Partitioning carbon dioxide emissions from soil organic matter and urea in warm and cold cropping seasons

Abstract

Soil-based emissions of carbon dioxide (CO2) triggered by intensive nitrogen (N) fertilization originate from different sources including fertilizer application and soil organic matter. It is crucial to understand each contributing source of the total CO2 fluxes to develop effective greenhouse gas mitigation strategies and enhance the soil organic carbon (SOC) accumulation approaches. A 2-year field experiment was conducted in the warm and cold upland cropping systems by incorporating urea as a N source at 0, 50, 100, and 200 % of urea, following the Korean recommendation levels for the chosen crops, while 13Carbon-labelled urea was used to investigate the source-specific CO2 emissions under different climatic conditions. N fertilizer for red pepper during the warm season was applied at 90 kg N ha−1, whereas that for garlic during the cold season was applied at 250 kg N ha−1. CO2 fluxes were highly influenced by increases in N fertilization application levels in correlation with soil temperature during the warm season but were not significantly affected during the cold season. The total CO2 fluxes from soil organic matter were not influenced by an increase in N fertilization level; however, the percentage of CO2 coming from urea was greatly influenced by increasing the N fertilizer application level. Additionally, CO2 fluxes from urea during the warm season were considerably higher than those from the cold upland soil. The current research may provide a comprehensive understanding of CO2 partitioning sources and factors responsible for the SOC balance between warm and cold upland cropping systems.