Abstract
Despite increased attention to the need for sustainable agriculture, fertilizer application rates above crop requirements remain common agricultural practices in South Korea, causing eutrophication of freshwater and coastal ecosystems. The aim of this study is to quantify phosphorus (P) inputs, outputs, and retention in a forested-agricultural watershed. The P budget showed that the combined use of chemical fertilizer and organic compost was the largest source of P (97.6% of the total) followed by atmospheric wet deposition (2.1% of the total P), whereas forest export (0.2% of the total) and sewage treatment plants (STPs) (0.1% of the total) were negligible. The P outputs were crop harvesting and hydrologic export to surface water. The P balance showed that P inputs are higher than the P outputs; approximately 87% of the total P input was retained in the soils within the watershed. However, P concentrations in drainage water were still high enough to cause eutrophication of downstream reservoirs. The results provide important details on the proportion of P export and retention in the watershed. This will help efforts to improve water quality and design better management strategies for agricultural nonpoint source pollution.
Highlights
Anthropogenic impacts on the global phosphorus (P) cycle have been a major research topic in the field of P biogeochemistry, especially in agricultural ecosystems
We found that fertilizer use is the largest P input to the Haean watershed
The detailed inventory of P inputs and outputs in this study has shown that P inputs are higher than the outputs (Table 8)
Summary
Anthropogenic impacts on the global phosphorus (P) cycle have been a major research topic in the field of P biogeochemistry, especially in agricultural ecosystems. Because of the increase in P fertilizer use during the last few decades, global P inputs from terrestrial to aquatic ecosystems have doubled and eutrophication remains a global issue [1,2]. Eutrophication is a serious environmental challenge in Korea and P export from agricultural fields has been identified as major contributor to nonpoint source (NPS) nutrient pollution [3]. The characteristic intense rainfall during the East Asian summer monsoon dramatically influences the export of NPS derived nutrients from highland agricultural croplands in Korea [4]. Some studies have shown that P export from agricultural fields in Korea is higher than in other regions [3,4]. P budget studies can help to identify and rank the sources
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