SUITMA 2005 Cairo - Impact of urbanization on soil quality evolution of Zhengzhou city in China
SUITMA 2005 Cairo
| This abstract is about the plenary presentation by Wu Kening, Sun Zhiying, Li Ling, Lv Qiaoling, and Fu Qiaoling of the SUITMA 2005 symposium. |
| Wu Kening,i | Sun Zhiying,ii |
| Li Ling,iii | Lv Qiaoling,iii |
| Fu Qiaoling.iii |
- ii - Institute of Soil Science, Chinese Academy of Sciences, Nanjing (China)
Zhengzhou city lies in the transition between loess hill and Huang-Huai-Hai plain, so it has a variety of soil types. Rapid urbanization brings about evident problems on soil quality and environment. For the optimal regionalization of agricultural cropping structure adjustment and assurance of agricultural product quality, it is of great significance to study the transition of different functions of soil resources, the spatial-temporal changes of soil fertility and environmental condition caused by land use changes during the urbanization.
In this paper, the districts that affiliated to Zhengzhou city, Jinshui, Zhongyuan, Guancheng, Erqi and Mangshan, were taken as the research area. The function transformation of soil resource, spatial-temporal change of soil fertility and condition of soil environment that land utility changes caused in the course of urbanization were studied. The main conclusions are as follows:
(1) Function transformation of soil resource. In the course of urbanization, the major transition of productivity function was mainly from the grain field to orchard and pond. It reflected influence of urbanization on the surrounding agricultural structure and as a result, food cropping was converted to more economically profitable forms of agricultural land use.
(2) The spatial-temporal variation of fertility. There was a general increase of the average contents of organic matter, total N, alkali N and available K, in the suburb of Zhengzhou from 1982 to 2003. The improvement of soil nutrients is relative to the large amount of chemical fertilizers application every year, the straw return to soil, and “K supplement program” that Soil and Fertilizer Work Station of Henan Province carried out. But Available P content decrease by 5.95mg/kg. As for spatial variation, the distribution of nutrient content was inclined to be homogeneous, especially for available P and K. Nutrient contents declined in the regions where they had been higher in the second soil survey, while nutrient contents increased where they had been lower, showing the impacts of agricultural planting structure adjustment caused by urbanization on soil nutrient contents.
(3) Heavy metal contents. Heavy metal contents were all lower than their backgrounds, except for the content of Pb was slightly higher. The regions with high heavy metal elements were located in the dirty irrigation area of north and east, the west and where had been planting vegetable for a long time. From this we can see that irrigation using dirty water discharged by cities and factories was a key reason for the increase of soil heavy metal contents.
