Balance de nirogeno inorganico en una parcela con drenaesubterraneo en el tropico humedo | Inorganic nitrogen balance in a plot with subsurface drainage in the humid tropics
2002
Estrada-Botello, M.A. | Nikolskii-Gavrilov, I. | Gavi-Reyes, F. | Etchevers-Barra, J.D. | Palacios-Velez, O.L.
There have been few studies on the inorganic nitrogen (N-NO3(-) + N-NH4(+)) balance in the soils of the humid tropics, even though the soil nitrogen losses through surface and subsurface drainage may threaten bodies of water. To analyze the nitrogen balance in the tropics, an experiment was conducted in the three rainiest months of 1997 in an experimental plot with subsurface drainage in Tabasco, Mexico. The principal components of input and output of water and nitrogen balances were measured. The only water input component was precipitation, and the output components (expressed in percentage of precipitation) were evapotranspiration (23%), surface runoff (45%), and discharge through subsurface drainage and open ditches (32%). The components of the inorganic nitrogen balance (expressed as percentage of all inputs) were (1) inputs: nitrogen fertilizer (38%), mineralized nitrogen (56%), and nitrogen in rain (6%), and (2) outputs (expressed in percentage of total output): nitrogen consumed by plants (60%), losses by volatilization and denitrification (20%), immobilization (5%), loss from surface runoff (3%), and leaching from the unsaturated zone into the water table (12%), which, by means of subsurface drainage, is that which can pollute bodies of water. The highest concentration of ammonium (6.8 mg L(-1) N-NH4(+)) was found in surface runoff and exceeded the permitted limit for human consumption. However, the highest concentration of nitrates (2.7 mg L(-1) N-NO3(-)) in subsurface drainage water did not exceed the limit. This indicates that the present intensity of drainage and agricultural practices in the study area do not yet constitute a serious threat for the bodies of water that receive the effluents of drainage.
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