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严格掌握大白菜播种期是抗灾、防病,达到高产稳产的一项关键性技术措施。参照本地区近年、当年秋季的天气演变动向和当地主栽品种生长特性、病害(三大病害)发生的轻重等具体情况,对大白菜播种适期,有必要作出恰当的估计。一、西安地区近年秋季天气演变动向 (一)气温与地温:西安地区常年8月平均气温25.4℃,地表温度29.7℃。1971-1975年8月平均气温升高至26.1℃,地表温随之升高至30.5℃。近年8月气温、地温的升高又突出地表现在中旬。常年8月中旬旬平均温度为25.0℃
Strict control of Chinese cabbage sowing period is a key technical measure to prevent and prevent disease and achieve high and stable yield. With reference to the specific circumstances of recent years, the evolution of autumn weather in that area, the growth characteristics of the local cultivars, and the severity of the diseases (major diseases), it is necessary to make proper estimates of the appropriate period of sowing Chinese cabbage. I. Evolution of Weather in Autumn in Recent Years in Xi’an (I) Temperature and Ground Temperature: The annual average temperature in August in Xi’an is 25.4 ℃ and the surface temperature is 29.7 ℃. From 1971 to August 1975, the average temperature increased to 26.1 ℃, and the surface temperature increased to 30.5 ℃. In recent years, the temperature in August, the increase in ground temperature and prominently in the middle. Perennial mid-August average temperature of 25.0 ℃