Carbon sequestration by rape and soybean under application of silicon-based biostimulants and water deficiency: greenhouse experiment

Abstract

Modern agriculture is a major source of greenhouse gas emissions leading to the loss of soil carbon storage. Globally, agricultural activities account for approximately 10.7 billion t CO₂eq of greenhouse gas emissions annually making about 20% of global emissions. In 2019, agricultural greenhouse gas emissions in Russia totaled 114.2 million t CO₂eq. Agricultural emissions accounted for 5.4% of total emissions. The application of silicon-containing biostimulants may help reduce emissions and enhance carbon sequestration. The research goal was to evaluate the effects of two products - amorphous silicon dioxide and monosilicic acid - on rape plant and soybean growth, their tolerance to water stress, and CO₂ fixation. The experiment was conducted in the phytotron that simulated the optimal and stress (50% of normal) irrigation regimes. The results showed that treatment with biostimulants significantly increased the biomass of both crops under both normal and stressed conditions. Amorphous silicon dioxide was more effective for rape plants while monosilicic acid was more effective for soybean. Under conditions of insufficient irrigation, the products significantly increased the content of photosynthetic pigments (chlorophylls and carotenoids) being indicative of increased plant resistance. Theoretical calculations showed that applying the silicon-containing biostimulants used in pot trials under field conditions could increase carbon sequestration by the root system: for rape plants, up to 189 kg CO₂ ha under normal conditions and 315.6 kg ha under stress; and for soybean, up to 85.2 kg ha and 94.7 kg ha, respectively. Thus, it may be assumed that the tested silicon-containing biostimulants may increase the resilience and productivity of crops as well as reduce the anthropogenic impact on the atmosphere by enhancing carbon sequestration.