracatu and Unaí, in the state of Minas Gerais. In the city of Goianésia (GO), the experiment was conducted in a family farming area with sprinkler irrigation. The study covered three crops and the cultivar used for the work was Pérola carioca beans.
Coinoculation is the addition of more than one beneficial microorganism to plants, with the aim of maximizing their contribution. In the case of the research, two commercial products were used for inoculation, one containing rhizobia (Rhizobium tropici), microorganisms responsible for biological nitrogen fixation (BNF); and another with Brazilian Azospirillum, a bacterium known for its plant growth-promoting action.
The rhizobia was used in the form of a peat inoculant (powder containing the bacteria) prepared in solution for seed treatment, with two doses applied per hectare. In case of azospirillum, the equivalent of one and two doses of product per hectare applied to the seed was used; and two and three doses per hectare via foliar spraying in the vegetative phase of the crop. In order to compare with nitrogen fertilization, nitrogen fertilizer in the form of urea (80 kilos per hectare) was adopted, distributed 20 kilos per hectare at sowing and 60 kilos per hectare 25 days after plant emergence.
One of the coordinators of this work, Embrapa Arroz e Feijão researcher Enderson Ferreira, said that the financial return on the investment in coinoculation to replace nitrogen fertilizers was positive, especially in one of the treatments carried out. “The best performance was obtained when treating seeds with rhizobia and three doses of Azospirillum sprayed on the plants. This resulted in return rates of 190% in Goiás and 214% in Minas Gerais, for commercial crops; and 113% in Goiás for family farming, which makes coinoculation economically profitable”, stated Enderson. The analysis was carried out based on prices and market indices depending on grain production from different treatments.
The total production cost was also estimated by the research. In this case, operational costs were involved with crop management, related to desiccation of the area, soil fertilization, pesticides, electricity, mechanization, harvesting and post-harvest activities such as drying, cleaning and storage. Components such as crop insurance and technical assistance were added. The calculations were carried out in a similar way for both agricultural systems - commercial and family. The difference was that, for family farming, sprinkler irrigation costs were taken into account and not central pivot irrigation costs.
Socioeconomist and researcher at Embrapa Arroz e Feijão Alcido Wander emphasized the fact that the total cost of production, when using nitrogen fertilizer, is 5% higher for commercial crops and 8,5% for family farming, compared to treatments carried out with coinoculation. He also highlighted the importance of this type of assessment for rural producers: nitrogen fertilizers represent a significant percentage of production costs, as they are imported products, priced in dollars. According to him, it is estimated that the cost of this input reaches around 14% of the total operational cost of production.
“Although there are reports of partial or total replacement of nitrogen fertilizers, there is little information available on the economic advantage of using coinoculation to replace nitrogen fertilizers. Therefore, research like this is important for farmers and to improve crop efficiency. The result we achieved shows that coinoculation is a profitable option for all bean producers, whether small, medium or large”, added Alcido.
The use of inputs that allow biological nitrogen fixation (BNF) is an attractive alternative from an environmental point of view, compared to nitrogen fertilizers. FBN does not have a negative impact on soil, water and air quality, unlike conventional fertilizers, which can, for example, increase the carbon footprint through the emission of greenhouse gases, such as CO2. Therefore, FBN is considered one of the sustainable techniques related to low-carbon agriculture.
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