球根花卉Zephyranthes屬造景利用與管理模式探討.docVIP

Environmental risk assessment on farming in marginal land- a case study of water melon planted on river bed in Wha-lien Taiwan. Ji-Wei Huang、Chung-Chi Lee、Chong-Xian Cai Dept. of Horticulture, National Ilan University Abstract Water melon is a high value cash crop in Taiwan but susceptible to several diseases particularly with repeated cultivation, however river beds provide very good environment for this crop and extra benefit of fruit pulp texture and quality is better from those plants cultivated on river beds. Around average 350,000 tons of water melons were harvested from 3450 hectares in Taiwan during 1990s and many of them were cultivated on or close to river beds. River authorities of Taiwan regard water melon cultivation is beneficial for dust storm control along river beds and therefore offer various incentives for farmers to cultivate water melon on the river beds which were usually owned and managed by the central government. The fluvial beds of main rivers are often wider than 1km in Taiwan and outcome of this policy drew wide public concern and objective environmental risk assessment is therefore vitally important for a correct and sustainable decision making. Typical planting modes and cropping system of water melon were analyzed and examined against dust storm patterns and features to evaluate the for and against. Wind erosion assessment was carried out by simulated circumstance of strong wind blown against land surface at the river beds and also in the experimental field. The weight of blown dust from various land use and plant species was measured. River bed covered with non-disturbed flora was observed the best land use type in terms of soil conservation in contrast with bare ground which is the worst but often a regular condition maintained in the water melon field and the non-disturbed flora of river beds also found to play roles of seed banks during flood season that all the crops were flushed into the water and an urgent volunteer p