Increased Soil Organic Carbon Losses Due to Soybean Monoculture in the Argentine Pampas: A Meta-Analysis

Abstract

Agricultural soils can act as a repository for atmospheric carbon and hence mitigate global warming. One of the best management practices that can increase the soil organic carbon (SOC) is the selection of high carbon input crops. Some crops like soybean would lead to SOC decrease due to its low residue production. This is the main crop in the Pampas region of Argentina. The objective of the present study was to determine how soybean monoculture impacts the SOC in the region. Data were collected from 11 long-term field experiments. Results of nine SOC comparisons of soybean monoculture with rotations and seven comparisons of other crop monocultures with rotations were extracted. Meta-analytic methods were used for the analysis. SOC stock in the 0–20 cm layer was 10% lower under monoculture of soybean than under rotations. The average duration of the experiments was 10 years. On the contrary, no differences of the SOC were detected when monocultures of wheat, corn or sunflower were compared with rotations. When the initial and final SOC stocks were compared in each treatment, it was estimated that in nearly all cases there were losses of SOC. The average loss of SOC was 8.1 t ha−1 under soybean monoculture and 3.9 t ha−1 under the corresponding rotations. Consequently, the reviewed experiments indicate losses of SOC due to agriculture in the Pampas that double with soybean monoculture.