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| Effects of cropping systems on distribution of water-stable aggregates and organic carbon and nitrogen in soils in semiarid farmland of the Loess Plateau |
| Received:September 11, 2015 |
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| KeyWord:Loess Plateau;semiarid farmland;cropping system;water-stable aggregates;organic carbon;total nitrogen |
| Author Name | Affiliation | E-mail | | WEI Yan-chun | College of Resources and Environment, Northwest A & F University, Yangling 712100, China | | | MA Tian-e | College of Resources and Environment, Northwest A & F University, Yangling 712100, China | | | WEI Xiao-rong | College of Resources and Environment, Northwest A & F University, Yangling 712100, China
State Key Laboratory of Soil Erosion and Dry Land Farming on the Loess Plateau, Northwest A & F University, Yangling 712100, China | xrwei78@163.com | | WANG Chang-zhao | Shaanxi Entry-Exit Inspection and Quarantine Bureau, Xi'an 710068, China | | | HAO Ming-de | College of Resources and Environment, Northwest A & F University, Yangling 712100, China | | | ZHANG Meng | College of Resources and Environment, Northwest A & F University, Yangling 712100, China | |
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| Abstract: |
| In this paper, we examined the distribution of water stable aggregates and organic carbon(OC) and nitrogen(N) in soils under different cropping systems, using a 27-year field experiment in the Loess Plateau. The relationships between OC and N contents in bulk soil and aggregates were also analyzed. Results showed that <0.053 mm aggregates, accounting for 35%, dominated the soil mass in 0~20 and 20~40 cm soil layers in the semiarid farmland of the Loess Plateau. The percentage of 0.25~2 mm aggregates was higher, but that of <0.053 mm aggregates was lower in the grass-grain rotation system than the other cropping systems. In the grass-grain rotation system, mean weight diameter and geometrical mean diameter of soil aggregates were also greater. The significant effects of cropping system on OC and N associated with aggregates mainly occurred in 0~20 cm layer. The OC content in >2 mm and 0.25~2 mm aggregates was significantly higher in grass-grain rotation system than in the other systems, while OC content in 0.053~0.25 mm and <0.053 mm aggregates did not differ among different cropping systems. The grass-grain system showed higher N content and lower C/N ratio in each aggregate compared with other systems. The OC and N content in bulk soils was positively correlated with OC and N content associated with aggregates. These results suggest that the responses of OC and N in the bulk soil to cropping systems mainly depend on OC and N associated with 0.25~2 mm and 0.053~0.25 mm aggregates. Additionally, grass-grain rotation system has greater potential to improve soil structure and increase the content of OC and N associated with aggregates. |
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