Evaluation of the stress on the environment of export-oriented asparagus farming in a Thai

该研究在泰国Nakorn Pathom省Nong Ngu Lauem村进行。在这个村子里，农民集中种植出口导向型芦笋，特别是日本。本研究调查了该地区种植系统中氮磷收支状况，并分析了该地区种植系统中氮磷收支的特点。芦笋种植每年每公顷需要840公斤氮，但只有4.7%的氮被带走，95%以上的氮留在土壤中。土壤中氮素的垂直分布表明，土壤各层硝态氮含量均高于甘蔗种植区。这表明过量的氮渗入了土壤。通过分析该村4年多来从16口威尔斯井中抽取的地下沃茨中的硝酸盐浓度，证实了这一点。记录的最高值为50 ppm，浓度波动。为减轻氮素对环境的胁迫，我们尝试施用缓释肥料和单组分氮肥，如尿素、46-0-0等。在两年的研究中，农民开始更加关注他们的环境。

The research was carried out in Nong Ngu Lauem village, Nakorn Pathom province, Thailand. In this village, farmers concentrated on export-oriented asparagus cultivation, particulary to Japan. This village produces about a half of the annual export of asparagus from Thailand to Japan.We have surveyed nitrogen and phosphorus budget in the cropping system. The asparagus farming needs 840 kg nitrogen per ha per year, but only 4.7% of the nitrogen is taken away in the product and more than 95% of the nitrogen remained in the soils. Vertical distribution of nitrogen in the soils revealed that nitrate concentrations of the soil layers are higher than those under sugarcane cultivation. This suggest that excessive nitrogen leach downward the soil. This was confirmed by analyzing nitrate concentrations in the underground waters which have been taken from 16 wells in the village for more than 4 years. The highest value of 50ppm was recorded, and the concentrations fluctuated. The highest concentrations in the rainy season and the lowest at the dry season, which suggests that nitrate moves downward in the soil layers by water movement.To decrease the nitrogen stress on the environment, we have tried to use slow-releasing fertilizers and single-component nitrogen fertilizers, such as urea, 46-0-0. During 2 years of the research, farmers have started to pay more attention to their environment.