一、 前言 大白菜(Brassica Campestris ssp Pe-rinensis)是我国北方地区秋季栽培的主要蔬菜之一,其栽培面积很大,它的丰歉直接影响到广大群众冬春的吃菜问题。但是由于大白菜播种于夏秋两季交界的时期,此时华北、西北的气候条件往往是伏旱高温或秋涝阴雨,严重影响了幼苗的正常 I. Introduction Chinese cabbage (Brassica Campestris ssp Pe-rinensis) is one of the main vegetables cultivated in autumn in northern China. Its cultivation area is very large, and its apology directly affects the eating habits of the masses in winter and spring. However, due to cabbage sowing in the summer and autumn at the junction of the two periods, at this time in North China and Northwest climate conditions are often high temperature drought or autumn floods, severe impact on the normal seedlings