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一、绪言东北地区受自然条件的限制,无霜期间一般为100—180天,在一年内非生产季节的时间较长,因而使蔬菜生产不能达到周年供应。在目前国家社会主义工业化的建设,工矿区的蓬勃发展和城市人口的增加,在冬季新鲜蔬菜供应方面,就更觉不足。以旅大市来说每年都需要从外地输入大宗蔬菜,不仅增加了国家的财务开支,而且牵涉很大的运输力量。因而各地
I. INTRODUCTION Due to the natural conditions in Northeast China, frost-free period is generally 100-180 days. Non-productive seasons take longer time in one year, so vegetable production can not reach the annual supply. In the present state of socialist industrialization, the vigorous development of industrial and mining areas and the increase of the urban population are even more inadequate in the supply of fresh vegetables in winter. In the case of LTA, importing large quantities of vegetables from overseas each year not only increases the country’s financial expenditure but also involves a great transport force. Thus all over