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| Soil greenhouse gases emission in response to the C/N |
| Received:November 23, 2017 |
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| KeyWord:C/N;greenhouse gases emission;dissolved organic carbon;dissolved organic nitrogen |
| Author Name | Affiliation | E-mail | | LI Bin-bin | Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China | | | WU Lan-fang | Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China | wulf@igsnrr.ac.cn |
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| Abstract: |
| The soil C/N is a key factor affecting the emission of greenhouse gases (GHGs) from soil and the nutrient availability, resulting from the microbial activity in soil. The retention of crop residues in soil, combined with the application of N fertilizer, is an important way to adjust the soil C/N. To investigate the effect of the soil C/N on GHGs emission, a batch of incubation experiments with 5 different treatments of C/N were conducted, that ground mature maize stalks and leaves along with urea N were mixed into the pre-incubated soil. The changing trends of soil GHG emissions, the dissolved organic carbon (DOC), and the dissolved organic nitrogen (DON) were observed during the 180 days of incubation. The soil CO2 efflux and the DOC content decreased throughout the incubation period and could be differentiated into 3 phases, the fast decreasing phase before the 30th day, the slow decreasing phase from the 30th to the 75th day, and tended towards a stable phase after the 75th day. Meanwhile, both the soil N2O efflux and DON content had a tendency to increase at first and then decline until keep stable; their peaks were observed on day 7 and day 14, respectively. The lower the soil C/N, the faster was the rate of soil organic C mineralization and N nitrification, consequently increasing CO2 and N2O emissions. The correlation analyses showed that the CO2 and N2O emissions of the soil were not only significantly related with the DOC and DON content, but were also related with the DOC/DON ratio in soils. The nitrate (N) content in the soil was related to the initial soil C/N. However, the changes in the nitrate (N) content in soils with different C/N were different; the changes increased at first and then decreased at low C/N, but the changes were just the opposite when the soil C/N was greater than 40. The results indicate that by adjusting the soil C/N with the correct application of N fertilizer, after crop residue retention in the soil, is a fundamental approach to mitigate GHGs emission and improve soil N availability in farming practices. As for the rates and times of N application along with the crop residues, managements are still necessary for further research for different cropping systems under different field conditions. |
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