Historical and Predictive Modeling of Soil Organic Carbon Stock Dynamics in Long-Term Field Experiment with Flax Crop Rotation

The RothC-26.3 model was used to reproduce the 62-year dynamics of soil organic carbon (SOC) in sod–medium-podzolic soil (Retisols) in a long-term field experiment of the Federal Research Center for Bast Fiber Crops. Simulation modeling was employed to assess a potential for increase in SOC stocks by 2090 through modifications to agrotechnological practices within a framework of two climate scenarios and two adaptive economic scenarios. The feasibility of using the alternative fertilizer sources and minimum tillage as supplementary approaches to SOC accumulation was examined. The results indicate that under existing management practices and future climate conditions, SOC stocks in the topsoil (0–20 cm) of investigated soils could increase by up to 34% of the initial content by 2090. Furthermore, with implementation of carbon-saving technologies, including adjustments to crop rotation structure, as well as the rates and sources of organic fertilizer application, SOC accumulation can ensure accrual of the stock up to 82% by 2090. The maximum sequestration rate was projected to reach up to 11‰ per year under different climate scenarios. Of the alternative organic fertilizers, the application of compost and peat mixtures yielded the most favorable outcomes, ensuring an additional SOC accumulation of up to 10.6 t ha–1 compared to the use of cattle manure. In contrast, the use of green-manure fallows and minimum tillage cannot be considered an optimal strategy for SOC sequestration, since these practices lead to the lower accumulation compared to cattle manure application. It was demonstrated that the investigated soils feature a considerable potential for organic carbon accumulation, while their cultivation is continued.