| Budget Amount *help |
¥5,500,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥600,000)
Fiscal Year 2007: ¥2,600,000 (Direct Cost: ¥2,000,000、Indirect Cost: ¥600,000)
Fiscal Year 2006: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
Asparagus fields in NongNguLauem village, NakhonPathom province, Thailand, were surveyed for the cultural practices adopted, yield, fertilizer use, nutrient accumulation in soils, and nitrate-nitrogen concentration of the underground water. In this village, asparagus is being cultivated under contract farming with a Japanese agribusiness company and 60% of the product is exported to Japan. Average application rates of nitrogen-and phosphorus-fertilizers were 840kg N and 286kg P ha-1 year-1, and less than 5% of the applied elements was recovered in the harvested products. Phosphorus accumulated in the surface 20cm soil significantly, unlike N determined by the Kjeldahl method. Higher concentration of nitrate-nitrogen was detecteddown to 1-m depth in the asparagus fields compared with the adjacent sugarcane fields. Underground water samples were taken from 15 wells of the village and their content of nitrate-nitrogen was determined once a month during a period of 48 months. Nitrate-nitrogen was distributed unevenly among the wells, and no periodic peaks in the concentrations were detected. Asparagus farming had started from the northern half of the village, and has developed to the southern half. The highest nitrate concentration was detected in the northern part, however, the concentrations have been decreasing recently. This is because of the lower input of chemical fertilizer and development of organic farming. On the other hand, the nitrate concentrations in the southern wells are increasing in the last two years. The highest value of 39g nitrate-nitrogen m^-3 was recorded, even though the restriction value is about 10 g nitrate-nitrogen m^-3. Also residual pesticide were analyzed in five asparagus fields around the village. Even though the consumption of the pesticide is substantial, the residues could not be detected neither in the soil and in the canal water. Tropical climate condition may stimulate rapid decomposition of the pesticides.
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