To investigate the relation between fertilizer and groundwater quality, the well water chemistry near tea plantations was studied. Well waters were classified by the difference of pH value into 3 types. A type is acidic, B type is acidic to neutral and C type is neutral. Average concentrations of NO3-N and HCO3-were: A type, 33.8mg/L and 0.1mg/L, B type, 13.1mg/L and 8.2mg/L; C type, 6.9mg/L and 60.0mg/L, respectively. The decrease in pH values was associated with the increase in the concentration of NO3-N. The concentration of carbonate increased with pH value. Therefore, the decrease of amount of nitrogen fertilization used in tea plantations and the sufficient carbonate were thought to induce rising the pH value. As concentrations of metal in well water increased with decrease in pH value, metal concentrations and pH values were influenced by the use of fertilizer and carbonate.
To investigate the influence of chemical fertilizers on groundwater and surface water neighboring tea plantations in central Shizuoka prefecture, a time series of chemical compositions and nitrogen isotopic ratios within local wells, springs, rivers and ponds were studied. The pH of spring and pond water in some areas maintained basic acidity with neither any noticeable changes in nitrogen isotopic ratios nor any disappearance of nitrate within the ponds and low concentrations of chlorophyll and phosphorus. Therefore, the activities of photosynthesis in the ponds of this area were very low due to low concentrations of phosphorus. However, the pH of spring water in the other areas maintained basic neutrality to alkali with high concentrations of Ca2+ and SO42" and low concentrations of NO,-because of soil and fertilizer improvement. Concentrations of Al, Co, Ni, Zn and Mn ions in the groundwater and surface water increased with the decrease of pH values. Then, soil and fertilizer improvement is important.
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