Simulating trends in soil organic carbon of in calcareous fluvo-aquic soil under long-term fertilization using the DNDC model

The objectives of this paper were to study the variation of soil organic carbon and the application of DNDC model under the long-term different fertilization. Based on the data available of pre-set long-term experiment, four treatments (CK、NPK、1/2NPK+1/2OM、OM) were chosen to study the characteristics of crop yield and content of soil organic carbon(SOC) variation. The trend of SOC in Fengqiu was also simulated by DNDC model with a time scale from 2000 to 2099. The results were as follows: there was a significant difference on average production between fertilization treatments and control. Application of chemical fertilizer (NPK、1/2NPK+1/2OM) increased yield compared to single application of manure, with the highest yield was observed for NPK (10811 kg/ha); However, no significant difference between NPK and 1/2NPK+1/2OM, and the lowest occurred in CK was observed. The content of average SOC in OM was the highest (7.90 g/kg), followed by NPK and 1/2NPK+1/2OM. The lowest SOC was found in CK being 4.15 g/kg. With a time frame of 15 years, the content of SOC in CK decreased slightly, kept constant in NPK, while kept increasing in 1/2NPK +1/2OM and OM. The simulated results of SOC trend in Fengqiu with a time scale of 100 years showed that the content of SOC under CK decreased by 52% compared to initial content. Application of chemical fertilizer uniquely (NPK) could maintain constant, while it rose significantly under 1/2NPK +1/2OM and OM treatment in the first 25 year, then it kept stable. The content of SOC increased by 24% and 25% compared to that in 2000 year, respectively. It could concluded that combined application of manure and chemical fertilizer could increased yield and SOC content in the soil, hence, improve the sustainable utilization of soils.