ILP accumulates soil carbon at rates three times greater than grain crop succession

A survey by Embrapa Arroz e Feijão (GO) estimated the rate of carbon accumulation in cerrado soil in Goiás considering a crop and livestock integration system (ILP) compared to a grain crop succession system (soybean-corn), both in direct planting and conventional planting. The result points to an increase in carbon retained in the soil in ILP, over 20 years, projected for the period between 2019 and 2039.

The projection of carbon accumulation was stipulated for the soil profile up to a depth of 30 centimeters and the result is that the highest accumulated carbon values ​​were for the ILP systems, in direct planting, with two arrangements (ILP1 and ILP2, see details below) showed a soil carbon accumulation rate between 0,60 and 0,90 tons per hectare per year. This represents a more than three-fold increase in carbon retained in the soil, when compared to the highest performance of succession systems between soybean and corn, which achieved soil carbon accumulation rates of around 0,11 and 0,21 tons. per hectare per year in direct planting.

The work

The study used the historical series of planting and area management data in ILP at Fazenda Capivara, belonging to Embrapa and located in Santo Antônio de Goiás (GO). The database of management information registered since 1990 supplied a model, known as CQESTR, which simulates the behavior of carbon in crop soil and is used to project how different management practices affect carbon dynamics.

In the work, two ILP systems were simulated within CQESTR and repeated throughout the evaluation time. The first (ILP1) included the cultivation of corn in the summer harvest followed by four and a half years of brachiaria pasture. The second (ILP2) was soybeans in the summer harvest, followed by fallow in the first year, with subsequent sowing of upland rice, followed by fallow again in the second year; and then the planting of corn with, finally, three and a half years of brachiaria pasture. In relation to crop succession (soybean-corn), alternations of annual crops in the summer were considered, as well as fallow periods; or even successions between the two crops (harvest and off-season).

Embrapa researcher Beáta Madari is one of those responsible for this work. She said that this result is in line with other studies in the area and can be explained by the presence of brachiaria forage, which is deeply rooted in the soil, which in addition to recycling nutrients, helps to increase the carbon stock in the system through the contribution of root and aerial biomass in ILP systems. Also according to Madari, a carbon accumulation rate of 0,9 tons per hectare per year surprised the researchers, as it is a high value taking into account the situation initially diagnosed in the conditions of the Embrapa farm in Goiás, which pointed to a clayey soil (more than 50% clay) and with a low to medium carbon content, approximately 2%.

carbon market

The annual rate of carbon accumulation in ILP, in direct planting, obtained in this work, also brings new elements to the scientific debate. According to Embrapa researcher Pedro Machado, there are other studies that reach even higher values ​​of carbon capture in ILP: annual accumulation rates of up to one ton per hectare per year. However, according to the scientist, research is generally conducted on a small scale, in plots, and lasting a few years or harvests. In this sense, he considered that the use of the CQESTR model was a differentiator. “This simulation tool was fundamental, as it allowed us to virtuously use the almost thirty-year-old database on crops on the Embrapa farm and project over time the dynamics of carbon accumulation as a function of soil preparation and agricultural management. With this, we can extend the analysis time on the effect of ILP in relation to carbon sequestration and achieve a result that we believe better predicts the behavior of the production system”, commented the researcher.

Machado added that CQESTR is a program used for scientific investigations inside and outside Brazil, but here in the country it was only used for situations in tropical regions of the Northeast and Southeast and has now been tested and approved for the conditions of the Cerrado biome.

Another issue mentioned by the researcher was that the study, in addition to opening up the possibility of more accurately quantifying the accumulation of carbon by an agricultural production system, makes it possible to project in the future how much carbon will be stored by the soil. In this work, for example, the projection was stipulated for the period from 2019 to 2039. This perspective, according to Machado, inserts the research as a point of support and qualification for the debate that has been taking place in Brazil on the regulation of a market of carbon credits, as well as for the establishment of fundamental strategies for the sustainability of agriculture and for the development of national public policies.

The study that was carried out is part of the doctoral thesis defended at the Federal University of Goiás (UFG) by researcher Janaína de Moura Oliveira entitled: “Carbon in the soil in integrated agricultural production systems in the Cerrado and in the Cerrado – Amazon transition”. This work also included participation from the Embrapa Labex-United States office and the University of Arkansas (UARK), in the United States. The study can be downloaded at this address.

Best for soil health

In the research carried out, the accumulation of carbon in the soil for all situations, whether in ILP or in crop succession, was greater in direct planting, compared to conventional soil preparation systems (plowing and harrowing). Embrapa researcher Márcia de Melo Carvalho, who participated in this study, observed that conservation practices, such as direct planting, contribute to the accumulation of carbon in relation to conventional systems, as not disturbing the soil favors greater structuring, with the formation of aggregates (small clods of soil) that “package” organic matter (see study at this link), protecting it from rapid decomposition. And, the more organic matter, the closer it gets to a state of saturation of the soil with carbon. However, she commented that, as important as saturating the soil with carbon, is the protection that direct planting provides to the soil. She explains that the practice promotes a protective layer of the soil (straw) against the impact of raindrops, allowing water infiltration, in addition to regulating the temperature in the soil. In addition, according to the scientist, management practices that result in the accumulation of carbon in the soil improve quality and productivity, through adaptation to environmental changes that are already a reality in the Cerrado of Goiás.

International Network

The result achieved by the scientific work can also be compared with other research on the accumulation of carbon in the soil. One of the main organizations in the world on the topic is the 4 per 1000 Initiative – soils for climate and food security. The Initiative brings together an international network of collaborators covering teaching and research institutions, farmer associations, governments, international organizations; and agroindustry and business segments. It advocates sustainable soil management practices to achieve an average annual carbon accumulation rate of 0,4% (or 4 per thousand) of the carbon stock currently present in the soil. For the conditions of the experimental area in the Brazilian Cerrado, this means around 0,26 tons per hectare per year. This rate, however, may vary depending on regional climate and soil conditions.

According to researcher Beáta Madari, as the results obtained in the research that was carried out were superior, this signals that the potential for sustainable soil and crop management in the Cerrado can play a very important role in mitigating greenhouse gas emissions. greenhouse effect such as carbon dioxide (CO2).

The 4 per 1000 Initiative was launched during the 2015 United Nations Climate Change Conference (COP 21) in Paris (France). Embrapa is one of the institutions that is part of this organization and researcher Beáta Madari is part of the scientific technical committee.