Modeling soil organic matter changes under crop diversification strategies and climate change scenarios in the Brazilian Cerrado

Authors: LOCATELLI, JORGE - Federal University Of Sao Paulo; Del Grosso, Stephen; SILVA SANTOS, RAFAEL - Colorado State University; HONG, MU - Colorado State University; GURUNG, RAM - Colorado State University; Stewart, Catherine; CHERUBIN, MAURICIO - Federal University Of Sao Paulo; BAYER, CIMELIO - Federal University Of Rio Grande Do Sul; CERRI, CARLOS - Federal University Of Sao Paulo

Submitted to: Agriculture, Ecosystems & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2024
Publication Date: 10/25/2024
Citation: Locatelli, J., Del Grosso, S.J., Silva Santos, R., Hong, M., Gurung, R., Stewart, C.E., Cherubin, M.R., Bayer, C., Cerri, C. 2024. Modeling soil organic matter changes under crop diversification strategies and climate change scenarios in the Brazilian Cerrado. Agriculture, Ecosystems & Environment. 379. Article e109334. https://doi.org/10.1016/j.agee.2024.109334.
DOI: https://doi.org/10.1016/j.agee.2024.109334

Interpretive Summary: Land conversion and agricultural management are leading sources of greenhouse gas emissions in Brazil. Observational data and ecosystem models are used to assess the abilities of different cropping strategies to reduce emissions and increase carbon storage in soils. First, we verified that the DayCent ecosystem model could reliably represent crop yields and soil measurements from 3 sites in the Cerrado, an important agricultural region. We then used the model to investigate how cropping systems and climate interact to control soil C levels. Results indicate that C stocks would decrease under a typical soybean-cotton rotation. However, mixing in crops such as millet, ruzigrass, and sunn hemp increased soil C levels, especially when combined with minimal tillage. Results suggest that diversified cropping systems are a promising strategy for increasing soil C sequestration and facilitate adaption to a changing climate.

Technical Abstract: In Brazil, land conversion and agricultural management have historically accounted for the largest share of the country’s GHG emissions, with the Cerrado region being one of the most affected areas. Although cropping diversification has been proposed as a potential strategy to mitigate GHG emissions through soil organic carbon (SOC) sequestration, the long-term effects of these systems in the Cerrado are unknown. The DayCent model was used to simulate the impact of crop diversification and tillage on SOC dynamics until 2070 (~50 years), including common crop succession systems and crop rotations associated with cover crops under climate change scenarios. First, we calibrated and evaluated the DayCent model using plant and soil observations from three sites in the region, where Pearson coefficients (r values) ranged from 0.50 to 0.94 (calibration sites) and 0.53 to 0.99 (validation site) for crop yields, SOC, and nitrogen. We then used the model to investigate how cropping systems and climate interact to control SOC levels. Results indicate that SOC stocks would decrease under the long-term (~50 years) soybean-cotton succession, regardless of soil management (-0.04 to -0.17 Mg C ha-1 year-1). Crop diversification with crop rotation and cover crops (i.e., millet, ruzigrass, sunn hemp) had the highest SOC accrual potential (~0.71 Mg C ha-1 year-1), resulting in SOC stocks of up to 130 Mg C ha-1 by 2070. Ruzigrass, either single or intercropped with maize on crop succession systems, showed substantial potential for soil C sequestration (~0.55 Mg C ha-1 year-1) and could be a viable strategy if implementing more complex rotations is not feasible. The SSP2 – 4.5 and SSP4 – 8.5 climate change scenarios increased SOC stocks by ~6.3 and 8.2% in SOC across treatments by 2070, respectively. Results suggest that diversified cropping systems are a promising strategy for increasing SOC sequestration, and they offer valuable guidance for enhancing current management practices in the region.