Croplands in the Pampas of Argentina will become an atmospheric carbon sink in coming decades

Abstract

Due to the possibility of using cultivated soils as atmospheric carbon sinks, studies are being carried out worldwide to estimate the potential of carbon sequestration in agricultural areas. In the Pampas, the soil organic carbon (SOC) stock has been calculated at regional scale but its temporal dynamic is unknown. Using information on land cover, yield trends of the main crops, SOC stocks at year 2008 and the AMG model validated with local experiments, the SOC balance of croplands in the Pampas was calculated between 2008 and 2050. Carbon inputs from grain crops were calculated using results of experimental field networks carried out in the Pampas and local coefficients were calculated for the effects of the cultivation of pastures and the adoption of cover crops on SOC. Between 2008 and 2025, the SOC balance of cultivated soils changed from slightly negative to nearly steady state as result of increases in yield and higher carbon inputs. If current rotations are maintained and the rate of increased crop productivity does not stagnate, the Pampas will become an atmospheric carbon sink between 2025 and 2050 as a result of the higher carbon inputs of crops. The adoption of cover crops will improve the balance of SOC but the main tool for sequestering carbon in soils is the replacement of part of the large area cultivated with soybean by greater biomass crops such as corn or the double crop in a year wheat/soybean. Soybean replacement will almost double the carbon sequestration rate compared to the current management and allow attaining the 4‰ goal around 2050. Pampean croplands could represent a sink for atmospheric carbon in the coming years and the management applied can determine how important the sink would be.