Lake Danao (also called Imelda Lake in former times) is a natural lake with an area of 1.9 km2 in the form of guitar located at 700 m above sea level (ASL) in the central highlands of Leyte, Philippines (see photo). Surrounded by mountains with young loamy volcanic soils (Andisols), the lake provides water for home consumption and industrial uses, and opportunities for livelihood of people living nearby. It is a national reserve and popular tourist attraction due to its beautiful scenery and generally cooler climate than the lowlands of
Until now there is lack of published data on the capacity of Philippine soils to filter pollutants as well as on the environmental impacts of the application of chemical and organic fertilizers to soils bordering surface water bodies like lakes and rivers.
In view of the above a laboratory study was conducted to find out if Lake Danao soil allowed leaching of nitrate and phosphate after addition of chemical fertilizers and manure. The leaching experimental set-up was designed and constructed using PVC cylinders containing the Lake Danao soil and amended with various amounts of poultry manure and chemical fertilizers like urea and solophos. The treatments were based on the application rate employed by the farmers around the lake. Results revealed that high amount of nitrate was leached from the soil amended with urea but only small amount in soil added with poultry manure. Findings also showed low amount of phosphate that was leached from the soil amended with either poultry manure or chemical fertilizer. Although field verification of the results maybe necessary, the study implies that the practice of using urea by the farmers can lead to eutrophication of the nearby lake. The use of poultry manure as fertilizer will minimize the said environmental effects.
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