Impact of agricultural intensification on soil organic carbon: A study using DNDC in Huantai County, Shandong Province, China

Using the biogeochemical model denitrification/decomposition (DNDC), the dynamic changes of soil organic carbon (SOC) of farmland from the 1980s to 2030s were investigated in Huantai County, a typical intensive agricultural region in the Huang-Huai-Hai Plain of China. Prior to modelling, validation of the DNDC model against field data sets of SOC from Quzhou Experimental Station in the Huang-Huai-Hai Plain was conducted at the site scale. We compared the simulated results with the observed SOC in Huantai County during 1982-2011 under two different classification methods of simulation unit (the first method integrated soil type and land use of Huantai County to form the overlapped modeling units; the second selected the 11 administrative towns as the modeling units), and achieved a high accuracy in the model simulation with the improvement of the model parameters. Regional SOC (0-20 cm) density and stocks for Huantai County in the years 2012-2031 were predicted under different scenarios of farming management. Compared with current management practices, optimized fertilization (20% decrease of mineral N), crop straw incorporation (90%) and appropriate animal manure input (40 kg N ha−1 yr−1) could achieve the highest level of SOC density (56.8% higher than 2011) in the period of 2012-2031. The research highlighted the importance of crop straw incorporation, optimized N fertilization and integration of crop production with animal husbandry on the farmland carbon sequestration for maintaining a high land productivity in the Huang-Huai-Hai Plain.