Abstract:

Based on the observed meteorological data within a greenhouse, tomato growth investigation data and meteorological data from weather stations in the middle of Hebei province, increasing temperature effect of greenhouse planting a species "Shouguang wudai" tomato was analyzed, and regression models about daily minimum temperature forecast index inside and outside greenhouse for freeze injury were established in different weather conditions. At the same time, the minimum temperature index for tomato freeze injury of different levels was ascertained, and time distribution and multi-time-scale features of freeze injury were discussed by methods of a regression analysis, a wavelet analysis and a climatic abrupt change analysis. The results show that the daily minimum temperature inside the greenhouse changes with that outside the greenhouse in clear, cloudy and overcast days, and both relationships can be fitted in terms of a quadratic curve. Corresponding correlation coefficients in three weather conditions are 0.896, 0.895 and 0.414, respectively. Temperature forecast index for severe freeze injury is Td (daily minimum temperature outside the greenhouse) ≤-15.0 ℃, Td≤-17.5 ℃ and Td ≤-16.5 ℃ in three weather conditions respectively; the corresponding values for moderate and mild freeze injury are -15 ℃＜Td ≤ -13.0 ℃, -17.5 ℃＜Td ≤ -14.5 ℃, 16.5 ℃＜Td ≤-14.0 ℃ and -13.0 ℃＜Td ≤-8.5 ℃, -14.0 ℃＜Td ≤ -9.5 ℃, -14.5 ℃＜Td ≤ -9.0 ℃ respectively. Annual mean freeze injury day is 42.0 days. It is 3.6 days for severe freeze injury and mainly occurs from early December to late February. It is in a decreasing trend for tomato freeze injury from the middle of 1970s to 2000s, and there is an abrupt change in 1986. There are 7 years and 15 years periods for the number of days of severe freeze injury, 5 years, 10 years and 20 years periods for that of moderate one, and 10 years and 18 years periods for that of mild one in the middle of Hebei province. Freeze injury can be divided into three types according to temperature outside the greenhouse, i.e. a clear-cold type, a spare sunlight type and a mixing type. The number of days for three types is 12.0 days, 22.0 days and 36.0 days from November of 2012 to February of 2013, and they account for 17.1%, 31.4% and 51.4% to the total freeze injury days.

Key words: Greenhouse, Tamato, Freeze injury, Meteorological index