The Effect of Long-Term Fertilization on Crop Production, Soil Nutrients and Soil CO2 and N2O Fluxes

A study was conducted to assess the effect of long-term fertilization on soil fertility, crop production and soil CO₂ and N₂O fluxes. The experiment was initiated in 1990 at the Yucheng Comprehensive Experiment Station located at the North China Plain. Five treatments comprising no fertilizer (0), NK, NP, PK and NPK were included. The yield effects of the chemical fertilizers were in the order of N>P>K. After long-term fertilization, only NPK treatment showed significant higher yields of wheat and maize. Chemical properties of soil were obviously affected by long-term fertilization practices. Soil organic carbon (SOC) increased in all fertilization treatments compared to initial content in the surface depth. While in the depth of 20-40 cm and 40-60 cm, all treatments showed decreased in SOC content. Total N of surface soil was higher in the NP, NK and NPK treatments with N application and with no significant difference in subsoil (20-60 cm) in all treatments. Available N in the 0-20 cm and 40- 60 cm showed significant higher in NP and NPK treatments. Available P and K increased in treatments received P or K fertilizers respectively. After long-term fertilization, soil CO₂ emissions were in the increasing order of no fertilizer, NK PK NP and NPK. The differences of CO₂ fluxes were related with the chemical properties after long-term fertilization. Soil N₂O flux was also affected by the application of N fertilizer during the measurement stage. No fertilizer and PK treatments showed lower N₂O emissions. NP, NK and NPK showed higher N₂O emission and obvious difference with no fertilizer.