Characterization and distribution of different phosphorus types in the agricultural areas of Daecheong Lake Watershed, South Korea

Abstract

Agricultural areas utilize various types of agrichemicals to enhance crop growth and production. As a consequence, areas treated with excessive amounts of agrichemicals become primary sources of environmental pollutants. This study was conducted to analyze the different types of phosphorus (P) in the agricultural soils in Deacheong Lake Watershed. The effects of cultivation activities in the availability of nutrients that can potentially cause eutrophication of receiving water bodies were also assessed. The total phosphorus (T-P) and phosphate (PO₄-P) concentrations in the tributaries draining into the Daecheong Lake were found to be three to seven times higher than the T-P and PO₄-P concentrations in Daecheong Lake. The P concentrations in the waterways exhibited significant correlations (p < 0.05) with the soil P, implying that agricultural activities may influence the water quality in Daecheong Lake. Dry field soils had higher T-P concentrations (1246.1 ± 579.9 mg/kg) as compared to paddy fields and in situ soils due to the continuous accumulation of P in the soil strata. Non-apatite inorganic phosphorus (NAI-P) was the most dominant type of P in paddy field soils, whereas organic-P had the highest fraction in dry field soils. Paddy fields can have higher potentials of contributing to eutrophication, since NAI-P is an indicator of algal-available P. T-P concentrations in agricultural soils planted with different crops follows the order: tobacco > corn > perilla > soybean > Chinese cabbage > barley > sweet potato > garlic > potato > red pepper > rice. Generally, shifts in agricultural practices can be used to assess the contribution of agricultural areas in the eutrophication potential of water bodies.

Keywords: Agriculture; Daecheong Lake; Eutrophication; Phosphorus; Soil.