Abstract:

The low temperature frozen injury is the main meteorological disaster of greenhouse winter vegetables in arid and semi arid areas of Shaanxi province. Quantitatively determine the risk of frozen injury and clear the heating boundary are significance to greenhouse design. Summarized the frozen indexes of different levels in northern area and Guanzhong area of Shaanxi. Proposed the monthly scales quantitative analysis and computation methods of the average risk of frozen injury of winter greenhouse vegetables based on county units. Analysed the time characteristics of the average risk of frozen injury of former winter months of 68 counties which in the study area. The results showed that the frequency of light frozen injury was more than the moderate and severe in all the counties and the frequency of frozen injury of each grade decrease successively from Jan. to Dec. and in the end of Feb. Severe frozen injury never appeared in some counties of Guanzhong area in Dec and Feb. The Cˉ value of Northern Shaanxi was 0.6-0.7 in Dec. and Jan. and 0.5-0.7 in Feb. The Cˉ value of Guanzhong area is 0.1-0.6 in Dec. and Feb. and 0.2-0.7 in Jan. The analysis of frozen injury risk showed that it had a big difference in different years and amplitude significantly. According to those characteristics and the production status of greenhouse vegetables in arid and semi arid areas of Shaanxi province, divided Shaanxi greenhouse area into three heating zone: winter continuous heating zone, simple heating zone, low temperature temporary heating zone and determined the heating boundary.