| Analysis on nitrogen input／output balance in croplands on county level in Gansu province |
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| DOI：10.7606/j.issn.1000-7601.2006.02.34 |
| Key Words: Gansu province county level nitrogen balance balance model |
| Author Name | Affiliation | | FENG Zhi-ming | Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China；Graduate School of the Chinese Academy of Sciences,Beijing 100039,China | | FANG Yu-dong | Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China；Graduate School of the Chinese Academy of Sciences,Beijing 100039,China |
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| Abstract: |
| It is difficult to illustrate the nitrogen-balanced mechanism of farmlands on regional level through pot-cultivation and field trials.Based on the analysis of output and input factors,6 inflows and 5 outflows were chosen to establish the nitrogen-balanced model of farmlands on county level.The surplus and deficit of nitrogen in Gansu province in 2000 were calculated and the attributes of its spatial distribution were explored.The results indicated:(1) The nitrogen input and output of farmlands in Gansu province in 2000 were 48.52×104 t and 59.87×104 t respectively,so the deficit of nitrogen in farmlands was 11×104 t and the deficit ratio was 23.4%,showing that the excessive depletion of nitrogen was evident.N surplus was widespread in Qilian mountain,Hexi corridor and its northern regions,and N deficit was prevalent in the east and middle regions of Gansu.(2) In the structure of N input in Gansu province in 2000,chemical fertilizer took the highest proportion, and next was organic fertilizer.The ratio of chemical fertilizer,organic fertilizer and other nitrogen sources was 65∶30∶5.(3) In the structure of N output,the proportion of soil erosion was the largest,and the biomass output took the second place.The effective output rate of biomass N in farmlands was 34.15%. |
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