Objective Effect of long-term use of organic fertilizers on the soil carbon pool at tea plantations was studied to optimize the fertilization practice.

Method A positioning soil quality test was conducted for 16 consecutive years on the field at the Scientific Observation and Research Station of the Ministry of Agriculture and Rural Areas in Ningde, Fujian. Six fertilizations were implemented for the experimentation using no fertilizer (CK), chemical fertilizer (NPK), and organic fertilizer to replace nitrogen fertilizer at the levels of 25% (M1), 50% (M2), 75% (M3), and 100% (M4). Soil and plant samples were collected to analyze the soil organic carbon (SOC) and its components, carbon pool management index (CPMI) in the soil as well as the yield of tea bushes grown on the respective lots.

Result Compared to CK, the fertilization treatments significantly increased SOC by 30.91%-49.57%; significantly raised the contents of easily oxidizable organic (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC), and recalcitrant organic carbon (ROC) by 58.39%-88.35%, 157.21%-561.30%, 7.69%-42.89%, and 20.50%-34.83%, respectively; heightened the CPMIs by 72.21%-110.93%; and boosted tea yield by 28.78-104.99% with a downward increasing trend as the nitrogen fertilizer replacement increased.

Conclusion Taking yield of tea, cost of fertilizer, and quality of soil into consideration, M1 that substituted 25% of nitrogen fertilizer with organic fertilizer was recommended for the area tea plantations.