Using DNDC model to simulate black soil organic carbon dynamics as well as its coordinate relationship with crop yield

ObjectivesThe effects of long-term fertilization on black soil organic carbon content and crop yield were researched and stimulated using the DNDC model in Northeast China, which will provide a scientific basis for the sustainable use of the arable land resources and scientific managements in the region.

MethodsData were collected from the long-term experiments carried out in National Fertility Monitoring Net in Gongzhuling City, Jilin Province. Six of the fertilization treatments were chosen to analyze the changes in soil organic carbon (SOC) and crop yield, including:no fertilizer (CK), only chemical fertilizer application (NPK), combining chemical and low levels of organic manure (NPKM1), 1.5 times of the amount of inorganic and organic fertilizer of NPKM1 (1.5(NPK)M1), combining chemical and high amount of organic manure (NPKM2), inorganic fertilizer plus straw (NPKS), and the DNDC model was validated using these data. The model was used to imitate the variation of SOC in the coming 40 years under the six fertilization treatments.

ResultsThe root mean square error (RMSE) of SOC in treatment was in range of 14.98%-37.91%, those of crop yields were in range of 8.28%-11.19%, which suggested that the simulated values were consistent with the observed values, so the DNDC model was reliable for the simulation purpose in the studied area. The simulated results indicated that the SOC in CK and NPK treatments would drop by 16.67% and 11.21% respectively, and those in NPKM1, NPKM2 and 1.5(NPK)M1 treatments would be steadily increasing in the next 40 years, with the most significant growth in treatment of 1.5 (NPK)M1. The SOC contents in NPKM1, 1.5 (NPK)M1 and NPKM2 will be increased by 13.65%, 15.74%, 15.84% from 2010 to 2050 respectively. The measured SOC content in NPKS treatment had slightly increased since the beginning of the experiment. When the nitrogen application was increased from 160 kg/hm²to 320 kg/hm², the SOC would simultaneously increase in magnitude of 1.00 g/kg, and the crop yields increase would drop from 44.48 kg/hm²to 15.95 kg/hm².

ConclusionAnalyzation of data from the measured and DNDC model simulated, combined application of straw, manure and inorganic fertilizer will be effective in increasing the content of soil organic carbon continuously, and leading to steadily increase of crop yields at the same time. When the nitrogen application rate is between 160 kg/hm²-320 kg/hm², the crop yields will keep increasing with the increasing of soil organic carbon content, and the hoist scope of SOC in increasing crop yield would fall with the increase of nitrogen application rate.