| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 100 === The use of chemical fertilizer has negatively impacted on environments in recent decades, mainly through water pollution by nitrogen and phosphate originating from agricultural activity. Intensive use of fertilizer for crops is responsible for nitrate and phosphate accumulation in both groundwater and surface waters. Water bodies polluted by nutrients create many environmental problems, including algal blooms and eutrophication in aquifers or in surface water bodies, and may pose potential hazards to human health. As a main crop and with the cultivation area about 0.25 million ha per year in Taiwan, Rice paddies account for a significant share of fertilizer consumption among agriculture crops.
The aim of this study is to evaluate the fertilization of paddy fields impacting on return flow water quality. Water quality monitoring continued for two crop-periods around subject to different water bodies, including the irrigation water, drainage, and shallow groundwater was conducted in the Hsinpu experimental paddy field located at Hsinchu County, north Taiwan. The results indicated that obviously increasing of ammonium-N, nitrate-N and TP concentrations in the surface drainage water were observed during the early stage of fertilizer applications, but reduced to relatively low concentrations in the remaining period of cultivation. Groundwater quality monitoring from three observation wells with difference water levels showed that the observation wells with the more shallow water depth, the more significant variation of concentrations of ammonium-N, nitrate-N and TP could be observed, which means that the major difference between the high and low contamination potential of nutrient of groundwater is related to the length of percolation route in this area. The ORP values of around –200 mV were measured within the 1 to 10 cm depth, indicating that the redox potential of the most part of root zone is dominated by the reduced condition after long-term flooding. The monitoring analysis also showed that the potential pollution load of nutrient could be further reduced by well drainage water control and rational fertilizer management, such as deep-water irrigation, reuse of return flow, the rational application of fertilizers, and the SRI (The System of Rice Intensification) method are recommended. The results of this study can provide as an evaluation basis to formulate effective measures for agricultural non-point pollution control and the reuse of return flow.
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