Abstract:

Based on the observation data of rape fixed-point experiment from 2011 to 2018, the effects of low temperature on rape podding rate and seed number per pod were analyzed in different flowering periods. Furthermore, the quantitative relationship between meteorological factors and seed loss rate was established. The results showed that: the effects of low temperature on seed setting were mainly moderate and severe before February 25, mainly mild in the middle and last ten days of March, and mainly mild and moderate from February 26 to March 10. The relationship between rape seed loss rate with the average daily minimum temperature and daily average rainfall during the flowering stage was not significant, but the relationship between seed loss rate with average temperature, average daily maximum temperature, average sunshine hours, and average daily relative humidity at flowering were significant. With the decrease of average flowering temperature, the average maximum temperature decreased and the relative humidity increased. When the relative humidity of air was 70% and the daily average temperature was ≤6.9℃, or the relative humidity of air was 80% and the daily average temperature was ≤8.0℃, rape would suffer from moderate damage. When the relative humidity of air in flowering time was 80% and the daily average temperature was ≤4.3℃, or the relative humidity of air was 85% and the daily average temperature was ≤4.8℃, the rape would suffer from severe damage. The cold accumulated temperature indexes of rape flowering and seed setting under different weather types were determined. When the cold accumulated temperature index of sunshine and low temperature weather was ≥16.5℃, or the index of cold accumulated temperature of no sunshine and low temperature rainy weather was ≥5.0℃, it was moderate damage. When the cold accumulated temperature index of sunshine and low temperature weather was ≥37.5℃, or the cold accumulated temperature index of no sunshine and low temperature rainy weather was ≥26.0℃, it was severe damage. The results could provide technical support for early warning evaluation and agrometeorological service of disaster reduction and prevention in rape production.

Key words: rape, flowering stage, meteorological factors, seed loss rate, cold accumulated temperature, disaster early warning assessment