Carbon Sequestration and Emission Reduction Effects of Tea Garden Soil under Different Organic Planting Years

To explore the impact of different organic planting years on carbon sequestration and emission reduction in tea garden soils, tea gardens with 23 years (T23a), 10 years (T10a) of organic planting, and conventional farming (CK) in Simao District, Yunnan Province, were selected as the research objects. Differences in soil carbon storage, greenhouse gas emission flux, and cumulative emissions in the 0-20, >20-40, and >40-60 cm layers were analyzed, and the influence of organic planting years on soil carbon sequestration and emission reduction was clarified. The results show that with the increase of organic planting years, the soil carbon sequestration and emission reduction showed a significant growth trend. Compared to CK treatment, the SOC content and storage in 0-60 cm soil layer in T23a and T10a treatments increased by 32.90% and 26.31%, 46.60% and 9.97%, respectively; and the CO₂ emission flux and cumulative emission increased by 14.37% and 31.27%, 14.29% and 30.55%, respectively; while the N₂O and CH₄ emission flux (86.27% and 86.60%, 114.29% and 171.43%) and cumulative emission (86.26% and 86.55%, 115.52% and 179.31%) significantly decreased (P<0.05). The global warming potential (GWP) of T23a and T10a treatments was significantly reduced by 87.07% and 89.12% compared to CK treatments (P<0.05), and the total greenhouse gas emissions from tea garden were also significantly reduced by 86.21% and 89.66% (P<0.05). Compared to the T10a treatment, the SOC content and storage of T23a treatment increased by 5.22% and 33.30%, respectively. Soil temperature and humidity, pH, TP, SOC and NO₃^--N were key factors affecting greenhouse gas emissions. In summary, organic planting enhances the carbon sequestration capacity of tea garden soil, reduces the cumulative emissions of N₂O and CH₄. The effects of carbon sequestration and emission reduction become more pronounced with the increase of organic planting years.