2. Study area, methods and materials
2.1. Study area
Fujian province is located on the southeastern coast of China (Fig. 1). It is characterized by a subtropical climate and rugged terrain, with mountainous and hilly lands accounting for 87.5% of the total area (12.1 million hectares). Red earth and lateritic red earth are the main soil types and are characterized by poor soil fertility and low pH (Soil Survey Group, 1991). The population of Fujian is 33 million, although the majority of people live along the coastal strip. Concentrated residential areas such as townships and urban areas usually occupy more flat lands in large valleys (Cao et al., 2003). In this study, 67 administrative units at the county level were selected to analyze nutrient balances. All cities without farmlands were excluded from calculations (Fig. 1).
The urban population in Fujian reached 11.1 million in 2002 with a 133.8% increase since 1989. However, the increase in urban population between 1989 and 1995 was only 13.2%, whereas the total population for the same period rose by 8.5%. Compared to the total population increase of 16.2% in the entire period 1989–2002, the urban population grew much faster than total population in Fujian, particularly from 1995 to 2002.
The increases in urban population at the county level varied considerably from 37% to over 10-fold between 1989 and 2002, whereas the increases were only between −2.6% and 85% from 1989 to 1995. The greatest increases occurred during 1995–2002 across all counties (Fig. 2) with few exceptions, rather than between 1989 and 1995 when the nation had its most rapid urban population growth (Zhang and Song, 2003).
2.2. Methods and materials
Differences between N, P input and output (IOD) were defined as the differences between the total quantity of anthropogenic N or P entering the surface soil and the total quantity of N or P output leaving the surface soil annually. The calculation was achieved by using a digital database and geographical information system in 67 county units of the province. The inorganic fertilizer, livestock manure and legume fixation were accounted for in the N input, while P input included inorganic fertilizer and manure. Crop harvest was the main output for both N and P. Denitrification and volatilization of N and mineralization of both N and P varied greatly with environmental conditions, and therefore, were not incorporated into the calculation. Atmospheric deposition was not included in the calculation due to unavailable monitoring data, though it might account for another N and P input.
The amount of inorganic N and P fertilizers applied, such as urea and ammonium bicarbonate, was obtained (Fujian Statistics Office, 1989, 1995, 2002). Total N and P in animal manure from each county were estimated using animal population data and the general N and P content in the manures (Lu et al., 1996). Products of excreted N or P and animal population in each animal type were summed up, whereas 25% of total animal excrements (Cao et al., 2005) was assumed to be applied as fertilizers in Fujian (Table 1).
2.1. Study area
Fujian province is located on the southeastern coast of China (Fig. 1). It is characterized by a subtropical climate and rugged terrain, with mountainous and hilly lands accounting for 87.5% of the total area (12.1 million hectares). Red earth and lateritic red earth are the main soil types and are characterized by poor soil fertility and low pH (Soil Survey Group, 1991). The population of Fujian is 33 million, although the majority of people live along the coastal strip. Concentrated residential areas such as townships and urban areas usually occupy more flat lands in large valleys (Cao et al., 2003). In this study, 67 administrative units at the county level were selected to analyze nutrient balances. All cities without farmlands were excluded from calculations (Fig. 1).
The urban population in Fujian reached 11.1 million in 2002 with a 133.8% increase since 1989. However, the increase in urban population between 1989 and 1995 was only 13.2%, whereas the total population for the same period rose by 8.5%. Compared to the total population increase of 16.2% in the entire period 1989–2002, the urban population grew much faster than total population in Fujian, particularly from 1995 to 2002.
The increases in urban population at the county level varied considerably from 37% to over 10-fold between 1989 and 2002, whereas the increases were only between −2.6% and 85% from 1989 to 1995. The greatest increases occurred during 1995–2002 across all counties (Fig. 2) with few exceptions, rather than between 1989 and 1995 when the nation had its most rapid urban population growth (Zhang and Song, 2003).
2.2. Methods and materials
Differences between N, P input and output (IOD) were defined as the differences between the total quantity of anthropogenic N or P entering the surface soil and the total quantity of N or P output leaving the surface soil annually. The calculation was achieved by using a digital database and geographical information system in 67 county units of the province. The inorganic fertilizer, livestock manure and legume fixation were accounted for in the N input, while P input included inorganic fertilizer and manure. Crop harvest was the main output for both N and P. Denitrification and volatilization of N and mineralization of both N and P varied greatly with environmental conditions, and therefore, were not incorporated into the calculation. Atmospheric deposition was not included in the calculation due to unavailable monitoring data, though it might account for another N and P input.
The amount of inorganic N and P fertilizers applied, such as urea and ammonium bicarbonate, was obtained (Fujian Statistics Office, 1989, 1995, 2002). Total N and P in animal manure from each county were estimated using animal population data and the general N and P content in the manures (Lu et al., 1996). Products of excreted N or P and animal population in each animal type were summed up, whereas 25% of total animal excrements (Cao et al., 2005) was assumed to be applied as fertilizers in Fujian (Table 1).
