Greenhouse Gases Emission From Soil And Carbon-nitrogen Budget In The Northern China Plain With High Productivity

Because of the population, plow land and water resource etc., the higher grain output is still very important. Many environment problems have appeared because of the excessive application of N fertilizer in the Northern China Plain with high productivity, for example, N2O concentration increase in the atmosphere. Because of the decomposition of soil organic carbon, CO2 concentration in atmosphere has also increased.The experiment site was located in Huantai County of Shandong Province. Soil greenhouse gases emission and carbon-nitrogen budget in the agoecosystem of this region were studied by the method of onsite survey, field experiment and biogeochemistry model simulation. The research results are as follows:1. CO2 and N2O emission from soil in the grain fields of this region changed regularly with the change of the season. The gas fluxes were highest in the summer and lowest in the winter. The peak value of CO2 flux appeared in July 30, and it was 33.86g-m-2-d-1. The CO2 emission was exponentially correlated with air temperature and soil temperature. There was no obvious relation between CO2 emission and soil moisture. The peak value of N2O flux appeared in June 30, and it was 351.31 g-m-2-h-1. The soil moisture was the most important influence factor of N2O. Compared with the grain fields, the seasonal change extents were smaller for CO2 and N2O emission in the protected vegetables fields because of the complicated farmland management and inner microclimate.2. The DNDC model results captured the seasonal change character of two greenhouse gases emission. The simulation results were in agreement with the field data. The carbon-nitrogen budget in the whole region were also simulated by DNDC, and the results showed the total SOC storage in farmland of Huantai County was 1.4 109kg in 2001 and for every hectare, the average SOC storage was 45115.21kg-hm-2. The inputs of carbon and nitrogen were higher than their outputs. From the point of substanable development, this region should increase the manure input and the proportion of crop straw return and decrease the N fertilizer application in the future.