Measurement of Nitrogen Leaching from Crop Fields Using Lysimeters

摘要

Coral limestone terraces developed in the tropical islands are characterized by karst topography (i.e., plateaus with shallow depressions and subterranean drainage). Due to the permeability of the underlying limestone, the possibility is high that nitrates derived from nitrogen in fertilizers, human waste, and livestock manure can leach underground and threaten water quality. Once the groundwater is polluted, decontamination becomes very difficult. A groundwater survey was done at a village in NegrosIsland, Philippines to measure nitrate-nitrogen concentrations. The survey showed that the concentration sometimes exceeded the maximum permissible limits of lOppm for drinking water (Fig. 1). Most local people reside on limestone terrace areas and drink from shallow water wells, hence preventing groundwater pollution is critical. A fundamental study aimed at conserving water quality in the tropical islands was conducted at the Tropical Agriculture Research Front (TARF) using lysimeters to quantify theamount of leached nitrogen. The part of the research using these lysimeters is presented in this article.