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[AHW20-21] Nitrate concentrations of groundwater and surface water in Sao Paulo State, Brazil.
The reasons why they are low.
Keywords:Nitrogen balance, Nitrate, Sao Paulo, Sugar cane, Water environments
Nitrogen, mainly nitrate, in water body in Sao Paulo, is commonly low, except around the downstream area of large cities; Application of N fertilizer is generally less than other countries such as Australia, for example, N-fertilizer application to sugar cane is generally 80-120 kg N ha-1yr-1; Fertilizer efficiencies are relatively high; Vinasse, liquid wastes of ethanol production from sugar cane, is recycled to sugar cane field and promotes BNF in the soil; Leaching from the cultivated lands with acidic soil is much less, which means riverine export is also low, while accumulation of nitrogen (SOM) in the soil is generally large; Many agricultural products are exported to foreign countries, that is, excess nitrogen seems to be reduced within Brazil; Eucalyptus plantation and riparian forests can uptake reactive nitrogen from environments; Soy bean can fix nitrogen as much as 170 kg N ha-1yr-1 or more under better conditions.
As the conclusion, combination of above-mentioned favorable natural and social conditions in the region keeps nitrogen of the water environments lower, though risks of degrading land and water environments are not necessarily eliminated.