With 36.9 million hectares of cultivated soybeans, and a production of 128.8 million tons, Brazil is currently the world’s largest soy producer. In the 2019/2020 harvest, the country was responsible for 38% of the world’s production. Soy farmers in Brazil can thus play an important role in reducing agriculture-driven greenhouse gas (GHG) emissions.
In order to stimulate this, Solidaridad wants to provide data with which management systems can significantly reduce GHG emissions and increase carbon sequestration in the soil, without profitability loss for producers. The Solidaridad-commissioned study “Carbon Balance in Soybean Production in Matopiba” is an important contribution to this process.
Juliana Monti, Projects Coordinator for Solidaridad in Brazil, explains how the study measured the carbon stock, taking into account changes in land use and best practices adopted.
Emission and capture drivers in farms
The study assessed 50 farms in 22 municipalities that are part of Matopiba, a region that includes the states of Maranhão, Tocantins, Piauí and Bahia in the Cerrado biome. The total area covered by the study was 150,000 hectares, the equivalent of 150,000 soccer stadiums.
The methodology used to calculate the carbon balance took into account 5 emission drivers and soil sequestration derived from good agricultural practices. The carbon stock captured in the biomass of native vegetation in farms was not included in the carbon balance calculations, but it was measured nonetheless. Legal reserves, permanent conservation areas, and areas of surplus forest within farms reached 3,059,577 tC.
On average, carbon emissions in the farms assessed reached 150,575.90 tCO2e/year during the 2019/2020 harvest. More than half (55.5%) of these emissions originated from the use of lime and gypsum to improve soil quality. The second source of emissions was the use of nitrogenous fertilizers (used mostly in second-season crops such as millet) contributing to 21.5% of total emissions, of which 60.9% originated from urea. The remaining 23% of emissions was related to indirect emissions from the burning of fuels, the decomposition of agricultural residues after harvesting, and electricity use.
Carbon balance and management models
The study assessed in each of the farms four different scenarios of land use change and/or management. In many of these scenarios, no-till farming played an important role. No till-farming is an agricultural technique for growing crops or pasture without disturbing the soil through tillage.
It decreases the amount of soil erosion and increases water infiltration, soil retention of organic matter, and nutrient cycling. This can lead to an increase of the amount and variety of life in and on the soil.
The four scenarios were:
- Scenario 1: Conversion of native vegetation (Cerrado) towards agricultural use under conventional farming.
- Scenario 2: Conversion of native vegetation towards agricultural use under no-till farming.
- Scenario 3: Conversion of degraded pastures towards agricultural use under no-till farming.
- Scenario 4: Agricultural use with conversion from conventional towards no-till farming.
Calculations were done to compare emissions and captures before and after the conversions took place. The carbon balance resulting in the farms varied between 1.89 tCO2e/ha/year (increased emissions) in scenario 1, to -0.79 tCO2e/ha/year (reduced emissions) in scenario 4. Scenarios 2 and 3 presented potential to reduce emissions. Scenario 4, though, was the only one showing capacity for capturing carbon (approximately 33% more against its baseline). The trend was the same in each of the four states of Matopiba.
“What we saw is that there is potential to reduce carbon emissions with practices that are already available to producers and that can be adapted to the reality of different regions, optimizing the use of natural and financial resources,” explains Juliana.
As long as the conversion of native vegetation is not the starting point, the mitigation potential of no-till farming stands out, for both soybeans and other grains, when comparing the different scenarios. If scenario 4 was adopted throughout the region, the emission reduction potential could reach -357.6 thousand tCO₂e/year.
According to Solidaridad’s carbon specialist, Camila Santos, studies such as this provide useful information for producers to reduce their environmental impact and enable them to take production decisions aligned with local and global priorities.
“Meanwhile, it is important to carry out more studies in producing regions, so that the results obtained mirror the reality of each place more and more faithfully. The soils of the Cerrado are different, for example, from those of the Pampas, so it is necessary to identify these differences and translate them so that the model is replicable”, she concludes.
The methodology developed for the study, as well as the carbon balance calculations done for the State of Bahia, will integrate the carbon calculator of the Environmental Information System of Western Bahia, a platform developed by the SENAI CIMATEC university center that will be managed by the producer association AIBA.
The study “Carbon Balance in soybean production in Matopiba” was supported by the Land Innovation Fund, the Norwegian Agency for Development Cooperation (Norad) through its International Climate and Forests Initiative (NICFI). It was carried out in partnership with the Association of Farmers and Irrigators of Bahia (AIBA) and conducted in collaboration with the Institute of Forest and Agricultural Management and Certification (Imaflora).